Journal articles on the topic 'Estuarine systems'
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1
Barabanshchikov, E. I., and S. G. Bolshakov. "ESTUARINE-COASTAL SYSTEMS – THE TRANSITIVE ZONE BETWEEN FRESHWATER AND SEA ECOSYSTEMS." Vladimir Ya. Levanidov’s Biennial Memorial Meetings 10 (June 21, 2023): 16–25. http://dx.doi.org/10.25221/levanidov.10.02.
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The typifi cation of estuaries and the division of estuary zones of the rivers of Primorsky Territory are considered. Based on the collected data on aquatic biota and the orography of water bodies, three main types of estuaries in Primorye were identifi ed – lowland rivers with an extended estuary zone (Razdolnaya, Tumannaya and Artemovka rivers), mountain rivers with an extended estuarine zone (Kievka, Avvakumovka, Partizanskaya, Milogradovka, Margaritovka and other rivers), mountain rivers with a short estuarine zone (Zerkalnaya, Sukhodol, Barabashevka, Narva, Ryazanovka and other rivers). Characteristics are given on the basis of which the boundaries of estuaries are distinguished. The defi nition of the estuary zone is given.
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Jung, Nathalie W., Guan-hong Lee, Yoonho Jung, Steven M. Figueroa, Kenneth D. Lagamayo, Tae-Chang Jo, and Jongwi Chang. "MorphEst: An Automated Toolbox for Measuring Estuarine Planform Geometry from Remotely Sensed Imagery and Its Application to the South Korean Coast." Remote Sensing 13, no. 2 (January 19, 2021): 330. http://dx.doi.org/10.3390/rs13020330.
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The rapid advance of remote sensing technology during the last few decades provides a new opportunity for measuring detectable estuarine spatial change. Although estuarine surface area and convergence are important hydraulic parameters often used to predict long-term estuarine evolution, the majority of automated analyses of channel plan view dynamics have been specifically written for riverine systems and have limited applicability to most of the estuaries in the world. This study presents MorphEst, a MATLAB-based collection of analysis tools that automatically measure estuarine planform geometry. MorphEst uses channel masks to extract estuarine length, convergence length, estuarine shape, and areal gain and loss of estuarine surface area due to natural or human factors. Comparisons indicated that MorphEst estimates closely matched with independent measurements of estuarine surface area (r = 0.99) and channel width (r = 0.92) of 39 estuaries along the South Korean coast. Overall, this toolbox will help to improve the ability to solve research questions commonly associated with estuarine evolution as it introduces a tool to automatically measure planform geometric features from remotely sensed imagery.
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Silva Junior, Milton Goncalves, Antonio Carlos Leal Castro, and Ulrich Saint-Paul. "Comparative Analysis of Distribution of Intertidal Fish Assemblages in Different Estuarine Systems on Northern Coast of Brazil." Journal of Sustainable Development 10, no. 2 (March 30, 2017): 26. http://dx.doi.org/10.5539/jsd.v10n2p26.
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The northern coast of Brazil has more than 30 estuaries distributed along 650 km of coastline. These conditions favor the presence of relatively large fish communities in estuarine environments, but published information on the fish fauna in tidal creeks in northern Brazil is only available for some mangrove systems, and comparative studies between fish estuarine communities in different tidal creeks are less common. The choice of the study area was based on the fact that it has been poorly investigated with regard to estuarine fish fauna in comparison in mangrove tidal creeks using the same fishing gear. The objective of the present study was to compare the composition of the relative biomass of taxonomic, functional and ecological guilds of fish assemblages occurring in estuarine systems along the northern coast of Brazil. The study area of the present comparative analysis extended from the southeastern edge of the Marajoara Gulf to the western edge of the Maranhense Gulf. A comparative analysis among different estuarine systems was performed using data from other studies. The abundance of juveniles was greater in the Caeté, Curuçá and Cururuca estuaries than other estuaries. Cluster analysis separated the estuaries into two distinct groups and significant differences between these groups only exist in relation to geographical proximity. The present investigation indicates that the coastal region between the states of Pará and Maranhão is characterized by high dynamics and environmental heterogeneity, particularly with regard to changes in river discharge and tidal fluctuations. The present results underscore the importance of ecological information on ichthyofauna in tropical estuaries in order to include appropriate descriptors in conservation or restoration processes of marine communities and habitats.
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Gillanders, Bronwyn M., Travis S. Elsdon, Ian A. Halliday, Gregory P. Jenkins, Julie B. Robins, and Fiona J. Valesini. "Potential effects of climate change on Australian estuaries and fish utilising estuaries: a review." Marine and Freshwater Research 62, no. 9 (2011): 1115. http://dx.doi.org/10.1071/mf11047.
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Estuaries are especially vulnerable to the impacts of climate change because changes in climatic and hydrologic variables that influence freshwater and marine systems will also affect estuaries. We review potential impacts of climate change on Australian estuaries and their fish. Geographic differences are likely because southern Australian climates are predicted to become warmer and drier, whereas northern regions may see increased precipitation. Environmental factors, including salinity gradients, suspended sediment, dissolved oxygen and nutrient concentrations, will be influenced by changing freshwater input and other climate variables. Potential impacts will vary depending on the geomorphology of the estuary and the level of build-up of sand bars across estuarine entrances. Changes to estuarine fish assemblages will depend on associated changes to salinity and estuarine-mouth morphology. Marine migrants may be severely affected by closure of estuarine mouths, depending on whether species ‘must’ use estuarine habitat and the level of migratory v. resident individuals. Depending on how fish in coastal waters locate estuaries, there may be reduced cues associated with estuarine mouths, particularly in southern Australia, potentially influencing abundance. In summary, climate change is expected to have major consequences for Australian estuaries and associated fish, although the nature of impacts will show significant regional variation.
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Bernardino, Angelo Fraga, Paulo Roberto Pagliosa, Ronaldo Adriano Christofoletti, Francisco Barros, Sergio A. Netto, Pablo Muniz, and Paulo da Cunha Lana. "Benthic estuarine communities in Brazil: moving forward to long term studies to assess climate change impacts." Brazilian Journal of Oceanography 64, spe2 (2016): 81–96. http://dx.doi.org/10.1590/s1679-875920160849064sp2.
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Abstract Estuaries are unique coastal ecosystems that sustain and provide essential ecological services for mankind. Estuarine ecosystems include a variety of habitats with their own sediment-fauna dynamics, all of them globally undergoing alteration or threatened by human activities. Mangrove forests, saltmarshes, tidal flats and other confined estuarine systems are under increasing stress due to human activities leading to habitat and species loss. Combined changes in estuarine hydromorphology and in climate pose severe threats to estuarine ecosystems on a global scale. The ReBentos network is the first integrated attempt in Brazil to monitor estuarine changes in the long term to detect and assess the effects of global warming. This paper is an initial effort of ReBentos to review current knowledge on benthic estuarine ecology in Brazil. We herein present and synthesize all published work on Brazilian estuaries that has focused on the description of benthic communities and related ecological processes. We then use current data on Brazilian estuaries and present recommendations for future studies to address climate change effects, suggesting trends for possible future research and stressing the need for long-term datasets and international partnerships.
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Mariano, Dante Luís Silva, and Francisco Barros. "Intertidal benthic macrofaunal assemblages: changes in structure along entire tropical estuarine salinity gradients." Journal of the Marine Biological Association of the United Kingdom 95, no. 1 (November 15, 2014): 5–15. http://dx.doi.org/10.1017/s002531541400126x.
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Spatial variation in the structure of macrobenthic assemblages on intertidal flats is known to be related to different environmental variables. Most of the studies have observed that along the estuarine gradient, salinity is the most important variable driving the patterns of the macrobenthic assemblages. However, the great majority of studies have been done on single estuarine systems in temperate regions. We investigated the relationship between the macrobenthic assemblages in intertidal habitats and the environmental variables along three tropical estuaries. From lower to upper estuarine regions we sampled benthic macrofauna, salinity and sediments. The structure of the benthic assemblages was primarily related to salinity. There was a decrease in the number of taxa from the upper to the lower estuarine regions, indicating important deviation from Remane's model of estuarine diversity. There were important similarities of taxa abundance along different estuarine salinity gradients which can be properly tested in other tropical and temperate regions. We advocate that in order to adopt general and robust management practices it is essential to identify broad patterns and general rules governing estuarine systems.
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Siddiqee, Mahbubul, Rebekah Henry, Rebecca Coulthard, Christelle Schang, Richard Williamson, Rhys Coleman, Graham Rooney, Ana Deletic, and David McCarthy. "Salmonella enterica Serovar Typhimurium and Escherichia coli Survival in Estuarine Bank Sediments." International Journal of Environmental Research and Public Health 15, no. 11 (November 21, 2018): 2597. http://dx.doi.org/10.3390/ijerph15112597.
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Estuarine bank sediments have the potential to support the survival and growth of fecal indicator organisms, including Escherichia coli. However, survival of fecal pathogens in estuarine sediments is not well researched and therefore remains a significant knowledge gap regarding public health risks in estuaries. In this study, simultaneous survival of Escherichia coli and a fecal pathogen, Salmonella enterica serovar Typhimurium, was studied for 21 days in estuarine bank sediment microcosms. Observed growth patterns for both organisms were comparable under four simulated scenarios; for continuous-desiccation, extended-desiccation, periodic-inundation, and continuous-inundation systems, logarithmic decay coefficients were 1.54/day, 1.51/day, 0.14/day, and 0.20/day, respectively, for E. coli, and 1.72/day, 1.64/day, 0.21/day, and 0.24/day for S. Typhimurium. Re-wetting of continuous-desiccated systems resulted in potential re-growth, suggesting survival under moisture-limited conditions. Key findings from this study include: (i) Bank sediments can potentially support human pathogens (S. Typhimurium), (ii) inundation levels influence the survival of fecal bacteria in estuarine bank sediments, and (iii) comparable survival rates of S. Typhimurium and E. coli implies the latter could be a reliable fecal indicator in urban estuaries. The results from this study will help select suitable monitoring and management strategies for safer recreational activities in urban estuaries.
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Slinger, J. H., and C. M. Breen. "Integrated research into estuarine management." Water Science and Technology 32, no. 5-6 (September 1, 1995): 79–86. http://dx.doi.org/10.2166/wst.1995.0566.
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Estuaries are under increasing pressure owing to agricultural, urban and industrial developments in their catchments and their status as favoured sites for coastal development and recreation. Effective research on South Africa estuaries requires the synthesis of available scientific knowledge to efficiently address management concerns and so ensure the sustainable utilisation of estuaries. The approach of the Consortium for Estuarine Research and Management to these problems and the results of a co-ordinated research programme on decision support for the management and conservation of estuarine systems are described in this paper. While the importance and current status of South African estuaries are considered, attention is devoted primarily to the development of an integrated modelling approach to the freshwater requirements of estuaries. In particular, the application of a linked system of five models to a case study, the Great Brak Estuary is described and the role of prediction in promoting wise decision making for estuaries is treated.
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Groeneveld, Johan C., Jorge Santos, Fiona MacKay, and Cosmas N. Munga. "A regional assessment of seasonal-to-decadal changes in estuarine socio-ecological systems in the Western Indian Ocean." Western Indian Ocean Journal of Marine Science, no. 1/2021 (December 23, 2021): 131–61. http://dx.doi.org/10.4314/wiojms.si2021.1.9.
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Estuarine socio-ecological systems (SES) in the Western Indian Ocean (WIO) region face mounting pressures from overexploitation, habitat degradation, impacts of climate change and governance inadequacies. A regional assessment of seasonal-to-decadal change in SES of three estuaries (Bons Sinais in Mozambique, Ruvu in Tanzania and Tana in Kenya) was undertaken along 2000 km of tropical coastline (3°-18°S), using a systems-oriented approach and information collected during the Estuarize-WIO project (2016-2019). All three estuaries were open and tidal, but differed along gradients of geomorphology, annual precipitation, exposure to tropical storms, drought, sea level rise, and rural to urban development. Despite physical differences, similar marine species, mangrove assemblages, seasonality in fish-based farming systems and cultivated crops, and fishing methods were apparent across the region. Key differences were related to the scale of anthropogenic disturbance, discerned from land use / land cover (LULC) change analysis, which showed decadal increases in developed-, cultivated- and grasslands, at the expense of wetlands and forests, and seasonal transformation of wetlands to agriculture and grasslands. The three estuaries represented a gradient along urban-production-conservation dimensions, brought about by rural to urban transformation, and by freshwater and sediment diversion for economic development in upstream catchment areas. Household surveys indicated strongly seasonal livelihood strategies, with highest diversity in peri-urban settings, and reliance on different combinations of ecosystem goods and services in coastal and upstream rural settings. Estuarine fisheriesranged from unselective, low trophic-level fisheries using fine-mesh nets at the urbanized and most-disturbed Bons Sinais Estuary, to a more complex organized fishery at the least-disturbed Tana. At Ruvu, fisheries and agriculture production exit the system to distant markets. The systems-oriented approach demonstrated that human-induced processes affected WIO estuaries and dependent livelihoods more deeply than inherent physical differences. A key conclusion is that research, management and governance will benefit from regional cooperation, given the similarities of the systems and the different levels of disturbance.
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Whitfield, AK. "Littoral habitats as major nursery areas for fish species in estuaries: a reinforcement of the reduced predation paradigm." Marine Ecology Progress Series 649 (September 10, 2020): 219–34. http://dx.doi.org/10.3354/meps13459.
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For many decades, the role of estuaries as important nursery areas for fishes was accepted as fact by scientists and environmental managers. At the turn of the 21st century, a question mark was raised in relation to the reduced predation component of the nursery function, with some scientists contending that both large and small piscivorous fish species had access to the estuarine habitats that juvenile fishes in estuaries occupied. If true on a global scale, the nursery designation for these habitats would be compromised and the long-held paradigm that estuaries are important nursery areas for fishes would need to be revised. In this review, I examine the nature of fish nursery areas in estuarine littoral habitats from a mainly predation perspective and, based on a variety of ichthyofaunal and avifaunal studies, come to the conclusion that apart from a few selected estuarine systems, there is limited predation on juvenile fishes in these particular areas. This, coupled with the abundant suitable food resources for juvenile fish from different trophic categories, shelter from high-energy marine wave action and biological connectivity between a variety of submerged and emergent macrophyte communities, renders shallow estuarine littoral areas ideal nursery areas for the juveniles of mostly euryhaline marine fish species, the dominant component of estuarine ichthyofaunas globally. In addition, there are strong indications from the fossil record that these littoral estuarine nursery areas have been functioning since the Devonian, more than 350 million years ago.
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Kennish, Michael J. "Environmental threats and environmental future of estuaries." Environmental Conservation 29, no. 1 (March 2002): 78–107. http://dx.doi.org/10.1017/s0376892902000061.
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Estuaries exhibit a wide array of human impacts that can compromise their ecological integrity, because of rapid population growth and uncontrolled development in many coastal regions worldwide. Long-term environmental problems plaguing estuaries require remedial actions to improve the viability and health of these valuable coastal systems. Detailed examination of the effects of pollution inputs, the loss and alteration of estuarine habitat, and the role of other anthropogenic stress indicates that water quality in estuaries, particularly urbanized systems, is often compromised by the overloading of nutrients and organic matter, the influx of pathogens, and the accumulation of chemical contaminants. In addition, the destruction of fringing wetlands and the loss and alteration of estuarine habitats usually degrade biotic communities. Estuaries are characterized by high population densities of microbes, plankton, benthic flora and fauna, and nekton; however, these organisms tend to be highly vulnerable to human activities in coastal watersheds and adjoining embayments. Trends suggest that by 2025 estuaries will be most significantly impacted by habitat loss and alteration associated with a burgeoning coastal population, which is expected to approach six billion people. Habitat destruction has far reaching ecological consequences, modifying the structure, function, and controls of estuarine ecosystems and contributing to the decline of biodiversity. Other anticipated high priority problems are excessive nutrient and sewage inputs to estuaries, principally from land-based sources. These inputs will lead to the greater incidence of eutrophication as well as hypoxia and anoxia. During the next 25 years, overfishing is expected to become a more pervasive and significant anthropogenic factor, also capable of mediating global-scale change to estuaries. Chemical contaminants, notably synthetic organic compounds, will remain a serious problem, especially in heavily industrialized areas. Freshwater diversions appear to be an emerging global problem as the expanding coastal population places greater demands on limited freshwater supplies for agricultural, domestic, and industrial needs. Altered freshwater flows could significantly affect nutrient loads, biotic community structure, and the trophodynamics of estuarine systems. Ecological impacts that will be less threatening, but still damaging, are those caused by introduced species, sea level rise, coastal subsidence, and debris/litter. Although all of these disturbances can alter habitats and contribute to shifts in the composition of estuarine biotic communities, the overall effect will be partial changes to these ecosystem components. Several strategies may mitigate future impacts.
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Laruelle, Goulven Gildas, Nicolas Goossens, Sandra Arndt, Wei-Jun Cai, and Pierre Regnier. "Air–water CO<sub>2</sub> evasion from US East Coast estuaries." Biogeosciences 14, no. 9 (May 15, 2017): 2441–68. http://dx.doi.org/10.5194/bg-14-2441-2017.
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Abstract. This study presents the first regional-scale assessment of estuarine CO2 evasion along the US East Coast (25–45° N). The focus is on 42 tidal estuaries, which together drain a catchment of 697 000 km2 or 76 % of the total area within this latitudinal band. The approach is based on the Carbon–Generic Estuary Model (C-GEM) that allows the simulation of hydrodynamics, transport, and biogeochemistry for a wide range of estuarine systems using readily available geometric parameters and global databases of seasonal climatic, hydraulic, and riverine biogeochemical information. Our simulations, performed using conditions representative of the year 2000, suggest that, together, US East Coast estuaries emit 1.9 Tg C yr−1 in the form of CO2, which corresponds to about 40 % of the carbon inputs from rivers, marshes, and mangroves. Carbon removal within estuaries results from a combination of physical (outgassing of supersaturated riverine waters) and biogeochemical processes (net heterotrophy and nitrification). The CO2 evasion and its underlying drivers show important variations across individual systems, but reveal a clear latitudinal pattern characterized by a decrease in the relative importance of physical over biogeochemical processes along a north–south gradient. Finally, the results reveal that the ratio of estuarine surface area to the river discharge, S∕Q (which has a scale of per meter discharged water per year), could be used as a predictor of the estuarine carbon processing in future regional- and global-scale assessments.
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Khojasteh, Danial, Shengyang Chen, Stefan Felder, Valentin Heimhuber, and William Glamore. "Estuarine tidal range dynamics under rising sea levels." PLOS ONE 16, no. 9 (September 20, 2021): e0257538. http://dx.doi.org/10.1371/journal.pone.0257538.
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How an estuary responds to sea level rise (SLR) is complex and depends on energy drivers (e.g., tides and river inflows), estuarine geometry (e.g., length and depth), intrinsic fluid properties (e.g., density), and bed/bank roughness. While changes to the tidal range under SLR can impact estuarine sediment transport, water quality, and vegetation communities, studies on the altered tidal range under SLR are often based on case studies with outcomes applicable to a specific site. As such, this study produced a large ensemble of estuarine hydrodynamic models (>1800) to provide a systematic understanding of how tidal range dynamics within different estuary types may change under various SLR and river inflow scenarios. The results indicated that SLR often amplifies the tidal range of different estuary types, except for short estuaries with a low tidal range at the mouth where SLR attenuates the tides. SLR alters the location of the points with minimum tidal range and overall tidal range patterns in an estuary. Variations in tidal range were more evident in converging estuaries, shallower systems, or in estuaries with strong river inflows. These findings provide an indication of how different estuary types may respond to estuaries and may assist estuarine managers and decision makers.
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Wei, Xi, Josette Garnier, Vincent Thieu, Paul Passy, Romain Le Gendre, Gilles Billen, Maia Akopian, and Goulven Gildas Laruelle. "Nutrient transport and transformation in macrotidal estuaries of the French Atlantic coast: a modeling approach using the Carbon-Generic Estuarine Model." Biogeosciences 19, no. 3 (February 15, 2022): 931–55. http://dx.doi.org/10.5194/bg-19-931-2022.
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Abstract. Estuaries are key reactive ecosystems along the land–ocean aquatic continuum, with significant ecological and economic value. However, they have been facing strong morphological management changes and increased nutrient and contaminant inputs, possibly leading to ecological problems such as coastal eutrophication. Therefore, it is necessary to quantify the import and export fluxes of the estuaries, their retention capacity, and estuarine eutrophication potential. The 1-D Carbon-Generic Estuary Model (C-GEM) was used to simulate the transient hydrodynamics, transport, and biogeochemistry for estuaries with different sizes and morphologies along the French Atlantic coast during the period 2014–2016 using readily available geometric, hydraulic, and biogeochemical data. These simulations allowed us to evaluate the budgets of the main nutrients (phosphorus – P; nitrogen – N; silica – Si) and total organic carbon (TOC), and their imbalance, providing insights into their eutrophication potential. Cumulated average annual fluxes to the Atlantic coast from the seven estuaries studied were 9.6 kt P yr−1, 259 kt N yr−1, 304 kt Si yr−1, and 145 kt C yr−1. Retention rates varied depending on the estuarine residence times, ranging from 0 %–27 % and 0 %–34 % to 2 %–39 % and 8 %–96 % for total phosphorus (TP), total nitrogen (TN), dissolved silica (DSi), and TOC, respectively. Large-scale estuaries had higher retention rates than medium and small estuaries, which we interpreted in terms of estuarine residence times. As shown by the indicator of eutrophication potential (ICEP), there might be a risk of coastal eutrophication, i.e., the development of non-siliceous algae that is potentially harmful to the systems studied due to the excess TN over DSi. This study also demonstrates the ability of our model to be applied with a similar setup to several estuarine systems characterized by different sizes, geometries, and riverine loads.
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Cianfaglione, Kevin. "Plant Landscape and Models of French Atlantic Estuarine Systems. Extended Summary of the Doctoral Thesis." Transylvanian Review of Systematical and Ecological Research 23, no. 1 (March 1, 2021): 15–36. http://dx.doi.org/10.2478/trser-2021-0002.
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Abstract The present study proposes a theoretical common model of environmental gradients and functioning of vegetation and Plant Landscape of the French Atlantic estuarine systems. This model offers a basis to improve classification and ecological studies of estuarine systems, and to helps the monitoring and assessment of land uses, land forms transformation and human impacts, thanks to the develop of a spatio-temporal predictive model based on actual and potential vegetation following a dynamico-catenal approach. In eight selected estuaries, fieldworks was undertook for a total of 98,315 ha highlighting two vegetation series and four geopermaseries, corresponding to 131 plant associations, 60 alliances, 43 orders, and 28 classes. The vegetation of three representative estuaries was mapped, for a total of 74,433 ha. A synthetic scheme of estuary vegetation landscape is proposed, integrating geographical and ecological gradients as well as geomorphologic forms.
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Lawson, Stephan Korblah, Hitoshi Tanaka, Keiko Udo, Nguyen Trong Hiep, and Nguyen Xuan Tinh. "Morphodynamics and Evolution of Estuarine Sandspits along the Bight of Benin Coast, West Africa." Water 13, no. 21 (October 21, 2021): 2977. http://dx.doi.org/10.3390/w13212977.
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It is well known that estuarine systems are significantly affected by hydrodynamic conditions such as river discharge, storm surges, waves and tidal conditions. In addition to this, human interferences through developmental projects have the capability of disrupting the natural morphological processes occurring at estuaries. In West Africa, the goal to improve standards of living through large-scale dam construction, offshore ports and coastal erosion countermeasures has triggered alarming changes in the morphodynamics of estuarine systems. The estuaries at the Volta River mouth (Ghana) and “Bouche du Roi” inlet (Benin), located along the Bight of Benin coast, West Africa, were selected as two case study sites to examine their long-term morphodynamics and sandspit evolution. In this study, we primarily analyzed estuarine morphology using remotely sensed images acquired from 1984 to 2020. We further estimated the longshore sediment transport for this region using results from the image analysis and the depth of active sediment motion. Our results reveal that the longshore sediment transport rates for this region are in the magnitude of 105–106 m3/year. Comparative analysis with other estuaries and sandy coasts suggests that the longshore sediment transport along this coast has one of the largest rates estimated in the world.
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Siemes, Rutger, Trang Minh Duong, Pim Willemsen, Bas Borsje, and Suzanne Hulscher. "ESTUARINE-WIDE SEDIMENT DYNAMICS UNDER HUMAN INTERVENTIONS AND CLIMATE CHANGE EFFECTS; AN IDEALISED MODEL STUDY." Coastal Engineering Proceedings, no. 37 (September 1, 2023): 12. http://dx.doi.org/10.9753/icce.v37.sediment.12.
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Estuaries worldwide are under constant anthropogenic pressure. They are susceptible to climate change effects, from the sea (sea level rise, changing wave climate) and from the river-side (changing river discharge). Besides, estuaries are channelised and embanked to improve flood safety and to reclaim land, and channels are deepened to allow bigger ships to enter the ports. To optimise estuarine functions and sustainably prepare for future challenges, improved understanding of estuarine sediment dynamics after potential changes in the systems configuration and forcings is desired. This paper aims to assess the annual sediment dynamics of an estuary under a climate change effects, and how this is affected by human interventions.
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Coleman, Daniel J., Alexander S. Kolker, and Karen H. Johannesson. "Submarine groundwater discharge and alkaline earth element dynamics in a deltaic coastal setting." Hydrology Research 48, no. 5 (September 13, 2016): 1169–76. http://dx.doi.org/10.2166/nh.2016.285.
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Submarine groundwater discharge is a process that is often considered negligible in deltaic systems given their low gradient and fine-grained sediment. However, hydrologic budgets and radon surveys indicate that it may be a significant component of the Mississippi River Delta system. To more concretely indicate groundwater's contribution to the local environment, we conducted an analysis of estuarine water chemistry. We focused on the mid-weight alkaline earth metals, which differ significantly in the system's three end-members: river, ocean, and groundwater. We found an anomaly of barium in the estuaries, which could not be completely explained by desorption. Through the construction of a three-end-member mixing model, groundwater was estimated to comprise 14–28% of Terrebonne and Barataria Bay estuarine water, which corresponds to a combined discharge of 160–480 m3/s. This groundwater discharge helps explain the hydrologic budget of the system, and could influence the chemistry of these large deltaic estuaries.
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Groeneveld, Johan C., Antonio M. Hoguane, Baraka Kuguru, Fiona Mackay, Cosmas Munga, and Jorge Santos. "Estuarize-WIO: A socio-ecological assessment of small-scale fisheries in estuaries of the Western Indian Ocean." Western Indian Ocean Journal of Marine Science, no. 1/2021 (December 23, 2021): 1–15. http://dx.doi.org/10.4314/wiojms.si2021.1.1.
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Estuaries provide unique ecosystem goods and services and have been focal points for human settlement andresource use throughout recorded history. In the Western Indian Ocean (WIO) region, the effects of human population growth, rapid economic development and climate change on estuaries threaten their ecological functioning and the sustainability of estuary-dependent livelihoods. Governance systems are ill-equipped to deal with the mounting challenges. Long-term datasets that describe estuary-scale trends are scarce, and socio-ecological interactions that support sustainable use of resources are incompletely understood. To address these gaps, the Estuarize-WIO project (2016-2019) compiled datasets on biophysical, ecological, socio-economic and fisheries aspects of selected estuaries in Mozambique (Bons Sinais), Tanzania (Ruvu) and Kenya (Tana), analysed trends per estuary, and used a socio-ecological systems (SES) framework to integrate information from multiple sources at local and regional levels. The introductory paper of this Special Issue of the Western Indian Ocean Journal of Marine Science provides regional context and reviews the relevant literature available for WIO estuaries. In succeeding papers, estuarine circulation is inferred from hydrological measurements, seasonal and decadal trends in land cover and land use are investigated using remote sensing images, household surveys are used to investigate socio-economic circumstances and resource use, and long-term catch survey data and field samples are used to describe small-scale fisheries. In the synthesis paper, a SES framework is constructed to investigate linkages and feedback loops in individual estuaries. A regionally comparative analysis across the WIO region was conducted, and recommendations were made for future research and governance. The methodological approach developed for Estuarize-WIO is well-suited to research of data poor systems with limited accessibility and research infrastructure.
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Roast, S. D., R. S. Thompson, B. ,. J. Widdows, and M. B. Jones. "Mysids and environmental monitoring: a case for their use in estuaries." Marine and Freshwater Research 49, no. 8 (1998): 827. http://dx.doi.org/10.1071/mf97099.
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Mysids (Crustacea : Mysidacea) are ubiquitous members of the permanent, endemic hyperbenthic fauna of estuarine and other coastal ecosystems. They often occur in high numbers and their ecological importance, particularly their role in food chains as a link between the benthic and pelagic systems, is becoming increasingly apparent. In general, mysids are omnivores, feeding on detritus, zooplankton and phytoplankton, and they contribute up to 40% of the standing stock of omnivores in some systems. In estuaries, specific mysid faunas often occur in discrete zones, usually as a result of different salinity tolerances, although responses to turbidity and water flow also determine mysid distributions. Many mysids are particularly sensitive to chemical contaminants as illustrated by their relatively low 96-h LC50 values. Due to this sensitivity, the United States Environmental Protection Agency promotes the use of Americamysis ( Mysidopsis) bahia for laboratory toxicity testing; however, there is growing interest in the use of local, endemic species rather than the standard American mysid. At Plymouth, novel and sensitive techniques are being developed for assessing sublethal responses to toxicants by use of the northern European estuarine mysid Neomysis integer. This paper summarizes the ecological role of mysids in estuaries and describes their potential for use for estuarine environmental monitoring.
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Feldman, Howard R., Christopher G. Maples, Allen W. Archer, Ronald R. West, and Erik P. Kvale. "An estuarine model for Pennsylvanian Lagerstätten." Paleontological Society Special Publications 6 (1992): 95. http://dx.doi.org/10.1017/s2475262200006559.
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Estuaries were important sites of deposition throughout most of the Pennsylvanian in the Midcontinent. Modern estuaries typically occur within flooded river valleys where marine and fresh waters mix. Characteristic estuarine circulation results in locally high rates of deposition of muddy sediment that can lead to good preservation of fossils. Several Pennsylvanian conservat-Lagerstätten are best interpreted as having formed within ancient estuaries. Three types of estuarine deposits have been identified. Type 1 estuarine systems are large-scale transgressive systems that start with fluvial sands overlying an erosional surface. This is overlain successively by middle-estuarine laminated mudstone, and finally marine mudstone and shale. Well-preserved fossils occur in laminated mudstones and siltstones. This sequence may include within in it type 3 estuarine Lagerstätten. An example is the Douglas Group (Missourian, Kansas).Type 2 estuarine Lagerstätten consist of thin estuarine deposits confined to narrow paleochannels. This includes the Garnett (Missourian, Kansas) and Hamilton (Virgilian, Kansas) deposits, both of which contain articulated vertebrates and well-preserved plants. Both channels are filled with mixed siliciclastic and carbonate sediments. Fine grained facies from which the best fossils are recovered in both contain evidence of tidal deposition, although tidal rhythmicity is best developed in the Hamilton channel. Plant assemblages in both are dominated by the conifer Walchia, probably indicating a relatively dry climate.Type 3 estuarine Lagerstätten consist of thick gray-shale wedges that overlie coals. The best-known example is the Francis Creek Shale (Desmoinesian, Illinois). A relatively wet climate is indicated by abundant fern and seed-fern foliage. Laminations in shale facies commonly show well-developed tidal rhythmicity. A typical stratigraphic succession starts with laminated shale overlying coal. This grades upwards into flaser and lenticular bedding to ripple and then large-scale cross-bedded sandstone. Upright trees rooted in the coal indicate rapid burial. Well-preserved fossils are recovered from early-diagenetic siderite concretions from the laminated shale.Preservation of fossils is best in laminated mudstones deposited in middle-estuarine environments where conditions are ideal for good preservation. In all cases so far studied the zones of best preservation are well laminated and have sparse (if any) burrows and sessile benthic fossils. Most of the well-preserved organisms are terrestrial, nektonic, or at least mobile. Brackish and fluctuating salinities restricted scavenging and burrowing organisms that may scatter skeletons. High turbidity and deposition rate may have further discouraged many organisms. Matching bedding rhythmicity with tidal cycles allows calculation of depositional rates of 1 cm or more of compacted sediment per 2-week neap-spring tidal cycle. This is consistent with the high rates of deposition known from modern tidal environments. High depositional rates assured that any organism that fell to the sea floor was buried in a few hours to a few days. Once buried anoxic conditions established around decaying carcasses may have led to early mineralization.
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Taddese, Fasil, Marc Schallenberg, Pavel Mikheev, Matt G. Jarvis, and Gerard P. Closs. "Ichthyofaunal assemblages in shallow littoral habitats of permanently open estuaries and intermittently closed and open lakes or lagoons in Otago, New Zealand." Marine and Freshwater Research 69, no. 8 (2018): 1222. http://dx.doi.org/10.1071/mf17334.
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Fish assemblages of New Zealand estuaries are poorly studied, and knowledge of the effects of estuary–ocean connections on the ichthyofaunal composition of estuaries remains limited. Understanding the status of fish composition of estuaries is crucial for planning for sustainable management of aquatic ecosystems. In the present study we sampled fish using a seine net from lower reaches of six permanently open estuaries and six intermittently closed and open lakes or lagoons (ICOLLs) along the Otago coastline during winter 2016 and summer 2017. Marked differences in ichthyofaunal composition were observed in the shallow littoral habitats of permanently open estuaries and ICOLLs. Fish assemblages reflected estuary–ocean connection status of estuaries during both seasons. ICOLLs showed greater fish abundance than permanently open systems. Fish abundance was higher in summer than in winter in both estuary types. Fish species with marine–estuarine opportunist and estuarine–migrant life histories dominated permanently open estuaries. Conversely, species with a diadromous life history but known to form landlocked populations were abundant in ICOLLs. Salinity and temperature were correlated with fish abundance in both estuary types.
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Aranda, María, Francisco Javier Gracia, and Gloria Peralta. "Estuarine Mapping and Eco-Geomorphological Characterization for Potential Application in Conservation and Management: Three Study Cases along the Iberian Coast." Applied Sciences 10, no. 13 (June 27, 2020): 4429. http://dx.doi.org/10.3390/app10134429.
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Geomorphological changes in recent decades in three estuaries along the Iberian coast were analysed using aerial orthophotographs. A hierarchical classification scheme, based on a literature review representing 26 estuarine eco-geomorphological features relevant to estuarine dynamics and functioning, is described. The estuaries selected were San Vicente de la Barquera (N Spain), Guadiana River (SW border between Spain and Portugal) and the Ebro River Delta mouth (NE Spain). For these systems, a 60-year time series of high-resolution maps was developed, analysing the changes in feature surfaces. The main subsystems analysed were beach, dunes, saltmarshes and the drainage network. The results of the cartographies showed general behaviour common to all transitional systems, relationships among main subsystems and processes inherent to each one. This work illustrates how beaches and dunes serve as a protective barrier for the tidal flats, acting as a sediment buffer for the entire system. The subsystems are connected by the drainage network responsible for the exchange of matter and energy between them. Furthermore, an accuracy assessment was performed in one of the study zones to identify the limitations of mapping with aerial photographs. The results explain the changes with time but also the processes and relationships between the estuarine features at a long-term scale. This work adds an important perspective towards a general understanding of their dependence on intrinsic and boundary conditions.
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Hodgkin, Ernest P., and Patrick Hesp. "Estuaries to salt lakes: Holocene transformation of the estuarine ecosystems of south-western Australia." Marine and Freshwater Research 49, no. 3 (1998): 183. http://dx.doi.org/10.1071/mf96109.
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When the estuaries of south-western Australia were first flooded by the Holocene marine transgression about 7000 years before present (BP), most were enclosed by limestone barrier dunes. Coastal sand drift built bars and flood-tide deltas in the narrow entrances, but until about 3500 years BP the estuaries remained tidal-dominated systems with a diverse marine–estuarine fauna. Now the bars/deltas so obstruct the small tides that estuary water is fresh in winter and marine to hypersaline in summer; the estuaries are river-flow-dominated systems and the ecosystems are characterised by a restricted euryhaline estuarine biota. Some estuaries are still permanently open, their bars/deltas never close, and some are seasonally open, their bars open with river flow in winter and close in summer. Other estuaries are normally closed, their bars remain closed for several years and break with episodic flood flow, or are permanently closed coastal salt lakes with bars that never or rarely break: they can become grossly hypersaline and may dry up altogether. An hypothesis to explain this Holocene transformation of the estuaries attributes it principally to sedimentary processes in an environment where river flow is highly seasonal, tides are microtidal, there was a fall in sea level, and there are differences in the volume and periodicity of flow and the degree of shelter to the entrances from the prevailing south-west winds and swell.
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White, Eric D., Ehab Meselhe, Denise Reed, Alisha Renfro, Natalie Peyronnin Snider, and Yushi Wang. "Mitigating the Effects of Sea-Level Rise on Estuaries of the Mississippi Delta Plain Using River Diversions." Water 11, no. 10 (September 28, 2019): 2028. http://dx.doi.org/10.3390/w11102028.
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Using the Mississippi River as a tool for restoration has been a key element of restoration planning in Louisiana for decades. The results of allowing river water and sediment back into the coastal system are manifested in a number of places in present day Louisiana, with additional plans for large scale sediment and water diversions from the Mississippi River. Many previous numerical modeling studies have focused on sediment delivery to Louisiana estuaries. This study examines the effects of river diversions on salinity gradients in receiving estuarine basins. The Integrated Compartment Model, a planning-level model that simulates multi-decadal change in estuarine hydrodynamics and wetland systems under assumed sea-level rise scenarios, was used to assess the estuarine salinity gradient under potential management regimes. The simulations for current conditions are compared to a future 50-year simulation with additional diversions, as well as cases with a variety of diversion options. This modeling analysis shows that without additional action, 50-years of sea-level rise could result in substantial increases in salinity throughout the Mississippi Delta Plain estuaries. This can be largely offset with additional large river diversions which can maintain variable salinity gradients throughout the estuary basins.
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Kisten, Yanasivan, Nadine A. Strydom, Renzo Perissinotto, and Sourav Paul. "Modelling the occurrence of postflexion stages of a marine estuarine-dependent fish in temperate South African estuaries." Scientia Marina 81, no. 1 (March 27, 2017): 27. http://dx.doi.org/10.3989/scimar.04521.05a.
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The movement of postflexion larvae of marine estuarine-dependent species into estuaries is critical for the survival of fishes reliant on estuaries as nurseries. However, detailed studies focused on environmental variability experienced by postflexion larvae entering a range of estuary types under varying conditions are rare. This study assessed the in situ conditions (temperature, salinity and water clarity) under which the southern African endemic fish Rhabdosargus holubi (Sparidae) recruits into estuaries. Postflexion larvae were sampled in three biogeographic regions (cool temperate, warm temperate and subtropical boundary), which included three estuary types (permanently open estuaries (POEs), temporarily open/closed estuaries and estuarine lake systems) on a seasonal basis, independent of each other. Rhabdosargus holubi larvae were more abundant in spring and summer, in POEs in the warm temperate region. Models predicted that higher larval occurrence in estuaries is a function of lower salinity (e.g. mesohaline zones of 5-17.9 salinity) and lower water clarity (e.g. 0-0.2 Kd, light extinction coefficient), particularly for warm, temperate POEs. This re-emphasizes the importance of freshwater for optimal nursery functioning, which may be compromised by impoundments, abstraction and climate change in water-short countries like South Africa.
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Govender, Joelene, Trishan Naidoo, Anusha Rajkaran, Senzo Cebekhulu, Astika Bhugeloo, and Sershen Sershen. "Towards Characterising Microplastic Abundance, Typology and Retention in Mangrove-Dominated Estuaries." Water 12, no. 10 (October 9, 2020): 2802. http://dx.doi.org/10.3390/w12102802.
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Plastic and, particularly, microplastic (MP) pollution is a growing research theme, dedicated largely to marine systems. Occurring at the land–sea interface, estuarine habitats such as mangroves are at risk of plastic pollution. This study compared MP pollution (level, morphotype, polymer composition, size and colour) across four South African estuaries, in relation to the built and natural environment. Mouth status, surrounding human population densities and land-use practices influenced the level and type of MP pollution. Systems that were most at risk were predominantly open estuaries surrounded by high population densities and diverse land use types. Microplastic levels and the diversity of types detected increased with increasing levels of anthropogenic disturbance. Overall, microfibres dominated in estuarine water (69%) and mangrove sediment (51%). Polyethylene (43%) and polypropylene (23%) were the dominant polymers overall. Weathered fishing gear, weathered packaging items and run-off from urban/industrial centres are probable sources of MP pollution. Increased run-off and river input during the wet/rainy season may explain the markedly higher MP loads in estuarine waters relative to the dry season. By contrast, MP deposition in mangrove sediment was higher during the dry season. Sediment MP abundance was significantly positively correlated with both pneumatophore density and sediment size (500–2000 µm). This study highlights the role of mangroves as MP sinks, which may limit movement of MPs into adjacent environments. However, under conditions such as flooding and extreme wave action, mangroves may shift from sinks to sources of plastic pollution.
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Rilo, Ana, Alexandre Oliveira Tavares, Paula Freire, José Luís Zêzere, and Ivan D. Haigh. "Enhancing Estuarine Flood Risk Management: Comparative Analysis of Three Estuarine Systems." Journal of Coastal Research 95, sp1 (May 26, 2020): 935. http://dx.doi.org/10.2112/si95-182.1.
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Lemos, Valéria M., Marianna Lanari, Margareth Copertino, Eduardo R. Secchi, Paulo Cesar O. V. de Abreu, José H. Muelbert, Alexandre M. Garcia, et al. "Patos Lagoon estuary and adjacent marine coastal biodiversity long-term data." Earth System Science Data 14, no. 3 (March 8, 2022): 1015–41. http://dx.doi.org/10.5194/essd-14-1015-2022.
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Abstract. Estuaries are among the most productive aquatic ecosystems and provide important ecological and economic services in coastal areas. However, estuarine systems have been threatened worldwide by natural and anthropogenic impacts acting on local, regional, and global scales. Long-term ecological studies contribute to the understanding and management of estuarine functioning and provide the baseline information for detection changes and modeling of predictive scenarios. Here, we describe long-term data on the biodiversity and physico-chemical parameters obtained from 1993 to 2016 for the Patos Lagoon estuary and adjacent marine coast (PLEA), in southern Brazil. We report 8 datasets containing 6972 sampling events with the occurrence and abundance records of 275 species (kingdoms: Bacteria, Protozoa, Chromista, Plantae, and Animalia) of functional groups plankton, benthos, and nekton. Datasets also include 22 190 abiotic records. The database is published in the Global Biodiversity Information Facility (GBIF) repository (see Sect. 3 “Data availability” and Table 3). The present compendium represents one of the most comprehensive and longest datasets from primary producers to top predators in an estuarine coastal system in South America, and their availability will be an important contribution to the understanding and predictability of estuarine dynamics around the world.
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Nidzieko, Nicholas J. "Allometric scaling of estuarine ecosystem metabolism." Proceedings of the National Academy of Sciences 115, no. 26 (June 11, 2018): 6733–38. http://dx.doi.org/10.1073/pnas.1719963115.
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There are still significant uncertainties in the magnitude and direction of carbon fluxes through coastal ecosystems. An important component of these biogeochemical budgets is ecosystem metabolism, the net result of organismal metabolic processes within an ecosystem. In this paper, I present a synthesis of published ecosystem metabolism studies from coastal ecosystems and describe an empirical observation that size-dependent patterns in aquatic gross primary production and community respiration exist across a wide range of coastal geomorphologies. Ecosystem metabolism scales to the 3/4 power with volume in deeper estuaries dominated by pelagic primary production and nearly linearly with area in shallow estuaries dominated by benthic primary production. These results can be explained by applying scaling arguments for efficient, directed transport networks developed to explain similar size-dependent patterns in organismal metabolism. The main conclusion from this synthesis is that the residence time of new, nutrient-rich water is a fundamental organizing principle for the observed patterns. Residence time changes allometrically with size in pelagic ecosystems because velocities change by only an order of magnitude across systems that span more than ten orders of magnitude in size. This nonisometric change in velocity with size requires lower specific metabolic rates at larger ecosystem sizes. This change in transport may also explain a shift from predominantly net heterotrophy to net autotrophy with increasing size. The scaling results are applied to the total estuarine area in the continental United States to estimate the contribution of estuarine systems to the overall coastal budget of organic carbon.
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Whitfield, A. "Predation on small juvenile fishes in shallow estuarine nursery areas: Reply to Baker & Sheaves (2021)." Marine Ecology Progress Series 662 (March 18, 2021): 209–14. http://dx.doi.org/10.3354/meps13678.
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The key criticism by Baker & Sheaves (2021; Mar Ecol Prog Ser 662:205-208) of the Whitfield (2020; Mar Ecol Prog Ser 649:219-234) estuarine littoral predation paradigm review is that shallow water fish nursery habitats contain abundant predator assemblages which may create high predation pressure on the juvenile fish cohorts that occupy these areas. The primary arguments supporting Baker & Sheaves’ criticism arise from a series of papers published by them on piscivorous fish predation in certain tropical Australian estuaries. The counter-argument that shallow littoral areas in estuaries do indeed provide small juvenile fishes with refuge from small and large piscivorous fishes is provided by published papers from 4 different estuary types in South Africa, covering both subtropical and warm-temperate systems. Based on the overall published information, the argument for shallow (<1 m depth) estuarine waters providing major protection for newly settled juveniles appears to be weak in northern Australia but strong in South Africa. The global situation, as outlined in this response, is more supportive of low piscivorous predation in shallow nursery habitats, but further targeted research is needed before we can confirm that littoral estuarine waters are indeed a universal keystone attribute in this regard.
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Pereira, Humberto, Magda C. Sousa, Luís R. Vieira, Fernando Morgado, and João M. Dias. "Modelling Salt Intrusion and Estuarine Plumes under Climate Change Scenarios in Two Transitional Ecosystems from the NW Atlantic Coast." Journal of Marine Science and Engineering 10, no. 2 (February 14, 2022): 262. http://dx.doi.org/10.3390/jmse10020262.
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The Minho and Lima estuaries, separated by approximately 20 km, are two important transitional systems from the NW Atlantic Portuguese coast. Considering their contrasting characteristics, the present work aims to investigate climate change impacts in salt intrusion and estuarine plumes interaction, through an integrated hydrological characterization. The three-dimensional numerical model Delft3D was implemented to explore the hydrological response of these two systems taking into account their interaction. The model was applied to investigate two different climate change scenarios (RCP 4.5 and RCP 8.5), where physical variables such as sea level and river outflow were varied following summer and winter conditions. The numerical results revealed typically estuarine hydrological patterns, although some different features were found for each estuary. The head and mouth of the estuaries may be the zones most affected by climate change. In the first zone, the salinity may increase in the future in response to freshwater reduction from the Minho and Lima rivers. Considering the cumulative impact of the sea level rise, the saline intrusion may increase in the future: in the Minho estuary it reaches 14 km for the Present scenario during the dry season, penetrating further under climate change conditions (15 km for the RCP 4.5 scenario, and 17 km for the RCP 8.5 scenario); in the Lima estuary, the salt propagates further inland, reaching 17 km for the Present scenario, 18 km for the RCP 4.5 scenario, and a maximum of 20 km for the RCP 8.5 scenario. In all scenarios, during winter conditions, the estuarine plumes are larger and wider, being predicted that in the future they will reduce their dimensions during the winter period, and remain unchanged during summertime. Concisely, this modelling study provided more expertise about the physical patterns of these two estuaries and their interaction, as well as to anticipate the climate change impacts in their dynamics.
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McManus, John. "Sedimentation associated with estuarine frontal systems." Geological Society, London, Special Publications 175, no. 1 (2000): 5–11. http://dx.doi.org/10.1144/gsl.sp.2000.175.01.02.
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Magalhães, Wagner F., and Francisco Barros. "Structural and functional approaches to describe polychaete assemblages: ecological implications for estuarine ecosystems." Marine and Freshwater Research 62, no. 8 (2011): 918. http://dx.doi.org/10.1071/mf10277.
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Polychaete assemblages are of special interest when studying dynamic environments such as estuaries because of their high plasticity in life strategies to cope with environmental variability. We tested the hypothesis that polychaete feeding guilds would be more related to environmental characteristics than to taxonomic composition. Polychaetes were sampled on two different occasions along three tropical estuarine systems in north-eastern Brazil. Different polychaete taxa replaced one another along the entire salinity gradient and the overall pattern from high- to low-salinity regions was from high species and feeding-guild diversities to dominance by a single species or a feeding group. We suggest that the relationships between structure and function of polychaete assemblages might provide a measure of the resilience of estuarine conditions; estuaries with a high redundancy in the trophic role of polychaetes might recover faster from disturbance and retain more natural ecological functions than those estuaries with low or no redundancy, because more species would have the capacity to expand their niches to compensate for the loss of neighbouring species. Integrative approaches allying species composition to their trophic role need to be thoroughly investigated to help understand such complex temporal and spatial organisation of benthic assemblages in estuaries.
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Keeley, Annika T. H., Alexander K. Fremier, Pascale A. L. Goertler, Patrick R. Huber, Anna M. Sturrock, Samuel M. Bashevkin, Blake A. Barbaree, et al. "Governing Ecological Connectivity in Cross-Scale Dependent Systems." BioScience 72, no. 4 (January 25, 2022): 372–86. http://dx.doi.org/10.1093/biosci/biab140.
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Abstract Ecosystem management and governance of cross-scale dependent systems require integrating knowledge about ecological connectivity in its multiple forms and scales. Although scientists, managers, and policymakers are increasingly recognizing the importance of connectivity, governmental organizations may not be currently equipped to manage ecosystems with strong cross-boundary dependencies. Managing the different aspects of connectivity requires building social connectivity to increase the flow of information, as well as the capacity to coordinate planning, funding, and actions among both formal and informal governance bodies. We use estuaries in particular the San Francisco Estuary, in California, in the United States, as examples of cross-scale dependent systems affected by many intertwined aspects of connectivity. We describe the different types of estuarine connectivity observed in both natural and human-affected states and discuss the human dimensions of restoring beneficial physical and ecological processes. Finally, we provide recommendations for policy, practice, and research on how to restore functional connectivity to estuaries.
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Nodo, P., N. C. James, A. R. Childs, and M. D. V. Nakin. "Response of demersal fish assemblages to an extreme flood event in a freshwater-deprived estuary in South Africa." Marine and Freshwater Research 69, no. 2 (2018): 253. http://dx.doi.org/10.1071/mf17096.
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The Kariega Estuary in South Africa, is an example of a freshwater-deprived estuary. Large-scale water abstraction and droughts have resulted in this estuary either being uniformly marine or hypersaline. A major episodic flood event in October 2012, the largest ever recorded in this system, provided us with an opportunity to investigate the prolonged effect of an episodic flood on the demersal fish assemblage of a freshwater-deprived estuary. A beam trawl net was used for sampling the fish assemblages from December 2013 to November 2014. The flood event before the sampling period ‘reset’ the system, such that there was a longitudinal salinity gradient from the head to the mouth, which resulted in ‘normal’ estuarine conditions, typical of most estuaries. There was an increase in the abundance of benthopelagic marine migrant species, particularly early juveniles of important fishery species, in the middle and upper reaches during the present study relative to previous studies conducted in this freshwater-deprived system. This suggests increased recruitment of these species into their estuarine nursery habitat. The present study highlights the importance of understanding the effect of freshwater inflow on the demersal estuarine fish assemblage and the nursery role of this and other estuarine systems and their management.
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Silva, Fred B., Janilson F. Silva, Ranilson S. Bezerra, and Paulo J. P. Santos. "Are biochemical composition parameters of sediment good tools for assessing the environmental quality of estuarine areas in tropical systems?" Journal of the Marine Biological Association of the United Kingdom 99, no. 1 (November 6, 2017): 9–18. http://dx.doi.org/10.1017/s0025315417001795.
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The present study aims to assess the environmental quality of six estuaries in north-eastern Brazil, using biochemical composition and quantity of organic matter in tropical sediments. Samples were collected monthly during spring low tide from August 2011 to July 2012, in the mid-littoral. Concentrations of organic matter and its biochemical composition reflected the degree of anthropogenic pressure. Although total concentrations of proteins and carbohydrates were similar among estuaries with contrasting levels of anthropogenic pressure, the protein to carbohydrates (PRT : CHO) ratio effectively reflected the trophic state of these areas. PRT : CHO ratios >1 were observed in all studied areas suggesting eutrophic conditions or an initial stage of eutrophication in all of them. Low Chl-a/Phaeo ratios may be associated with the level of eutrophication of each area, however it may also reflect the natural productivity or the presence of mangrove debris. These results were compared with those obtained in previous environmental assessments of the same estuarine areas using the AZTI Marine Biotic Index and monitoring reports showing good agreement. The present study confirmed for the first time in tropical estuarine areas that the biochemical approach can be successfully used to assess the trophic state of the benthic compartment.
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Beard, Jason M., Natalie A. Moltschaniwskyj, Christine M. Crawford, John A. E. Gibson, and D. Jeff Ross. "Using macrofaunal communities to inform estuarine classification." Marine and Freshwater Research 70, no. 3 (2019): 371. http://dx.doi.org/10.1071/mf17372.
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Worldwide, geomorphological classifications of estuaries are often used to guide the design of monitoring programs and management strategies. However, if classifications do not reflect biotic patterns, the effectiveness of monitoring and management is potentially reduced. In this study, we consider the effectiveness of one classification scheme in describing biotic patterns by examining and comparing spatial variation of macrofaunal assemblages and their relationship with the environment in 12 estuaries of 2 geomorphological types (mesotidal river dominated and permanently open barrier estuaries). Estuaries were sampled at three locations (upper, mid and lower) for macroinvertebrates and environmental characteristics. Differences in macrofaunal assemblages occurred between the estuary types at the lower and mid locations, but not the upper. Similarities in the upper locations were related to sediment, whereas at the mid and lower locations differences were linked to salinity, dissolved oxygen concentrations and seagrass area. Within estuaries, location effects were definitive and unique within each estuary type, correlating to changes in sediment particle size, nitrogen concentration, microphytobenthos and percentage organic carbon. These results suggest that estuarine classification based on physical attributes alone does have the potential to capture important biological attributes if the biological scales of variability within these systems are well understood.
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Punchihewa, N. N., S. R. Krishnarajah, and P. Vinobaba. "Mysid (Crustacea: Mysidacea) Distribution in the Bolgoda Estuarine System and Lunawa Lagoon, Sri Lanka." International Journal of Environment 6, no. 1 (February 28, 2017): 23–30. http://dx.doi.org/10.3126/ije.v6i1.16865.
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Mysids are one of the most abundant and important fauna in estuarine hyperbenthic communities. They form important links in estuarine food chains and play a critical role in the cycling of energy within estuarine systems. Therefore, it is important to recognize the distribution of estuarine mysids in Sri Lanka. The present study was undertaken in Bolgoda estuarine system and Lunawa lagoon, in order to find out the distribution of mysids in these brackish water systems. Reconnaissance surveys were conducted, in Bolgoda North Lake, Panadura estuary of the Bolgoda estuarine system and the Lunawa lagoon from April 2012 to February 2013. The samples were collected using a hand held dip net, during day time at low tide along an eighty meter transect at the boundary of the estuarine waters. Mesopodopsis zeylanica was the only mysid species observed from the low water areas of the lagoon along the boundary of the stream. In each collection, it was recorded, higher percentages of females than the males. Mysids were recoded only from unpolluted areas and they were absent, where Eichhornia crassipes (water hyacinth) was widespread. The findings of this analysis could be used to establish the fact that boundary condition and polluted condition are having a great effect on presence of mysids. It may be due to their specific niche requirements and specialized habitats. Accordingly, mysids serve as pollution indicator species in estuarine ecosystems. An immediate management strategy is required in protecting the Bolgoda estuarine systems from dumping household pollutants as well as other pollutants and complete elimination of the invader plants like E. crassipes, in order to protect estuarine biodiversity.INTERNATIONAL JOURNAL OF ENVIRONMENT Volume-6, Issue-1, Dec-Feb 2016/17, page: 23-30
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McCall, Grant S., Anthony Akpan, Doru Banaduc, Diego Figueroa, Nelson Fontoura, Robert Hitchcock, Sherman Horn, Devashish Kar, and Thong Tran. "The Estuarine Ecological Knowledge Network Makes Progress: International Project Sites and Potential Ways Forward." Marine Technology Society Journal 56, no. 3 (June 8, 2022): 116–17. http://dx.doi.org/10.4031/mtsj.56.3.28.
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Abstract The Estuarine Ecological Knowledge Network (EEKN) brings together scientists and coastal fishing communities in seeking new ways forward for Earth's major river deltas and estuaries, including the Mississippi (United States), Rio Grande (United States), Danube (Romania/Ukraine), Ganges (India/Bangladesh), Niger (Nigeria), and Mekong (Vietnam) river deltas, and the Patos Lagoon (Brazil). Such environments are universally understood as crucial for the biological productivity of oceans and they are home to hundreds of millions of human inhabitants, many of whom directly depend on that marine richness in terms of the operation of their socioeconomic systems. As human-induced climate change and its consequences for Earth's oceans and coastlines increases, estuarine ecosystems are particularly threatened by problems such as sea-level rise, coastal erosion, saltwater intrusion, and increased impacts from tropical storms. These problems are often amplified by human dynamics of environmental degradation, including overfishing, pollution, and large-scale landscape modification projects. The EEKN is designed to enhance communication and cooperation between fishing communities, scientists, and policy makers in learning about the complexity of both ecological and socioeconomic systems in estuaries and deltas, and in developing more effective policy for managing fisheries, protecting and restoring coastlines, and increasing the resilience of coastal communities.
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Reid, David J., Luca D. Chiaroni, Judi E. Hewitt, Drew M. Lohrer, Christoph D. Matthaei, Ngaire R. Phillips, Mike R. Scarsbrook, et al. "Sedimentation effects on the benthos of streams and estuaries: a cross-ecosystem comparison." Marine and Freshwater Research 62, no. 10 (2011): 1201. http://dx.doi.org/10.1071/mf11056.
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Connected ecosystems can be detrimentally affected by the same stressor, such as occurs when excess fine sediment moves from streams into estuaries. However, no previous study has directly compared sedimentation effects across these ecosystems. Responses of benthic macroinvertebrate communities to sedimentation were predicted to vary between streams and estuaries, because of intersystem differences in the physical environment and representation of species traits. To compare these responses, fine terrigenous sediment was added simultaneously to replicated plots in stream-run habitats and the adjacent estuary. Although sediment addition to streams caused reduced invertebrate densities after 1 week, no changes in taxon richness or consistent changes in community structure were detected, and densities had recovered another week later. In contrast, sediment addition to estuarine sites caused large declines in invertebrate densities and changes in community structure, which remained evident at the innermost sites 16 days after addition. Across both systems, sedimentation effects were detectable only for some of the common taxa, and biological traits were not predictive of effects. The potential for more severe effects in estuaries should be considered when predicting the implications of land-use changes that may increase sedimentation, and when setting guidelines for maintaining stream and estuarine condition.
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Austin, Timothy, Ana Vila-Concejo, Andrew Short, and Roshanka Ranasinghe. "A Multi-Scale Conceptual Model of Flood-Tide Delta Morphodynamics in Micro-Tidal Estuaries." Geosciences 8, no. 9 (August 29, 2018): 324. http://dx.doi.org/10.3390/geosciences8090324.
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Wave and tide induced sediment transport pathways and rates govern the morphological evolution of estuarine systems. An understanding of the morphodynamics of these systems is required to maintain their commercial, biological and recreational value. The morphodynamics of Port Stephens estuary, a micro-tidal estuary located on a wave dominated southeast coast of Australia were investigated using bathymetric surveys and current velocity data from several locations over the estuary. This provided detailed insight into the rates and direction of movement for the main sedimentary features of the system, and how these features interact with the processes that drive their evolution. We used these findings to develop a conceptual model for estuarine morphodynamics that accounts for fair weather and storm conditions. Our model explains how sediment eroded from the estuarine beaches is trapped by the adjacent flood-tide delta. The model is applicable to fetch-limited estuaries that do not have offshore sources of sediment, where the tidal currents are weak in relation to the incident ocean waves, and that have a wide, stable entrance through which ocean waves can propagate into the estuary. The model is multi-scale in that it encapsulates both short-term and local process, and large scale evolution of an estuary; therefore, it represents a tool that may be used in developing sustainable estuary management strategies.
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Davis, Melanie J., Isa Woo, Susan E. W. De La Cruz, Christopher S. Ellings, Sayre Hodgson, and Glynnis Nakai. "Allochthonous marsh subsidies enhances food web productivity in an estuary and its surrounding ecosystem mosaic." PLOS ONE 19, no. 2 (February 29, 2024): e0296836. http://dx.doi.org/10.1371/journal.pone.0296836.
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Terrestrial organic matter is believed to play an important role in promoting resilient estuarine food webs, but the inherent interconnectivity of estuarine systems often obscures the origins and importance of these terrestrial inputs. To determine the relative contributions of terrestrial (allochthonous) and aquatic (autochthonous) organic matter to the estuarine food web, we analyzed carbon, nitrogen, and sulfur stable isotopes from multiple trophic levels, environmental strata, and habitats throughout the estuarine habitat mosaic. We used a Bayesian stable isotope mixing model (SIMM) to parse out relationships among primary producers, invertebrates, and a pelagic and demersal fish species (juvenile Chinook salmon and sculpin, respectively). The study was carried out in the Nisqually River Delta (NRD), Washington, USA, a recently-restored, macrotidal estuary with a diverse habitat mosaic. Plant groupings of macroalgae, eelgrass, and tidal marsh plants served as the primary base components of the NRD food web. About 90% of demersal sculpin diets were comprised of benthic and pelagic crustaceans that were fed by autochthonous organic matter contributions from aquatic vegetation. Juvenile salmon, on the other hand, derived their energy from a mix of terrestrial, pelagic, and benthic prey, including insects, dipterans, and crustaceans. Consequently, allochthonous terrestrial contributions of organic matter were much greater for salmon, ranging between 26 and 43%. These findings demonstrate how connectivity among estuarine habitat types and environmental strata facilitates organic matter subsidies. This suggests that management actions that improve or restore lateral habitat connectivity as well as terrestrial-aquatic linkages may enhance allochthonous subsidies, promoting increased prey resources and ecosystem benefits in estuaries.
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Dyson, I. A. "GREENSAND RESERVOIRS IN SILICICLASTIC SHORELINE SYSTEMS: FACIES MODELS FOR HYDROCARBON EXPLORATION." APPEA Journal 38, no. 2 (1998): 132. http://dx.doi.org/10.1071/aj97085.
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Greensand reservoirs are particularly significant in siliciclastic shoreline systems. Formation of autochthonous glauconite is restricted almost exclusively to the rising limb of the relative sea level (RSL) curve. Depositional environments that are typically developed in response to a rise in RSL are estuaries, barrier bars and shoreface sands. In this setting, the greensands are diachronous and exploration for hydrocarbon reservoirs should ideally be based on a sequence stratigraphic framework. These deposits are characterised by a number of significant surfaces that differ greatly in their origin, geographic extent and chronostratigraphic significance, and their thickness depends on the rate of RSL rise and sediment supply. The identification of significant surfaces bounding or contained within depositional sequences is critical, especially where drillhole samples are either unreliable or not available for geochemical and palynological analysis. Abrupt physical and chemical changes often occur on or across these surfaces, e.g. porosity, permeability and the presence of Fe-rich authigenic minerals such as glauconite and siderite. Greensands deposited in estuarine, barrier bar and shoreforce environments have excellent oil and gas potentail. Early Cretaceous greensand reservoirs from the North West Shelf are best developed where they overlie ravinement surfaces. Recognition of greensands within estuarine, barrier bar and shoreface environments is dependent on the correct identification of facies and the subsequent interpretation of the bounding discontinuities.
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DiGiacomo, Alexandra E., Walker E. Harrison, David W. Johnston, and Justin T. Ridge. "Elasmobranch Use of Nearshore Estuarine Habitats Responds to Fine-Scale, Intra-Seasonal Environmental Variation: Observing Coastal Shark Density in a Temperate Estuary Utilizing Unoccupied Aircraft Systems (UAS)." Drones 4, no. 4 (December 8, 2020): 74. http://dx.doi.org/10.3390/drones4040074.
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Many coastal shark species are known to use estuaries of the coastal southeastern United States for essential purposes like foraging, reproducing, and protection from predation. Temperate estuarine landscapes, such as the Rachel Carson Reserve (RCR) in Beaufort, NC, are dynamic habitat mosaics that experience fluctuations in physical and chemical oceanographic properties on various temporal and spatial scales. These patterns in abiotic conditions play an important role in determining species movement. The goal of this study was to understand the impact of environmental conditions around the RCR on shark density within the high-abundance summer season. Unoccupied Aircraft System (UAS) surveys of coastal habitats within the reserve were used to quantify shark density across varying environmental conditions. A combination of correlation analyses and Generalized Linear Modelling (GLM) revealed that density differs substantially across study sites and increases with rising water temperatures, conclusions that are supported by previous work in similar habitats. Additionally, density appears to increase moving towards dawn and dusk, potentially supporting crepuscular activity in coastal estuarine areas. By describing shark density dynamics in the RCR, this study provides new information on this population and presents a novel framework for studying elasmobranchs in temperate estuaries.
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Cyrus, D. P. "TURBIDITY AND OTHER PHYSICAL FACTORS IN NATAL ESTUARINE SYSTEMS PART 2: ESTUARINE LAKES." Journal of the Limnological Society of Southern Africa 14, no. 2 (January 1988): 72–81. http://dx.doi.org/10.1080/03779688.1988.9632841.
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Cyrus, D. P. "TURBIDITY AND OTHER PHYSICAL FACTORS IN NATAL ESTUARINE SYSTEMS PART 1: SELECTED ESTUARIES." Journal of the Limnological Society of Southern Africa 14, no. 2 (January 1988): 60–71. http://dx.doi.org/10.1080/03779688.1988.9632840.
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Mackay, C. F., and D. P. Cyrus. "Is freshwater quality adequately defined by physico-chemical components? Results from two drought-affected estuaries on the east coast of South Africa." Marine and Freshwater Research 52, no. 3 (2001): 267. http://dx.doi.org/10.1071/mf98063.
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From 1992 to 1994 the physico-chemical conditions of two systems on the east coast of southern Africa shifted from estuarine to freshwater as a result of mouth closure during the prevailing drought. Although there was gradual colonization by freshwater benthic invertebrates, both systems were dominated by estuarine benthic infauna. The upper reaches of the Siyaya Estuary were entirely characterized by freshwater taxa (95%) by 1994, whereas Nhlabane Estuary showed a smaller increase in the number of these fauna. Non-metric multidimensional scaling plotted benthic populations as separate groups each year. These groups were not the result of a gradual shift in benthic fauna from an estuarine towards a freshwater bias. Rather, the upper estuarine reaches were dominated by taxa characteristic of freshwater environments, despite similar water quality conditions along all reaches. Three quarters of the zoobenthic communities (expressed as density m–2) were still estuarine in nature. The two populations were comparable to those occurring in nearby freshwater coastal lakes, which have been subject to marine influence in geological history. It was concluded that assessment of the biological component in addition to the physico-chemical properties should be considered when defining water quality in such systems.
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Woodroffe, C. D. "Mangrove response to sea level rise: palaeoecological insights from macrotidal systems in northern Australia." Marine and Freshwater Research 69, no. 6 (2018): 917. http://dx.doi.org/10.1071/mf17252.
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Accelerated sea-level rise threatens coastal wetlands; it is unclear whether sediment accretion beneath mangroves will be sufficient to keep pace. A conceptual framework, used to describe the response of reefs, can also be applied to mangroves, discriminating drowning or back-stepping with rapid rise from keep-up or catch-up under moderate rates. In macrotidal estuaries of northern Australia, different mangrove species grow across particular elevation ranges and accretion rates decrease with tidal elevation. Palaeoecological reconstructions, from drilling, dating and pollen analysis, record mangrove distribution over past millennia. Estuarine plains are underlain by a vertically continuous stratigraphy of muds, implying continuity of widespread ‘big swamp’ mangrove forests during decelerating stages of post-glacial sea-level rise c. 7000 years ago. In contrast, on higher-energy open coasts, mangroves back-stepped, but re-established as the shoreline prograded when the nearshore built to suitable elevation: a catch-up mode. These results demonstrate that mangrove response to sea-level rise has varied, determined by the availability of sediment and the oceanographic processes by which it is redistributed. How mangrove forests adjust in future will also vary as a function of local topography and sediment availability. Extensive plains flanking estuarine systems are particularly vulnerable to tidal creek extension and saline incursion under future higher sea levels.
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Whitfield, A. K. "A CHARACTERIZATION OF SOUTHERN AFRICAN ESTUARINE SYSTEMS." Southern African Journal of Aquatic Sciences 18, no. 1-2 (June 1992): 89–103. http://dx.doi.org/10.1080/10183469.1992.9631327.
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