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1
Cheung, Ma Shan. "Trophic transfer of metals along marine rocky shore food chains /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?AMCE%202007%20CHEUNG.
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Teng, Jack 1979. "Structure and energetics in theoretical food webs." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80884.
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This thesis studies how structure and energetics influence complex food web dynamics. In Chapter 1, I approach the question by studying a simple food web model that can be modified to include different structural and energetic features. In Chapter 2, I study stability and food web properties in assembled webs that are structured by body-size restrictions and a generalist-specialist tradeoff. The results of both chapters suggest that structure and energetics must be considered to understand food web dynamics. In Chapter 1, I find that food web structure can be modified by weak and strong energetic flows and stabilize dynamics through asynchrony. In Chapter 2, I find that food web assembly with different assemblages of generalists or specialists leads to structures that have corresponding differences in the stability and properties of food webs. Hence, my thesis reexamines the relationship of complexity and dynamics from a topological and energetic framework.
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Hall, Mia Rachael. "THE EFFECTS OF LIGHT AND NUTRIENTS ON FOOD CHAIN EFFICIENCY IN THREE-LEVEL FOOD CHAINS WITH BLUEGILL." Miami University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=miami1344018242.
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Vander, Zanden M. Jake. "Trophic position in aquatic food webs." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ55390.pdf.
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Cecchine, Gary Anthony III. "Combinations of natural and anthropogenic stressors affect populations of freshwater rotifers." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/25398.
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Kelly, Barry C. "Bioaccumulation potential of organic contaminants in an Arctic marine food web /." Burnaby B.C. : Simon Fraser University, 2006. http://ir.lib.sfu.ca/handle/1892/2662.
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Thesis (Ph.D.) - Simon Fraser University, 2006.Theses (School of Resource and Environmental Management) / Simon Fraser University. Senior supervisor : Dr. Frank A. P. C. Gobas. Included bibliographical references : leaves 226-248.
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Folkard, Nicholas Francis Goring. "An experimental study of the plant-arthropod-bird food chain in the southwestern Yukon." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28985.
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I describe an experimental study of the importance of food limitation and predation at three trophic levels in a terrestrial food web. The study system was the herb layer vegetation - arthropod - insectivorous bird food chain in the boreal forest near Kluane Lake, southwestern Yukon. Since little is known about boreal bird communities, I conducted a descriptive study of the community of passerine and piciform birds at Kluane in addition to the main study. Variable circular plot point counts were used to estimate bird populations in 1987 through 1990. Species' habitat preferences, use of foraging substrates and diets were studied in 1988 and 1989. Population densities, species richness and evenness were all low. Yellow-rumped warblers (Dendroica coronata) and dark-eyed juncos (Junco hyemalis) dominated the community. Common species differed markedly in their habitat preferences, and showed generally low overlaps in their use of foraging substrates. There was little evidence of dietary specialization. There was rather little spatial variation in the community, and species composition and total density remained approximately the same through time. However, there were large fluctuations in some species' populations between 1987 and 1989.
The experimental study was conducted at two scales. Chemical fertilizer was applied to two 570m x 570m areas in 1987, 1988 and 1989. I compared arthropod populations, bird populations and bird reproductive performance in these areas with those in two control areas. Two experiments using 5m x 5m plots were performed in 1988 to examine the effects of fertilization on plants and arthropods in more detail, and to study the responses of these trophic levels to the exclusion of passerine birds and mammalian herbivores. All three trophic levels responded positively to
fertilization, but the results were variable and there were no very large increases in biomass or population size. Dark-eyed juncos nested one week earlier in fertilized areas, which may have enhanced their reproductive success. Passerine exclusion did not increase arthropod biomass, but exclusion of mammalian herbivores increased plant biomass. "Bottom-up" limitation by food appears to dominate this system, but "top-down" limitation also operates at at least one level. More work is needed to fully understand how the system functions.Science, Faculty of
Zoology, Department of
Graduate
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Li, Oi-yee. "Shredders and leaf litter breakdown in Hong Kong streams." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/b40203505.
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Cabana, Gilbert. "A comparative study of food-web processes in aquatic systems using stable isotopes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0026/NQ29900.pdf.
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Pangle, Kevin L. "The role of non-consumptive effects in the net effect of an invasive predator in the Laurentian Great Lakes." Diss., Connect to online resource - MSU authorized users, 2008.
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Thesis (Ph. D.)--Michigan State University. Fisheries and Wildlife, Ecology, Evolutionary Biology, and Behavior, 2008.Title from PDF t.p. (viewed on July 2, 2009) Includes bibliographical references (p. 143-159). Also issued in print.
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Campeau, Suzanne. "The relative importance of algae and vascular plant detritus to freshwater wetland food chains /." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60458.
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This study examines the relative contribution of algae and vascular plant litter to the food chains of freshwater marshes. Twelve enclosures (5 m diam.) were deployed in a nutrient-poor marsh of the Interlake region of Manitoba. Algae levels in six of the enclosures were increased by fertilizing the water column. In addition, the hardstem bulrush (Scirpus lacustris glaucus (Sm.) Hartm) litter present was replaced with a non-nutritive artificial substrate in half of the fertilized and unfertilized enclosures. Fertilization did not affect the dry weight loss of bulrush litter, but N and P concentrations were higher in the decomposing litter of the fertilized treatments. Dominant taxa of nektonic herbivores-detritivores responded to fertilization but were not affected by the replacement of plant litter by a non-nutritive substrate. Epiphytic herbivores-detritivores responded to changes in both detritus and algal food sources. Fertilization resulted in early peaks of emergence for the Chironominae, Tanypodinae and Orthocladiinae. Emergence data late in the study period suggest that the importance of litter as a food source may increase as decomposition progresses.
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Rowland, Freya E. "Light and nutrients differentially regulate energy transfer through experimental benthic and pelagic food chains." Miami University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1272463759.
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Lau, Chun-pong. "Applications of stoichiometry, stable isotopes, and fatty acids for elucidating the relative importance of allochthonous and autochthonous resources in Hong Kong streams." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40040185.
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Kristensen, Nadiah Pardede. "Goal functions and ecosystem contraints : thermodynamic goal functions, local stability, maximal resilience, and permanence /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18700.pdf.
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Vasseur, David Alan. "Temporal and hierarchical scales mediate environmental and ecological variability in food webs." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102226.
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Temporal changes in the environmental conditions upon which life depend are ubiquitous in nature, acting at every level of organisation from cells to ecosystems. Although the actions themselves are often poorly understood, they strongly depend on the temporal and hierarchical (organisational) scales at which they are measured; ecosystems are relatively stable through time while their species composition may undergo vast changes. Likewise any hierarchical level may be relatively stable in the short-term, but undergo vast long-term changes. This thesis aims to better understand the importance of these scales for mediating the impact of environmental variability on ecological systems.The approach used herein employs both mathematical models and empirical data which represent food webs responding to environmental variability at different hierarchical scales. Within each of these representative food webs, the influence of environmental variability on the stability of the food web is determined using an approach which accounts for the effects of temporal scale. This thesis demonstrates that the stability of simple model food webs (high hierarchical scale) is tightly linked to environmental variability and the temporal scales at which these changes occur dictate which species in the model are most affected. At lower scales of organisation, empirical data indicate that environmental variability generally has a lesser impact on stability and that only certain temporal scales are responsible for this trend. At these temporal scales some species respond differently to environmental variability, negative changes in one species (or group) are offset by positive changes in another - a process known as compensation. These results highlight the importance of both temporal and hierarchical scale in mediating the response of food webs to environmental variability. Ultimately, they will serve to better understand how models and experiments should scale-up from low to high hierarchical and temporal scales.
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Jenkins, David G. "Effects of an herbicide on a planktonic food web." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/90948.
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In situ microcosms of a planktonic community were exposed to the triazine herbicide simazine. Randomly selected sets of microcosms were collected and sampled each week for three weeks (plus Week 0). Samples of ambient water were collected each week for evaluation of enclosure effects. Physical and chemical parameters were measured per microcosm. Simazine was measured at Weeks 0 and 3 only. The following organisms were preserved and quantified: phytoplankton, bacteria, and zooplankton, including ciliates, copepod nauplii, cladocerans and rotifers.
Simazine decreased dissolved oxygen and pH, but increased nitrate and ammonia concentrations compared to control microcosms. A temporary decrease in temperature occurred at Week 1.
Phytoplankton were differentially affected by simazine. Sensitive taxa included Trachelomonas, Glenodinium, diatoms and several species of relatively minor significance. Dinobryon and miscellaneous coccoids were not significantly affected. Phytoplankton ≥9 um were more affected by simazine than phytoplankton <9 um. Many cells <9 um may be facultative or obligate heterotrophs and not susceptible to simazine. Although data were variable, bacteria were also not affected by phytoplankton changes or simazine.
Rotifers were the major zooplankters and the two dominant species, Kellicottia bostoniensis and Keratella cochlearis, were reported to graze exclusively on cells <9 um. Polyarthra vulgaris and Synchaeta pectinata also graze in this size range but are not limited to it. Copepod nauplii/copepodids were present, but adult copepods and cladocerans were rare. The tintinnid ciliate Codonella exhibited a temporary population increase during the study.
Zooplankton were not affected by simazine-induced changes in the phytoplankton. Kellicottia bostoniensis was the only zooplankter affected by simazine: it had lesser mortality in higher concentrations of simazine. Possible reasons for this enhanced survival were discussed. The zooplankton (primarily rotifers) appeared to feed more on heterotrophic cells than on autotrophic cells, largely as a function of food size, and may have been more closely associated with the detrital food chain than the autotrophic food chain.M.S.
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Hickerson, Cari-Ann M. "Interactions among top-down regulators in a temperate forest floor ecosystem effects on macrofauna, mesofauna, microbes and litter decay /." Cleveland, Ohio : Cleveland State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=csu1276104836.
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Thesis (Ph.D.)--Cleveland State University, 2010.Abstract. Title from PDF t.p. (viewed on June 16, 2010). Includes bibliographical references (p. 137-142). Available online via the OhioLINK ETD Center and also available in print.
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Hill, Jaclyn Marie. "A stable isotope approach to trophic ecology resolving food webs in intertidal ecosystems." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005459.
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There are broad differences in regional oceanography and primary production around the South African coast, which we might expect to give rise to major differences in trophic pathways. δ⁻¹³C and δ⁻¹⁵N isotopic ratios of suspended particulate matter (SPM), mussels, various intertidal consumers and common macroalgae along the South African coastline were explored using stable isotope analysis to investigate biogeographic and temporal variability of isotopic signatures of marine intertidal consumers and their food sources around the coast of South Africa, with a focus on evaluating the dependence of intertidal mussels on phytoplankton and macroalgal-derived organic carbon. Isotopic equilibration rates of four mussel tissues were determined through laboratory feeding experiments, which established that adductor tissue had the slowest isotopic turnover rate, and was subsequently used as an indication of overall mussel diet. Biogeographic, temporal and nearshore/offshore trends of isotopic ratios of SPM were investigated along 10km transects perpendicular to the coast and SPM exhibited overall trends of carbon depletion when moving from west to east along the coastline and from nearshore to offshore water, in both cases suggesting a shift from macrophyte detritus to a phytoplankton signature. δ⁻¹³C signatures of SPM also revealed temporal and biogeographic variation that had strong ties to local oceanography, being closely correlated to regional hydrographic features and tidal influences. Mixing models indicated filter feeders demonstrated over 50% dependence on nearshore SPM for organic carbon and it was possible to categorize them into geographic groups based on their carbon and nitrogen signatures, suggesting biogeographic shifts in resources. Biogeographic shifts in diet were also seen in some grazers. Difficulties in relating macroalgae to mussel diet led to investigations into the isotopic changes associated with macroalgal decomposition. Variation in photosynthetic fractionation, leaching and microbial mineralization are believed to have resulted from species-specific patterns of degradation. Although the strong links between carbon signatures and local oceanography indicate that stable isotope analysis is a powerful tool for the study of water mixing and coastal hydrography in relation to food-web analyses, substantial variation in fractionation of primary consumers, along with different periods of time integration between consumers and their food sources must be considered in future studies, to resolve trophic links in marine food webs successfully.
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Medeiros, Elvio S. F. "Trophic ecology and energy sources for fish on the floodplain of a regulated dryland river Macintyre River, Australia /." Connect to this title online, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20051115.174552/.
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Hunte-Brown, Meshagae Endrene Kilham Susan Soltau. "The effects of extirpation of frogs on the trophic structure in tropical montane streams in Panama /." Philadelphia, Pa. : Drexel University, 2006. http://dspace.library.drexel.edu/handle/1860%20/883.
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Persson, Jonas. "Food Quality Effects on Zooplankton Growth and Energy Transfer in Pelagic Freshwater Food Webs." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7811.
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Katechakis, Alexis. "Selected interactions between phytoplankton, zooplankton and the microbial food web: Microcosm experiments in marine and limnic habitats." Diss., Connect to this title online, 2006. http://edoc.ub.uni-muenchen.de/archive/00005047/.
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Thesis (doctoral)--Ludwig-Maximilians-Universität München, 2006.Title from PDF t.p. (viewed on May 14, 2006). Includes reprints of papers co-authored with others. Vita. Includes bibliographical references.
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Ortiz, Ivonne. "Ecosystem dynamics of the Aleutian Islands /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/5370.
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Cellineri, Katie Rose Boissonneault. "Microbial food web interactions in two Long Island embayments /." Online version, 1999. http://hdl.handle.net/1912/2064.
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Chagnon, Guillaume. "The relative contribution of pelagic primary production to the littoral food web of lakes /." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31205.
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A dual stable isotope approach (delta13C and delta15N) was used to assess the importance of pelagic organic carbon in littoral secondary production and explore its predictability. Forty-seven sites were sampled in Lake Memphremagog (Quebec--Vermont) to characterize the isotopic position of the primary producers and filter-feeding freshwater mussels, as well as macrophyte biomass, chlorophyll-a concentration, and site exposure. The different sites spanned a wide range in the three environmental variables. For each site, littoral, terrestrial, and pelagic contributions to the diet of the mussels were calculated from mussel isotopic position, corrected for trophic enrichment. The mean contributions were: littoral---8%, terrestrial---27%, and pelagic---65%. However, the magnitude of the pelagic contribution was not related to macrophyte biomass, site exposure or chlorophyll-a concentration. The finding that the unionid mussels, a major littoral zone filter-feeder, obtain about two-thirds of their nutrition from pelagic zone particles washed into the littoral zone provides evidence for a close coupling in carbon flow of the littoral and pelagic zone. This study represents an important step towards a better understanding of carbon flow in aquatic food webs.
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Burnes, Brian Sydnor. "Identification and characterization of genes required for Mn(IV) reduction by Shewanella putrefaciens." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/25336.
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Duernberger, Kimberley. "Tracing nitrogen through the food chain in an urbanized tidal creek." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-1/r3/duernbergerk/kimberleyduernberger.pdf.
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Tarantino, William J. "Effects of Adaptive Foragers on the Diversity and Functioning of Assembled Model Communities." W&M ScholarWorks, 2008. http://www.vims.edu/library/Theses/Tanantino08.pdf.
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Gillett, David James. "Effects of habitat quality on secondary production in shallow estuarine waters and the consequences for the benthic-pelagic food web." W&M ScholarWorks, 2010. http://www.vims.edu/library/Theses/Gillett10.pdf.
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陳興 and Hing Chan. "The use of trash fish wastewater and inorganic fertilizers in larval fish food chains: the ecological consequencesand the potential applications in aquaculture." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31234070.
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Slater, Jennifer M. "Effects of the maternal rearing environment on pea aphid (Acyrthosiphon pisum) trophic interactions." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=238395.
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The maternal rearing environment (MRE) of an organism can be a key determinant of an organism's host choice decisions, its own fitness, or the fitness of its offspring. Here, it is investigated if the MRE of an organism can influence lower or higher trophic levels. A series of reciprocal cross-over experiments was conducted using pea aphids (Acyrthosiphon pisum), bean (Vicia faba) or pea (Pisum sativum) plants, and an aphid natural enemy, the parasitoid wasp Aphidius ervi, as model organisms. In each experiment, pea aphid offspring experienced either the same or an alternative plant host to that experienced by their mothers. This PhD showed that the MRE of pea aphids and parasitoid wasps was not a main contributory factor of host choice decisions or offspring fitness but influenced mother parasitoid wasp fecundity. Additionally, the MRE of pea aphids influenced the foliar nutrient concentration of pea plants when infested with the aphid's offspring. First, over shorter infestation periods, variation in foliar nitrogen and essential amino acid concentrations of pea leaves could be explained by pea aphid MRE. Over longer infestation periods, variation in foliar nitrogen and essential amino acid concentrations of pea leaves was explained by a combination of pea aphid MRE and aphid genotype. Second, the 13C concentration of pea leaf tissue, an indicator of stomatal aperture and leaf water stress, varied with pea aphid MREs over longer infestation periods. However, stomatal conductance and the expression of abscisic acid-responsive genes did not vary in a manner that was consistent with leaf water stress. Additional components of an organism's maternal rearing conditions are considered, including symbioses, as a more realistic MRE compared with that observed in nature. Taking account of MREs could provide a better understanding of the factors influencing the fitness of many organisms interacting in natural and managed ecosystems.
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Paterson, Harriet. "Microzooplankton from oligotrophic waters off south west Western Australia : biomass, diversity and impact on phytoplankton." University of Western Australia. School of Animal Biology, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0031.
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[Truncated abstract] The role of marine microzooplankton in aquatic food webs has been studied in most regions of the world’s oceans, with the exception of the subtropical/temperate eastern Indian Ocean. This thesis addresses this gap in knowledge by investigating microzooplankton from five stations on a cross continental shelf transect and in two mesoscale features ∼300 km offshore of south west Western Australia. My primary focus was to measure and evaluate microzooplankton community change over space and time and their impact on phytoplankton on a cross shelf transect, sampling five stations from February 2002 December 2004 as part of a large multidisciplinary investigation into the pelagic ecosystem on the shelf (Chapter 2). This transect was named the Two Rocks transect. I also investigated an eddy pair (Chapter 5), which had originated from water in the vicinity of the Two Rocks transect, also undertaken as part of a larger study, investigating biophysical coupling within mesoscale eddies off south west Western Australia . . . The distribution of mixotrophic cells differed across the transect. Those mixotrophs that use photosynthesis as their primarily energy source exploited nutrient limited conditions inshore consuming particles, while mixotrophs that are primarily heterotrophic survived low prey conditions offshore by photosynthesizing. In the eddies, the grazing behaviour of microzooplankton was dependent on the specific phytoplankton assemblage in each eddy. The warm core eddy had a resident population of diatoms that were consumed by heterotrophic dinoflagellates present in high numbers. The cold core eddy had a warm cap which prevented upwelled water reaching the surface, resulting in stratification and a very active microbial food web, particularly in the surface.
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Cadena, Mendoza Gissela de la. "Eliminación de impedimentos taxonómicos y ecológicos en "hot-spots" de biodiversidad mediante herramientas moleculares: los Chrysomelidae y sus asociaciones tróficas en el bosque seco tropical de Nicaragua." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/402736.
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El bosque seco tropical estacional (BSTE), con una gran riqueza de especies y endemismos, suele estar integrado en hotspots de biodiversidad y, debido a las amenazas por actividades antropogénicas, ha sido catalogado como uno de los bioma terrestre más amenazado del planeta. Se estima que a nivel global queda menos de un 2% de su distribución original, por lo cual su estudio es prioritario para poder acometer su restauración y conservación. El objetivo general de esta tesis fue aplicar protocolos para evaluar de forma rápida y eficiente la diversidad biológica en áreas tropicales. Para este propósito, se integraron herramientas y métodos moleculares con taxonomía y ecología para delimitar el número de especies, así como las asociaciones tróficas de dos grandes grupos de Chrysomelidae en el BSTE de Nicaragua, donde la riqueza de insectos es abrumadora y aún desconocida. Específicamente, para analizar la diversidad de crisomélidos, el trabajo se centró en dos subfamilias especialmente ricas en especies, Cassidinae y Galerucinae sensu lato. El muestreo se realizó en cuatro localidades de BSTE en el rango de distribución en Nicaragua, y se procesaron 1.320 individuos pertenecientes a 251 morfoespecies. Utilizando dos métodos objetivos de delimitación de especies a partir de filogenias de un gen mitocondrial (cox1)—el modelo Generalizado Mixto de Yule y Coalescencia y el modelo de Árboles por Procesos de Poisson—se infirieron hasta 265 especies putativas. Los linajes evolutivos independientes que se identificaron fueron contrastados con evidencia morfológica y en general fueron altamente congruentes con ésta y entre métodos. Los estimadores de riqueza de especies, mostraron que nuestro muestreo no describió la diversidad total, y alcanzó a representar el 64 % de la biodiversidad esperada para crisomélidos de BSTE. Las cuatro comunidades de crisomélidos estudiadas fueron muy diferentes, y en buena parte debido al reemplazamiento de especies (ßsor > 0,681). Adicionalmente, se aplicaron metodologías moleculares para inferir las asociaciones tróficas de los crisomélidos a partir de la amplificación de secuencias cloroplásticas hipotéticamente provenientes de la dieta de los animales, y cuyo ADN estaría presente en sus extracciones de ADN total. Tras evaluar la posibilidad de contaminación ambiental sesgando las inferencias de dieta, pudimos aprovechar fragmentos cloroplásticos para 872 ejemplares de 257 especies putativas, a partir de los que se realizaron 1.133 inferencias de dieta sobre 188 especies vegetales de 43 órdenes, siendo Acanthaceae, Amaranthaceae, Asteraceae, Bignoniaceae, Cordiaceae, Euphorbiaceae, Malvaceae, Poaceae, Rubiaceae, Solanaceae, y muy en particular Fabaceae, las familias que representaron el mayor número de interacciones con las comunidades de Chrysomelidae en el BSTE de Nicaragua. Se aplicaron varias medidas descriptoras de las interacciones tróficas entre crisomélidos y sus plantas hospederas, las cuales permitieron mejorar la compresión de esta interacción, y mostraron que una localidad (Reserva Miraflores-Moropotente) sería la más afectada ante alteraciones del hábitat, al contar con plantas que sustentan muchas interacciones. Finalmente, se exploraron variables ambientales, ecológicas, florísticas y geográficas para evaluar el grado de influencia que éstas podrían tener para explicar las diferencias en composición de las comunidades de crisomélidos en el BSTE en Nicaragua. Los análisis de correlación múltiple entre estas variables mostraron que las diferencias en flora explicarían el 92 % de la variación respecto a las diferencias en las comunidades de crisomélidos, con escasa contribución del componente climático. Una visión de conjunto sobre nuestros resultados sugiere que propuestas de conservación sobre zonas de bosque con los niveles más altos de diferenciación en su composición florística, promoverían la conservación de comunidades únicas y muy ricas de los coleópteros herbívoros que habitan en estos fragmentos de bosque.The seasonally dry tropical forest (SDTF) with high species richness and endemism, is usually integrated in biodiversity hotspots. Due to several threats by anthropogenic activities, has been listen as one of the world’s most endangered terrestrial biomes. It is estimated that globally only remains less than 2% of its original distribution, so their study is priority to undertake its restoration and conservation. The general objective of this thesis was to implement protocols to assess quickly and efficiently biodiversity in tropical areas. For this purpose, tools and molecular methods were integrated with taxonomy and ecology, to define the number of species and their trophic associations of two large groups of Chrysomelidae in Nicaraguan STDF, where the richness of insects is overwhelming and unknown. Specifically, to analyse the diversity of beetles, this work focused on two subfamilies especially rich in species: Cassidinae and Galerucinae sensu lato. Sampling was conducted at four locations of SDTF in Nicaragua, and 1320 individuals belonging to 251 morphospecies were processed. Using two objectives methods of species delimitation from mitochondrial gene phylogenies (cox1)—the Generalized Mixed Yule and Coalescence model and the Poisson Tree Processes model—they were inferred up to 265 putative species. Those independent evolutionary lineages were compared with morphological evidence and were generally highly consistent with this and between methods. The estimators of species richness showed that our sampling did not describe the total diversity, reaching to represent 64% of the expected leaf beetles biodiversity of SDTF. Four well-studied Chrysomelidae communities were very different, and largely due to the turnover of species (ßsor > 0,681). Additionally, molecular methodologies for inferring Chrysomelidae trophic associations from chloroplast sequences retrieved from gut contents were applied. After evaluating possible environmental contamination skewing inference diets, we could use chloroplastic fragments from 872 individuals belonging to 257 putative species. From these species, we obtained 1133 diet inferences on 188 plant species of 43 orders. Fabaceae, Asteraceae, Solanaceae, and Malvaceae accounted for the largest number of interactions with Chrysomelidae communities in the SDTF of Nicaragua. Several descriptive measures of trophic interactions between leaf beetles and their host plants were applied, and it showed that one locality (Miraflores-Moropotente Reserve) would be the most affected to habitat alterations, by having plants that support many interactions. Finally, environment, ecological, floristic, and geographical variables were explored to assess the degree of influence they might have to explain differences in community composition of leaf beetles in SDTF of Nicaragua. The multiple correlation analyses between these variables showed that differences in flora explain 92% of the variation from differences in leaf beetles communities with little contribution of climate component. A overview of our results suggest that conservation proposals on forest areas with the highest levels of differentiation in its floristic composition, promote the conservation of unique and very rich communities of herbivorous beetles that inhabit these forest fragments.
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Chan, Ka-yee, and 陳嘉儀. "Application of fatty acid profiles in field- and laboratory -based investigations of trophic relationships in Hong Kong wetland." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48199436.
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This study primarily aimed to evaluate the usefulness of fatty acids (FAs) in revealing trophic relationships in Hong Kong wetlands, through a combination of field studies and laboratory experiments.
A field-based study in Mai Po mangroves involved FA profiling of basal food sources (i.e., leaf litter from three mangrove species, diatoms and macroalgae, and sediments) and consumers (particularly crabs). FA composition of all mangroves was similar, and lacked some polyunsaturated FAs present in diatoms and macroalgae. Uca and Sesarma crabs, with different feeding mechanisms, had divergent FA profiles: Uca arcuata FAs reflected a diet of macroalgae and diatoms, while FAs of Sesarma spp. were typical of mangrove leaves. Temporal changes in consumer FA profiles between 2001 and 2007 appeared attributable to increased sedimentation at Mai Po and shifts in organic content of the substratum.
A second field-based study was conducted at Luk Keng marsh where a salinity gradient (0 to 30?) allowed investigation of the effects of salinity changes in FA profiles and stable isotope (carbon and nitrogen) signatures of the consumers and their foods. Basal food sources were leaf litter, including a fungal biomarker of decomposition (ergosterol), fine particulate organic matter (FPOM) and periphyton. Both FPOM and periphyton (but not leaf litter) contained 20:4 and 20:5 FAs, but their concentrations were affected by salinity. FA 20:4 occurred at higher levels in samples from fresh water, whilst FA 20:5 exhibited the opposite pattern and was more abundant under saline conditions, and thus the ratio of FA 20:4 to FA 20:5 decreased with increasing salinity. Combined application of FA biomarkers and isotopic signatures were able to elucidate trophic relationships between consumers and their food at Luk Keng confirming that FA 20:4 as a useful biomarker in the freshwater portion and FA 20:5 in the more saline area. FA 20:4 was particularly associated with predatory freshwater insects that had high δ15N values, but was scarce in primary consumers (snails, detritivorous beetles) with low δ15N values.
Two laboratory experiments were undertaken to investigate: 1) the effect of diet on FA profiles in the apple snail, Pomacea canaliculata, and 2) interacting effects of diet and salinity on FA profiles of the Indian medaka fish, Oryzias melastigma. The results of the apple snail study showed that dietary-mediated changes in FA profiles were only reflected in the snail tissues after at least three months, and FA profiles of digestive tissues and neutral lipids were first to respond to the dietary change. The results of the medaka study demonstrated that the ratio of FA 20:4 to FA 20:5 was affected by both diet and salinity, reflecting a similar finding in the Luk Keng field study, although diet had a stronger effect on this ratio.
The results of both field studies supported the use of FA profiles as food web tracers in wetlands and were complemented by laboratory results that yielded insights which will allow refinement of FA biomarker applications in food-web studies.published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy
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Boissonneault, Katie Rose 1973. "Microbial food web interactions in two Long Island embayments." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1912/2064.
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Thesis (S.M. in Biology)--Joint Program in Biological Oceanography (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 1999.Includes bibliographical references (leaves 23-30).
Phytoplankton mortality (herbivory) and bacterivory were examined experimentally in West Neck Bay and Coecles Harbor, Long Island, NY from April through September, 1998. Small algae (<5 [tm diameter) dominated phytoplankton communities in both ecosystems throughout the summer, and zooplankton were also small (mostly <40 tm). Generally, plankton abundances were indicative of eutrophic ecosystems. Oscillations in standing stocks and mortality of prey indicated tight coupling of growth and grazing mortality in both bays. Phytoplankton mortality rates accounted for the removal of 14% to 65% of total phytoplankton standing stocks daily, while bacterivory accounted for the removal of 14% to 88% of total bacterial standing stocks daily. Estimates of carbon consumption revealed high energy flux through the nano- and microzooplankton assemblages of these estuarine environments.
by Katie Rose Boissonneault Cellineri.
S.M.in Biology
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Rodríguez, Lozano Pablo. "Fire legacies in Mediterranean streams: the key roles of the riparian canopy and the top predator on food webs." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/385275.
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Wildfires are expected to increase in frequency and intensity because of climate change and changes in land use and management. In last decades, the research on fire effects on aquatic systems has grown, but it has been mainly conducted in the short- and mid-term (<5 years). Therefore, longer time frames are needed to assess fire effects on freshwater ecosystems. For instance, fire impacts on riparian and upland forests can be long-lived and wildfires often extirpate fish populations from streams, which may not recover due to barriers within the river network. Regarding fish extirpations, it is worth noting that freshwater fish are one of the most threatened fauna worldwide, especially the small-bodied species. In this context, the overarching goal of this PhD thesis was to investigate the long-term effects of a wildfire in Mediterranean streams. Specifically, this PhD thesis covered the indirect effects of two fire legacies: (1) the riparian canopy reduction and (2) the local extinction of the top predator in these streams, the endangered small-bodied fish Barbus meridionalis.
The findings of this PhD thesis showed how the fire legacy in the riparian forest accelerated leaf-litter breakdown in an intermittent Mediterranean stream eight years after fire. The opening of the riparian forest canopy by fire increased light levels and water temperatures and reduced terrestrial-to-aquatic litter inputs. The increased water temperatures engendered by removal of canopy cover enhanced microbial mediated leaf breakdown. The reduction in leaf-litter inputs probably led to lower benthic organic matter levels, bringing to the observed increased shredder aggregation in leaf packs, thereby accelerating leaf breakdown rates.
Our results demonstrated that the apex consumer was functionally irreplaceable, its local extinction led to the loss of an important functional role that resulted in major changes to the ecosystem's structure and function. Our mesocom experiment showed that Barbus meridionalis absence led to 'mesopredator release, and also to 'prey release despite intraguild predation, which contrasted with traditional food web theory. Top predator extirpation also changed whole macroinvertebrate community composition and increased total macroinvertebrate density. Regarding ecosystem function, periphyton primary production decreased in apex consumer absence. Moreover, we studied the feeding ecology of B. meridionalis from a functional perspective. Our results indicated that prey morphological and behavioral traits may explain prey vulnerability to predation. Specifically, the trait-based analysis showed that 10 of the 13 traits tested significantly influenced food choice (e.g. body size, concealment, locomotion, aggregation tendency, feeding habits). In addition, the leaf bags experiment confirmed that top predator absence enhanced leaf-litter breakdown, which was caused by the increase in shredder and scraper biomass in the absence of the predatory fish top-down control. Fish absence reduced leaf fungal biomass, but did not decrease microbially mediated leaf breakdown. These results suggested that leaf fungal biomass was stimulated from the bottom-up through nutrient recycling by the top predator.
This PhD thesis demonstrated that past fires may have current influence on the structure and function of Mediterranean streams. Moreover, our findings evidenced that intermittent streams can be affected by the consequences of apex consumers’ extinctions, and that the loss of small-bodied top predators can lead to complex ecosystem changes. This PhD thesis interconnected several current topics in ecology research (i.e. fire effects on aquatic systems, top predator declines, and intermittent streams). Its relevance lies in the projected increase in fires in the Mediterranean region and in the current high extinction risk of small-bodied fish in freshwater ecosystems.Debido al cambio climático y a los cambios en el uso y la gestión de la tierra, se espera que la frecuencia e intensidad de los incendios forestales aumenten. La mayoría de los estudios sobre los efectos de los incendios forestales en los ecosistemas acuáticos continentales cubren el corto y medio plazo (<5 años), siendo necesarias series temporales más largas. En este contexto, el objetivo general de esta tesis doctoral fue investigar los efectos a largo plazo de un incendio forestal en ríos mediterráneos. En concreto, esta tesis doctoral se centra en los efectos de dos legados del fuego: (1) la reducción de la cobertura del bosque de ribera y (2) la extinción local del superdepredador en estos ríos, Barbus meridionalis, un pez amenazado de pequeño tamaño. Los resultados de esta tesis doctoral probaron cómo el legado del fuego en el bosque de ribera aceleró la descomposición de la hojarasca en un arroyo mediterráneo intermitente ocho años después del incendio. Nuestros resultados también demostraron que el superdepredador era funcionalmente insustituible. Nuestro experimento de mesocosmos mostró que la ausencia de Barbus meridionalis provocó el incremento de los depredadores y de los consumidores primarios, y redujo la producción primaria del perifiton. El estudio de la ecología trófica de B. meridionalis desde una perspectiva funcional reveló que los rasgos morfológicos y de comportamiento de los macroinvertebrados pueden explicar su vulnerabilidad a la depredación. Esta tesis también confirmó que la ausencia del superdepredador modificó otra función clave del ecosistema, aceleró la descomposición de las hojas. Nuestros resultados también sugirieron que el superdepredador tiene un papel clave en el reciclado de nutrientes. Esta tesis doctoral ha demostrado que los incendios del pasado pueden influir en la estructura y función actual de los ríos mediterráneos. Además, también ha evidenciado que los ríos intermitentes pueden verse afectados por las consecuencias de la extinción de sus superdepredadores. La relevancia de esta tesis doctoral radica en el incremento esperado de los incendios forestales en la región mediterránea y en el alto riesgo de extinción de los peces de pequeño tamaño en los ecosistemas acuáticos continentales.
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Lau, Chun-pong, and 劉振邦. "Applications of stoichiometry, stable isotopes, and fatty acids for elucidating the relative importance of allochthonous and autochthonousresources in Hong Kong streams." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40040185.
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Bliesner, Kasey Lauren. "Trophic ecology and bioenergetics modeling of Sacramento perch (Archoplites interruptus) in Abbotts Lagoon, Point Reyes National Seashore /." Online Access, 2005. http://www.humboldt.edu/~cuca/documents/theses/bliesnerthesis.pdf.
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DeBruyn, Adrian M. H. "Sewage and the ecology of the St. Lawrence River." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38176.
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This thesis examines the ecological consequences of sewage disposal in aquatic ecosystems. Sewage simultaneously represents a form of enrichment and a source of stress to a receiving system. Enrichment effects dominate when sewage loading does not exceed the capacity of the system to assimilate waste, as is presently the case in the St. Lawrence River. We developed a method to quantify the assimilation of sewage-derived organic matter by riverine biota, then used this method to examine the pathways by which sewage enhances secondary production in the St. Lawrence. We showed that the relative importance of dissolved nutrients and particulate organic matter to the river food web is to a large degree dictated by the physical and biological characteristics of the local environment. The effects of this enrichment on the receiving water community were also influenced by habitat characteristics. Analysis of body size distributions revealed that only the largest organisms had higher densities at enriched sites, and that the identity of these organisms depended on habitat structure. Densities of smaller organisms were controlled by a combination of habitat characteristics and feeding interactions. This pattern was consistent with food web models of top-down (consumer) control. At each trophic level, relatively invulnerable (large) prey achieved higher densities, whereas densities of more vulnerable (small) prey were controlled by their predators. Finally, we synthesized the ideas outlined above to predict how conditions in the St. Lawrence will change in the future as a result of lower water levels. More extensive macrophyte cover, slower current, and warmer temperatures in a shallower St. Lawrence will all enhance the ability of the system to physically retain and biologically process sewage nutrients, but will also increase the likelihood of negative effects such as anoxia.
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Chumbley, Kathryn. "Prey biomass abundance, distribution, and availability to the endangered stellar sea lion (Eumetopias jubatus) population at Ugamak Island, Alaska, 1995-99." Online pdf file accessible through the World Wide Web, 2007. http://archives.evergreen.edu/masterstheses/Accession86-10MES/Chumbley_K%20MESThesis%202007.pdf.
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Chan, Hing. "The use of trash fish wastewater and inorganic fertilizers in larval fish food chains : the ecological consequences and the potential applications in aquaculture /." [Hong Kong] : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B14763904.
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Tewfik, Alexander. "Patterns and effects of disturbance in Caribbean macrophyte communities." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85654.
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This thesis examines a number of natural and anthropogenic disturbances within marine macrophyte habitats of the Caribbean. Understanding the effects of disturbance and the patterns associated with such dynamics is fundamental to ecological studies. Dynamics of interest included: interactions between populations; interactions between life history strategies; successional regimes; and alterations of community structure including loss of trophic heterogeneity and the possibility of "alternate" states. First I explored natural physical disturbance and succession. The dominance of macroalgae in the mid-shore, between areas of seagrass, challenged "classic" succession in such communities. I therefore proposed a model that included chronic "stress" by wave energy that could lead to a reversal in the climax state. Next, I investigated the importance of other grazers (i.e. trophic heterogeneity) in mediating the strength of trophic cascades (e.g. overgrazing). The enclosure experiments used suggested that different life history strategies respond differently to experimental conditions and that interference competition between specialist (conch) and generalist (urchins) grazers results in urchins switching to alternate resources and displaying lower condition. This dynamic may indirectly "buffer" the community against population expansions of urchins and overgrazing of diversity enhancing detritus. Under high nutrient enrichment, urchins maintained themselves, the trophic cascade and low diversity by switching to "expanded" autochthonous and "new" allochthonous resources. I continued to examine the effects of increasing nutrient enrichment, which correlated well with increasing human density, by examining eleven seagrass beds. The patterns of increasing consumer density and decreasing consumer diversity corresponded well to increasing enrichment and loss of autochthonous detritus. At high levels of enrichment, the community was dominated (> 90%) b
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Li, Oi-yee, and 李靄儀. "Shredders and leaf litter breakdown in Hong Kong streams." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40203505.
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Trudeau, Véronique. "Factors affecting stable carbon and nitrogen isotopic signatures in food webs of the Ste. Marguerite River system (Quebec, Canada)." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82442.
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Deeper understanding of the factors controlling stable isotopic signatures of aquatic organisms of all trophic levels is required if we are to properly use them in food web studies and as environmental indicators. The present field study conducted in the Ste. Marguerite River system, Quebec, compared periphyton signatures found in eight reaches (sections of a river/tributary) each composed of a series of sites with different flow regimes. Similar to patterns found in the laboratory, periphyton delta13C significantly decreased with increasing water velocity. In addition, periphyton biomass positively affected periphyton delta13C. Isotopic fractionation in favour of 12C by the periphyton communities likely leads to build-up of the heavier isotope in the boundary layer of algae. This study allows a better understanding of aquatic plant delta13C fluctuations. It also suggests how much variability in aquatic consumer delta13 C can be explained by water velocity in lotic systems.
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Pazzia, Ivano. "The influence of food web structure on the growth and bioenergetics of lake trout (Salvelinus namaycush) /." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31525.
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Most fish species tend to feed on larger prey as their size increases. The lack of suitable prey during critical periods of their life can prevent them from shifting their diet to larger prey and also from reaching larger body sizes. In this study, we compared the energy budget of lake trout ( Salvelinus namaycush) populations with contrasting food webs. Non-piscivorous lake trout (NPLT) populations reached a much smaller size and grew at a much slower rate than picivorous lake trout (PLT) populations. Food consumption rates were on average, 2--3 times higher in NPLT when they were expressed on a wet weight basis. However, only a slight difference in their energy intake was detected (less than 10%) once consumption rates were corrected for differences in prey caloric content. Growth efficiency was about two times lower in NPLT compared to PLT, while their metabolic costs were higher and assimilation efficiency was lower. It is most likely that the increased metabolic costs were associated with higher foraging costs, since more feeding attempts must be made to acquire a given quantity of food when fish are feeding on smaller prey. Furthermore, the portion of indigestible matter is likely to be higher in the diet of NPLT than in PLT (e.g. chitin versus bone). These results are consistent with theoretical models of fish growth that have showed that lake trout must have access to larger prey, even if they are rare, to reach larger body sizes. Our study also illustrates how the restructuring of a prey community by the arrival of an exotic species into a food web could alter the growth rate of a top predator. Furthermore, our study suggests that age at first maturity is influenced by growth efficiency in indigenous populations of fish. Therefore, the dynamic of a population and its vulnerability to exploitation are likely to be influenced by their energy allocation strategy.
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Ellis, Julia K. "Diet of the Sandbar Shark, Carcharhinus plumbeus, in Chesapeake Bay and Adjacent Waters." W&M ScholarWorks, 2003. http://www.vims.edu/library/Theses/Ellis03.pdf.
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Weeber, Russell C. "Nutrient addition and the use of stable isotope techniques in wetlands of the Interlake Region of Manitoba, Canada." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22825.
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This study examines the relationship between nutrient additions and algae and invertebrate productivity in a nutrient-poor wetland of the Interlake Region of Manitoba, Canada. Alfalfa hay was added to experimental enclosures in May 1992. Alfalfa additions were made in unprocessed and ground forms and consisted of three treatments: ground low, whole low, and whole high. Dissolved oxygen, surface water nutrients, algae standing crop, and invertebrate production were monitored at open marsh sites and in treatment and control enclosures during 1992 and 1993. Stable $ sp{13}$C, $ sp{15}$N and $ sp{34}$S isotope ratios were determined for the alfalfa additions, and for surface water, algae, macrophytes, sediments and invertebrates.In general, the effects of nutrient additions were confined to 1992. Treatment enclosure dissolved oxygen levels decreased immediately following fertilization, recovering in the low treatments by early June. Low oxygen conditions persisted in whole high enclosures throughout most of 1992. Dissolved and suspended nutrient concentrations, and phytoplankton chlorophyll a increased but, with the exception of dissolved N, were soon lost from the water column. Treatment enclosure epiphytic algae increased while epipelon did not respond to fertilization. The primary effect of fertilization on invertebrate production was an increase in treatment enclosure chironomid larvae during 1992. As with productivity measures, stable isotope ratio values suggested a temporary presence of alfalfa nutrients in the enclosed food webs. Only the isotope ratios of metaphytic algae and snails collected during August 1992 indicated an incorporation of alfalfa nutrients.
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Bezuidenhout, Karien. "Sandy beach food webs and trophic linkages with estuaries: a stable light isotope approach." Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1269.
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Two pocket sandy beaches, Eastern Cape, South Africa, were investigated, to determine whether these beaches were subsidised by an adjacent mangrove estuary, by using stable light isotope (δ 13C and δ 15N) analyses. The trophodynamics and macrofaunal food webs of these two beaches, situated between the Mgazi and Mgazana estuaries (in a warm-temperate/subtropical transition zone,), were described. Two to 2.5 trophic levels were identified for the macrobenthic community, with suspension feeders and omnivorous scavengers as the primary consumers, and carnivores as the secondary consumers. Mangrove material and terrigenous inputs were not driving the sandy beach food webs. Instead, marine allochthonous inputs (carrion, macroalgae), possibly phytoplankton, sediment organic matter, and resident macroinfauna were the dominant food sources. Cattle dung could have been the only important terrigenous food source utilised by the beach benthos. The macroinfauna displayed generalist/omnivorous feeding strategies, but within the limits of predominantly marine food sources. There was evidence that carnivores actively preyed on resident beach fauna. Omnivory and intraguild feeding might also be important biological processes in these communities. Seasonal and spatial variability in stable isotope composition of the fauna was observed, but few patterns were evident. There was a general trend of more enriched δ 15N and δ 13C composition of animal tissues in summer as opposed to winter. This was accompanied by a general decrease in C:N ratios in summer. It was hypothesised that these isotopic and biochemical changes were in response to increased food availability during summer. Although mangrove material appeared not to play an important role in the nutrition of these sandy beach communities, it was suggested that a high retention time of particles in the bay could enhance bacterial decay of particulate mangrove material, which could then act as fine, bacterial-enriched particulate food to the macrobenthos. This remains to be tested.
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Moloney, Coleen Lyn. "A size-based model of carbon and nitrogen flows in plankton communities." Doctoral thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/22132.
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Bibliography: pages 163-183.A generic, size-based simulation model is developed to investigate the dynamics of carbon and nitrogen flows in plankton communities. All parameters in the model are determined by body size using empirically-determined relationships calculated from published data. The model is robust with respect to most parameters and assumptions. Because the model is based on general ecological principles, it can be used to simulate microplankton community interactions in any planktonic ecosystem. Two coastal ecosystems from the southern Benguela region in South Africa are simulated; one typical of the relatively stable surface waters on the Agulhas Bank and one typical of upwelling plumes, usually found off the west coast of South Africa. Simulated communities compare well with field observations in terms of standing stocks and size composition, and simulation results indicate that the small-scale structure of the two ecosystems and the processes occurring within them are relatively well understood. Consequently, the dynamic functioning of the two systems is investigated at the ecosystem level, using the simulation results. Hypothetical carbon flow networks are constructed, and the average importance of different flow pathways at different times is assessed. In both ecosystems, the vast majority of carbon flows pass through short, efficient-transfer pathways, although longer pathways are potentially possible. Simulation analyses are extended from coastal to oceanic food webs, and the model results are consistent with the hypothesis that oceanic phytoplankton have rapid rates of primary production. At-sea sampling of a phytoplankton bloom is mimicked by "sampling" from simulation output, and interpretation of the data using standard techniques is compared with the model output. The dangers of extrapolating from snapshot measurements is highlighted, and the experiment emphasizes the importance of size-fractionated sampling of phytoplankton. A hypothetical pelagic food web is described, consisting of at least five different trophic pathways from phytoplankton to pelagic fish. It is suggested that coastal waters probably have all the different pathways, and the relative importance and efficiency of the different pathways will determine the total fish production in an ecosystem.
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Westera, Mark B. "The effect of recreational fishing on targeted fishes and trophic structure, in a coral reef marine park." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2003. https://ro.ecu.edu.au/theses/1499.
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Recreational line fishing is highly targeted at predatory fishes, making them vulnerable to overfishing. These same fishes play a role in trophic structure by regulating prey species. Despite increasing numbers of fishers, few studies have investigated the potential effects of recreational fishing on fish populations and subsequent trophic effects. This project investigated whether there were differences in fishes and benthos between unfished and recreationally fished areas, and whether the removal of targeted fishes influenced trophic structure. The study was conducted at the Ningaloo Marine Park, Western Australia, which had Sanctuary (no-take) and Recreation {recreationally fished) Zones. Data were collected from three regions (Mandu, Osprey and Maud) and replicated over time. Fish assemblages, benthos and trophic interactions were compared between zones at each region. At Ningaloo the lethrinids (emperors) are a top-order predatory fish and the preferred target of recreational anglers. The algal-grazing urchin Echinometra mathaei comprised 51% of macro invertebrate abundances and was heavily preyed upon by lethrinids, being recorded in 50% of the guts of sampled fish. In nil regions, Sanctuary Zones had a greater biomass of lethrinids than Recreation Zones, but there were no differences in non-targeted fishes between zones. Despite the consistent effect on lethrinids, there were inconsistencies among regions in the predator-prey relationships. At Mandu, Echinometra mathaei abundances were inversely related to lethrinid biomass, suggesting a strong predator-prey interaction. In the Recreation Zone, the abundances of E. mathaei were four times greater, and macro-algal cover was half, that of the Sanctuary Zone. Furthermore, algal composition differed between zones, and this was driven by fucoid brown algae, which dominated the diets of E. mathaei. This was interpreted as evidence of a trophic cascade resulting from the removal of lethrinids at the Recreation Zone. At Maud, different results were recorded. Abundances of Echinometro mathaei and lethrinids were both higher in the Sanctuary Zone, than the adjacent Recreation Zone. E. mathaei reside in the crevices of rock, dead coral or Echinapora coral, which provided refuge from predation and this habitat was more available in the Sanctuary Zone. It is suggested that the availability of this habitat confounded the effects of predation. Macro- algal cover was lower in the Sanctuary Zone indicating a grazing effect from E. mathaei. At Osprey there was higher cover of E. mathaei habitat in the Sanctuary than the Recreation Zone. However, there were no differences in macro-algal cover, which was consistent with a lack of difference in E. mathaei abundances. The effect of E. mathaei grazing was unlikely to have been confounded by fishes that graze macro-algae, as they did not differ between zones at any region. These results indicate that recreational fishing reduced fish populations below that of adjacent protected areas at Ningaloo Marine Park, and in one region this resulted in a trophic cascade. This may be the first study that has recorded evidence of a trophic cascade where recreational line fishing is the only means of extraction. However, the results also show that this is not a consistent response to reduced fishing pressure; in other regions, changes in predatory fish abundance did not result in differences in the abundances of their prey, suggesting no trophic cascade. The studies have contributed towards an understanding of fish-habitat interactions and provide a baseline for future monitoring of the Ningaloo Marine Park. They also have important implications for marine park managers in terms of defining their expectations when implementing Sanctuary Zones. The results also show that Sanctuary Zones have the potential to be effective tools for fisheries management.