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1
Garrison, Lance P. "Spatial and dietary overlap in the Georges Bank groundfish community." Canadian Journal of Fisheries and Aquatic Sciences 57, no. 8 (August 1, 2000): 1679–91. http://dx.doi.org/10.1139/f00-117.
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Patterns in spatial and trophic resource partitioning in the fish community of the Georges Bank region are identified, accounting for size-based changes in diets. During autumn and spring, this community is divided into geographic assemblages of species that have high spatial overlap. Similarity in spatial distribution is primarily related to similarity in depth preferences, and seasonal differences in species composition within assemblages are related to migrations. There is also important trophic structure within the Georges Bank community separating predators based upon prey size and location in the water column. Ontogenetic changes in diets are an important feature of the trophic structure in this system, particularly in the major piscivores. Seasonal changes in trophic structure reflect both predator and prey migrations. Dietary overlap among predator types is independent of either spatial overlap or depth preferences. There is spatial segregation within trophic guilds, and this spatial partitioning reduces the potential for exploitative competition within this community. Given the observed spatial patterns in trophic structure, the geographic assemblages on Georges Bank may be considered ecologically distinct functional units within this ecosystem.
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Sampaio, Ana Lúcia A., João Paulo A. Pagotto, and Erivelto Goulart. "Relationships between morphology, diet and spatial distribution: testing the effects of intra and interspecific morphological variations on the patterns of resource use in two Neotropical Cichlids." Neotropical Ichthyology 11, no. 2 (June 2013): 351–60. http://dx.doi.org/10.1590/s1679-62252013005000001.
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Considering th e morphology, diet and spatial distribution of Satanoperca pappaterraand Crenicichla britskii (Perciformes: Cichlidae) in the Upper Paraná River floodplain (Brazil), the following questions were investigated: (1) Could the body shape predict the use of trophic resources and habitat by C. britskiiand S. pappaterra? (2) Could the relationship between morphology and use of trophic resources and habitat be also extended to the intraspecific scale? (3) What are the most important morphological traits used to predict the variation on diet and habitat occupation within and between species? We hypothesized that intra and interspecific differences in morphological patterns imply in different forms of resource exploitation and that the ecomorphological analysis enables the identification of trophic and spatial niche segregation. Fish samplings were performed in different types of habitats (rivers, secondary channels, connected and disconnected lagoons) in the Upper Paraná River floodplain. Analyses of the stomach content was conducted to characterize the feeding patterns and twenty-two ecomorphological indices were calculated from linear morphological measurements and areas. A principal component analysis (PCA) run with these indices evidenced the formation of two significant axes, revealing in the axis 1 an ecomorphological ordination according to the type of habitat, regardless the species. The individuals of both species exploiting lotic habitats tended to have morphological traits that enable rapid progressive and retrograde movements, braking and continuous swimming, whereas individuals found in lentic and semi-lotic habitats presented morphology adapted to a greater maneuverability and stabilization in deflections. On the other hand the axis 2 evidenced a segregation related to the feeding ecology, between S. pappaterra and C. britskii. The relationship between morphology and use of spatial and feeding resource was corroborated by the Mantel test performed at inter and intraspecific levels. Therefore the hypothesis was accepted suggesting that analyses incorporating both intraspecific and interspecific morphological variations can contribute to a greater understanding about the ecological structure of fish assemblages by providing evidences on the niche characteristics of each species.
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Puerta, Patricia, Mary E. Hunsicker, Manuel Hidalgo, Patricia Reglero, Lorenzo Ciannelli, Antonio Esteban, María González, and Antoni Quetglas. "Community–environment interactions explain octopus-catshark spatial overlap." ICES Journal of Marine Science 73, no. 7 (May 26, 2016): 1901–11. http://dx.doi.org/10.1093/icesjms/fsw053.
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Abstract The octopus Eledone cirrhosa and the catshark Scyliorhinus canicula present the same feeding habits and distributional preferences in the Mediterranean Sea. We explore patterns of spatial overlap between these species to address coexistence and infer possible competition from spatial patterns in the western Mediterranean Sea. A spatially explicit modelling approach revealed that spatial overlap mainly responded to the distribution of shared resources, where coexistence is allowed by different ecological processes. Catshark (k-strategy) was highly abundant and widely distributed. However, the fluctuating population dynamics of octopus (r-strategy) explained the variations in spatial patterns of overlap. Spatial structuring across the study area was observed both in population distributions and in species interactions (coexistence or exclusion). Areas with high resources in terms of specific prey items (Catalan Sea) or alternative supplies, such as niche opportunities and ecosystem functions defined by community diversity (Balearic Islands), favoured species coexistence. Sea surface temperature showed opposite effects on overlap in northern and southern regions of the study area, which were not related to differences in species sensitivity. We suggest a surface trophic link, where different phytoplankton communities at each region might have opposite responses to temperature. This triggers contrasting mechanisms of food transfer to deeper benthic communities that subsequently facilitates species overlap. Characterizing how benthic and pelagic seascape properties shape species interactions across space and time is pivotal to properly address community spatial dynamics and move towards ecosystem-based management for sustainable fisheries and conservation planning.
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Liao, Chenmei, Yifan Zuo, Rob Law, Yingying Wang, and Mu Zhang. "Spatial Differentiation, Influencing Factors, and Development Paths of Rural Tourism Resources in Guangdong Province." Land 11, no. 11 (November 15, 2022): 2046. http://dx.doi.org/10.3390/land11112046.
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Rural tourism resources are the core carriers of rural tourism. It is, therefore, beneficial to further optimize the layout of rural tourism and to explore the spatial differentiation of rural tourism resources and their influencing factors. Taking 4670 rural tourism resources in Guangdong Province in China as the research object, this study explores the spatial distribution patterns of rural tourism resources through the nearest neighbor index, grid dimension analysis, kernel density analysis, and standard deviation ellipse method. Geodetectors are used to identify the influencing factors of the spatial heterogeneity of these resources in Guangdong Province. The findings reveal the following: (1) The distribution of rural tourism resources in Guangdong Province shows a tendency of agglomeration along the Tropic of Cancer, and the spatial distribution is unbalanced. The hot and cold spots show a “northeast-southwest” distribution trend. Furthermore, most of the hotspots form three high-density core areas, the sub-dense stretch zones connect into a w-shaped belt, and the sub-cold areas and sub-hot areas show a large expansion trend, thus forming five radiation areas. (2) The distribution of rural tourism resources in Guangdong Province is affected by multiple factors. In particular, the force of agricultural resource endowment, tourism resource endowment and transportation location are relatively strong, and social economy and tourist source market are the weak factors.
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Benoit-Bird, Kelly J., and Margaret A. McManus. "Bottom-up regulation of a pelagic community through spatial aggregations." Biology Letters 8, no. 5 (May 2, 2012): 813–16. http://dx.doi.org/10.1098/rsbl.2012.0232.
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The importance of spatial pattern in ecosystems has long been recognized. However, incorporating patchiness into our understanding of forces regulating ecosystems has proved challenging. We used a combination of continuously sampling moored sensors, complemented by shipboard sampling, to measure the temporal variation, abundance and vertical distribution of four trophic levels in Hawaii's near shore pelagic ecosystem. Using an analysis approach from trophic dynamics, we found that the frequency and intensity of spatial aggregations—rather than total biomass—in each step of a food chain involving phytoplankton, copepods, mesopelagic micronekton and spinner dolphins ( Stenella longirostris ) were the most significant predictors of variation in adjacent trophic levels. Patches of organisms had impacts disproportionate to the biomass of organisms within them. Our results are in accordance with resource limitation—mediated by patch dynamics—regulating structure at each trophic step in this ecosystem, as well as the foraging behaviour of the top predator. Because of their high degree of heterogeneity, ecosystem-level effects of patchiness such as this may be common in many pelagic marine systems.
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Siqueira, Alexandre C., Renato A. Morais, David R. Bellwood, and Peter F. Cowman. "Planktivores as trophic drivers of global coral reef fish diversity patterns." Proceedings of the National Academy of Sciences 118, no. 9 (February 16, 2021): e2019404118. http://dx.doi.org/10.1073/pnas.2019404118.
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One of the most prominent features of life on Earth is the uneven number of species across large spatial scales. Despite being inherently linked to energetic constraints, these gradients in species richness distribution have rarely been examined from a trophic perspective. Here we dissect the global diversity of over 3,600 coral reef fishes to reveal patterns across major trophic groups. By analyzing multiple nested spatial scales, we show that planktivores contribute disproportionally to the formation of the Indo-Australian Archipelago (IAA) marine biodiversity hotspot. Besides being “hotter” at the hotspot, planktivorous fishes display the steepest decline in species numbers with distance from the IAA when compared to other trophic groups. Surprisingly, we did not detect differences in diversification, transition, and dispersal rates in extant species phylogenies that would explain this remarkable gradient in planktivorous fish richness. Thus, we identify two potential complementary drivers for this pattern. First, exceptional levels of partitioning among planktivorous coral reef fishes were driven by temporally stable oceanographic conditions and abundant planktonic resources in the IAA. Second, extinctions of planktivores outside the IAA have been particularly pronounced during Quaternary climate fluctuations. Overall, our results highlight trophic ecology as an important component of global species richness gradients.
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Ursenbacher, Sylvain, Philippe Christe, and César Metzger. "Testing the competitive exclusion principle using various niche parameters in a native (Natrix maura) and an introduced (N. tessellata) colubrid." Amphibia-Reptilia 30, no. 4 (2009): 523–31. http://dx.doi.org/10.1163/156853809789647031.
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AbstractDespite the increase of animal and plant introductions worldwide and the strong augmentation of the reptile trade, few invasive snake populations have been studied. Dice snakes (Natrix tessellata) were introduced to the shores of Lake Geneva (Switzerland) in the early 1920s, and are now well established. This region of introduction was previously inhabited by Viperine snakes (N. maura). Ever since these two species have been under monitoring (which began in 1996) the Viperine snake population has shown drastic decline. We examine here the possibility of trophic competition by analysing diet composition, prey size and trophic niche overlap. Spatial distribution is also assessed in order to address the question of spatial competitive exclusion. We found very similar diets, and thus a high trophic niche overlap, indicating no partitioning of the trophic resource. No arguments in favour of spatial competitive exclusion were found. Our study suggests that trophic competition may occur between the two natricines and that it may give an explanation for the drastic decline of the Viperine snake in this area. Other pathways potentially playing a role in the exclusion of the Viperine snake are discussed.
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Codron, Jacqueline, Kevin J. Duffy, Nico L. Avenant, Matt Sponheimer, Jennifer Leichliter, Oliver Paine, Paul Sandberg, and Daryl Codron. "Stable isotope evidence for trophic niche partitioning in a South African savanna rodent community." Current Zoology 61, no. 3 (June 1, 2015): 397–411. http://dx.doi.org/10.1093/czoolo/61.3.397.
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Abstract Species’ partitioning of resources remains one of the most integral components for understanding community assembly. Analysis of stable carbon and nitrogen isotopes in animal tissues has the potential to help resolve patterns of partitioning because these proxies represent the individual’s diet and trophic niche, respectively. Using free-ranging rodents in a southern African savanna as a model community, we find that syntopic species within habitats occupy distinct isotope niches. Moreover, species with strongly overlapping isotope niches did not overlap in their spatial distribution patterns, suggesting an underlying effect of competitive exclusion. Niche conservatism appears to characterize the behaviour of most species in our sample - with little or no observed changes across habitats - with the exception of one species, Mastomys coucha. This species displayed a generalist distribution, being found in similar abundances across a variety of habitats. This spatial pattern was coupled with a generalist isotope niche that shifted across habitats, likely in response to changes in species composition over the same spatial gradient. The case for M. coucha supports contentions that past competition effects played a significant evolutionary role in shaping community structures of today, including the absence of strong interspecific niche overlaps within particular habitats. Our study highlights the value of stable isotope approaches to help resolve key questions in community ecology, and moreover introduces novel analytical approaches to quantifying isotope niche breadths and niche overlaps that are easily comparable with traditional metrices.
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Santamaría, Silvia, Camilla Aviaaja Enoksen, Jens M. Olesen, Giacomo Tavecchia, Andreu Rotger, José Manuel Igual, and Anna Traveset. "Diet composition of the lizard Podarcis lilfordi (Lacertidae) on 2 small islands: an individual-resource network approach." Current Zoology 66, no. 1 (May 21, 2019): 39–49. http://dx.doi.org/10.1093/cz/zoz028.
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Abstract Despite it is widely accepted that intrapopulation variation is fundamental to ecological and evolutionary processes, this level of information has only recently been included into network analysis of species/population interactions. When done, it has revealed non-random patterns in the distribution of trophic resources. Nestedness in resource use among individuals is the most recurrent observed pattern, often accompanied by an absence of modularity, but no previous studies examine bipartite modularity. We use network analysis to describe the diet composition of the Balearic endemic lizard Podarcis lilfordi in 2 islets at population and individual levels, based on the occurrence of food items in fecal samples. Our objectives are to 1) compare niche structure at both levels, 2) characterize niche partition using nestedness and modularity, and 3) assess how size, sex, season, and spatial location influence niche structure. At population-level niche width was wide, but narrow at the level of the individual. Both islet networks were nested, indicating similar ranking of the food preferences among individuals, but also modular, which was partially explained by seasonality. Sex and body size did not notably affect diet composition. Large niche overlap and therefore possibly relaxed competition were observed among females in one of the islets and during spring on both islets. Likewise, higher modularity in autumn suggests that higher competition could lead to specialization in both populations, because resources are usually scarce in this season. The absence of spatial location influence on niche might respond to fine-grained spatio-temporally distribution of food resources. Behavioral traits, not included in this study, could also influence resource partitioning.
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Almeida, Nathalie, Jaime A. Ramos, Isabel Rodrigues, Ivo dos Santos, Jorge M. Pereira, Diana M. Matos, Pedro M. Araújo, Pedro Geraldes, Tommy Melo, and Vitor H. Paiva. "Year-round at-sea distribution and trophic resources partitioning between two sympatric Sulids in the tropical Atlantic." PLOS ONE 16, no. 6 (June 21, 2021): e0253095. http://dx.doi.org/10.1371/journal.pone.0253095.
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In the oligotrophic tropical marine environment resources are usually more patchily distributed and less abundant to top predators. Thus, spatial and trophic competition can emerge, especially between related seabird species belonging to the same ecological guild. Here we studied the foraging ecology of two sympatric species–brown booby (BRBO) Sula leucogaster (breeding) and red-footed boobies (RFBO) Sula sula (non-breeding)–at Raso islet (Cabo Verde), across different seasons. Sexual segregation was only observed during Jun-Oct, when RFBO were present, with larger females BRBO remaining closer to the colonies, while males and RFBO travelled further and exploited different habitats. Overall, species appeared to prefer areas with specific oceanic features, particularly those related with oceanic currents and responsible for enhancing primary productivity in tropical oceanic areas (e.g. Sea Surface Height and Ocean Mixed Layer Thickness). Female BRBOs showed high foraging-site fidelity during the period of sympatry, while exploiting the same prey species as the other birds. However, during the months of co-existence (Jun.-Oct.), isotopic mixing models suggested that female BRBO would consume a higher proportion of epipelagic fish, whereas female RFBO would consume more squid compared to the other birds, possibly due to habitat-specific prey availability and breeding energy-constraints for BRBO. We conclude that divergent parental roles, environmental conditions, habitat preference and competition could be mechanisms simultaneously underlying sexual segregation for BRBO during a period of co-existence, while inter-specific foraging differences appear to be more affected by habitat preference and different breeding stages. These results support previous statements that BRBO can adapt their foraging ecology to different circumstances of environmental conditions and competition, and that marine physical features play an important role in foraging decisions of boobies.
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Mario Arthur Favretto, Elton Orlandin, Emili Bortolon dos Santos, and Osvaldo Onghero-Junior. "Functional feeding groups and spatial variation of aquatic insects in a hydrographic basin of Southern Brazil." Acta Biológica Catarinense 5, no. 3 (December 17, 2018): 50–64. http://dx.doi.org/10.21726/abc.v5i3.406.
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In Brazil, river basins are geographic units used for environmental and water resources management. Few studies focus on the variation of biodiversity in these units. We present the results on the spatial variation of aquatic insects in streams of the catchment area of Peixe River, southern Brazil. The insect composition was analyzed for relative abundance of families, functional trophic group and environmental assessment indices. The insects had a heterogeneous distribution among the sample areas of the basin. The most abundant families were Hydropsychidae, Philopotamidae and Leptophlebiidae, a fact that shows a good oxygenation in the waters of these streams. The most abundant functional trophic groups were collector-collector (20%) and scraper (18.92%). The indices indicate that the bed of the streams is stable, with a high presence of fine particulate organic matter, being considered heterotrophic. However, the indices also indicated a low abundance of shredders, which may be related to unsatisfactory environmental conditions in the riparian forests. Spatial variation was found in aquatic insects and the indices indicated that the main human impacts on the streams may originate from deforestation and inadequate soil use. Data obtained also contribute to reinforce the importance of watersheds as geographic units for environmental conservation.
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Favretto, Mario Arthur, Elton Orlandin, Emili Bortolon Dos Santos, and Osvaldo Onghero-Jr. "Functional trophic groups and spatial variation of aquatic insects in a hydrographic basin of Southern Brazil." Acta Biológica Catarinense 5, no. 3 (December 13, 2018): 50. http://dx.doi.org/10.21726/abc.v5i3.447.
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In Brazil hydrographic basins are geographical unities used to environmental and hydric resources management, but few studies focus in the biodiversity variation within these unities. Here we present the results of spatial variation of aquatic insects in streams of a hydrographic basin in Southern Brazil. The insect composition was analyzed in relation to abundance of the families, functional trophic group and environmental evaluation indexes proposed by literature. The insects had a heterogeneous distribution in the sampling areas of the hydrographic basin. The most abundant families were Hydropsychidae, Philopotamidae and Leptophlebiidae, which demonstrate a good oxygenation of the water in the sampling streams. The most abundant functional trophic groups were gatherer-collector (20%) and scraper (18.92%). The indexes demonstrated the riverbeds of the streams are stable, with a high presence of fine particulate organic matter and they were considered heterotrophic. However, they also indicated a low abundance of shredders, which may be related to poor environmental conditions in the riparian forests. Therefore, here we found spatial variation of aquatic insects and indexes performed indicated the main human impacts as deforestation and inadequate land use. The data obtained also contributed to reinforce the importance of hydrographic basin as geographical unities for environmental conservation.
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Chukwuka, Azubuike Victor, Adedeji Hameed Adebowale, and Oloyede Adeyemi Adekolurejo. "Morphological Differences and Trophic Niche Breadth of Sarotherodon galilaeus and Oreochromis niloticus from the Freshwater Lake Geriyo, North-Eastern Nigeria." Croatian Journal of Fisheries 77, no. 1 (March 1, 2019): 19–32. http://dx.doi.org/10.2478/cjf-2019-0003.
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Abstract The relationship between morphological traits and feeding ecology of the only two tilapiine cichlids (Sarotherodon galilaeus and Oreochromis niloticus) in Lake Geriyo, northeastern Nigeria, was examined. Stomach contents of 504 individuals were examined and analyzed to relate morphological differences of each species to its dietary preferences. Eleven ecological relevant morphological variables, including total length, standard length, head length, body depth, eye diameter, pectoral spine length, pelvic spine length, dorsal fin ray count, dorsal spine count and anal fin ray count, were also measured and subjected to Principal coordinate analysis (PCoA) to relate morphological differences of each species to its dietary preferences. The PCoA (using Euclidean distance) revealed a large morphological distance between species indicating adaptation for different spatial and vertical distributions within the lake. Furthermore, the correlation of these morphological differences with particular diet categories suggests a potential for specialized trophic tendencies, however, the high occurrence of two major food types (macrophytes and plankton) in stomach contents of both species indicate generalist trophic tendencies. While a high trophic overlap index (0.98) was recorded for both species, the trophic niche breadth was higher for S. galilaeus (4.18±0.32), compared to O. niloticus (3.33±0.24). Despite the large morphological differences of both tilapias, the high trophic overlaps indicate limited food options within Lake Geriyo. In addition, the successful coexistence of the tilapias in the face of limited food resources indicates suitable partitioning of food resources in the lake.
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Smith, Joshua G., Joseph Tomoleoni, Michelle Staedler, Sophia Lyon, Jessica Fujii, and M. Tim Tinker. "Behavioral responses across a mosaic of ecosystem states restructure a sea otter–urchin trophic cascade." Proceedings of the National Academy of Sciences 118, no. 11 (March 8, 2021): e2012493118. http://dx.doi.org/10.1073/pnas.2012493118.
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Consumer and predator foraging behavior can impart profound trait-mediated constraints on community regulation that scale up to influence the structure and stability of ecosystems. Here, we demonstrate how the behavioral response of an apex predator to changes in prey behavior and condition can dramatically alter the role and relative contribution of top-down forcing, depending on the spatial organization of ecosystem states. In 2014, a rapid and dramatic decline in the abundance of a mesopredator (Pycnopodia helianthoides) and primary producer (Macrocystis pyrifera) coincided with a fundamental change in purple sea urchin (Strongylocentrotus purpuratus) foraging behavior and condition, resulting in a spatial mosaic of kelp forests interspersed with patches of sea urchin barrens. We show that this mosaic of adjacent alternative ecosystem states led to an increase in the number of sea otters (Enhydra lutris nereis) specializing on urchin prey, a population-level increase in urchin consumption, and an increase in sea otter survivorship. We further show that the spatial distribution of sea otter foraging efforts for urchin prey was not directly linked to high prey density but rather was predicted by the distribution of energetically profitable prey. Therefore, we infer that spatially explicit sea otter foraging enhances the resistance of remnant forests to overgrazing but does not directly contribute to the resilience (recovery) of forests. These results highlight the role of consumer and predator trait-mediated responses to resource mosaics that are common throughout natural ecosystems and enhance understanding of reciprocal feedbacks between top-down and bottom-up forcing on the regional stability of ecosystems.
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Flores-Ortega, Juan R., Enrique Godínez-Domínguez, Gaspar González-Sansón, Jorge A. Rojo-Vázquez, Antonio C. López-Prado, and María Y. Morales-Jauregui. "Abundance, distribution, feeding habits and trophic interactions in five flatfish species (Pleuronectiformes) in the Mexican central Pacific." Latin American Journal of Aquatic Research 41, no. 3 (March 2, 2017): 423–39. http://dx.doi.org/10.3856/vol41-issue3-fulltext-6.
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We analyzed the spatial distribution patterns of the five most abundant flatfish species caught by shrimp trawl nets on the continental shelf of the Mexican central Pacific. Food diets and trophic interactions between of the flatfish species are described as well. Flatfishes are distributed between 20 and 60 m depth. Bothus leopardinus showed the greatest abundance during the cold season (January-May), the other species did not show significant differences between seasons (cold and warm). The diet of the flatfish species consist of crustaceans, fishes and cephalopods. B. leopardinus and Syacium ovale are consumers of crustaceans, such as crabs, shrimps and stomatopods. Cyclopsetta panamensis, C. querna and Monolene assaedae based their diet in fishes and cephalopods. The feeding strategy of the five species analyzed is considered to be generalist, consuming a high number of preys in both seasons. Between the flatfish species, low values of overlapping in the diets were observed in size class and periods of the year. The flatfish species consume the available food resources and could change the preys consumed, according to prey availability, to avoid intra and interspecific competition.
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Doong, Marielle Kristine, Jonathan Anticamara, and Francis Magbanua. "Spatial Variations in the Distribution of Benthic Macroinvertebrate Functional Feeding Groups in Tropical Rivers." Indonesian Journal of Limnology 2, no. 1 (June 30, 2021): 35–52. http://dx.doi.org/10.51264/inajl.v2i1.11.
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Functional feeding group (FFG) is an approach that classifies macroinvertebrates based on their utilization of organic matter food resources. Across streams and rivers, variations in the distribution of FFGs reflect the unequal distribution of food resources, which are affected by varying environmental conditions and disturbances to the ecosystem. In the tropics, the distribution of FFGs does not follow the pattern observed in temperate streams. This study aims to (1) determine the FFGs present in selected Philippine tropical streams, (2) assess the variations in FFG distributions and how the distributions vary across space, and (3) evaluate how FFG distributions are affected by certain environmental factors and habitat structure. Benthic macroinvertebrates were collected in 2010 from five sites and assigned to their primary FFG based on published literature. Across study sites, the macroinvertebrates collected were classified into gathering collectors (total n = 4,640), scrapers (n = 1,670), filtering collectors (n = 1,545), predators (n = 632), and shredders (n = 270). Within and between sites, these FFGs varied significantly. Variations explained the upstream-downstream and north-south variations in the mean of FFG abundance in width and depth of the stream, discharge, temperature, pH, riparian vegetation, and habitat stability and variability. This study reveals that the FFG approach is a useful bioassessment tool in tropical aquatic systems. However, there is still a need for verification of the findings in other streams and seasons.
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Abrahms, Briana, Kylie L. Scales, Elliott L. Hazen, Steven J. Bograd, Robert S. Schick, Patrick W. Robinson, and Daniel P. Costa. "Mesoscale activity facilitates energy gain in a top predator." Proceedings of the Royal Society B: Biological Sciences 285, no. 1885 (August 22, 2018): 20181101. http://dx.doi.org/10.1098/rspb.2018.1101.
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How animal movement decisions interact with the distribution of resources to shape individual performance is a key question in ecology. However, links between spatial and behavioural ecology and fitness consequences are poorly understood because the outcomes of individual resource selection decisions, such as energy intake, are rarely measured. In the open ocean, mesoscale features (approx. 10–100 km) such as fronts and eddies can aggregate prey and thereby drive the distribution of foraging vertebrates through bottom-up biophysical coupling. These productive features are known to attract predators, yet their role in facilitating energy transfer to top-level consumers is opaque. We investigated the use of mesoscale features by migrating northern elephant seals and quantified the corresponding energetic gains from the seals' foraging patterns at a daily resolution. Migrating elephant seals modified their diving behaviour and selected for mesoscale features when foraging. Daily energy gain increased significantly with increasing mesoscale activity, indicating that the physical environment can influence predator fitness at fine temporal scales. Results show that areas of high mesoscale activity not only attract top predators as foraging hotspots, but also lead to increased energy transfer across trophic levels. Our study provides evidence that the physical environment is an important factor in controlling energy flow to top predators by setting the stage for variation in resource availability. Such understanding is critical for assessing how changes in the environment and resource distribution will affect individual fitness and food web dynamics.
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McBride, MM, O. Schram Stokke, AHH Renner, BA Krafft, OA Bergstad, M. Biuw, AD Lowther, and JE Stiansen. "Antarctic krill Euphausia superba: spatial distribution, abundance, and management of fisheries in a changing climate." Marine Ecology Progress Series 668 (June 24, 2021): 185–214. http://dx.doi.org/10.3354/meps13705.
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Antarctic krill Euphausia superba, a keystone species in the Southern Ocean, is highly relevant for studying effects of climate-related shifts on management systems. Krill provides a key link between primary producers and higher trophic levels and supports the largest regional fishery. Any major perturbation in the krill population would have severe ecological and economic ramifications. We review the literature to determine how climate change, in concert with other environmental changes, alters krill habitat, affects spatial distribution/abundance, and impacts fisheries management. Findings recently reported on the effects of climate change on krill distribution and abundance are inconsistent, however, raising questions regarding methods used to detect changes in density and biomass. One recent study reported a sharp decline in krill densities near their northern limit, accompanied by a poleward contraction in distribution in the Southwest Atlantic sector. Another recent study found no evidence of long-term decline in krill density or biomass and reported no evidence of a poleward shift in distribution. Moreover, with predicted decreases in phytoplankton production, vertical foraging migrations to the seabed may become more frequent, also impacting krill production and harvesting. Potentially cumulative impacts of climate change further compound the management challenge faced by CCAMLR, the organization responsible for conservation of Antarctic marine living resources: to detect changes in the abundance, distribution, and reproductive performance of krill and krill-dependent predator stocks and to respond to such change by adjusting its conservation measures. Based on CCAMLR reports and documents, we review the institutional framework, outline how climate change has been addressed within this organization, and examine the prospects for further advances toward ecosystem risk assessment and an adaptive management system.
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Muto, Elizabeti Y., Thaïs Navajas Corbisier, Leandro Inoe Coelho, Lidia Paes Leme Arantes, André Chalom, and Lucy Satiko Hashimoto Soares. "Trophic Groups Of Demersal Fish Of Santos Bay And Adjacent Continental Shelf, São Paulo State, Brazil: Temporal And Spatial Comparisons." Brazilian Journal of Oceanography 62, no. 2 (July 2014): 89–102. http://dx.doi.org/10.1590/s1679-87592014045906202.
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The temporal and spatial variations of feeding habits and trophic groups of demersal fish species of Santos Bay and the adjacent continental shelf were investigated. The samples were taken in September 2005 and March 2006 by bottom otter trawling. The stomach content analysis of 2,328 specimens of 49 species showed most fish fed on a large range of food items but relied heavily on shrimp, crabs/swimming-crabs, amphipods, mysids, polychaetes, ophiuroids, squids, and teleosteans. The species were classified into ten trophic groups. Shrimp were an important food source in the Santos bay and inner shelf, while ophiuroids were important prey for predators of the middle shelf. Many species relied on crabs/swimming-crabs during the summer, especially on the middle shelf. The spatial and temporal variability in food resource utilization by fish were related to the pattern of distribution and abundance of their prey. The predation on shrimp and crabs/swimming-crabs seems to be related to the water mass dynamics of the region. Intraspecific comparisons demonstrated that most of the species display spatial and/or temporal variation in their diet. The demersal ichtyofauna can also be divided into the more general categories of piscivores, nektonic invertebrate feeders, benthic invertebrate feeders and planktonic invertebrate feeders.
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Polunina, Ju Ju, E. K. Lange, and V. A. Krechik. "The structure and distribution of autumnal zooplankton in the South-Eastern part of the Baltic sea in 2015." Океанология 59, no. 1 (April 18, 2019): 72–81. http://dx.doi.org/10.31857/s0030-157459172-81.
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Were found peculiarities of the structure and distribution in the autumn plankton of the South -Eastern part of the Baltic sea (SEB) in October 2015 taking into account hydrological and hydrochemical data. There were no changes registered as to the taxonomic composition of phyto- and zooplankton, including no increase in the number of the stenothermic and stenohaline species, as well as no significant differences in the hydrological parameters in comparison with the long-term analogous data. Thus, there was no influence of the winter Major Baltic Inflow in December 2014 on the plankton SEB next autumn. The level of phytoplankton vegetation in the upper homogeneous layer (125±39 thous. cells/l, 664±143 mg/m3) was higher compared to the long-term data. The abundance and biomass of zooplankton (5.1-16.8 thous. ind/m3 and 49-143 mg/m3) were within the typical value for autumn in the studied area. Peculiarity of zooplankton spatial distribution were related to trophic resources and the thermohaline structure of the water column.
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Alexander, Timothy J., Pascal Vonlanthen, and Ole Seehausen. "Does eutrophication-driven evolution change aquatic ecosystems?" Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1712 (January 19, 2017): 20160041. http://dx.doi.org/10.1098/rstb.2016.0041.
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Eutrophication increases primary production and changes the relative abundance, taxonomic composition and spatial distribution of primary producers within an aquatic ecosystem. The changes in composition and location of resources alter the distribution and flow of energy and biomass throughout the food web. Changes in productivity also alter the physico-chemical environment, which has further effects on the biota. Such ecological changes influence the direction and strength of natural and sexual selection experienced by populations. Besides altering selection, they can also erode the habitat gradients and/or behavioural mechanisms that maintain ecological separation and reproductive isolation among species. Consequently, eutrophication of lakes commonly results in reduced ecological specialization as well as genetic and phenotypic homogenization among lakes and among niches within lakes. We argue that the associated loss in functional diversity and niche differentiation may lead to decreased carrying capacity and lower resource-use efficiency by consumers. We show that in central European whitefish species radiations, the functional diversity affected by eutrophication-induced speciation reversal correlates with community-wide trophic transfer efficiency (fisheries yield per unit phosphorus). We take this as an example of how evolutionary dynamics driven by anthropogenic environmental change can have lasting effects on biodiversity and ecosystem functioning. This article is part of the themed issue ‘Human influences on evolution, and the ecological and societal consequences'.
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Poulsen, Bent Otto. "A comparison of bird richness, abundance and trophic organization in forests of Ecuador and Denmark: are high-altitude Andean forests temperate or tropical?" Journal of Tropical Ecology 18, no. 4 (July 2002): 615–36. http://dx.doi.org/10.1017/s0266467402002407.
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The fact that certain climatic variables are similar in high-latitude temperate zones and at high-altitude sites in the tropics, has led to assumptions about ecologically equivalent situations. The altitudinal differences between two data sets obtained in forests in temperate Denmark at sea level and in tropical Ecuador at 3000–3350 m above sea level provided a comparison suitable for examining whether high-altitude Andean forests are temperate or tropical from the standpoint of avian richness, abundance and trophic organization. Sampling methods at the two locations were similar. The Ecuadorian high-altitude sites were found to be significantly more species-rich than Danish temperate sites at all spatial scales studied (from point census to 10 km2). Additionally, species–area curves from the two countries displayed positive correlations, as expected, but with different rates of increase. The high-altitude Andean curve demonstrated a higher rate of increase causing the two curves to separate widely as more area was added. This means that when increasing areas are considered, proportionately more species squeeze into the Ecuadorian high-altitude forest landscape than do into the temperate Danish forest landscape. Corresponding to the data on richness, bird abundance was significantly higher at the Ecuadorian sites than at the Danish ones. The analysis of rank–abundance plots from Denmark and Ecuador throws light on the organization of bird species and abundance. The majority of communities in both countries fitted both the log-series and the log-normal models, making statistical distinction impossible. However, a visual inspection of the rank-ordered abundance distributions demonstrated that the Danish communities, in contrast to the Ecuadorian ones, had dominant species with relatively higher abundance, had more species with intermediate abundance, and had fewer species ‘rare by abundance’. Some major food resources (especially fruit and nectar) exploited in high-altitude sites of Ecuador were not reliably available in temperate Denmark leading also to differences in the distribution of bird species within six major trophic categories. In conclusion, the ecological characteristics of birds of the high Andes apparently are similar to those of the tropical and tropical lower montane sites (increased richness and abundance, similar organization of richness and abundance, similar additional trophic categories, similar clutch sizes), and not to those of the high- and low-latitude temperate sites.
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Mustamäki, Noora, Henri Jokinen, Matias Scheinin, Erik Bonsdorff, and Johanna Mattila. "Seasonal shifts in the vertical distribution of fish in a shallow coastal area." ICES Journal of Marine Science 73, no. 9 (March 29, 2016): 2278–87. http://dx.doi.org/10.1093/icesjms/fsw038.
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Abstract Depth structures aquatic habitats, creating substantial differences in the species composition of underwater communities even at small intervals. Those communities also undergo considerable cyclic variation annually. In this study, we surveyed variation in the vertical distribution of fish in a shallow (20 m) coastal basin in the northern Baltic Sea during the ice-free period from May to October. The waters were strongly mixed throughout the season and only transient signs of stratification were observed. As production shifted towards higher trophic levels over summer, with sequential biomass peaks in zooplankton and juvenile fish, the vertical distribution of the entire fish assemblage became increasingly even. The results suggest that spatial resource partitioning can be strongly correlated with seasonal productivity cycles even in physically uniform environments with high connectivity. Further, the results stress the importance of sampling design (seasonal and vertical coverage) of fish studies in shallow coastal areas.
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Rodrigues, C. F., A. Hilário, and M. R. Cunha. "Chemosymbiotic species from the Gulf of Cadiz (NE Atlantic): distribution, life styles and nutritional patterns." Biogeosciences 10, no. 4 (April 17, 2013): 2569–81. http://dx.doi.org/10.5194/bg-10-2569-2013.
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Abstract. Previous work in the mud volcanoes from the Gulf of Cadiz (South Iberian Margin) revealed a high number of chemosymbiotic species, namely bivalves and siboglinid polychaetes. In this study we give an overview of the distribution and life styles of these species in the Gulf of Cadiz, determine the role of autotrophic symbionts in the nutrition of selected species using stable isotope analyses (δ13C, δ15N and δ34S) and investigate the intra-specific variation of isotope signatures within and between study sites. During our studies, we identified twenty siboglinidae and nine bivalve chemosymbiotic species living in fifteen mud volcanoes. Solemyid bivalves and tubeworms of the genus Siboglinum are widespread in the study area, whereas other species were found in a single mud volcano (e.g. "Bathymodiolus" mauritanicus) or restricted to deeper mud volcanoes (e.g. Polybrachia sp., Lamelisabella denticulata). Species distribution suggests that different species may adjust their position within the sediment according to their particular needs, and to the intensity and variability of the chemical substrata supply. Tissue stable isotope signatures for selected species are in accordance with values found in other studies, with thiotrophy as the dominant nutritional pathway, and with methanotrophy and mixotrophy emerging as secondary strategies. The heterogeneity in terms of nutrient sources (expressed in the high variance of nitrogen and sulphur values) and the ability to exploit different resources by the different species may explain the high diversity of chemosymbiotic species found in the Gulf of Cadiz. This study increases the knowledge on distributional patterns and resource partitioning of chemosymbiotic species and highlights how trophic fuelling varies on spatial scales with direct implications to seep assemblages and potentially to the biodiversity of continental margin.
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Tsybulin, Vyacheslav, Toan Dang Ha, and Pavel Zelenchuk. "Nonlinear dynamics of the predator – prey system in a heterogeneous habitat and scenarios of local interaction of species." Izvestiya VUZ. Applied Nonlinear Dynamics 29, no. 5 (September 30, 2021): 751–64. http://dx.doi.org/10.18500/0869-6632-2021-29-5-751-764.
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The purpose of this work is to study the influence of various local models in the equations of diffusion–advection– reaction on the spatial processes of coexistence of predators and prey under conditions of a nonuniform distribution of the carrying capacity. We consider a system of nonlinear parabolic equations to describe diffusion, taxis, and local interaction of a predator and prey in a one-dimensional habitat. Methods. We carried out the study of the system using the dynamical systems approach and a computational experiment based on the method of lines and a scheme of staggered grids. Results. The behavior of the predator – prey system has been studied for various scenarios of local interaction, taking into account the hyperbolic law of prey growth and the Holling effect with nonuniform carrying capacity. We have established paradoxical scenarios of interaction between prey and predator for several modifications of the trophic function. Stationary and nonstationary solutions are analyzed considering diffusion and directed migration of species. Conclusion. The trophic function that considers the heterogeneity of the resource is proposed, which does not lead to paradoxical dynamics.
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Zhao, Chunxu, Chunyan Shen, Andrew Bakun, Yunrong Yan, and Bin Kang. "Purpleback Flying Squid Sthenoteuthis oualaniensis in the South China Sea: Growth, Resources and Association with the Environment." Water 13, no. 1 (December 31, 2020): 65. http://dx.doi.org/10.3390/w13010065.
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The purpleback flying squid (Ommastrephidae: Sthenoteuthis oualaniensis) is an important species at higher trophic levels of the regional marine ecosystem in the South China Sea (SCS), where it is considered to show the potential for fishery development. Accordingly, under increasing climatic and environmental changes, understanding the nature and importance of various factors that determine the spatial and temporal distribution and abundance of S. oualaniensis in the SCS is of great scientific and socio-economic interest. Using generalized additive model (GAM) methods, we analyzed the relationship between available environmental factors and catch per unit effort (CPUE) data of S. oualaniensis. The body size of S. oualaniensis in the SCS was relatively small (<19.4 cm), with a shorter lifespan than individuals in other seas. The biological characteristics indicate that S. oualaniensis in the SCS showed a positive allometric growth, and could be suitably described by the logistic growth equation. In our study, the sea areas with higher CPUE were mainly distributed at 10°–11° N, with a 27–28 °C sea surface temperature (SST) range, a sea surface height anomaly (SSHA) of −0.05–0.05 m, and chlorophyll-a concentration (Chl-a) higher than 0.18 μg/L. The SST was the most important factor in the GAM analysis and the best fitting GAM model explained 67.9% of the variance. Understanding the biological characteristics and habitat status of S. oualaniensis in the SCS will benefit the management of this resource.
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Paschoalini, Victor Uber, and Marcos César de Oliveira Santos. "Movements and habitat use of bottlenose dolphins, Tursiops truncatus, in south-eastern Brazil." Journal of the Marine Biological Association of the United Kingdom 100, no. 4 (May 21, 2020): 651–62. http://dx.doi.org/10.1017/s0025315420000387.
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AbstractBottlenose dolphins (Tursiops truncatus) have been surveyed for at least two decades on the southern Brazilian coast. However, little is known about their distribution and habitat use in lower latitudes of the South-western Atlantic Ocean. Aiming to study the movements and distribution of the species along the south-eastern Brazilian coast, we made a comparison of photo-identified individuals of the species catalogued in 21 cruises conducted between 2012 and 2015. Additionally, we performed stable isotope analyses of carbon and nitrogen in skin samples (N = 35) to provide some insights of dolphin habitat use and trophic ecology through comparisons among individuals of distinct surveyed sectors (northern and southern) and sex. A total of 177 individuals were identified. Re-sightings (N = 24) occurred at intervals from 82 to 979 days at distances from 7 to 179 km. No individual was sighted in both sectors, suggesting spatial segregation. Isotopic comparisons showed no significant differences in carbon and nitrogen signatures between distinct sectors. However, ecological divergences were found when we divided the samples by gender. Wider isotopic niches were found for the northern bottlenose dolphins vs the southern ones, which could be related to temporal and spatial variation in the availability of resources, as well as possible differences in the home ranges of males and females in each region. This study represents a preliminary evaluation of ecological aspects of bottlenose dolphins along the Brazilian south-eastern coast, however, long-term studies on the feeding ecology and habitat use of this species are important to further improve our knowledge.
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Suryan, Robert M., and Karen N. Fischer. "Stable isotope analysis and satellite tracking reveal interspecific resource partitioning of nonbreeding albatrosses off Alaska." Canadian Journal of Zoology 88, no. 3 (March 2010): 299–305. http://dx.doi.org/10.1139/z10-002.
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Albatrosses (Diomedeidae) are the most threatened family of birds globally. The three North Pacific species ( Phoebastria Reichenbach, 1853) are listed as either endangered or vulnerable, with the population of Short-tailed Albatross ( Phoebastria albatrus (Pallas, 1769)) less than 1% of its historical size. All North Pacific albatross species do not currently breed sympatrically, yet they do co-occur at-sea during the nonbreeding season. We incorporated stable isotope analysis with the first simultaneous satellite-tracking study of all three North Pacific albatross species while sympatric on summer (nonbreeding season) foraging grounds off Alaska. Carbon isotope ratios and tracking data identify differences in primary foraging domains of continental shelf and slope waters for Short-tailed Albatrosses and Black-footed Albatrosses ( Phoebastria nigripes (Audubon, 1839)) versus oceanic waters for Laysan Albatrosses ( Phoebastria immutabilis (Rothschild, 1893)). Short-tailed and Black-footed albatrosses also fed at higher trophic levels than Laysan Albatrosses. The relative trophic position of Black-footed and Laysan albatrosses, however, appears to differ between nonbreeding and breeding seasons. Spatial segregation also occurred at a broader geographic scale, with Short-tailed Albatrosses ranging more north into the Bering Sea than Black-footed Albatrosses, which ranged more to the southeast, and Laysan Albatrosses more to the southwest. Differences in carbon isotope ratios among North Pacific albatross species during the nonbreeding season likely reflect the relative proportion of neritic (more carbon enriched) versus oceanic (carbon depleted) derived nutrients, and possible differential use of fishery discards, rather than latitudinal differences in distribution.
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Unsworth, Richard K. F., and Emma G. Butterworth. "Seagrass Meadows Provide a Significant Resource in Support of Avifauna." Diversity 13, no. 8 (August 6, 2021): 363. http://dx.doi.org/10.3390/d13080363.
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Seagrass meadows are known to be rich in fauna, with complex food webs that provide trophic subsidy to species and habitats way beyond the extent of their distribution. Birds are an often-overlooked part of marine ecosystems; not only are they crucial to the health of marine ecosystems, but their populations are also supported by the productivity and biodiversity of marine ecosystems. The links of birds to specific habitat types such as seagrass meadows are largely not considered except in the context of direct herbivorous consumption. Here, we examine the linkages between seagrass and birds and propose a conceptual framework for how seagrasses may support bird populations beyond their distribution in both direct and indirect pathways. We present evidence that seagrass meadows are globally foraged for fish and invertebrates by coastal birds. They are also targeted by herbivorous wildfowl and potentially benefit birds further afield indirectly as a result of their support for offshore marine fish species at critical times in their life cycle (e.g., Atlantic Cod and King George Whiting). Evidence from the literature indicates that seagrass does provide support for birds, but reveals a field of research requiring much gap filling as studies are globally sparse, mechanistically limited, and small in spatial and temporal scales.
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Palacz, A. P., M. A. St John, R. J. W. Brewin, T. Hirata, and W. W. Gregg. "Distribution of phytoplankton functional types in high-nitrate, low-chlorophyll waters in a new diagnostic ecological indicator model." Biogeosciences 10, no. 11 (November 22, 2013): 7553–74. http://dx.doi.org/10.5194/bg-10-7553-2013.
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Abstract. Modeling and monitoring plankton functional types (PFTs) is challenged by the insufficient amount of field measurements of ground truths in both plankton models and bio-optical algorithms. In this study, we combine remote sensing data and a dynamic plankton model to simulate an ecologically sound spatial and temporal distribution of phyto-PFTs. We apply an innovative ecological indicator approach to modeling PFTs and focus on resolving the question of diatom–coccolithophore coexistence in the subpolar high-nitrate and low-chlorophyll regions. We choose an artificial neural network as our modeling framework because it has the potential to interpret complex nonlinear interactions governing complex adaptive systems, of which marine ecosystems are a prime example. Using ecological indicators that fulfill the criteria of measurability, sensitivity and specificity, we demonstrate that our diagnostic model correctly interprets some basic ecological rules similar to ones emerging from dynamic models. Our time series highlight a dynamic phyto-PFT community composition in all high-latitude areas and indicate seasonal coexistence of diatoms and coccolithophores. This observation, though consistent with in situ and remote sensing measurements, has so far not been captured by state-of-the-art dynamic models, which struggle to resolve this "paradox of the plankton". We conclude that an ecological indicator approach is useful for ecological modeling of phytoplankton and potentially higher trophic levels. Finally, we speculate that it could serve as a powerful tool in advancing ecosystem-based management of marine resources.
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Palacz, A. P., M. A. St John, R. J. W. Brewin, T. Hirata, and W. W. Gregg. "Distribution of phytoplankton functional types in high-nitrate low-chlorophyll waters in a new diagnostic ecological indicator model." Biogeosciences Discussions 10, no. 5 (May 15, 2013): 8103–57. http://dx.doi.org/10.5194/bgd-10-8103-2013.
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Abstract. Modeling and monitoring plankton functional types (PFTs) is challenged by insufficient amount of field measurements to ground-truth both plankton models and bio-optical algorithms. In this study, we combine remote sensing data and a dynamic plankton model to simulate an ecologically-sound spatial and temporal distribution of phyto-PFTs. We apply an innovative ecological indicator approach to modeling PFTs, and focus on resolving the question of diatom-coccolithophore co-existence in the subpolar high-nitrate and low-chlorophyll regions. We choose an artificial neural network as our modeling framework because it has the potential to interpret complex nonlinear interactions governing complex adaptive systems, of which marine ecosystems are a prime example. Using ecological indicators that fulfill the criteria of measurability, sensitivity and specificity, we demonstrate that our diagnostic model correctly interprets some basic ecological rules similar to ones emerging from dynamic models. Our time series highlight a dynamic phyto-PFT community composition in all high latitude areas, and indicate seasonal co-existence of diatoms and coccolithophores. This observation, though consistent with in situ and remote sensing measurements, was so far not captured by state-of-the-art dynamic models which struggle to resolve this "paradox of the plankton". We conclude that an ecological indicator approach is useful for ecological modeling of phytoplankton and potentially higher trophic levels. Finally, we speculate that it could serve as a powerful tool in advancing ecosystem-based management of marine resources.
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Mellon-Duval, Capucine, Mireille Harmelin-Vivien, Luisa Métral, Véronique Loizeau, Serge Mortreux, David Roos, and Jean Marc Fromentin. "Trophic ecology of the European hake in the Gulf of Lions, northwestern Mediterranean Sea." Scientia Marina 81, no. 1 (March 27, 2017): 7. http://dx.doi.org/10.3989/scimar.04356.01a.
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The European hake, Merluccius merluccius, is an important resource for Mediterranean fisheries. This study focuses on juvenile and adult hake feeding ecology in the Gulf of Lions, using information from scientific surveys carried out during two seasons and three years (2004-2006). Stomach content and stable isotope (δ15N, δ13C) analyses were performed, and the main factors explaining variations in δ15N were investigated using GLMs. In the Gulf of Lions, hake mostly fed on crustaceans and fish and a dominant piscivorous regime was reached at 15 cm total length. Pelagic fish (sardine, anchovy and small blue whiting) were the main source of prey (40%-80%) and cannibalism was low (< 5%). The results confirmed that hake is an opportunistic feeder and also showed that the size and diversity of prey vary among hake size classes, probably as a result of the different spatial distribution and/or foraging migrations. The present study finally postulates that the unbalanced sex ratio (80% female against 20% male) observed at the adult stage could be related to the combination of growth pattern differences, diet and exploitation rate on the continental shelf, where the males spend a longer period of time.
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Hsiao, Po-Yuan, Teruhisa Shimada, Kuo-Wei Lan, Ming-An Lee, and Cheng-Hsin Liao. "Assessing Summertime Primary Production Required in Changed Marine Environments in Upwelling Ecosystems Around the Taiwan Bank." Remote Sensing 13, no. 4 (February 19, 2021): 765. http://dx.doi.org/10.3390/rs13040765.
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The Taiwan Bank (TB) is located in the southern Taiwan Strait, where the marine environments are affected by South China Sea Warm Current and Kuroshio Branch Current in summer. The bottom water flows upward along the edge of the continental shelf, forming an upwelling region that is an essential high-productivity fishing ground. Using trophic dynamic theory, fishery resources can be converted into primary production required (PPR) by primary production, which indicates the environmental tolerance of marine ecosystems. This study calculated the PPR of benthic and pelagic species, sea surface temperature (SST), upwelling size, and net primary production (NPP) to analyze fishery resource structure and the spatial distribution of PPR in upwelling, non-upwelling, and thermal front (frontal) areas of the TB in summer. Pelagic species, predominated by those in the Scombridae, Carangidae families and Trachurus japonicus, accounted for 77% of PPR (67% of the total catch). The benthic species were dominated by Mene maculata and members of the Loliginidae family. The upwelling intensity was the strongest in June and weakest in August. Generalized additive models revealed that the benthic species PPR in frontal habitats had the highest deviance explained (28.5%). Moreover, frontal habitats were influenced by NPP, which was also the main factor affecting the PPR of benthic species in all three habitats. Pelagic species were affected by high NPP, as well as low SST and negative values of the multivariate El Niño–Southern Oscillation (ENSO) index in upwelling habitats (16.9%) and non-upwelling habitats (11.5%). The composition of pelagic species varied by habitat; this variation can be ascribed to impacts from the ENSO. No significant differences were noted in benthic species composition. Overall, pelagic species resources are susceptible to climate change, whereas benthic species are mostly insensitive to climatic factors and are more affected by NPP.
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Le-Alvarado, Meliza, Alfonsina E. Romo-Curiel, Oscar Sosa-Nishizaki, Oscar Hernández-Sánchez, Leticia Barbero, and Sharon Z. Herzka. "Yellowfin tuna (Thunnus albacares) foraging habitat and trophic position in the Gulf of Mexico based on intrinsic isotope tracers." PLOS ONE 16, no. 2 (February 24, 2021): e0246082. http://dx.doi.org/10.1371/journal.pone.0246082.
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Yellowfin tuna (YFT, Thunnus albacares) is a commercially important species targeted by fisheries in the Gulf of Mexico (GM). Previous studies suggest a high degree of residency in the northern GM, although part of the population performs movements to southern Mexican waters. Whether YFT caught in southern waters also exhibit residency or migrate to the northern gulf is currently uncertain, and little is known regarding their trophic ecology. The isotopic composition (bulk & amino acids) of YFT muscle and liver tissues were compared to a zooplankton-based synoptic isoscape from the entire GM to infer feeding areas and estimate Trophic Position (TP). The spatial distribution of δ15Nbulk and δ15NPhe values of zooplankton indicated two distinct isotopic baselines: one with higher values in the northern GM likely driven by denitrification over the continental shelf, and another in the central-southern gulf, where nitrogen fixation predominates. Based on the contribution of the two regional isotopic baselines to YFT tissues, broad feeding areas were inferred, with a greater contribution of the northern GM (over a one-year time scale by muscle), and to a lesser extent in the central-southern GM (over the ca. 6-month scale by liver). This was corroborated by similarities in δ15NPhe values between YFT and the northern GM. TP estimates were calculated based on stable isotope analysis of bulk (SIA) and compound-specific isotope analysis (CSIA-AA) of the canonical source and trophic amino acids. Mean TP based on SIA was 4.9 ± 1.0 and mean TP based on CSIA-A was 3.9 ± 0.2. YFT caught within the Mexican region seem to feed in northern and in central and southern GM, while feeding in the northern GM has a temporal component. Thus, management strategies need to consider that YFT caught in US and Mexican waters are a shared binational resource that exhibit feeding migrations within the GM.
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Jiang, Shun Yao, Qin Xue Xiong, and Jian Qiang Zhu. "Evaluation of Lake Eutrophication Based on the HJ-1 Satellite Multispectral Data." Applied Mechanics and Materials 519-520 (February 2014): 1184–87. http://dx.doi.org/10.4028/www.scientific.net/amm.519-520.1184.
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Chinese domestic satellite HJ-1 was launched in 2008, now it has become a significant resource for environment monitoring because its Multispectral data are characterized by 2-day temporal resolution, 30 m spatial resolution and 700 km breadth. A study case was made that HJ-1 multispectral data were used for retrieving aggregative trophic level index (TLI()) of water body of lakes in Wuhan, China. The aim of this study is to evaluate the probability of HJ-1 Multispectral data on estimating the eutrophic level of inland water. At first, the TLI() of sampling spots of some lakes in Wuhan were calculated using the monitoring water quality data. In the mean time, the NDVI of corresponding spots were calculated from the HJ-1 multispectral data which had been taken radiometric calibration and geometric correction beforehand. After that, a remote sensing inversion model for TLI() had been built through linear regression using the NDVI as independent variables. Finally, the TLI() of all water bodies of Wuhan lakes were inversed with this model and a map for its spatial distribution was drawn up. Results demonstrated that there were good linear correlation relationships between the TLI() and NDVI of HJ-1 Multispectral data, and the distribution of inversed TLI() of the lakes accorded with the reality quite well. According to the above, an inference can be made that the methods to evaluate lakes eutrofication based on the HJ-1 satellite multispectral data may provide a cheap and rapid way for real-time monitoring and evaluation of lakes eutrophication.
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Welsh Jr, H. H., G. R. Hodgson, J. J. Duda, and J. M. Emlen. "Faunal assemblages and multi-scale habitat patterns in headwater tributaries of the South Fork Trinity River – an unregulated river embedded within a multiple-use landscape." Animal Biodiversity and Conservationa 33, no. 1 (2010): 63–87. http://dx.doi.org/10.32800/abc.2010.33.0063.
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Headwaters can represent 80% of stream kilometers in a watershed, and they also have unique physical and biological properties that have only recently been recognized for their importance in sustaining healthy functioning stream networks and their ecological services. We sampled 60 headwater tributaries in the South Fork Trinity River, a 2,430 km2, mostly forested, multiple-use watershed in northwestern California. Our objectives were: (1) to differentiate unique headwater types using 69 abiotic and vegetation variables measured at three spatial scales, and then to reduce these to informative subsets; (2) determine if distinct biota occupied the different tributary types; (3) determine the environmental attributes associated with the presence and abundance of these biotic assemblages; and (4) using niche modeling, determine key attribute thresholds to illustrate how these biota could be employed as metrics of system integrity and ecological services. Several taxa were sufficiently abundant and widespread to use as bio-indicators: the presence and abundance of steelhead trout (Oncorhynchus mykiss), herpetofauna (reptile and amphibian) species richness, and signal crayfish (Pacifastacus leniusculus) represented different trophic positions, value as commercial resources (steelhead), sensitivity to environmental stress (amphibians), and indicators of biodiversity (herpetofauna species richness). Herpetofauna species richness did not differ, but abundances of steelhead trout, signal crayfish, and amphibian richness all differed significantly among tributary types. Niche models indicated that distribution and abundance patterns in both riparian and aquatic environments were associated with physical and structural attributes at multiple spatial scales, both within and around reaches. The bio-indicators responded to unique sets of attributes, reflecting the high environmental heterogeneity in headwater tributaries across this large watershed. These niche attributes represented a wide range of headwater environments, indicating responses to a number of natural and anthropogenic conditions, and demonstrated the value of using a suite of bio-indicators to elucidate watershed conditions, and to examine numerous disturbances that may influence ecological integrity.
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Mammola, Stefano, and Marco Isaia. "Day–night and seasonal variations of a subterranean invertebrate community in the twilight zone." Subterranean Biology 27 (September 19, 2018): 31–51. http://dx.doi.org/10.3897/subtbiol.27.28909.
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Being characterized by the absence of light and a reduced environmental cyclicity, the subterranean domain is generally regarded as temporally stable. Yet, in the proximity of cave entrances (twilight zones), patterns of sunlight and darkness can be detected within the 24-hour day–night cycle. In parallel, changes in the abiotic and biotic conditions are expected; however, these patterns have been rarely explored in animal communities dwelling in the twilight zone. We performed a biological investigation in a small abandoned mine in the Western Alps, monitoring it once per season, both during the day and at night. At each survey, we collected data on the spatial distribution of the resident species, their activity patterns, and the main microclimatic parameters. We observed significant daily variations in the environmental conditions during winter and spring, namely higher temperature, relative humidity and availability of trophic resources at night. In conjunction with these disparate nocturnal conditions, the abundance of troglophile species was also higher, as well as the activity patterns of one of the most frequent species inhabiting the entrance area – the orb-weaver spiderMetamenardi. We further documented temporal changes in the composition of the parietal community, due to species using the mine as a diurnal, nocturnal or overwintering shelter. Overall, our results suggest that the communities of the twilight zone are not temporally stable and we highlight the importance of taking into account not only their seasonal, but also their daily variations.
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Yakovenko, Vladimir, Nickolai Shadrin, and Elena Anufriieva. "The Prawn Palaemon adspersus in the Hypersaline Lake Moynaki (Crimea): Ecology, Long-Term Changes, and Prospects for Aquaculture." Water 14, no. 18 (September 7, 2022): 2786. http://dx.doi.org/10.3390/w14182786.
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For several years, the prawn Palaemon adspersus population was studied in a hypersaline lake (Crimea) for the first time. P. adspersus is a more halotolerant species than previously thought and can survive and breed up to a salinity of 55 g/L and probably higher. A significant positive correlation was found between the number and biomass of the prawns and the seagrass Ruppia shoot density. The spring temperature increase from 5.5 to 24 °C was accompanied by a significant increase in the prawn number (p = 0.001). In the males and females, the spatial heterogeneity of the distribution of prawns significantly (p = 0.005) negatively correlated with the abundance of prawns. In the period from 2018 to 2021, the area of Ruppia cover and the prawn abundance in the lake decreased, and a significant correlation was found between those changes. High salinity, judging by our data, can reduce the production potential of the species, but the absence of predators in Lake Moynaki allowed the prawns to reach a higher abundance than was observed in other habitats. P. adspersus can be successfully cultivated in hypersaline waters with a salinity up to 55 g/L as a perspective object for Integrated Multi-Trophic Aquaculture. The development of aquaculture in hypersaline waters may help to save freshwater resources, and the development of aquaculture in brines formed during the desalination of seawater will make it more economically viable to obtain freshwater from seawater.
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Li, Jingtai, Yao Liu, Siying Xie, Min Li, Li Chen, Cuiling Wu, Dandan Yan, and Zhaoqing Luan. "Landsat-Satellite-Based Analysis of Long-Term Temporal Spatial Dynamics of Cyanobacterial Blooms: A Case Study in Taihu Lake." Land 11, no. 12 (December 4, 2022): 2197. http://dx.doi.org/10.3390/land11122197.
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Cyanobacterial blooms in large and shallow freshwater lakes have become one of the most severe ecological problems threatening the environment and public health. Although great progress has been made in Taihu Lake in cyanobacterial bloom monitoring, most previous studies have used MODIS images with a resolution greater than 250 m, available after 2000, while the fine-scale studies on its long-term spatio-temporal dynamics to date are insufficient. This study monitored the spatiotemporal distribution of cyanobacterial blooms in Taihu Lake between 1984 and 2021 using Landsat images of 30 m resolution on the cloud computation platform Google Earth Engine and calculated the cyanobacterial blooms’ area percentage and the cyanobacterial bloom frequency index. Then, we investigated the influence of water quality and meteorological factors on area and frequency using Spearman correlation and principal component analysis. The results show that cyanobacterial blooms spread from the northern to the central, western, and eastern parts of Taihu Lake from 1984 to 2021. With the exception of East Lake, the area and frequency of cyanobacterial blooms increased significantly. Hypereutrophic water conditions, high temperatures, abundant sunshine hours, and low wind velocities all favor cyanobacteria blooms in Taihu Lake, and the key influencing factors of dynamics in cyanobacterial blooms are the comprehensive trophic level index, annual sunshine hours, and annual maximum wind speed. This study can serve as a reference for lake eutrophication monitoring and water resource management and protection.
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Crees, Jennifer J., Ben Collen, and Samuel T. Turvey. "Bias, incompleteness and the ‘known unknowns’ in the Holocene faunal record." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1788 (November 4, 2019): 20190216. http://dx.doi.org/10.1098/rstb.2019.0216.
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Long-term faunal data are needed to track biodiversity change and extinction over wide spatio-temporal scales. The Holocene record is a particularly rich and well-resolved resource for this purpose but nonetheless represents a biased subset of the original faunal composition, both at the site-level assemblage and when data are pooled for wider-scale analysis. We investigated patterns and potential sources of taxonomic, spatial and temporal bias in two Holocene datasets of mammalian occurrence and abundance, one at the global species level and one at the continental population-level. Larger-bodied species are disproportionately abundant in the Holocene fossil record, but this varies according to trophic level, probably owing to past patterns of human subsistence and exploitation. Despite the uneven spatial distribution of mammalian occurrence records, we found no specific source of sampling bias, suggesting that this error type can be avoided by intensive data collection protocols. Faunal assemblages are more abundant and precisely dated nearer to the present as a consequence of taphonomy, past human demography and dating methods. Our study represents one of the first attempts to quantify incompleteness and bias in the Holocene mammal record, and failing to critically assess the quality of long-term faunal datasets has major implications for understanding species decline and extinction risk. This article is part of a discussion meeting issue ‘The past is a foreign country: how much can the fossil record actually inform conservation?’
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GKANASOS, ATHANASIOS, EUDOXIA SCHISMENOU, KOSTAS TSIARAS, STYLIANOS SOMARAKIS, MARIANNA GIANNOULAKI, SARANTIS SOFIANOS, and GEORGE TRIANTAFYLLOU. "A three dimensional, full life cycle, anchovy and sardine model for the North Aegean Sea (Eastern Mediterranean): Validation, sensitivity and climatic scenario simulations." Mediterranean Marine Science 22, no. 3 (October 10, 2021): 653. http://dx.doi.org/10.12681/mms.27407.
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We present the development of a 3D full-lifecycle, individual-based model (IBM) for anchovy and sardine, online coupled to an existing hydrodynamic/biogeochemical low-trophic level (LTL) model for the North Aegean Sea. It was built upon an existing 1D model for the same species and area, with the addition of a horizontal movement scheme. In the model, both species evolve from the embryonic stage (egg+yolk sac larva) to the larval, juvenile, and adult stages. Somatic growth is simulated with the use of a “Wisconsin” type bioenergetics model and fish populations with an adaptation of the ‘super individuals’ (SI) approach. For the reference simulation and model calibration, in terms of fish growth and population biomass, the 2000-2010 period was selected. Interannual biomass variability of anchovy was successfully represented by the model, while the simulated biomass of sardine exhibited low variability and did not satisfactorily reproduce the observed interannual variability from acoustic surveys. The spatial distribution of both species’ biomass was in relatively good agreement with field data. Additional single-species simulations revealed that species compete for food resources. Temperature sensitivity experiments showed that both species reacted negatively to a temperature increase. Anchovy, in particular, was more affected since its spawning and larval growth periods largely overlap with the period of maximum yearly temperature and low prey concentration. Finally, simulation experiments using IPCC climatic scenarios showed that the predicted temperature increase and zooplankton concentration decrease in the future will negatively affect anchovy, resulting in sardine prevalence.
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Viola, M. N. Paso, L. Riccialdelli, A. Jaureguizar, H. O. Panarello, and H. L. Cappozzo. "Variation in the isotopic composition of striped weakfish Cynoscion guatucupa of the Southwest Atlantic Ocean in response to dietary shifts." Brazilian Journal of Biology 78, no. 2 (August 17, 2017): 202–10. http://dx.doi.org/10.1590/1519-6984.01416.
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Abstract The aim of this study was to analyze the isotopic composition in muscle of striped weakfish Cynoscion guatucupa from Southwest Atlantic Ocean in order to evaluate a possible variation in δ13C and δ15N in response to dietary shifts that occur as animals grow. We also explored for isotopic evidence of differences between sample locations. The results showed an agreement between isotope analysis and previous conventional studies. Differences in the isotope composition between sampling location were not observed. A positive relation exists between isotope values and total body length of the animals. The Cluster analysis defined three groups of size classes, validated by the MDS. Differences in the relative consumption of prey species in each size class were also observed performing isotope mixing models (SIAR). Variation in δ15N among size classes would be associated with the consumption of a different type of prey as animals grow. Small striped weakfish feed on small crustaceans and progressively increase their consumption of fish (anchovy, Engraulis anchoita), increasing by this way their isotope values. On the other hand, differences in δ13C values seemed to be related to age-class specific spatial distribution patterns. Therefore, large and small striped weakfish remain specialized but feeding on different prey at different trophic levels. These results contribute to the study of the diet of striped weakfish, improve the isotopic ecology models and highlight on the importance of accounting for variation in the isotopic composition in response to dietary shifts with the size of one of the most important fishery resources in the region.
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Díaz, Silvia, Arturo Aguirre-León, Erika Mendoza-Sánchez, and Ana Laura Lara-Domínguez. "Factores ambientales que influyen en la ictiofauna de la laguna La Mancha, sitio Ramsar, Golfo de México." Revista de Biología Tropical 66, no. 1 (December 13, 2017): 246. http://dx.doi.org/10.15517/rbt.v66i1.28495.
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La Mancha lagoon in the Gulf of Mexico, is a coastal system with Ramsar category because of its high biodiversity, many species of fish depend on it to complete their life cycles. In this study we analyzed the spatial and temporal variation of fish diversity, abundance and associations, and its relationship with physicochemical factors. Between April 2005 and January 2008, 95 daytime samplings were carried out at seven sites, where water characteristics and the composition of fish community were recorded. The system presented spatial-temporal variations of the physicochemical parameters, defining contrasting environments according to the local gradients. A total of 5 974 fish individuals, belonging to 50 species, 39 genera and 25 families were collected; four species were new records for the system. The diversity and richness of species were high in the brackish environment and low in freshwaters areas. In September (rainy season) and November (“nortes” season), diversity (H' = 1.52) and richness (D = 1.99) were highest. Fish abundance was greater towards the mouth connecting with the sea. The density and biomass (1.17 ind/m2, 4.33 g/m2) was higher in April (dry season) and the average weight (30.82 g/ind) in July (rainy season). The Importance Value Index (IVI) defined four dominant species representing 75 % of the numerical abundance and 46 % of the total catch in weight. The Canonical Correspondence Analysis (CCA) showed that the fish-habitat relationship was explained in 57 % of the total variance for the first two axes, where the variations in temperature, salinity, dissolved oxygen and depth were the environmental factors that determined the composition, distribution, community components and trophic categories of the fish community. This study provides information on the relationship between the environment and the structure of the fish community in La Mancha, and represents a basis for ecological monitoring to increase the knowledge needed about the ecosystem and fish populations, in order to boost management strategies for the fishery resources conservation in Veracruz.
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Volkov, Anatoly F. "Integral values of biomass and stock of zooplankton in the epipelagic layer of the area 71 in the North Pacific, including the Bering and Okhotsk Seas, and patterns of distribution for mass species." Izvestiya TINRO 180, no. 1 (March 30, 2015): 140–60. http://dx.doi.org/10.26428/1606-9919-2015-180-140-160.
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The Okhotsk and Bering Seas and the subarctic zone of the North Pacific are surveyed well by the expeditions conducted by Pacific Fish. Res. Center (TINRO) in the last three decades (115 surveys in 1984-2013), with sampling of zooplankton for monitoring of feeding resources of commercial species. Mean total zooplankton biomass and biomasses of size fractions of zooplankton, its taxonomic groups and mass species are calculated, by biostatistical areas. General patterns of the biomass distribution between the biostatistical areas are determined and presented as the charts of the biomass averaged by the areas. The most abundant species of zooplankton with similar systematic and trophic status are spatially separated that allows them to reduce competition for food, for example the pairs of small-sized, medium-sized and large-sized Copepoda species ( Pseudocalanus minutus - Oithona similis, Metridia pacifica - M. okhotensis , Calanus glacialis - Neocalanus plumchrus ), the pair of Hyperiida species ( Themisto pacifica - T. libellula ) and four Euphausia species ( Thysanoessa raschii - Th. inermis - Th. longipes - Euphausia pacifica ) in the Okhotsk Sea. Detailed tables on biomass and stock of the main components of zooplankton are presented, by regions and biostatistical areas.
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Murray, S. J., P. N. Foster, and I. C. Prentice. "Evaluation of global continental hydrology as simulated by the Land-surface Processes and eXchanges Dynamic Global Vegetation Model." Hydrology and Earth System Sciences Discussions 7, no. 4 (July 6, 2010): 4219–51. http://dx.doi.org/10.5194/hessd-7-4219-2010.
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Abstract. Global freshwater resources are sensitive to changes in climate, land cover and population density and distribution. The Land-surface Processes and eXchanges Dynamic Global Vegetation Model (LPX-DGVM) is a development of the Lund-Potsdam-Jena model with improved representation of fire-vegetation interactions. It allows simultaneous consideration of the effects of changes in climate, CO2 concentration, natural vegetation and fire regime shifts on the continental hydrological cycle. Here the model is assessed for its ability to simulate large-scale spatial and temporal runoff patterns, in order to test its suitability for modelling future global water resources. Comparisons are made against observations of streamflow and a composite dataset of modelled and observed runoff (1986–1995). The model captures the main features of the geographical distribution of global runoff, but tends to overestimate runoff in much of the Northern Hemisphere (where this can be largely accounted for by freshwater extractions and the unrealistic accumulation of the simulated winter snowpack in permafrost regions) and the southern tropics. Interannual variability is represented reasonably well at the large catchment scale, as are seasonal flow timings and monthly high and low flow events. Further improvements to the simulation of intra-annual runoff might be achieved via the addition of river flow routing. Overestimates of runoff in some basins could likely be corrected by the inclusion of transmission losses and direct-channel evaporation.
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Chen, He, Zhenzhong Zeng, Jie Wu, Liqing Peng, Venkataraman Lakshmi, Hong Yang, and Junguo Liu. "Large Uncertainty on Forest Area Change in the Early 21st Century among Widely Used Global Land Cover Datasets." Remote Sensing 12, no. 21 (October 25, 2020): 3502. http://dx.doi.org/10.3390/rs12213502.
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Forests play an important role in the Earth’s system. Understanding the states and changes in global forests is vital for ecological assessments and forest policy guidance. However, there is no consensus on how global forests have changed based on current datasets. In this study, five global land cover datasets and Global Forest Resources Assessments (FRA) were assessed to reveal uncertainties in the global forest changes in the early 21st century. These datasets displayed substantial divergences in total area, spatial distribution, latitudinal profile, and annual area change from 2001 to 2012. These datasets also display completely divergent conclusions on forest area changes for different countries. Among the datasets, total forest area changes range from an increase of 1.7 × 106 km2 to a decrease of 1.6 × 106 km2. All the datasets show deforestation in the tropics. The accuracies of the datasets in detecting forest cover changes were evaluated by a global land cover validation dataset. The spatial patterns of accuracies are inconsistent among the datasets. This study calls for the development of a more accurate database to support forest policies and to contribute to global actions against climate change.
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Murray, S. J., P. N. Foster, and I. C. Prentice. "Evaluation of global continental hydrology as simulated by the Land-surface Processes and eXchanges Dynamic Global Vegetation Model." Hydrology and Earth System Sciences 15, no. 1 (January 13, 2011): 91–105. http://dx.doi.org/10.5194/hess-15-91-2011.
Full textAbstract:
Abstract. Global freshwater resources are sensitive to changes in climate, land cover and population density and distribution. The Land-surface Processes and eXchanges Dynamic Global Vegetation Model is a recent development of the Lund-Potsdam-Jena model with improved representation of fire-vegetation interactions. It allows simultaneous consideration of the effects of changes in climate, CO2 concentration, natural vegetation and fire regime shifts on the continental hydrological cycle. Here the model is assessed for its ability to simulate large-scale spatial and temporal runoff patterns, in order to test its suitability for modelling future global water resources. Comparisons are made against observations of streamflow and a composite dataset of modelled and observed runoff (1986–1995) and are also evaluated against soil moisture data and the Palmer Drought Severity Index. The model captures the main features of the geographical distribution of global runoff, but tends to overestimate runoff in much of the Northern Hemisphere (where this can be somewhat accounted for by freshwater consumption and the unrealistic accumulation of the simulated winter snowpack in permafrost regions) and the southern tropics. Interannual variability is represented reasonably well at the large catchment scale, as are seasonal flow timings and monthly high and low flow events. Further improvements to the simulation of intra-annual runoff might be achieved via the addition of river flow routing. Overestimates of runoff in some basins could likely be corrected by the inclusion of transmission losses and direct-channel evaporation.
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Leon, Ramon G., Renán Agüero, and Diego Calderón. "Diversity and Spatial Heterogeneity of Weed Communities in a Sugarcane Cropping System in the Dry Tropics of Costa Rica." Weed Science 65, no. 1 (November 16, 2016): 128–40. http://dx.doi.org/10.1614/ws-d-16-00066.1.
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Weed diversity, structure, and distribution within and outside agricultural fields affect not only ecological processes but also weed management strategies. We studied how areas managed differently within and outside the field determine weed communities in a sugarcane cropping system in the dry tropics of Costa Rica. A total of 120 weed species were detected, which was similar to surveys conducted in subtropical and temperate conditions. Weed species richness was highest in undisturbed field borders and lowest in rows and furrows. The area where tractors turn within the field (turn area) had similar richness compared with the borders, despite being one of the most disturbed management areas studied. The most predominant weed species were divided between generalists and species that exhibited clear preferences for management area or soil texture. Soil texture was more important for determining weed community structure than management area when considering weed species affecting weed control decisions. The results indicated that disturbance in the management area and, especially, weed control practices are critical factors affecting weed diversity, but availability of resources for weed growth such as nutrients, soil moisture, and light can mitigate some of the limitations imposed by weed control on weed diversity, especially in the turn area. Differences in weed communities between management areas within fields indicated the existence of conditions that favor key weed species, and this information can be used to anticipate their population growth and help determine when and where more intensive control should be implemented.
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Kerimoglu, Onur, Richard Hofmeister, Joeran Maerz, Rolf Riethmüller, and Kai W. Wirtz. "The acclimative biogeochemical model of the southern North Sea." Biogeosciences 14, no. 19 (October 12, 2017): 4499–531. http://dx.doi.org/10.5194/bg-14-4499-2017.
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Abstract. Ecosystem models often rely on heuristic descriptions of autotrophic growth that fail to reproduce various stationary and dynamic states of phytoplankton cellular composition observed in laboratory experiments. Here, we present the integration of an advanced phytoplankton growth model within a coupled three-dimensional physical–biogeochemical model and the application of the model system to the southern North Sea (SNS) defined on a relatively high resolution (∼ 1.5–4.5 km) curvilinear grid. The autotrophic growth model, recently introduced by Wirtz and Kerimoglu (2016), is based on a set of novel concepts for the allocation of internal resources and operation of cellular metabolism. The coupled model system consists of the General Estuarine Transport Model (GETM) as the hydrodynamical driver, a lower-trophic-level model and a simple sediment diagenesis model. We force the model system with realistic atmospheric and riverine fluxes, background turbidity caused by suspended particulate matter (SPM) and open ocean boundary conditions. For a simulation for the period 2000–2010, we show that the model system satisfactorily reproduces the physical and biogeochemical states of the system within the German Bight characterized by steep salinity; nutrient and chlorophyll (Chl) gradients, as inferred from comparisons against observation data from long-term monitoring stations; sparse in situ measurements; continuous transects; and satellites. The model also displays skill in capturing the formation of thin chlorophyll layers at the pycnocline, which is frequently observed within the stratified regions during summer. A sensitivity analysis reveals that the vertical distributions of phytoplankton concentrations estimated by the model can be qualitatively sensitive to the description of the light climate and dependence of sinking rates on the internal nutrient reserves. A non-acclimative (fixed-physiology) version of the model predicted entirely different vertical profiles, suggesting that accounting for physiological flexibility might be relevant for a consistent representation of the vertical distribution of phytoplankton biomass. Our results point to significant variability in the cellular chlorophyll-to-carbon ratio (Chl : C) across seasons and the coastal to offshore transition. Up to 3-fold-higher Chl : C at the coastal areas in comparison to those at the offshore areas contribute to the steepness of the chlorophyll gradient. The model also predicts much higher phytoplankton concentrations at the coastal areas in comparison to its non-acclimative equivalent. Hence, findings of this study provide evidence for the relevance of physiological flexibility, here reflected by spatial and seasonal variations in Chl : C, for a realistic description of biogeochemical fluxes, particularly in the environments displaying strong resource gradients.
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Moen, Jon, Tarja Oksanen, and Nancy Huntly. "Herbivory in a Spatially Heterogeneous Environment- Pikas Ochotona princeps and High Alpine Vegetation." UW National Parks Service Research Station Annual Reports 18 (January 1, 1994): 131–34. http://dx.doi.org/10.13001/uwnpsrc.1994.3213.
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Landscape ecology has been very influential in developing tools for describing both structure (e.g. the distribution and sizes of patches) and function (i.e. the flow among patches) of heterogeneous environments (Turner 1989, Turner & Gardner 1991). This approach has shown that spatial heterogeneity on a landscape level may influence many types of ecological processes (Kolasa & Pickett 1991, Wiens et al. 1993). However, it is also clear that landscape structure and function must be described from an organism-centered view (Kolasa & Pickett 1991), which invites the use of population dynamic hypotheses, and presents the challenging task of merging population ecology with landscape ecology. Standard, non-spatial, predator-prey models predict that the grazing pressure in a given area is related to primary productivity (Oksanen et al. 1981). The model assumes that the number of dynamically important trophic levels is dependent on primary productivity and, in its simplest form, it can be outlined as follows: In extremely unproductive areas (e.g. boulder-fields), plant biomass is too low to sustain mammalian herbivores. In undisturbed areas, plants will thus eventually deplete their resources and compete. In moderately productive areas (e.g.arctic and alpine heaths), plant production is high enough to sustain herbivores, albeit at low densities, lower than what is needed for efficient predators to have a positive growth rate. Uncontrolled by predation, these herbivores are predicted to exert a strong grazing pressure on the vegetation. In more productive areas (e.g. tall herb meadows), plant production is high enough to sustain both herbivores and predators. With herbivores controlled by predation, plants will experience a low grazing pressure, and competition will be an important structuring factor for the plants. According to these models, a productivity gradient from extremely barren areas to productive areas should contain a zone of strong grazing pressure at intermediate productivities. A reÂanalysis using two types of patches with different primary productivity (T. Oksanen 1990) shows that the exact predictions depend on the proportion of these two patches in the habitat. Predation pressure could be high (and thus grazing pressure low) in a patch of intermediate productivity if it is embedded in a matrix of more productive patches, and, reversely, a productive patch might have a high grazing pressure if it is embedded in a matrix of less productive patches. These predictions parallel those of the source-sink model of Pulliam (1988) where a habitat where the consumer has a high growth rate "exports" juveniles to a habitat where the consumer growth rate is lower or even negative, thus creating a higher grazing pressure in the latter habitat than would have been possible without this continuous restocking of individuals. The general conclusion from these models is that grazing pressure may vary between patches both as a consequence of differences in productivity and also because of the spatial arrangements of patches. Any comprehensive understanding of the interactions between herbivores and plants in a heterogeneous environment must thus be based on experiments and observations that explicitly take the spatial heterogeneity of the study area into account.