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Journal articles on the topic 'Tropical river ecosystems'
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1
Hairan, Mohammad Haroon, Nor Rohaizah Jamil, Mohammad Noor Amal Azmai, Ley Juen Looi, and Moriken Camara. "Environmental Flow Assessment of a Tropical River System Using Hydrological Index Methods." Water 13, no. 18 (September 9, 2021): 2477. http://dx.doi.org/10.3390/w13182477.
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Tropical rivers and wetlands are recognized as one of the greatest and most abundant ecosystems in terms of ecological and social benefits. However, climate change, damming, overfishing, water pollution, and the introduction of exotic species threaten these ecosystems, which puts about 65% of river flow and aquatic ecosystems under a moderate to high level of threat. This paper aims to assess the environmental flow of the Selangor River based on the hydrological index method using the Global Environmental Flow Calculator (GEFC) and Indicators of Hydrological Alterations (IHA) software. The daily flow data collected by the Department of Irrigation and Drainage (DID), Malaysia, over a 60-year period (1960–2020) was used in this study to assess the Selangor River flow alterations. As per the results, the river flow has had two distinct periods over the last 60 years. In the first period, the river flows without any alteration and has a natural flow with high flood pulses and low flow pulses. While in the second, or post-impact, period, the flow of the river has a steady condition throughout the year with very little fluctuations between the dry and wet seasons of the year. From the overall comparison of the pre- and post-impact periods, it can be concluded that the minimum flow in the dry seasons of the year has increased, while the maximum flow has decreased in the monsoon seasons during the post-impact period. As a result, the Flow Duration Curve (FDC) and Environmental Management Class (EMC) analysis of the river flow recommends that the Selangor River be managed under EMC “C” to provide sufficient water for both human use and ecosystem conservation, which would also help to avoid a water level drop in the reservoirs. However, further holistic studies are suggested for a detailed analysis of the effects of the dams on aquatic biodiversity and ecosystem services in the Selangor River Basin.
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Huang, Jr-Chuan, and Tsung-Yu Lee. "Hydrological Impact of Typhoon on Rivers." Water 13, no. 8 (April 7, 2021): 1009. http://dx.doi.org/10.3390/w13081009.
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Rivers link terrestrial and marine ecosystems, not only transporting numerous substances downstream but also shaping landscapes and fostering aquatic ecosystems through physical interactions and biogeochemical processes with numerous agents. On the other hand, hydraulic facilities, such as reservoirs, hydropower plants, and banks are deployed to utilize water resources for sustaining human society. In the river network systems, rainstorms, as episodic/periodic strong triggers, can induce mass wasting from hillslopes, accelerating nutrient transport, which causes sequential effects. In recent decades, global warming has been accelerating water cycling via thermodynamics, and thus, the frequency and intensity of extreme rainstorms are increasing in intensity. In the West Pacific, typhoons (alias tropical cyclones in Asia) characterized by strong wind and torrential rainfall are evidenced to be getting stronger. The intensified typhoons inevitably stimulate the response of river systems through sediment and nutrient transport and threaten the safe operation of the hydraulic facilities and even coastal communities through storm surge flooding. These strong impacts on river systems should be comprehensively explored. This issue aims to improve the understanding of typhoon effects in river systems. Inter- and cross-disciplinary studies on different watershed scales, linking ecosystem services and watershed management, are particularly addressed.
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de Necker, Lizaan, Tinyiko Neswiswi, Richard Greenfield, Johan van Vuren, Luc Brendonck, Victor Wepener, and Nico Smit. "Long-Term Water Quality Patterns of a Flow Regulated Tropical Lowland River." Water 12, no. 1 (December 20, 2019): 37. http://dx.doi.org/10.3390/w12010037.
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Floodplain ecosystems in Africa are under threat due to direct anthropogenic pressure and climate change. The lower Phongolo River and associated floodplain is South Africa’s largest inland floodplain ecosystem and has been regulated by the Pongolapoort Dam since the 1970s. The last controlled flood release from the dam occurred in December 2014, after which a severe drought occurred and only a base flow was released. The central aims of this study were to determine the historic and present water quality state of the middle and lower Phongolo River and assess the possible effects of the most recent drought may have had. Historic water quality data (1970s to present) were obtained from monitoring stations within the Phongolo River catchment to assess the long-term water quality patterns. Using multivariate statistical analyses as well as the Physicochemical Driver Assessment Index (PAI), a water quality index developed for South African riverine ecosystems, various in situ and chemical water variables were analysed. Key findings included that the water quality of the middle and lower Phongolo River has degraded since the 1970s, due to increased salinity and nutrient inputs from surrounding irrigation schemes. The Pongolapoort Dam appears to be trapping nutrient-rich sediments leading to nutrient-depleted water entering the lower Phongolo River. The nutrient levels increase again as the river flows through the downstream floodplain through input from nutrient rich soils and fertilizers. The drought did not have any significant effect on water quality as the PAI remained similar to pre-drought conditions.
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Goulart, Michael, and Marcos Callisto. "Mayfly diversity in the brazilian tropical headwaters of Serra do Cipó." Brazilian Archives of Biology and Technology 48, no. 6 (November 2005): 983–96. http://dx.doi.org/10.1590/s1516-89132005000800015.
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The objectives of this study were to evaluate spatial and seasonal distribution, assemblage structure and substrate associations of mayfly nymphs in five lotic ecosystems in the headwaters of the Doce River and São Francisco River watersheds, Brazil. Samples were taken in 24 sampling stations during rainy and dry seasons in 1998. In total, 7,066 organisms were collected, belonging to 27 genera and 6 families of Ephemeroptera. The dominant taxa were Americabaetis, Paracloeodes, Leptohyphes and Hagenulus. During the rainy period, the São Francisco River watershed showed higher taxonomic richness, diversity and evenness, while in the dry period, the taxonomic richness was higher in Doce River watershed. No significant differences were found in the taxonomic richness, diversity, evenness and density of mayfly assemblages between the two studied sampling periods. The results suggested that the diversity of the mayfly assemblages in tropical headwaters of Serra do Cipó would be probably due to ecosystem and watershed characteristics.
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Day, J. W., A. L. Lara Dominguez, J. Herrera-Silveira, and G. Paul Kemp. "Climate Change in Areas of the Gulf of Mexico With High Freshwater Input – A Review of Impacts and Potential Mitigation." JAINA Costas y Mares ante el Cambio Climático 1, no. 1 (July 2019): 87–108. http://dx.doi.org/10.26359/52462.0619.
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The Gulf of Mexico currently spans the transition from tropical to temperate coastal ecosystems but this is changing as the northern Gulf undergoes tropicalization and the entire Gulf will become tropical in this century. The objective of this paper was to review information on climate change impacts on coastal ecosystems with high freshwater input for the Gulf of Mexico and review mitigation measures for dealing with climate change. There are two high freshwater discharge areas, one surrounding the Mississippi River in the north central Gulf and one in the southern Gulf, which is associated with the Grijalva-Usumacinta River and adjacent rivers and ground water discharge from the Yucatan Peninsula. Both of these areas are characterized by extensive coastal wetlands, and in the southern Gulf, submerged aquatic vegetation. These coastal ecosystems support important natural resources, have high petroleum production, and important maritime trade. Climate change will impact both of these areas strongly. Sea level is projected to increase by a meter or more by 2100 and there will be more strong hurricanes that will be larger, have more intense rainfall, will move slower, and the rate of intensification will increase. In the north, peak Mississippi River discharge is projected to increase by 10 to 60%. In the southern Gulf, it is projected that precipitation and freshwater discharge will decrease associated with the Mesoamerican climate hotspot. Coastal management to accommodate climate change should mimic ecosystem functioning. Specific actions include protection of natural areas, full use of freshwater and sediment resources, maintain con-nections between freshwater input and coastal systems, allow inland migration of coastal wetlands, and careful management of land use changes. Keywords: Gulf of Mexico, climate change impacts, coastal ecossytems.
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Howley, C., M. Devlin, and M. Burford. "Assessment of water quality from the Normanby River catchment to coastal flood plumes on the northern Great Barrier Reef, Australia." Marine and Freshwater Research 69, no. 6 (2018): 859. http://dx.doi.org/10.1071/mf17009.
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Understanding the flux and fate of nutrients and sediments from rivers is of global importance because of the effects of these materials on coastal ecosystems. The present study followed three flood events from upper tributaries of the Normanby River to Princess Charlotte Bay in the northern Great Barrier Reef (GBR) lagoon, Australia. During each event, nutrients and suspended sediment concentrations were measured along a freshwater to marine transect. The upper catchment provided the majority of suspended sediments and nutrients supplied to the river system, although concentrations of most materials decreased by 52–85% between the upper catchment and estuary. As an exception, ammonium concentrations doubled within the estuary, indicating that undisturbed coastal ecosystems can provide a significant source of dissolved inorganic nitrogen to tropical river flood plumes. The dissolved nutrients in floodwaters stimulated phytoplankton blooms that inundated seagrass meadows and coral reefs. Northern GBR marine ecosystems are increasingly threatened by climate change and catchment development. The results of this study show that increased anthropogenic loads of nutrients and sediments from the upper Normanby catchment have the potential to affect the condition of marine ecosystems at Princess Charlotte Bay.
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Bruijnzeel, L. A. "Nutrient input–output budgets of tropical forest ecosystems: a review." Journal of Tropical Ecology 7, no. 1 (February 1991): 1–24. http://dx.doi.org/10.1017/s0266467400005010.
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ABSTRACTAtmospheric gains and hydrologic losses of calcium, magnesium, potassium, phosphorus and nitrogen for 25 tropical forest sites on a variety of geological substrates are reviewed. The data set comprised 19 lowland and six montane sites. Twenty studies were subjected to further analysis after initial quality control. These were subdivided into forests on (1) very infertile soils (N = 5), (2) (moderately) infertile soils (N = 5), (3) moderately fertile soils (N = 4) and (4) fertile soils (N = 4). Two studies pertaining to large river basins were treated separately. Although variation in nutrient fluxes was large, reflecting both natural and methodological factors, scatter plots of annual calcium, magnesium and potassium losses v. annual runoff for small catchment areas revealed four groups with characteristic nutrient export patterns that corresponded closely with soil fertility levels. Element losses from the two large basins were much higher than those recorded for small basins in the same areas and were interpreted in terms of depths of weathering front, river incision and root network. Phosphorus accumulated in virtually all cases, reflecting the low mobility of the element. Nitrogen budgets were generally very incomplete. There is a need for more and careful studies of tropical forest nutrient budgets, especially for nitrogen. Standardization of methodology is essential if comparability of results is to be improved.
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Brodie, Jon E., and Alan W. Mitchell. "Nutrients in Australian tropical rivers: changes with agricultural development and implications for receiving environments." Marine and Freshwater Research 56, no. 3 (2005): 279. http://dx.doi.org/10.1071/mf04081.
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In tropical Australia, intensive studies of river suspended sediment (SS) and nutrient dynamics have been restricted to streams on the north-east coast between the Fitzroy and Normanby Rivers (Queensland), Magela Creek/East Alligator River (Northern Territory) and the Ord River (Western Australia). Historical conditions in these rivers were probably characterised by low–moderate SS concentrations and low concentrations of dissolved inorganic nitrogen and phosphorus in flow events. Introduction of agriculture has transformed SS and nutrient dynamics. Grazing has led to soil erosion and increased SS and particulate nutrient concentrations and fluxes in event flows. Fertilised cropping has increased nutrient inputs to catchments, where it forms a substantial proportion of the catchment area. Consequently, both particulate and dissolved inorganic nutrient concentrations and fluxes have increased. Australian tropical rivers have episodic flows, with most material transport occurring during large flow events. The restricted period of these highly energetic flows means little trapping of materials in waterways occurs. Loads are transported efficiently downstream and processes such as denitrification and in-channel sedimentation may be of limited importance. Owing to excessive nutrient inputs associated with agriculture, a number of northern freshwater, estuarine and coastal ecosystems are now eutrophic. Continued development, especially fertilised cropping, without adequate management of nutrient losses is likely to exacerbate these problems.
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Ahmad, A. K., A. Hafizah, and S. O. Sharifah Aisyah. "Chironomidae (Order: Diptera) diversity in relation to water quality of highland rivers at Cameron Highlands, Malaysia." Journal of Environmental Biology 42, no. 3(SI) (May 31, 2021): 824–31. http://dx.doi.org/10.22438/jeb/42/3(si)/jeb-14.
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Aim: This study aims to determine Chironomidae diversity and distribution in three small rivers at Cameron Highlands in relation to their response to water quality conditions. Methodology: Fifteen sites from three rivers (Palas River, Pauh River and Bertam River) were chosen for water quality measurements and Chironomidae sampling. Water quality was analysed following APHA standard methods and chironomid was identified to genus level. The rivers were classified based on Malaysian’s Water Quality Index (WQI) and macroinvertebrates diversity and distribution was analysed using diversity indices. Comparison between sites and river was undertaken using one-way ANOVA and chironomid appearance in relation to water quality was evaluated using Pearson correlation test. Results: Chironomidae (Order: Diptera) distribution at high altitude rivers in Malaysia is not well documented although this group of insect has a wide range of distribution in tropical region. Based on Malaysian water quality index (WQI), result shows all rivers were in Class I. Although still in Class I, Bertam River has slight lower water quality due to higher ammoniacal nitrogen and total suspended solids. The diversity indices also demonstrate that Bertam Rivers was in stress conditions, and other two were in moderate conditions. Three subfamilies (Chironominae, Orthocladiinae and Tanypodinae) were recorded, which comprises of 1963 individuals. Tvetenia (Subfamily: Orthocladiinae) was the most dominant but only dominated Palas River and Pauh River. Another genus from Orthocladiinae (Crocotopus and Rheocrocotopus) also recorded dominant only in Palas River and Pauh River, but lesser in Bertam River. Only Polypedilum (Subfamily: Chironominae) which was second highest recorded, dominated in all rivers, even highest in Bertam River. Amongst dominant genus, only Polypedilum was found dominant in all rivers, others were only dominating Palas River and Pauh River only. Interpretation: This findings exhibit wide range of adaptations and potential use of Polypedilum as biological indicator. Due to availability of incomplete keys, identification to species level cannot be undertaken. However, this study reveals thirteen different sub-group of Polypedilum based mouthpart organs, which represent different species for tropical ecosystems.
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Costa, Davi Freire da, and Ênio Wocyli Dantas. "Diversity of phytoplankton community in different urban aquatic ecosystems in metropolitan João Pessoa, state of Paraíba, Brazil." Acta Limnologica Brasiliensia 23, no. 4 (June 14, 2012): 394–405. http://dx.doi.org/10.1590/s2179-975x2012005000018.
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AIM: The aim of the present study was to identify which environmental factors affect the seasonal phytoplankton structure in different types of tropical aquatic ecosystems. Phytoplankton sampling was performed bi-monthly from August 2009 to June 2110 at three sites in the Solon de Lucena Lake, Jaguaribe River and Águas Minerais reservoir. METHODS: The environmental variables were water temperature, transparency, depth, degree of infestation of aquatic macrophytes, air temperature, wind speed, solar radiation and precipitation. The phytoplankton community was studied in terms of richness, density, diversity and evenness. The data were treated with analysis of variance and canonical correspondence analysis. RESULTS: Spatial variations in the data only occurred between ecosystems (p < 0.05). The reservoir and river exhibited typical phytoplankton of lotic environments, with a greater richness of Bacillariophyta (52.8% and 47.8%, respectively). The lake exhibited the typical richness lentic environments, with the greatest contribution from Chlorophyta (52.8%). This ecosystem was characterized by an absence of macrophytes, a low degree of water transparency (0.3 ± 0 m) and high algal density (89,903 ± 38,542 ind. mL-1), with a dominance of Aphanocapsa nubilum. In the river environment, the lesser diversity (0.64 ± 0.24 bit.ind-1 ) was associated to lesser richness (2.4 ± 0.5 spp.) and lesser evenness (0.39 ± 0.19) in comparison to the other ecosystems. The influence of macrophytes in the river and reservoir contributed toward the introduction of metaphytes and epiphytes in the phytoplankton, which was explained by the direct relationship between the density of these species and macrophytes. CONCLUSION: Thus, water transparency and macrophytes were the main factors related to fluctuations between the different aquatic ecosystems studied.
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Alemayehu, Tadesse, Ann van Griensven, Befekadu Taddesse Woldegiorgis, and Willy Bauwens. "An improved SWAT vegetation growth module and its evaluation for four tropical ecosystems." Hydrology and Earth System Sciences 21, no. 9 (September 7, 2017): 4449–67. http://dx.doi.org/10.5194/hess-21-4449-2017.
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Abstract. The Soil and Water Assessment Tool (SWAT) is a globally applied river basin ecohydrological model used in a wide spectrum of studies, ranging from land use change and climate change impacts studies to research for the development of the best water management practices. However, SWAT has limitations in simulating the seasonal growth cycles for trees and perennial vegetation in the tropics, where rainfall rather than temperature is the dominant plant growth controlling factor. Our goal is to improve the vegetation growth module of SWAT for simulating the vegetation variables – such as the leaf area index (LAI) – for tropical ecosystems. Therefore, we present a modified SWAT version for the tropics (SWAT-T) that uses a straightforward but robust soil moisture index (SMI) – a quotient of rainfall (P) and reference evapotranspiration (ETr) – to dynamically initiate a new growth cycle within a predefined period. Our results for the Mara Basin (Kenya/Tanzania) show that the SWAT-T-simulated LAI corresponds well with the Moderate Resolution Imaging Spectroradiometer (MODIS) LAI for evergreen forest, savanna grassland and shrubland. This indicates that the SMI is reliable for triggering a new annual growth cycle. The water balance components (evapotranspiration and streamflow) simulated by the SWAT-T exhibit a good agreement with remote-sensing-based evapotranspiration (ET-RS) and observed streamflow. The SWAT-T model, with the proposed vegetation growth module for tropical ecosystems, can be a robust tool for simulating the vegetation growth dynamics in hydrologic models in tropical regions.
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Imoobe, T. O. T., and M. L. Adeyinka. "Zooplankton-based assessment of the trophic state of a tropical forest river in Nigeria." Archives of Biological Sciences 61, no. 4 (2009): 733–40. http://dx.doi.org/10.2298/abs0904733i.
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In this study, we explore the usefulness of zooplankton as a tool for assessing the trophic status of a Nigerian forest river. The river was sampled monthly and investigated for water physico-chemistry and zooplankton community structure using basic statistical measurement of diversity indices to characterize the zooplankton fauna. The trophic sta?tus of the river evaluated from its physico-chemical parameters indicates that the river is oligotrophic. The zooplankton composition was typical of a tropical freshwater river, with a total of 40 species, made up of 16 rotifers, 12 cladocerans, and 12 copepods and their developing stages in the following order of dominance: Rotifera > Cladocera > Cyclopoida > Calanoida. There were strong correlations between the lake's trophic status and its zooplankton communities. The zoo?plankton community was dominated by numerous species of rotifers and crustaceans, which are typical of oligotrophic to mesotrophic systems, such species including Conochilus dossuarius and Synchaeta longipes. However, the most dominant zooplankton species in West African freshwater ecosystems, viz., Keratella tropica, Keratella quadrata, Brachionus angularis, Trichocerca pusilla, Filinia longiseta, Pompholyx sulcata, and Proales sp., and others that are indicator species of high trophic levels, were not recorded in the river. The river is very clear and can be used for all manner of recreational activities.
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Singh, Atul K. "State of aquatic invasive species in tropical India: An overview." Aquatic Ecosystem Health & Management 24, no. 2 (April 1, 2021): 13–23. http://dx.doi.org/10.14321/aehm.024.02.05.
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Abstract India, a megadiverse tropical country is grappling with the rising trend of aquatic invasions. Out of 532 introduced non-native fish, 16 species of freshwater aquaculture and aquarium were assessed invasive by using a risk assessment protocol, ‘Fish Invasiveness Screening Test’. Six major identified invasion pathways of the aquatic invasive species were inadvertent or deliberate releases, escapes, contaminants from hatcheries, river corridors, stowaways and unaided introductions. Invasion mechanism further elucidated the factors promoting successful invasion in freshwater ecosystems. For predictive future performance of invasive fish, the concrete and predictive values based on mean abundance by weight was calculated. Over 28.67% and 29.02 % persistent increased yield of the invasive Tilapia and Common Carp respectively was predicted in the Ganga river in the coming decades. Single species Tilapia invasion facilitated multiple species fish invasion, manifesting in invasion meltdown. The trophic changes due to fish invasion exhibited biotic homogenization with trophic downgrading. Aquatic invasive species were found highly competitive interacting with native species causing serious biodiversity loss, health hazards, and economic damage consequently affecting the ecosystem services. In spite of available regulatory approaches and guidelines to manage aquatic invasive species, fish invasion has been on the rise. This paper suggests modifications and stringent implementation of the existing regulatory mechanisms besides adopting linkages, cutting-edge research on invasion science and modern molecular containment tools for effective management.
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Li, R. H., S. M. Liu, Y. W. Li, G. L. Zhang, J. L. Ren, and J. Zhang. "Nutrient dynamics in tropical rivers, estuarine-lagoons, and coastal ecosystems along the eastern Hainan Island." Biogeosciences Discussions 10, no. 6 (June 5, 2013): 9091–147. http://dx.doi.org/10.5194/bgd-10-9091-2013.
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Abstract. Nutrient dynamics were studied along the eastern Hainan Island based on field observations during 2006–2009, to understand nutrient biogeochemical processes and to have an overview of human perturbations on coastal ecosystems in this tropical region. The concentrations of nutrients in the rivers had seasonal variations enriched with dissolved inorganic nitrogen (DIN). High riverine concentrations of nitrate were mainly originated from agricultural fertilizer input. The ratios of DIN : PO43− ranged from 37 to 1063, suggesting preferential PO43− relative to nitrogen in the rivers. The areal yields of dissolved silicate (DSi) varied from 76 to 448 × 103 mol km−2 yr−1 due to erosion over the drainage area, inducing high levels of DSi among worldwide tropical systems. Aquaculture ponds contained high concentrations of NH4&plus; (up to 157 μM) and DON (up to 130 μM). Particulate phosphorus concentrations (0.5 ∼1.4 μM) were in lower level comparied with estuaries around the world. Particulate silicate levels in rivers and lagoons were lower than global average level. Nutrient biogeochemistry in coastal areas were affected by human activities (e.g. aquaculture, agriculture), as well as natural events such as typhoon. Nutrient concentrations were low because open sea water dispersed land-derived nutrients. Nutrient budgets were built based on a steady-state box model, which showed that riverine fluxes would be magnified by estuarine processes (e.g. regeneration, desorption) in the Wenchanghe/Wenjiaohe Estuary, Wanquan River estuary, and the Laoyehai Lagoon except in the Xiaohai Lagoon. Riverine and groundwater input were the major sources of nutrients to the Xiaohai Lagoon and the Laiyehai Lagoon, respectively. Riverine input and aquaculture effluent were the major sources of nutrients to the eastern coastal of Hainan Island. Nutrient inputs to the coastal ecosystem can be increased by typhoon-induced runoff of rainwater, and phytoplankton bloom in the sea would be caused.
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Moruff, Adelakun Kehinde, Mu’azu Mohammed Mu’azu, Amali Rosemary Patric, and Omotayo Olabode Lawrence. "Diversity of Phytoplankton Communities in a Tropical River Basin, Nigeria." Hydro Nepal: Journal of Water, Energy and Environment 19 (July 26, 2016): 52–56. http://dx.doi.org/10.3126/hn.v19i0.15353.
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Biological assessment is a useful alternative for understanding the ecological quality of aquatic ecosystems because biological communities integrate the environmental effects of water. This work investigates the diversity and abundance of phytoplankton in the Upper Jebba Basin of the Niger River in Nigeria. We sampled phytoplanktons by dragging plankton nets at three stations from March to May 2015 for qualitative and quantitative samples. Qualitative plankton samples were collected by towing 55μm mesh hydrobios plankton nets just below the water surface for five minutes at each sampling station. Quantitative samples, on the other hand, were collected by filtering 100 litres of water fetched with a bucket through a 55μm mesh hydrobios net. Both samples were preserved separately in a 4% buffered formalin solution. A total of 3160 cells/ml of phytoplanktons from taxa were identified in the study. High dominance of Oscillatoria sp., Microcystis sp., Chlorella sp., Pediastrum sp. and Synendra indicate that this lake has high amount of organic waste, polluted predominantly by upstream concerns (i.e., mining, agricultural, and domestic) and should be monitored strictly by relevant agencies in order to additional reduced health hazards caused by these pollutants.HYDRO Nepal JournalJournal of Water, Energy and EnvironmentIssue: 19Page: 52-56
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ZAMORA GONZÁLEZ, HILLDIER. "Freshwater macroinvertebrates registered during the rainy season in three tropical rivers of the foothill on the eastern plains of Colombia." Revista Colombiana de Ciencia Animal - RECIA 7, no. 2 (July 2, 2015): 139. http://dx.doi.org/10.24188/recia.v7.n2.2015.243.
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This study was carried out in three tropical rivers, namely Humadea (488m. above sea level), Marayal (503m. asl) and Camoa (450m. asl), located in the foothill on the Eastern Plains of Colombia, with average temperature as high as 24ºC, and 4000mm average annual precipitation. The samplings were carried in rainy seasons during 2003 to 2007 to date. During the field survey stage, hydro physicochemical indices were obtained and analyzed, and the Acuatic Macroinvertebrates Epicontinental (AME) were captured. Based on laboratory survey and sampling work Shannon- Weaver (H’), Sorensen (s) and BMWP (Biological Monitoring Working Party Score System)(2007) adapted to Colombia. During the study period, not recorded naturally or by human intervention strong or severe disturbance of ecological status of these three ecosystems that alter their structure and dynamics, aspects to date (July 2014) of preparation of this article remain unchanged. 56 Genera, 40 families, 13 Orders, four Classes and three Phyla were recorded. The highest value for diversity according to the Shannon Weaver index was found in the river Marayal (2.72), while the lowest diversity was found in the Humadea river (2.53). On the BMWP index the three systems present water quality levels ranging between good and very good. The ecosystems registering the highest similarity were Marayal and Camoa (81%) while Humadea and Camoa had the lowest (56%).
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Judson Kenworthy, W. "The role of sexual reproduction in maintaining populations of Halophila decipiens: implications for the biodiversity and conservation of tropical seagrass ecosystems." Pacific Conservation Biology 5, no. 4 (1999): 260. http://dx.doi.org/10.1071/pc000260.
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In subtropical and tropical communities, seagrass species commonly range over an order of magnitude in size and biomass. This biodiversity corresponds with differences in the relative importance of sexual (seed production) and asexual (clonal growth) life history strategies in the maintenance of seagrass populations. Clonal growth and vegetative reproduction are important in maintaining populations of larger-bodied species. As size of species and degree of clonality decrease, the importance of sexual reproduction increases. World-wide, the smallest species in tropical seagrass ecosystems are represented by the most taxonomically diverse, sexually fecund genus, Halophila. A four-year study of the submarine light regime and seasonal growth cycles of Halophila decipiens and other seagrasses in the Indian River Lagoon, Florida, USA provides a comparative context in which to illustrate the relative importance of different life history strategies in tropical seagrass ecosystems world-wide. While sexual reproduction is critical for maintaining some geographically extensive small-bodied seagrass systems in disturbed and extreme environments, there is also evidence to suggest that the quantitative importance of sexual reproduction may be underestimated for larger, highly clonal species like Thalassia testudinum. Future efforts to conserve tropical seagrass ecosystems necessitates a more comprehensive understanding of the evolutionary consequences of sexual reproduction and a more quantitative evaluation of the population dynamics resulting from the sexual life history strategies of different species.
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Statzner, Bernhard, and Bert Higler. "Questions and Comments on the River Continuum Concept." Canadian Journal of Fisheries and Aquatic Sciences 42, no. 5 (May 1, 1985): 1038–44. http://dx.doi.org/10.1139/f85-129.
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The River Continuum Concept (RCC) is a generalized conceptual framework for characterization of pristine running water ecosystems. Of the numerous tenets of the concept we particularly reevaluated the following: biological analogues of energy equilibrium and entropy in the physical system; maximization of energy consumption through continuous species replacement over a year; absence of succession in stream ecosystems, which can thus be viewed in a time-independent fashion; and maximization of biotic diversity in midreaches of streams as a result of the occurrence of highest environmental variability there together with spatial abundance shifts of insects, molluscs, and crustaceans. When emphasis is placed on rapid changes in the downstream hydraulics dependent on discharge and slope (both of which are expressed by stream order in the RCC and are key factors of the concept) and on results from tropical studies, some of these tenets are partly refuted or need extension. Some of them are in conflict with the current state of knowledge in other domains of stream ecology or are at least open to various interpretations. Therefore, we advocate modifications of the theoretical background of the RCC.
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Pérez-Gómez, Gabriela, Ana Eugenia Jiménez-Rocha, and Tania Bermúdez-Rojas. "Parásitos gastrointestinales de aves silvestres en un ecosistema ribereño urbano tropical en Heredia, Costa Rica." Revista de Biología Tropical 66, no. 2 (May 24, 2018): 788. http://dx.doi.org/10.15517/rbt.v66i2.33409.
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Gastrointestinal parasites of wild birds in a tropical riverine urban ecosystem in Heredia, Costa Rica. In urban ecosystems, rivers provide various ecosystem services, among them, serving as interurban biological corridor, allowing birds to move and shelter in the middle of the city. However, high levels of pollution expose them, and even humans, to several health problems. Hence the importance of performing environmental diagnoses that allows to identify alterations and mitigate them in a timely manner. This study provides a first diagnosis of the parasitic situation of wild birds along the Pirro river which is located in an urban environment, fragmented and with high levels of surface water pollution. The sampling was carried out at the upper and middle part of the Pirro river in Heredia, Costa Rica. Mist-nets were used to capture the birds, and a general objective exam (GOE) was conducted in order to evaluate their nutritional and hydration state, as well as their physical state. In addition, stool samples were collected in order to characterize the gastrointestinal parasites (GPI). This procedure was carried out on 158 birds, belonging to 30 species, three PGI groups were identified: protozoa, nematodes and cestodes. The highest percentages of infection were represented by coccidia, with 97.6 %, followed by nematodes and cestodes with 2.4 %. Within the group of coccidios, it was possible to identify Eimeria spp., Isospora spp., in the nematodes: at the Strongylida group level and at the Capillaria spp., and for the cestodes: Choanotaenia spp. GOE resulted regular-to-good in all individuals captured, however, a general linear model was used to identify that the oral cavity and the state of the plumage could be the more linked variables with the percentage of infection by gastrointestinal parasites in birds, due to the fact that the oral cavity is the bird’s main route of ingestion, as well as the state of the plumage shows its vigor. Rev. Biol. Trop. 66(2): 788-798. Epub 2018 June 01.
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Keppeler, Friedrich Wolfgang, Gustavo Hallwass, and Renato Azevedo Matias Silvano. "Influence of protected areas on fish assemblages and fisheries in a large tropical river." Oryx 51, no. 2 (June 15, 2016): 268–79. http://dx.doi.org/10.1017/s0030605316000247.
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AbstractProtected areas are one of the main tools for biological conservation worldwide. Although they have contributed to an increase in fish abundance and alleviated the impacts of fishing on marine ecosystems, the impacts of fishing and of protected areas in freshwater ecosystems are less well known. We compared fishing productivity and fish assemblage descriptors of two distinct protected areas designated for sustainable use of natural resources and an unprotected area in the Tapajós River, in the Brazilian Amazon. Two hypotheses were tested: (1) fishers from protected areas have higher catch per unit effort than those from unprotected areas; and (2) fish assemblages in protected areas have higher biomass, abundance, presence of target species, species richness, fish size and mean trophic level than those in unprotected areas. A total of 2,013 fish landings were recorded and two surveys were undertaken to sample fishes. Eleven environmental parameters were quantified to distinguish between effects of environmental heterogeneity and protected areas. The catch per unit effort of fishers was higher within protected areas than in unprotected areas, suggesting that protected areas reduce the levels of fishing pressure and increase fishing productivity. However, the fish assemblage descriptors were correlated more with environmental variables than with protected areas, indicating a relatively weak effect of protected areas on fish communities in lakes. The results highlight the importance of considering the influence of environmental heterogeneity in fish conservation programmes, and the positive effect of protected areas on fishing productivity in freshwater environments.
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Crookes, Steven, Tej Heer, Rowshyra A. Castañeda, Nicholas E. Mandrak, Daniel D. Heath, Olaf L. F. Weyl, Hugh J. MacIsaac, and Llewellyn C. Foxcroft. "Monitoring the silver carp invasion in Africa: a case study using environmental DNA (eDNA) in dangerous watersheds." NeoBiota 56 (April 29, 2020): 31–47. http://dx.doi.org/10.3897/neobiota.56.47475.
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Biodiverse habitats are increasingly subject to an intensification of anthropogenic stressors that may severely diminish species richness. Invasive species pose a dominant threat to biodiversity and biosecurity, particularly in biodiversity hotspots like Kruger National Park, South Africa. The invasive silver carp, Hypophthalmichthys molitrix, was introduced into the Olifants River and may experience range spread owing to favorable environmental conditions. Intensive monitoring protocols are necessary to effectively manage invasions of species like silver carp. Unfortunately, tropical and sub-tropical aquatic systems are difficult to monitor using conventional methods (e.g., netting, electrofishing and snorkeling) owing to a range of factors including the presence of dangerous megafauna. Conservation of such systems may be advanced by the adoption of novel methods, including environmental DNA (eDNA) detection. Here, we explore the utility of environmental DNA (eDNA) to conduct safe, reliable and repeatable surveys in dangerous watersheds using silver carp as a case study. We conducted eDNA surveys at 12 sites in two neighbouring watersheds, and determined that the species has expanded its range within the Olifants River and to the south in the Sabie River. Expansion in the former is consistent with the presence of suitable spawning conditions. We discuss the implications of this survey for biodiversity monitoring in similar aquatic systems in the tropics and advocate an integrative approach to biomonitoring in these ecosystems.
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Lee, Calvin K. F., Clare Duncan, Emily Nicholson, Temilola E. Fatoyinbo, David Lagomasino, Nathan Thomas, Thomas A. Worthington, and Nicholas J. Murray. "Mapping the Extent of Mangrove Ecosystem Degradation by Integrating an Ecological Conceptual Model with Satellite Data." Remote Sensing 13, no. 11 (May 22, 2021): 2047. http://dx.doi.org/10.3390/rs13112047.
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Anthropogenic and natural disturbances can cause degradation of ecosystems, reducing their capacity to sustain biodiversity and provide ecosystem services. Understanding the extent of ecosystem degradation is critical for estimating risks to ecosystems, yet there are few existing methods to map degradation at the ecosystem scale and none using freely available satellite data for mangrove ecosystems. In this study, we developed a quantitative classification model of mangrove ecosystem degradation using freely available earth observation data. Crucially, a conceptual model of mangrove ecosystem degradation was established to identify suitable remote sensing variables that support the quantitative classification model, bridging the gap between satellite-derived variables and ecosystem degradation with explicit ecological links. We applied our degradation model to two case-studies, the mangroves of Rakhine State, Myanmar, which are severely threatened by anthropogenic disturbances, and Shark River within the Everglades National Park, USA, which is periodically disturbed by severe tropical storms. Our model suggested that 40% (597 km2) of the extent of mangroves in Rakhine showed evidence of degradation. In the Everglades, the model suggested that the extent of degraded mangrove forest increased from 5.1% to 97.4% following the Category 4 Hurricane Irma in 2017. Quantitative accuracy assessments indicated the model achieved overall accuracies of 77.6% and 79.1% for the Rakhine and the Everglades, respectively. We highlight that using an ecological conceptual model as the basis for building quantitative classification models to estimate the extent of ecosystem degradation ensures the ecological relevance of the classification models. Our developed method enables researchers to move beyond only mapping ecosystem distribution to condition and degradation as well. These results can help support ecosystem risk assessments, natural capital accounting, and restoration planning and provide quantitative estimates of ecosystem degradation for new global biodiversity targets.
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Nogueira, MG, M. Ferrareze, ML Moreira, and RM Gouvêa. "Phytoplankton assemblages in a reservoir cascade of a large tropical - subtropical river (SE, Brazil)." Brazilian Journal of Biology 70, no. 3 suppl (October 2010): 781–93. http://dx.doi.org/10.1590/s1519-69842010000400009.
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The phytoplankton assemblages from eight reservoirs of the Paranapanema River were studied during two consecutive years. Chlorophyceae and Bacillaryophyceae dominated in richness. The observed high number of taxa, 234, reflects the extensive sampling programme and evidences the necessity of considering the whole hydrograph basin to assess the biodiversity status of inland water ecosystems. The dams had a negative effect on phytoplankton richness, with higher number of taxa associate to riverine (non-regulated) stretches. The tributary rivers also exhibited high species richness, showing the importance of considering the lateral dimension, in addition to the longitudinal one, for aquatic biota inventories in large river basins/reservoirs. Richness and diversity were also positively influenced by the connectivity with lateral wetlands (macrophyte-dominated lakes) due to the periphyton influence. The phytoplankton abundance/biomass was not influenced by higher water retention time. Higher values occurred in the middle basin stretches (river-passage reservoirs) due to the increase in the trophic conditions. There was a positive correlation with phosphorus. Poorer light conditions in the cascade do not limit the phytoplankton biomass, with assemblages dominated by species tolerant to turbulent conditions and high mineral turbidity. Bacillariophyceae and Cryptophyceae dominated numerically. The first group (unicellular forms) was prominent in the large and oligotrophic upstream reservoirs. The second was highly abundant in the river-passage (low retention time), and more eutrophic, reservoirs. Cyanophyceae growth is probably controlled by advection processes (wash-out effect). The zooplankton does not control the phytoplankton biomass and the diversity of both groups is positively associated in the cascade. The structure of the phytoplankton assemblages showed to be a good indicator of the operationally distinct reservoirs of the Paranapanema cascade and also reflected the changes in the trophic conditions along the basin.
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Rodríguez-Romero, Alexis, Axel Rico-Sánchez, Erick Mendoza-Martínez, Andrea Gómez-Ruiz, Jacinto Sedeño-Díaz, and Eugenia López-López. "Impact of Changes of Land Use on Water Quality, from Tropical Forest to Anthropogenic Occupation: A Multivariate Approach." Water 10, no. 11 (October 26, 2018): 1518. http://dx.doi.org/10.3390/w10111518.
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Worldwide, it is acknowledged that changes of land use influence water quality; however, in tropical forests, the relationship between land use and water quality is still poorly understood. This study assessed spatial and seasonal variations in water quality, and the relationship between water quality and changes of land use in the Bobos-Nautla River, whose upper course runs across a patch of a tropical cloud forest. Spatial and seasonal variations in water quality and land use were assessed with multivariate tools. A cluster analysis, as well as a Principal Component Analysis (PCA-3D), identified three groups of sites: (1) an upper portion, which showed the best water quality and the broadest natural vegetation coverage; (2) a middle course, with high nitrogen and phosphorus concentrations associated with extensive agricultural uses; and (3) a lower course, characterized by the highest levels of total and fecal coliforms, as well as ammonia nitrogen, associated with the highest percentage of urbanization and human settlements. Our findings demonstrate the impact of changes of land use on water quality of rivers running through cloud forests in tropical zones, which are currently endangered ecosystems.
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Ambe, Benjamin A., and Usang N. Onnoghen. "Ecosystems Services of the Tropical Rain Forest Environment: Lessons from the Cross River National Park, Nigeria." Journal of Geoscience and Environment Protection 07, no. 11 (2019): 1–10. http://dx.doi.org/10.4236/gep.2019.711001.
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Zurbrügg, R., S. Suter, M. F. Lehmann, B. Wehrli, and D. B. Senn. "Organic carbon and nitrogen export from a tropical dam-impacted floodplain system." Biogeosciences 10, no. 1 (January 4, 2013): 23–38. http://dx.doi.org/10.5194/bg-10-23-2013.
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Abstract. Tropical floodplains play an important role in organic matter transport, storage, and transformation between headwaters and oceans. However, the fluxes and quality of organic carbon (OC) and organic nitrogen (ON) in tropical river-floodplain systems are not well constrained. We explored the quantity and characteristics of dissolved and particulate organic matter (DOM and POM, respectively) in the Kafue River flowing through the Kafue Flats (Zambia), a tropical river-floodplain system in the Zambezi River basin. During the flooding season, > 80% of the Kafue River water passed through the floodplain, mobilizing large quantities of OC and ON, which resulted in a net export of 69–119 kg OC km−2 d−1 and 3.8–4.7 kg ON km−2 d−1, 80% of which was in the dissolved form. The elemental C : N ratio of ~ 20, the comparatively high δ13C values of −25‰ to −21‰, and its spectroscopic properties (excitation-emission matrices) showed that DOM in the river was mainly of terrestrial origin. Despite a threefold increase in OC loads due to inputs from the floodplain, the characteristics of the riverine DOM remained relatively constant along the sampled 410-km river reach. This suggests that floodplain DOM displayed properties similar to those of DOM leaving the upstream reservoir and implied that the DOM produced in the reservoir was relatively short-lived. In contrast, the particulate fraction was 13C-depleted (−29‰) and had a C : N ratio of ~ 8, which indicated that POM originated from phytoplankton production in the reservoir and in the floodplain, rather than from plant debris or resuspended sediments. While the upstream dam had little effect on the DOM pool, terrestrial particles were retained, and POM from algal and microbial sources was released to the river. A nitrogen mass balance over the 2200 km2 flooded area revealed an annual deficit of 15 500–22 100 t N in the Kafue Flats. The N isotope budget suggests that these N losses are balanced by intense N-fixation. Our study shows that the Kafue Flats are a significant local source of OC and ON to downstream ecosystems and illustrates how the composition of riverine OM can be altered by dams and floodplains in tropical catchments.
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Kroon, F. J., and J. A. Ludwig. "Response and recovery of fish and invertebrate assemblages following flooding in five tributaries of a sub-tropical river." Marine and Freshwater Research 61, no. 1 (2010): 86. http://dx.doi.org/10.1071/mf08357.
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The response and recovery of aquatic ecosystems to major flooding is directly associated with the resistance and resilience of the perturbed ecosystem. In this 2-year study, we document the response of taxa assemblages in five tributary creeks of the Clarence River, Australia, following two sequential floods. Prior to the floods, we observed clear differences of taxa assemblages among tributaries, and clear but relatively small seasonal changes in all creeks. Flooding triggered large shifts in taxa assemblages in all creeks; however, only a few species out of the 106 taxa analysed were contributing to this pulse response. Combinations of specific water quality variables were significantly associated with the observed patterns in taxa assemblages in all but one creek. After an initial rapid recovery period, taxa compositions in all tributaries more slowly returned to resemble those before the floods. This strong resilience to major floods is most likely associated with high flushing rates, spatial and temporal refugia and life history characteristics of key biota. Overall, the results suggest that the current state of the Clarence floodplain has achieved a strong resilience to major flood disturbances, and that a shift to an alternate, potentially more desirable state may be difficult to achieve.
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Gabardo, I. T., M. E. R. Carneiro, L. V. Falcão, M. F. G. Meniconi, S. M. Barband, and E. B. Platte. "Oil Spills in a Tropical Country – Brazilian Case Studies." International Oil Spill Conference Proceedings 2003, no. 1 (April 1, 2003): 1039–49. http://dx.doi.org/10.7901/2169-3358-2003-1-1039.
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ABSTRACT Faced with the latest experiences on Brazilian oil spill incidents, Petrobras has been trying to overcome many challenges in environmental management and operational safety, aiming to prevent environmental risks. This paper presents the oil characterizations and monitoring studies in affected ecosystems such as the hot spots on soils affected by the Iguassu River oil spill (occurred in July 2000, due to a pipeline rupture in the scraper area of REPAR, a Petrobras refinery located in the state of Parana), by the Vessel Vergina II oil spill in São Sebastião channel (located in the state of São Paulo, occurred in November 2000) and lastly, the Guanabara Bay oil spill (a pipeline rupture that occurred in January 2000, due to a pipeline rupture between oil terminal and REDUC, a Petrobras refinery located in the state of Rio de Janeiro). Chemical analysis were performed in different sample matrixes including many parameters such as total petroleum hydrocarbons (TPH), aliphatic compounds (n-alkanes), unresolved complex mixtures (UCM), benzene, toluene, ethylbenzene and xylenes (BTEX), polycyclic aromatic hydrocarbons (PAH), terpanes and steranes, that are the parameters usually monitored after a spill oil. Visual inspections were also performed mainly in Guanabara Bay in order to identify the affected ecosystems by the spilled oil and to plot maps of classified regions based on the level of visual oil contamination. The acute toxicity was evaluated in water soluble fraction (WSF) of the spilled oils using ecotoxicological tests.
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Barrios E. and Herrera R. "Nitrogen cycling in a Venezuelan tropical seasonally flooded forest: soil nitrogen mineralization and nitrification." Journal of Tropical Ecology 10, no. 3 (August 1994): 399–416. http://dx.doi.org/10.1017/s0266467400008075.
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ABSTRACTSeasonally flooded forests represent a transition between terrestrial and aquatic ecosystems. The Mapire river, a tributary of the Orinoco river, floods its surrounding forests during the wet season (May–December). The soils are very acid and the total nitrogen concentration (0.1%) is only half that found in nearby soils flooded by Orinoco waters. Ammonium-nitrogen predominates in the soil during the flooded period while nitrate-nitrogen concentrations are higher in the dry period. Wide fluctuations in the inorganic nitrogen fractions did not considerably affect the annual course of soil nitrogen.The predominance of mineralization versus nitrification (56 and 5 μgsoil month−1respectively) and possibly the synchronization of nitrogen availability with plant demand could be considered as nitrogen conserving mechanisms.In synchrony with the hydrologic cycle, the seasonally flooded forest studied shows a nitrogencycle where inputs and accumulation are maximized when the system is under minimum stress (dry season). During flooding, the system enters a period of dormancy making minimal use of nutrient and energy to avoid or tolerate anaerobiosis.
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Camargo, M., T. Giarrizzo, and AJS Jesus. "Effect of seasonal flooding cycle on litterfall production in alluvial rainforest on the middle Xingu River (Amazon basin, Brazil)." Brazilian Journal of Biology 75, no. 3 suppl 1 (August 2015): 250–56. http://dx.doi.org/10.1590/1519-6984.00514bm.
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Abstract The assumption for this study was that litterfall in floodplain environments of the middle Xingu river follows a pattern of seasonal variation. According to this view, litterfall production (total and fractions) was estimated in four alluvial rainforest sites on the middle Xingu River over an annual cycle, and examined the effect of seasonal flooding cycle. The sites included two marginal flooded forests of insular lakes (Ilha Grande and Pimentel) and two flooded forests on the banks of the Xingu itself (Boa Esperança and Arroz Cru). Total litterfall correlated with rainfall and river levels, but whereas the leaf and fruit fractions followed this general pattern, the flower fraction presented an inverse pattern, peaking in the dry season. The litterfall patterns recorded in the present study were consistent with those recorded at other Amazonian sites, and in some other tropical ecosystems.
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Koletić, Nikola, Antun Alegro, Anja Rimac, Nina Vuković, Vedran Šegota, and Tihana Vilović. "Environmental preferences of Polysiphonia subtilissima (Ceramiales, Rhodophyta) in transitional, oligohaline and fresh waters of the East Adriatic coast." Nova Hedwigia 111, no. 1 (August 1, 2020): 39–58. http://dx.doi.org/10.1127/nova_hedwigia/2020/0593.
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Polysiphonia subtilissima is originally a marine macroalga with a wide tolerance for salinity and therefore present on nearly all the coastlines of the planet. However, the transition of P. subtilissima toward freshwater ecosystems has been noticed worldwide, with numerous authors recording oligohaline and intertidal populations of notable size, although only three localities (Florida, Jamaica and Spain) with truly freshwater populations have been registered to date. This paper reports large populations of P. subtilissima in transitional, oligohaline and freshwater ecosystems of the Adriatic Sea Basin (Croatia, Southeast Europe). The alga was recorded in salinity ranging from 0.42 to 4.59 in the waters of the Neretva River Valley, and at 18.2 in transitional waters in the Zrmanja River. Along with P. subtilissima, the freshwater tropical red alga Compsopogon caeruleus has been recorded in the Neretva River Valley, being the first record of this species for Croatia and SE Europe. This particular combination of species has previously been recorded in freshwater localities only in Florida, Jamaica and Spain. Measured environmental parameters and species composition were analysed using canonical correspondence analysis and Gaussian response model, which showed that both species prefer waters with temperatures above 20 °C, high water conductivity, pH values above 7.5, and elevated water turbidity.
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Rocha, RRA, SM Thomaz, P. Carvalho, and LC Gomes. "Modeling chlorophyll-a and dissolved oxygen concentration in tropical floodplain lakes (Paraná River , Brazil)." Brazilian Journal of Biology 69, no. 2 suppl (June 2009): 491–500. http://dx.doi.org/10.1590/s1519-69842009000300005.
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The need for prediction is widely recognized in limnology. In this study, data from 25 lakes of the Upper Paraná River floodplain were used to build models to predict chlorophyll-a and dissolved oxygen concentrations. Akaike's information criterion (AIC) was used as a criterion for model selection. Models were validated with independent data obtained in the same lakes in 2001. Predictor variables that significantly explained chlorophyll-a concentration were pH, electrical conductivity, total seston (positive correlation) and nitrate (negative correlation). This model explained 52% of chlorophyll variability. Variables that significantly explained dissolved oxygen concentration were pH, lake area and nitrate (all positive correlations); water temperature and electrical conductivity were negatively correlated with oxygen. This model explained 54% of oxygen variability. Validation with independent data showed that both models had the potential to predict algal biomass and dissolved oxygen concentration in these lakes. These findings suggest that multiple regression models are valuable and practical tools for understanding the dynamics of ecosystems and that predictive limnology may still be considered a powerful approach in aquatic ecology.
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Moore, S., V. Gauci, C. D. Evans, and S. E. Page. "Fluvial organic carbon losses from a Bornean blackwater river." Biogeosciences Discussions 7, no. 6 (November 12, 2010): 8319–43. http://dx.doi.org/10.5194/bgd-7-8319-2010.
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Abstract. The transport of carbon from terrestrial ecosystems such as peatlands into rivers and out to the oceans plays an important role in the carbon cycle because it provides a link between the terrestrial and marine carbon cycles. Concentrations of dissolved organic carbon (DOC) and particulate organic carbon (POC) were analysed from the source to the mouth of the River Sebangau in Central Kalimantan, Indonesia during the dry and wet seasons in 2008/2009 and an annual total organic carbon (TOC) flux estimated. DOC concentrations were higher and POC concentrations lower in the wet season compared to the dry season. As seen in other tropical blackwater rivers, DOC concentration is consistently around 10 times greater than POC concentration. We estimate the annual TOC flux discharged to the Java Sea to be 0.46 Tg year−1 comprising of 93% (0.43 Tg) DOC and 7% (0.03 Tg) POC. This equates to a fluvial TOC loss flux per unit area over the entire Sebangau catchment of 88 g C m−2 yr−1. When extrapolating this TOC loss flux to the peat covered area of Indonesia (206 950 km2), we estimate a TOC loss of 18.2 Tg C yr−1 or ~10% of current estimates of the global annual riverine DOC discharge into the ocean.
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Martínez-Camilo, Rubén, José Alberto Gallardo-Cruz, Jonathan V. Solórzano, Candelario Peralta-Carreta, Derio Antonio Jiménez-López, Ofelia Castillo-Acosta, Miguelina Sánchez-González, and Jorge A. Meave. "An Assessment of the Spatial Variability of Tropical Swamp Forest along a 300 km Long Transect in the Usumacinta River Basin, Mexico." Forests 11, no. 12 (November 24, 2020): 1238. http://dx.doi.org/10.3390/f11121238.
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The provision of valuable ecosystem services by tropical swamp forests (mainly carbon sequestration and storage in biomass and soil) explains their ecological importance. Current efforts toward the conservation of these ecosystems, however, face strong limitations as their spatial variation is largely unknown, particularly in regions where they occur over large areas. Here, we analyze the α-diversity (i.e., effective number of species or true diversity) and community structure variability of three tropical swamp forest communities distributed along an approximately 300 km long portion of the Usumacinta River Basin, southern Mexico. We sampled eighty-three 625-m2 plots to characterize the diversity and structural attributes of the woody plant communities. We recorded 2302 individuals belonging to 60 species and 25 families. Both α-diversity and structural attributes differed significantly among the three communities. The most inland community stood out for having the highest α-diversity for three true diversity values. Interestingly, the mangrove Rhizophora mangle L. was one of the dominant species, both in the swamp forest located closest to the coast and in the community farthest away from the sea. Basal area and density of individuals also had their maxima in the most inland swamp forest. The diversity and structural differences observed among the examined swamp forests seem to be related to contrasting environmental conditions, such as water salinity, distance to the coastline, and the hydrological dynamics of the Usumacinta River. We emphasize the urgency to conserve R. mangle populations in the swamp forest located farthest away from the coast due to its unusual habitat association, which appears to be a relictual condition.
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Chará-Serna, Ana M., Julián D. Chará, María Del Carmen Zúñiga, Gloria X. Pedraza, and Lina P. Giraldo. "Clasificación trófica de insectos acuáticos en ocho quebradas protegidas de la ecorregión cafetera colombiana." Universitas Scientiarum 15, no. 1 (January 1, 2010): 27. http://dx.doi.org/10.11144/javeriana.sc15-1.tcoa.
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<p><strong>Objective. </strong>To determine the trophic structure of an aquatic insect assembly associated to eight streams in the Colombian coffee-growing ecoregion. <strong>Materials and methods. </strong>Aquatic insects were collected in eight forested streams located in La Vieja river basin. The taxa collected were assigned to dietary groups according to a regional classification based on the gut content analysis of aquatic insects associated to forested streams of the Otún river basin. <strong>Results. </strong>2019 individuals belonging to 73 taxa were collected and 60 were classified into dietary groups. The most abundant group was collectors (55%), followed by shredders (31%) and predators (10%). Scrapers represented only 0.05% of the sample and the remaining 3.95% could not be classified due to lack of information. <strong>Conclusions. </strong>The dominance of collectors and shredders reveals the importance of coarse particulate organic matter (leaf litter) as a food resource for the insect fauna. Similarities between the trophic structure of this community and other communities studied in similar streams, suggest the possibility of a common pattern for Andean streams. This study evidenced the absence of knowledge on trophic ecology of tropical aquatic insects; 50% of the taxa collected had no associated information for the tropics and 20% had no information neither for the tropics nor temperate zones.</p> <p><strong>Key words</strong>: Andean streams, aquatic insects, dietary groups, trophic structure, tropical ecosystems.</p><br />
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Barr, J. G., J. D. Fuentes, M. S. DeLonge, T. L. O'Halloran, D. Barr, and J. C. Zieman. "Summertime influences of tidal energy advection on the surface energy balance in a mangrove forest." Biogeosciences 10, no. 1 (January 25, 2013): 501–11. http://dx.doi.org/10.5194/bg-10-501-2013.
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Abstract. Mangrove forests are ecosystems susceptible to changing water levels and temperatures due to climate change as well as perturbations resulting from tropical storms. Numerical models can be used to project mangrove forest responses to regional and global environmental changes, and the reliability of these models depends on surface energy balance closure. However, for tidal ecosystems, the surface energy balance is complex because the energy transport associated with tidal activity remains poorly understood. This study aimed to quantify impacts of tidal flows on energy dynamics within a mangrove ecosystem. To address the research objective, an intensive 10-day study was conducted in a mangrove forest located along the Shark River in the Everglades National Park, FL, USA. Forest–atmosphere turbulent exchanges of energy were quantified with an eddy covariance system installed on a 30-m-tall flux tower. Energy transport associated with tidal activity was calculated based on a coupled mass and energy balance approach. The mass balance included tidal flows and accumulation of water on the forest floor. The energy balance included temporal changes in enthalpy, resulting from tidal flows and temperature changes in the water column. By serving as a net sink or a source of available energy, flood waters reduced the impact of high radiational loads on the mangrove forest. Also, the regression slope of available energy versus sink terms increased from 0.730 to 0.754 and from 0.798 to 0.857, including total enthalpy change in the water column in the surface energy balance for 30-min periods and daily daytime sums, respectively. Results indicated that tidal inundation provides an important mechanism for heat removal and that tidal exchange should be considered in surface energy budgets of coastal ecosystems. Results also demonstrated the importance of including tidal energy advection in mangrove biophysical models that are used for predicting ecosystem response to changing climate and regional freshwater management practices.
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Barr, J. G., J. D. Fuentes, M. S. DeLonge, T. L. O'Halloran, D. Barr, and J. C. Zieman. "Influences of tidal energy advection on the surface energy balance in a mangrove forest." Biogeosciences Discussions 9, no. 8 (August 30, 2012): 11739–65. http://dx.doi.org/10.5194/bgd-9-11739-2012.
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Abstract. Mangrove forests are ecosystems susceptible to changing water levels and temperatures due to climate change as well as perturbations resulting from tropical storms. Numerical models can be used to project mangrove forest responses to regional and global environmental changes, and the reliability of these models depends on surface energy balance closure. However, for tidal ecosystems, the surface energy balance is complex because the energy transport associated with tidal activity remains poorly understood. This study aimed to quantify impacts of tidal flows on energy dynamics within a mangrove ecosystem. To address the research objective, an intensive study was conducted in a mangrove forest located along the Shark River in the Everglades National Park, FL. Forest-atmosphere energy exchanges were quantified with an eddy covariance system deployed on a flux tower. The lateral energy transport associated with tidal activity was calculated based on a coupled mass and energy balance approach. The mass balance included tidal flows and accumulation of water on the forest floor. The energy balance included temporal changes in enthalpy, resulting from tidal flows and temperature changes in the water column. By serving as a net sink or a source of available energy, tidal flows reduced the impact of high radiational loads on the mangrove forest. Including tidal energy advection in the surface energy balance improved the 30-min daytime energy closure from 73% to 82% over the study period. Also, the cumulative sum of energy output improved from 79% to 91% of energy input during the study period. Results indicated that tidal inundation provides an important mechanism for heat removal and that tidal exchange should be considered in surface energy budgets of coastal ecosystems. Results also demonstrated the importance of including tidal energy advection in mangrove biophysical models that are used for predicting ecosystem response to changing climate and regional freshwater management practices.
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Molinari, Bianca, Ben Stewart-Koster, Tim J. Malthus, and Stuart E. Bunn. "Assessing Spatial Variation in Algal Productivity in a Tropical River Floodplain Using Satellite Remote Sensing." Remote Sensing 13, no. 9 (April 28, 2021): 1710. http://dx.doi.org/10.3390/rs13091710.
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Studies of tropical floodplains have shown that algae are the primary source material for higher consumers in freshwater aquatic habitats. Thus, methods that can predict the spatial variation of algal productivity provide an important input to better inform management and conservation of floodplains. In this study, a prediction of the spatial variability in algal productivity was made for the Mitchell River floodplain in northern Australia. The spatial variation of aquatic habitat types and turbidity were estimated using satellite remote sensing and then combined with statistical modelling to map the spatial variation in algal primary productivity. Open water and submerged plants habitats, covering 79% of the freshwater flooded floodplain extent, had higher rates of algal production compared to the 21% cover of emergent and floating aquatic plant habitats. Across the floodplain, the predicted average algal productivity was 150.9 ± 95.47 SD mg C m−2 d−1 and the total daily algal production was estimated to be 85.02 ± 0.07 SD ton C. This study provides a spatially explicit representation of habitat types, turbidity, and algal productivity on a tropical floodplain and presents an approach to map ‘hotspots’ of algal production and provide key insights into the functioning of complex floodplain–river ecosystems. As this approach uses satellite remotely sensed data, it can be applied in different floodplains worldwide to identify areas of high ecological value that may be sensitive to development and be used by decision makers and river managers to protect these important ecological assets.
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Norris, Darren, Fernanda Michalski, and James P. Gibbs. "Beyond harm’s reach? Submersion of river turtle nesting areas and implications for restoration actions after Amazon hydropower development." PeerJ 6 (January 8, 2018): e4228. http://dx.doi.org/10.7717/peerj.4228.
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The global expansion of energy demands combined with abundant rainfall, large water volumes and high flow in tropical rivers have led to an unprecedented expansion of dam constructions in the Amazon. This expansion generates an urgent need for refined approaches to river management; specifically a move away from decision-making governed by overly generalized guidelines. For the first time we quantify direct impacts of hydropower reservoir establishment on an Amazon fresh water turtle. We conducted surveys along 150 km of rivers upstream of a new dam construction during the low water months that correspond to the nesting season of Podocnemis unifilis in the study area. Comparison of nest-areas before (2011, 2015) and after (2016) reservoir filling show that reservoir impacts extend 13% beyond legally defined limits. The submerged nesting areas accounted for a total of 3.8 ha of nesting habitat that was inundated as a direct result of the reservoir filling in 2016. Our findings highlight limitations in the development and implementation of existing Brazilian environmental impact assessment process. We also propose potential ways to mitigate the negative impacts of dams on freshwater turtles and the Amazonian freshwater ecosystems they inhabit.
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Cantonati, Poikane, Pringle, Stevens, Turak, Heino, Richardson, et al. "Characteristics, Main Impacts, and Stewardship of Natural and Artificial Freshwater Environments: Consequences for Biodiversity Conservation." Water 12, no. 1 (January 16, 2020): 260. http://dx.doi.org/10.3390/w12010260.
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In this overview (introductory article to a special issue including 14 papers), we consider all main types of natural and artificial inland freshwater habitas (fwh). For each type, we identify the main biodiversity patterns and ecological features, human impacts on the system and environmental issues, and discuss ways to use this information to improve stewardship. Examples of selected key biodiversity/ecological features (habitat type): narrow endemics, sensitive (groundwater and GDEs); crenobionts, LIHRes (springs); unidirectional flow, nutrient spiraling (streams); naturally turbid, floodplains, large-bodied species (large rivers); depth-variation in benthic communities (lakes); endemism and diversity (ancient lakes); threatened, sensitive species (oxbow lakes, SWE); diverse, reduced littoral (reservoirs); cold-adapted species (Boreal and Arctic fwh); endemism, depauperate (Antarctic fwh); flood pulse, intermittent wetlands, biggest river basins (tropical fwh); variable hydrologic regime—periods of drying, flash floods (arid-climate fwh). Selected impacts: eutrophication and other pollution, hydrologic modifications, overexploitation, habitat destruction, invasive species, salinization. Climate change is a threat multiplier, and it is important to quantify resistance, resilience, and recovery to assess the strategic role of the different types of freshwater ecosystems and their value for biodiversity conservation. Effective conservation solutions are dependent on an understanding of connectivity between different freshwater ecosystems (including related terrestrial, coastal and marine systems).
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Sheaves, Marcus, Nguyen Huu Duc, and Nguyen Xuan Khoa. "Ecological attributes of a tropical river basin vulnerable to the impacts of clustered hydropower developments." Marine and Freshwater Research 59, no. 11 (2008): 971. http://dx.doi.org/10.1071/mf08029.
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The Vu Gia – Thu Bon River Basin in central Vietnam is subject to extensive hydropower development, with eight major and at least 34 minor hydropower installations planned for completion over the next 10 years. This intense clustering of hydropower developments has the potential to impact on aquatic fauna and ecosystems extensively. We sampled freshwater and estuarine fish across the river basin to evaluate the current status of the fish fauna, to determine the extent of zonal and habitat specialisation, to determine the prevalence of migration as a component of life-history strategies, to evaluate the likely magnitude of impacts, and to highlight areas where management intervention is needed and where more extensive study is most urgently required. Given the current high levels of exploitation, the fish fauna appeared surprisingly intact; however, a number of attributes of the fauna, such as the prevalence of migration as a life-history tactic, make this fauna particularly vulnerable to the impacts of hydropower development. Without extensive mitigation, the combinations of habitat alteration in dam and diversion areas and the imposition of a proliferation of barriers to migration will lead to severe population fragmentation, increasing the potential for local extinction, and severely compromise opportunities for recolonisation.
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Buschman, F. A., A. J. F. Hoitink, S. M. de Jong, P. Hoekstra, H. Hidayat, and M. G. Sassi. "Suspended sediment load in the tidal zone of an Indonesian river." Hydrology and Earth System Sciences 16, no. 11 (November 13, 2012): 4191–204. http://dx.doi.org/10.5194/hess-16-4191-2012.
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Abstract. Forest clearing for reasons of timber production, open pit mining and the establishment of oil palm plantations generally results in excessively high sediment loads in tropical rivers. The increasing sediment loads pose a threat to coastal marine ecosystems, such as coral reefs. This study presents observations of suspended sediment loads in the Berau River (Kalimantan, Indonesia), which debouches into a coastal ocean that is a preeminent center of coral diversity. The Berau River is relatively small and drains a mountainous, still relatively pristine basin that receives abundant rainfall. In the tidal zone of the Berau River, flow velocity was measured over a large part of the river width using a horizontal acoustic Doppler current profiler (HADCP). Surrogate measurements of suspended sediment concentration were taken with an optical backscatter sensor (OBS). Averaged over the 6.5 weeks covered by the benchmark survey period, the suspended sediment load was estimated at 2 Mt yr−1. Based on rainfall-runoff modeling though, the river discharge peak during the survey was supposed to be moderate and the yearly averaged suspended sediment load is most likely somewhat higher than 2 Mt yr−1. The consequences of ongoing clearing of rainforest were explored using a plot-scale erosion model. When rainforest, which still covered 50–60% of the basin in 2007, is converted to production land, soil loss is expected to increase with a factor between 10 and 100. If this soil loss is transported seaward as suspended sediment, the increase in suspended sediment load in the Berau River would impose a severe stress on this global hotspot of coral reef diversity.
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Unami, Koichi, Rasha M. Fadhil, and Md Rowshon Kamal. "Rainfall-Runoff Models with Fractional Derivatives Applied to Kurau River Basin, Perak, Malaysia." Basrah Journal of Agricultural Sciences 34 (August 19, 2021): 34–40. http://dx.doi.org/10.37077/25200860.2021.34.sp1.4.
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Kurau River Basin (KRB), which covers an area of 322 km2 and is the main drainage artery pouring into Bukit Merah Reservoir (BMR), is located in Perak State of Malaysia. The study of rainfall-runoff processes in KRB is important because BMR plays a vital role in rice production, flood control, ecosystems, and tourism in the region. This study proposes a new approach to rainfall-runoff modeling based on the fractional calculus. A dataset of daily rainfall and streamflow has been acquired. Then, the standard linear autoregressive with exogenous input (ARX) model is identified from the dataset in the sense of least square error. We consider the ARX model as a discretized differential equation with fractional orders. Such a model with fractional derivatives is versatile to represent hysteresis, which is intrinsically linked to the real runoff processes in tropical catchment basins like KRB.
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de Lima Barros, Alessandra Maciel, Maria do Carmo Sobral, and Günter Gunkel. "Modelling of point and diffuse pollution: application of the Moneris model in the Ipojuca river basin, Pernambuco State, Brazil." Water Science and Technology 68, no. 2 (July 1, 2013): 357–65. http://dx.doi.org/10.2166/wst.2013.086.
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Emissions of pollutants and nutrients are causing several problems in aquatic ecosystems, and in general an excess of nutrients, specifically nitrogen and phosphorus, is responsible for the eutrophication process in water bodies. In most developed countries, more attention is given to diffuse pollution because problems with point pollution have already been solved. In many non-developed countries basic data for point and diffuse pollution are not available. The focus of the presented studies is to quantify nutrient emissions from point and diffuse sources in the Ipojuca river basin, Pernambuco State, Brazil, using the Moneris model (Modelling Nutrient Emissions in River Systems). This model has been developed in Germany and has already been implemented in more than 600 river basins. The model is mainly based on river flow, water quality and geographical information system data. According to the Moneris model results, untreated domestic sewage is the major source of nutrients in the Ipojuca river basin. The Moneris model has shown itself to be a useful tool that allows the identification and quantification of point and diffuse nutrient sources, thus enabling the adoption of measures to reduce them. The Moneris model, conducted for the first time in a tropical river basin with intermittent flow, can be used as a reference for implementation in other watersheds.
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Kim, Jong-Suk, Shaleen Jain, and Taesam Lee. "Changes in the wintertime hydroclimatic regime in St. John River, Maine, USA." Journal of Water and Climate Change 12, no. 5 (February 2, 2021): 2082–92. http://dx.doi.org/10.2166/wcc.2021.230.
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Abstract Changes in the flow regime in snowmelt- and ice-dominated rivers have important implications for navigation, flood hazard, recreation, and ecosystems. We investigated recent changes in the high flows of the St. John River basin in Maine, USA, with a view to quantify changes in high-flow characteristics, as well as extreme event estimates. The results analyzed herein demonstrate shifts in springtime streamflow as well as in emergent wintertime (January–February) streamflow over the past four decades. A Poisson-based regression approach was applied to develop a model for the diagnosis of weather–climate linkage. The sensitivity of episodic warm weather events to the negative phase of the Tropical–Northern Hemisphere (TNH) atmospheric teleconnection pattern is evident. Although a modest sample size of historical data on the weather–climate linkage imposes a limit in terms of reliability, the approach presented herein shows a modest role of the TNH pattern, in response to the warm phase of El Niño/Southern Oscillation, as one of the factors that contribute to hydroclimate variability in the St. John River basin. This diagnostic study sought to investigate the changes in the wintertime streamflow regime and the relative linkages with short-term concurrent weather events, as well as large-scale climatic linkages. This improved an understanding of hydrological extremes within a climatological context and offers new knowledge to inform water resources planning and decision-making.
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Gelete, Gebre, Huseyin Gokcekus, and Tagesse Gichamo. "Impact of climate change on the hydrology of Blue Nile basin, Ethiopia: a review." Journal of Water and Climate Change 11, no. 4 (October 3, 2019): 1539–50. http://dx.doi.org/10.2166/wcc.2019.014.
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Abstract Climate change alters the spacial and temporal availability of water resources by affecting the hydrologic cycle. The main objective of this paper is to review the climate change effect on the water resources of the Blue Nile River, Ethiopia. The impact of climate change on water resources is highly significant as all natural ecosystems and humans are heavily dependent on water. It alters precipitation, temperature, and streamflow of the Blue Nile river basin which is threatening the lives and livelihoods of people and life-supporting systems. Rainfall within the Blue Nile river basin is highly erratic and seasonal due to it being located in the inter-tropical convergent zone. The temperature and sediment load are shown to increase in the future while the rainfall and streamflow are decreasing. The Blue Nile basin is characterized by highly erosive rainfall, erodible soil, and shrinking forest cover. Therefore, mitigation and adaptation measures should be applied by considering these characteristics of the basin. Watershed management methods like afforestation and water conservation are recommended to reduce the impact on the Blue Nile basin.
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Betts, R. A., N. Golding, P. Gonzalez, J. Gornall, R. Kahana, G. Kay, L. Mitchell, and A. Wiltshire. "Climate and land use change impacts on global terrestrial ecosystems and river flows in the HadGEM2-ES Earth system model using the representative concentration pathways." Biogeosciences 12, no. 5 (March 3, 2015): 1317–38. http://dx.doi.org/10.5194/bg-12-1317-2015.
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Abstract. A new generation of an Earth system model now includes a number of land-surface processes directly relevant to analyzing potential impacts of climate change. This model, HadGEM2-ES, allows us to assess the impacts of climate change, multiple interactions, and feedbacks as the model is run. This paper discusses the results of century-scale HadGEM2-ES simulations from an impacts perspective – specifically, terrestrial ecosystems and water resources – for four different scenarios following the representative concentration pathways (RCPs), used in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2013, 2014). Over the 21st century, simulated changes in global and continental-scale terrestrial ecosystems due to climate change appear to be very similar in all 4 RCPs, even though the level of global warming by the end of the 21st century ranges from 2 °C in the lowest scenario to 5.5° in the highest. A warming climate generally favours broadleaf trees over needleleaf, needleleaf trees over shrubs, and shrubs over herbaceous vegetation, resulting in a poleward shift of temperate and boreal forests and woody tundra in all scenarios. Although climate related changes are slightly larger in scenarios of greater warming, the largest differences between scenarios arise at regional scales as a consequence of different patterns of anthropogenic land cover change. In the model, the scenario with the lowest global warming results in the most extensive decline in tropical forest cover due to a large expansion of agriculture. Under all four RCPs, fire potential could increase across extensive land areas, particularly tropical and sub-tropical latitudes. River outflows are simulated to increase with higher levels of CO2 and global warming in all projections, with outflow increasing with mean temperature at the end of the 21st century at the global scale and in North America, Asia, and Africa. In South America, Europe, and Australia, the relationship with climate warming and CO2 rise is less clear, probably as a result of land cover change exerting a dominant effect in those regions.
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Betts, R. A., N. Golding, P. Gonzalez, J. Gornall, R. Kahana, G. Kay, L. Mitchell, and A. Wiltshire. "Climate and land use change impacts on global terrestrial ecosystems, fire, and river flows in the HadGEM2-ES Earth System Model using the Representative Concentration Pathways." Biogeosciences Discussions 10, no. 4 (April 2, 2013): 6171–223. http://dx.doi.org/10.5194/bgd-10-6171-2013.
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Abstract. A new generation of an Earth System Model now includes a number of land surface processes directly relevant to analyzing potential impacts of climate change. This model, HadGEM2-ES, allows us to assess the impacts of climate change, multiple interactions, and feedbacks as the model is run. This paper discusses the results of century-scale HadGEM2-ES simulations from an impacts perspective–specifically, terrestrial ecosystems and water resources–for four different scenarios following the Representative Concentration Pathways (RCPs), being used for next assessment report of the Intergovernmental Panel on Climate Change (IPCC). Over the 21st Century, simulated changes in global and continential-scale terrestrial ecosystems due to climate change appear to be very similar in all 4 RCPs, even though the level of global warming by the end of the 21st Century ranges from 2 °C in the lowest scenario to 5.5° in the highest. A warming climate generally favours broadleaf trees over needleleaf, needleleaf trees over shrubs, and shrubs over herbaceous vegetation, resulting in a poleward shift of temperate and boreal forests and woody tundra in all scenarios. Although climate related changes are slightly larger in scenarios of greater warming, the largest differences between scenarios arise at regional scales as a consequence of different patterns of anthropogenic land cover change. In the model, the scenario with the lowest global warming results in the most extensive decline in tropical forest cover due to a large expansion of agriculture. Under all four RCPs, fire potential could increase across extensive land areas, particularly tropical and sub-tropical latitudes. River outflows are simulated to increase with higher levels of CO2 and global warming in all projections, with outflow increasing with mean temperature at the end of the 21st Century at the global scale and in North America, Asia, and Africa. In South America, Europe, and Australia, the relationship with climate warming and CO2 rise is less clear, probably as a result of land cover change exerting a dominant effect in those regions.
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Chen, Yixiang, Shiquan Lin, Chunsheng Wang, Juan Yang, and Dong Sun. "Response of size and trophic structure of zooplankton community to marine environmental conditions in the northern South China Sea in winter." Journal of Plankton Research 42, no. 3 (May 2020): 378–93. http://dx.doi.org/10.1093/plankt/fbaa022.
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Abstract The South China Sea (SCS) is a semi-enclosed marginal sea. And in the northern SCS (NSCS), the Pearl River plume, mesoscale eddies and Kuroshio intrusion may influence the structure of pelagic ecosystems. Here, based on mesozooplankton samples collected in the NSCS from December 2014 to January 2015, spatial variations of mesozooplankton biomass, abundance, normalized biomass size spectra (NBSS), size structure and trophic structure were analyzed to study the response of mesozooplankton community to the influence of highly variable oceanographic environment. High biomass, abundance and intercept of NBSS for the mesozooplankton community were observed in highly productive regions (net primary production > 400 mg C m−2 day−1), such as river plume and cold eddy. No consistent spatial variation was observed for the slope of NBSS, probably because of highly dynamic marine environment in the NSCS. For the trophic structure of mesozooplankton community, the ratio of total chaetognaths biovolume to herbivores/omnivores biovolume (RTCH) was significantly high in river plume and Kuroshio intrusion. The high RTCH indicated unstable trophic structures, which may be due to extreme high proportion of smaller size individuals supported by discharge of river and transport of warm water species from the tropical western Pacific by Kuroshio intrusion, respectively.
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Chamberlain, Debbie A., Stuart R. Phinn, and Hugh P. Possingham. "Mangrove Forest Cover and Phenology with Landsat Dense Time Series in Central Queensland, Australia." Remote Sensing 13, no. 15 (August 2, 2021): 3032. http://dx.doi.org/10.3390/rs13153032.
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Wetlands are one of the most biologically productive ecosystems. Wetland ecosystem services, ranging from provision of food security to climate change mitigation, are enormous, far outweighing those of dryland ecosystems per hectare. However, land use change and water regulation infrastructure have reduced connectivity in many river systems and with floodplain and estuarine wetlands. Mangrove forests are critical communities for carbon uptake and storage, pollution control and detoxification, and regulation of natural hazards. Although the clearing of mangroves in Australia is strictly regulated, Great Barrier Reef catchments have suffered landscape modifications and hydrological alterations that can kill mangroves. We used remote sensing datasets to investigate land cover change and both intra- and inter-annual seasonality in mangrove forests in a large estuarine region of Central Queensland, Australia, which encompasses a national park and Ramsar Wetland, and is adjacent to the Great Barrier Reef World Heritage site. We built a time series using spectral, auxiliary, and phenology variables with Landsat surface reflectance products, accessed in Google Earth Engine. Two land cover classes were generated (mangrove versus non-mangrove) in a Random Forest classification. Mangroves decreased by 1480 hectares (−2.31%) from 2009 to 2019. The overall classification accuracies and Kappa coefficient for 2008–2010 and 2018–2020 land cover maps were 95% and 95%, respectively. Using an NDVI-based time series we examined intra- and inter-annual seasonality with linear and harmonic regression models, and second with TIMESAT metrics of mangrove forests in three sections of our study region. Our findings suggest a relationship between mangrove growth phenology along with precipitation anomalies and severe tropical cyclone occurrence over the time series. The detection of responses to extreme events is important to improve understanding of the connections between climate, extreme weather events, and biodiversity in estuarine and mangrove ecosystems.