Articles de revues : « Estuary-coast gradient »

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Yao, Ru, LiNa Cai, JianQiang Liu et MinRui Zhou. « GF-1 Satellite Observations of Suspended Sediment Injection of Yellow River Estuary, China ». Remote Sensing 12, n^o 19 (23 septembre 2020) : 3126. http://dx.doi.org/10.3390/rs12193126.

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We analyzed the distribution of suspended sediments concentration (SSC) in the Yellow River Estuary based on data from GaoFen-1 (GF-1), which is a high-resolution satellite carrying a wide field-of-view (WFV) sensor and panchromatic and a multispectral (PMS) sensor on it. A new SSC retrieval model for the wide field-of-view sensor (M-WFV) was established based on the relationship between in-situ SSC and the reflectance in blue and near infrared bands. SSC obtained from 16 WFV1 images were analyzed in the Yellow River Estuary. The results show that (1) SSC in the study area is mainly 100–3500 mg/L, with the highest value being around 4500 mg/L. (2) The details of suspended sediment injection phenomenon were found in the Yellow River Estuary. The SSC distribution in the coastal water has two forms. One is that the high SSC water evenly distributes near the coast and the gradient of the SSC is similar. The other is that the high SSC water concentrates at the right side of the estuary (Laizhou Bay) with a significantly large area. Usually, there is a clear-water notch at the left side of the estuary. (3) Currents clearly influenced the SSC distribution in the Yellow River Estuary. The SSC gradient in the estuary was high against the local current direction. On the contrary, the SSC gradient in the estuary was small towards the local current direction. Eroding the coast and resuspension of the bottom sediments, together with currents, are the major factors influencing the SSC distribution in nearshore water in the Yellow River Estuary.

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Ramos, S., C. B. Paris et M. M. Angélico. « Larval fish dispersal along an estuarine–ocean gradient ». Canadian Journal of Fisheries and Aquatic Sciences 74, n^o 9 (septembre 2017) : 1462–73. http://dx.doi.org/10.1139/cjfas-2016-0325.

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The present study investigated the larval fish dispersal along an estuarine–ocean gradient to explore connectivity between ocean and estuaries. During spring 2009, a combined ocean–estuarine survey was conducted along the Lima estuarine salinity gradient and in two transects off the adjacent coast (northwestern Iberian Peninsula), until the 100 m isobaths. Salinity, total particulate matter, particulate organic matter, total dissolved carbon, and dissolved organic carbon reached higher values at the ocean, and chlorophyll a and nutrients increased at the estuary. From the total 56 taxa identified, 14 were present along the gradient, including estuarine species (ES), marine stragglers (MS), and migrants (MM). Canonical correspondence analysis showed that species were separated along the gradient according to their ecological functional classification. MM associated with high salinity were separated from ES correlated with lower salinities and high chlorophyll a concentrations of inner estuary. Flounder (Platichthys flesus) showed a typical spatial gradient of MM, with abundance increasing from the ocean towards inner estuary. The dispersal of larvae along the Lima estuarine–ocean gradient was indicative of connectivity between habitats, emphasizing the need to consider this feature in management plans, mainly for species exploited by commercial fisheries.

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Huang, Ju, Rui Yuan et Jianrong Zhu. « Numerical Simulation and Analysis of Water and Suspended Sediment Transport in Hangzhou Bay, China ». Journal of Marine Science and Engineering 10, n^o 9 (5 septembre 2022) : 1248. http://dx.doi.org/10.3390/jmse10091248.

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Hangzhou Bay is a large, high-turbidity shallow bay located on the southern side of the Changjiang Estuary, China. The process and dynamic mechanisms of water and sediment transport in the bay are not yet clear. An improved three-dimensional sediment numerical model that combined various dynamic factors was established to simulate and analyze these mechanisms. The residual current cannot properly represent the net water and sediment transport, and the residual unit width water flux (RUWF) and residual unit width sediment flux (RUSF) were used to explain the water and sediment transport. The results of numerical simulations indicate that in summer, the surface RUWF from the Changjiang Estuary near Nanhui Cape flows westward along the coast, in which the major part flows southward to the Zhenhai area, and the small part flows further westward along the north coast and then turns to the south coast and eastward, forming the water transport pattern of north-landward and south-seaward, which is stronger in the spring tide than in the neap tide. The bottom RUWF near Zhenhai flows northward to Nanhui Cape in the neap tide, which is larger in the neap tide than in the spring tide. In the middle and western parts of the bay, the RUWF has the same pattern as the surface water transport and is stronger in the spring tide than in the neap tide. The pattern of RUSF is roughly similar to the water flux transport. During the spring tide, the water and sediment transport fluxes near Nanhui Cape are from the Changjiang Estuary into Hangzhou Bay, but from Hangzhou Bay into the Changjiang Estuary during the neap tide. In the winter, the distributions of RUWF, RUSF, and suspended sediment concentration (SSC) are similar to those in the summer. In addition, the distance of surface water transport westward along the north coast is shorter than that in the summer, the magnitude of the bottom RUWF is smaller than that in the summer due to the weaker salinity gradient, and the bottom RUSF near Nanhui Cape is weaker than that in the summer during the neap tide. The net transect water flux (NTWF) and the net transect sediment flux (NTSF) near Nanhui Cape are from the Changjiang Estuary into Hangzhou Bay during the spring tide; during the neap tide, the NTWF is still from the Changjiang Estuary into Hangzhou Bay, but the NTSF is from Hangzhou Bay into the Changjiang Estuary because the SSC is much higher in the bottom layer than in the surface layer. The dynamic reason for the temporal and spatial variation in RUWF and RUSF is that the barotropic pressure gradient force is larger than the baroclinic pressure gradient force during the spring tide and is the opposite during the neap tide.

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Montagna, Paul. « How a Simple Question About Freshwater Inflow to Estuaries Shaped a Career ». Gulf and Caribbean Research 32 (2021) : ii—xiv. http://dx.doi.org/10.18785/gcr.3201.04.

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Chance and good luck led to a career studying how freshwater inflow drives estuary processes. In 1986, someone asked me: How much fresh water has to flow to a bay for it to be healthy? The question shaped my career. There is probably no better place on Earth to compare effects caused by inflow differences than the Texas coast, because the major estuarine systems lie in a climatic gradient where runoff decreases 56—fold from the Louisiana border in the northeast to the Mexico border in the southwest. This estuary—comparison experiment was used to study inflow effects. The science evolved from the idea in the 1990’s that organisms responded directly to inflow rates to the domino theory in the 2000’s of indirect effects where inflow drives estuary conditions and that organisms respond to those habitat conditions. Today it is hypothesized that climate drives hydrology, which drives estuary dynamics; and thus, climatic factors can indirectly shape estuarine structure and function. Assuming change along the inflow gradient is analogous to effects of altering estuaries over time, we can now predict ecosystem change with changing climate or land—use change.

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Miyata, Ryuhei, Reiko Akiyama, Takehito Horie, Yasuhito Noshi et Kei Iguchi. « THE CASE OF SEDIMENT OUTFLOW FROM MOUNTAIN TO THE COAST DUE TO SMALL AND MEDIUM-SIZE FLOODS ». Coastal Engineering Proceedings, n^o 37 (1 septembre 2023) : 64. http://dx.doi.org/10.9753/icce.v37.sediment.64.

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Smaller rivers in Japan can be characterized as having short distances from the mountainous areas of the source of sediment production to the estuary and steep slopes. Therefore, sediment produced from the mountains and river channels at the time of flooding immediately contributes significantly to the sediment dynamics at the estuary and coast in a short period of time. On the other hand, there have been few observations or studies that have measured the volume of landslides and riverbed fluctuations in the mountains in the entire basin before and after the occurrence of flooding, and quantitatively linked them to the amount of landslide movement and shoreline changes in the entire basin. This paper discusses the Chitose River basin (basin area A: 30km2, river channel distance L: 0.179km, stream gradient I: 1/14) and the Niizaki River basin (A: 16km2, L: 0.213km, I:1/17), which have an estuary on the Yugawara coast in Kanagawa Prefecture. The effect of sediment production from mountains and riverbeds at the time of flooding on coastal sediment dynamics on July 3rd, 2021.

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de Carvalho, Fabrício Lopes, et Erminda da Conceição Guerreiro Couto. « Environmental variables influencing the Callinectes (Crustacea : Brachyura : Portunidae) species distribution in a tropical estuary—Cachoeira River (Bahia, Brazil) ». Journal of the Marine Biological Association of the United Kingdom 91, n^o 4 (11 novembre 2010) : 793–800. http://dx.doi.org/10.1017/s0025315410001700.

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The genus Callinectes comprises seven species of blue crab found on the Brazilian coast, almost all are recorded in Cachoeira River estuary. The objective of this study is to analyse distribution of Callinectes species in the estuary of Cachoeira River (Ilhéus, Bahia). Monthly collections were conducted in the low tide of neap tide for a year and in five stations distributed according to the estuary salinity gradient. Six traps were assembled and submerged at each station for two hours. Sediment samples were collected for granulometric characterization and measuring of organic matter content. Temperature, salinity and pH were also measured in the bottom water, as well as water transparency at the start of each collection. Five species were collected: Callinectes danae, C. ornatus, C. exasperatus, C. larvatus and C. bocourti. The species presented different distribution patterns based on the salinity gradient and transversal profile of the estuary. Only C. danae was found in all collection points, and was the most abundant species throughout the study period. Callinectes ornatus was restricted to external estuarine areas, which presented higher salinity and transparency values. Callinectes larvatus predominantly occurred in the external station and estuary partitions, mainly in the margin. In spite of the occurrence of C. exasperatus throughout the entire estuary, this species was restricted to the margin. This study supports the assumption that species distribution patterns of this genus are the result of both variable influence, namely salinity, and complex intraspecific and interspecific relations between the congeneric species.

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Moura, Victor Lacerda, et Luiz Drude de Lacerda. « Mercury Sources, Emissions, Distribution and Bioavailability along an Estuarine Gradient under Semiarid Conditions in Northeast Brazil ». International Journal of Environmental Research and Public Health 19, n^o 24 (19 décembre 2022) : 17092. http://dx.doi.org/10.3390/ijerph192417092.

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In the semiarid coast of northeast Brazil, climate change and changes in land use in drainage basins affect river hydrodynamics and hydrochemistry, modifying the estuarine environment and its biogeochemistry and increasing the mobilization of mercury (Hg). This is particularly relevant to the largest semiarid-encroached basin of the region, the Jaguaribe River. Major Hg sources to the Jaguaribe estuary are solid waste disposal, sewage and shrimp farming, the latter emitting effluents directly into the estuary. Total annual emission reaches 300 kg. In that estuary, the distribution of Hg in sediment and suspended particulate matter decreases seaward, whereas dissolved Hg concentrations increase sharply seaward, suggesting higher mobilization at the marine-influenced, mangrove-dominated portion of the estuary, mostly in the dry season. Concentrations of Hg in rooted macrophytes respond to Hg concentrations in sediment, being higher in the fluvial endmember of the estuary, whereas in floating aquatic macrophytes, Hg concentrations followed dissolved Hg concentrations in water and were also higher in the dry season. Animals (fish and crustaceans) also showed higher concentrations and bioaccumulation in the marine-influenced portion of the estuary. The variability of Hg concentrations in plants and sediments agrees with continental sources of Hg. However, Hg fractionation in water and contents in the animals respond to higher Hg availability in the marine-dominated end of the estuary. The results suggest that the impact of anthropogenic sources on Hg bioavailability is modulated by regional and global environmental changes and results from a conjunction of biological, ecological and hydrological characteristics. Finally, increasing aridity due to global warming, observed in northeast Brazil, as well as in other semiarid littorals worldwide, in addition to increased water overuse, augment Hg bioavailability and environmental risk and exposure of the local biota and the tradition of human populations exploiting the estuary’s biological resources.

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Cavalcante, Geórgenes H., David A. Feary et Björn Kjerfve. « Effects of Tidal Range Variability and Local Morphology on Hydrodynamic Behavior and Salinity Structure in the Caeté River Estuary, North Brazil ». International Journal of Oceanography 2013 (8 septembre 2013) : 1–10. http://dx.doi.org/10.1155/2013/315328.

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Tidal influence and local morphology on circulation and salt transport are investigated in the Caeté river estuary, a well-mixed estuary along the north coast of Brazil. Velocity, temperature, and salinity data were collected in three different locations along the estuary’s main channel, over three single, 13 h tidal cycles. The aim of this study was to investigate the relationship between tidal distortion and salinity by using classical methods of comparison of three cross-channel circulation characteristics, as well as computation of salt flux and vertical mixing. Findings indicate a flood-ebb asymmetry in currents, due to the distinct funneling morphology of the estuary, with shallow marginal areas being dominant towards the estuary head, while both stratification and shear dominate near the estuary mouth. The tidal currents enhanced vertical diffusion in the mid- and lower reaches, explaining the prevailing weakly stratified conditions, while the dominant well-mixed conditions in the upper estuary are a result of a combination of stronger flood currents and negligible vertical saline gradient. The predominant downstream salt transport supports the conclusion that there is little accumulation of salt in the Caeté river estuary. In addition, findings indicate that tidal correlation and Stokes drift are important components in the upper estuary, while tidal correlation played an important role in the middle estuary, with fluvial discharge most important in the lower estuary.

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Van de Broek, Marijn, Stijn Temmerman, Roel Merckx et Gerard Govers. « Controls on soil organic carbon stocks in tidal marshes along an estuarine salinity gradient ». Biogeosciences 13, n^o 24 (16 décembre 2016) : 6611–24. http://dx.doi.org/10.5194/bg-13-6611-2016.

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Abstract. Tidal marshes are sedimentary environments and are among the most productive ecosystems on Earth. As a consequence they have the potential to reduce atmospheric greenhouse gas concentrations by sequestering organic carbon (OC). In the past decades, most research on soil organic carbon (SOC) storage in marsh environments has focused on salt marshes, leaving carbon dynamics in brackish and freshwater marshes largely understudied and neglecting the diversity among tidal marshes. We therefore conducted an extensive sampling campaign to quantify and characterize SOC stock in marshes along a salinity gradient in the Scheldt estuary (Belgium and the Netherlands). We find that SOC stocks vary significantly along the estuary, from 46 in freshwater marshes to 10 kg OC m−2 in salt marshes. Our data also show that most existing studies underestimate total SOC stocks due to shallow soil sampling, which also influences reported patterns in OC storage along estuaries. In all sampled tidal marsh sediments the SOC concentration is more or less constant from a certain depth downward. However, this concentration decreases with increasing salinity, indicating that the amount of stable SOC decreases from the upper estuary towards the coast. Although the net primary production of macrophytes differs along the estuary, our data suggest that the differences in OC storage are caused mainly by variations in suspended sediment concentration and stable particulate OC (POC) content in the water along the estuary. The fraction of terrestrial suspended sediments and POC that is transported downstream of the maximum turbidity zone is very limited, contributing to smaller amounts of long-term OC sequestration in brackish and salt marsh sediments. In addition, high rates of sediment deposition on freshwater tidal marshes in the maximum turbidity zone promote efficient burial of OC in these marsh sediments.

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Nyakeya, Kobingi, James Onchieku, Frank Masese, Zipporah Gichana, Albert Getabu et Jane Nyamora. « Trends in Water Quality in a Tropical Kenyan River-estuary System : Responses to Anthropogenic Activities ». Asian Journal of Biology 20, n^o 6 (11 mai 2024) : 34–51. http://dx.doi.org/10.9734/ajob/2024/v20i6413.

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Aims: To determine the spatial variation in physico-chemical water quality attributes in estuarine ecosystems of South Coast Kenya to inform its management. Study Design: We employed diagnostic research design where such factors as anthropogenic activities, hydrology, and accessibility were considered in choosing 12 sampling stations. A mixed sampling design (probability and non-probability) was used to sample. Place and Duration of Study: Four discharging rivers into estuarine system with a reference point were identified. 12 sampling points were earmarked and sampled for 12 months. Methodology: Nine selected water quality parameters were collected in triplicates monthly for 12 months. Temperature, dissolved oxygen, pH, conductivity, salinity and TDS were collected in situ using YSI Multiparameter meter (Professional plus) while nutrients were analyzed in the laboratory calorimetrically. Data was tested for normality and homogeneity of variances using Levene's and Shapiro-Wilk tests. Two-way analysis of variance (ANOVA), and Principal Component Analysis (PCA) were done using the 64-bit R Software version 4.3.0 to test for significant differences and correlate the parameters among the sampling sites respectively. Observed differences were considered statistically significant at P < 0.05. Results: The measured environmental variables differed significantly among the sampling stations (P < 0.05). temperature and salinity exhibited moderate to strong effect on water quality, while pH and nutrients (phosphates, nitrates, and ammonia) exhibited mixed effects with both negative and positive loadings on the Principal Components. It is demonstrated that the south coast estuary, Kenya is affected by two gradients: mineralization from the sea and the organic matter gradient at the upstream stations dominated by the fluvial inflows from the respective rivers. Conclusion: The south coast of Kenya estuary is impacted by natural processes and anthropogenic activities. we recommend for continued regular water quality assessment and monitoring to acquire sufficient data to shape policy frameworks towards its sustainable management.

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Niveditha, S. Krishna, C. K. Haridevi, Revati Hardikar et Anirudh Ram. « Phytoplankton assemblage and chlorophyll a along the salinity gradient in a hypoxic eutrophic tropical estuary-Ulhas Estuary, West Coast of India ». Marine Pollution Bulletin 180 (juillet 2022) : 113719. http://dx.doi.org/10.1016/j.marpolbul.2022.113719.

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Harrison, S. J. « Climatic conditions over the estuary and Firth of Forth, Scotland ». Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 93, n^o 3-4 (1987) : 245–58. http://dx.doi.org/10.1017/s0269727000006710.

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SynopsisThe pattern of climatic variation over estuaries and their environs is, to a considerable extent, controlled by aspect, slope and elevation in addition to orientation of the major relief features with respect to the movement of principal weather systems. Data from the few climatological stations within the immediate vicinity of the estuary and Firth of Forth demonstrate the essentially maritime nature of climate, and indicate also that there is a dominantly west–east gradient of change in most climatological variables. Below the high water mark the movement of water in tidal ebb and flow and river inflow modify atmosphere–surface interactions over relatively short spatial and temporal scales. Observations from a fixed instrument tower on Skinflats in the middle estuary and from Inchkeith Lighthouse indicate that tidal water movements exert varying degrees of control over sub-surface heat fluxes, air movement in the atmospheric boundary layer and the inland penetration of coastal weather systems such as the typical east coast haar.

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Cordovil, Gleydson, et Mauricio Camargo. « ANÁLISE POPULACIONAL DO PEIXE–ESPADA, Trichirus lepturus (PERCIFORMES;TRICHIURIDAE), NO ESTUÁRIO DO RIO CAETÉ, COSTA NORTE DO BRASIL ». Scientific Magazine UAKARI 3, n^o 1 (4 août 2008) : 104–8. http://dx.doi.org/10.31420/uakari.v3i1.24.

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This study describes frequency distribution of the total length and estimates the weight-length relation of Trichiurus lepturus in the estuary of the Caeté River, northeastern Brazil. These population parameters were compared among four areas along the latitudinal gradient of the South American coast. Samples were gathered in the estuarine area of the Caeté River from October 1996 to August 1997. The total length of T. lepturus at the River varied between 27-81 cm, with a mode at 57 cm. No significant differences were detected among the four stocks. Different stock responses to environmental factors such as food availability, local seasonality and variations among years might probably explain these findings.

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Malamud-Roam, Frances, et B. Lynn Ingram. « Late Holocene δ13C and pollen records of paleosalinity from tidal marshes in the San Francisco Bay estuary, California ». Quaternary Research 62, n^o 2 (septembre 2004) : 134–45. http://dx.doi.org/10.1016/j.yqres.2004.02.011.

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Records of stable carbon isotopes (δ13C) are presented from cores collected from four San Francisco Bay marshes and used as a proxy for changes in estuary salinity. The δ13C value of organic marsh sediments are a reflection of the relative proportion of C3 vs. C4 plants occupying the surface, and can thus be used as a proxy for vegetation change on the marsh surface. The four marshes included in this study are located along a natural salinity gradient that exists in the San Francisco Bay, and records of vegetation change at all four sites can be used to infer changes in overall estuary paleosalinity. The δ13C values complement pollen data from the same marsh sites producing a paleoclimate record for the late Holocene period in the San Francisco Bay estuary. The data indicate that there have been periods of higher-than-average salinity in the Bay estuary (reduced fresh water inflow), including 1600–1300 cal yr B.P., 1000–800 cal yr B.P., 300–200 cal yr B.P., and ca. A.D. 1950 to the present. Periods of lower-than-average salinity (increased fresh water inflow) occurred before 2000 cal yr B.P., from 1300 to 1200 cal yr B.P. and ca. 150 cal yr B.P. to A.D. 1950. A comparison of the timing of these events with records from the California coast, watershed, and beyond the larger drainage of the Bay reveals that the paleosalinity variations reflected regional precipitation.

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Goñi-Urriza, MS, D. Point, D. Amouroux, R. Guyoneaud, OFX Donard, P. Caumette et R. Duran. « Bacterial community structure along the Adour estuary (French Atlantic coast) : influence of salinity gradient versus metal contamination ». Aquatic Microbial Ecology 49 (16 octobre 2007) : 47–56. http://dx.doi.org/10.3354/ame01128.

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Valério-Berardo, M. T., M. N. Flynn, L. M. R. Rodrígues et F. S. Attollini. « SEASONAL COMPOSITION AND SPATIAL DISTRIBUTION OF MACROBENTHIC ASSOCIATIONS ALONG AN ESTUARINE GRADIENT IN ITANHAÉM, SÃO PAULO, BRAZIL ». CICIMAR Oceánides 21, n^o 1-2 (31 décembre 2006) : 1. http://dx.doi.org/10.37543/oceanides.v21i1-2.24.

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Macrobenthos distribution along the salinity gradient and the pattern of species temporal changes were investigated in the Itanhaém River Estuary. Environmental variables such as grain size, sediment organic content, water salinity, water temperature and dissolved oxygen were examined as factors likely to influence the distribution of species. A total of 2130 individuals, distributed in 16 taxa (species/genera) were collected from the 12 samples obtained. The most abundant species were Cyprideis salebrosa, Heteromastus similis, Scololepsis squamata, Nephtys squamosa, Diplodonta sp. and Tellina sp. The canonical ordinations analysis indicated the presence of three benthic associations: a marine Diplodonta sp. - Tellina sp. community; a brackish water C. salebrosa - N. squamosa community and a wide spread S. squamata - H. similis community. The distribution of the estuarine macrozoobenthic species seems to be mainly controlled by salinity and the observed gradient in species compositon and dominance in the marine and brackish part of the Itanhaém River Estuary is similar to the one occurring in other mixohaline habitats of the Brazilian South eastern Coast. Composición estacional y distribución espacial de asociaciones macrobentónicas en un gradiente estuarino de Itanhaém, São Paulo, Brasil La distribución de los macrobentos a lo largo del gradiente de la salinidad y el patrón de los cambios temporales de las especies fueron investigados en el estuario del Río Itanhaém. Las variables ambientales tales como tamaño de grano, contenido orgánico del sedimento, salinidad del agua, temperatura del agua y el oxígeno disuelto fueron examinados como factores que determinan la distribución de las especies. Se recolectaron un total de 2130 individuos, de 16 taxa (especies/géneros) de las 12 muestras obtenidas. Las especies más abundantes fueron Cyprideis salebrosa, Heteromatus similis, Scololepsis squamata, Nephtys squamosa, Diplodonta sp. y Tellina sp. El análisis canónico de correspondencia indicó la presencia de tres asociaciones bentónicas: una comunidad marina, Diplodonta sp. - Tellina sp.; una comunidad de agua salobre, C. salebrosa - N. squamosa y una comunidad de extensión amplia, S. squamata - H. similis. La distribución de la especies macrozoobentónica de estuario parece ser controlada principalmente por la salinidad y el gradiente observados en composición. La dominancia de especies en las partes marina y salobre del estuario del Río de Itanhaém es similar a la de otros hábitats mixohalinos de la costa del sudeste brasileño.

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Valério-Berardo, M. T., M. N. Flynn, L. M. R. Rodrígues et F. S. Attollini. « SEASONAL COMPOSITION AND SPATIAL DISTRIBUTION OF MACROBENTHIC ASSOCIATIONS ALONG AN ESTUARINE GRADIENT IN ITANHAÉM, SÃO PAULO, BRAZIL ». CICIMAR Oceánides 21, n^o 1-2 (31 décembre 2006) : 1. http://dx.doi.org/10.37543/oceanides.v21i1-2.24.

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Macrobenthos distribution along the salinity gradient and the pattern of species temporal changes were investigated in the Itanhaém River Estuary. Environmental variables such as grain size, sediment organic content, water salinity, water temperature and dissolved oxygen were examined as factors likely to influence the distribution of species. A total of 2130 individuals, distributed in 16 taxa (species/genera) were collected from the 12 samples obtained. The most abundant species were Cyprideis salebrosa, Heteromastus similis, Scololepsis squamata, Nephtys squamosa, Diplodonta sp. and Tellina sp. The canonical ordinations analysis indicated the presence of three benthic associations: a marine Diplodonta sp. - Tellina sp. community; a brackish water C. salebrosa - N. squamosa community and a wide spread S. squamata - H. similis community. The distribution of the estuarine macrozoobenthic species seems to be mainly controlled by salinity and the observed gradient in species compositon and dominance in the marine and brackish part of the Itanhaém River Estuary is similar to the one occurring in other mixohaline habitats of the Brazilian South eastern Coast. Composición estacional y distribución espacial de asociaciones macrobentónicas en un gradiente estuarino de Itanhaém, São Paulo, Brasil La distribución de los macrobentos a lo largo del gradiente de la salinidad y el patrón de los cambios temporales de las especies fueron investigados en el estuario del Río Itanhaém. Las variables ambientales tales como tamaño de grano, contenido orgánico del sedimento, salinidad del agua, temperatura del agua y el oxígeno disuelto fueron examinados como factores que determinan la distribución de las especies. Se recolectaron un total de 2130 individuos, de 16 taxa (especies/géneros) de las 12 muestras obtenidas. Las especies más abundantes fueron Cyprideis salebrosa, Heteromatus similis, Scololepsis squamata, Nephtys squamosa, Diplodonta sp. y Tellina sp. El análisis canónico de correspondencia indicó la presencia de tres asociaciones bentónicas: una comunidad marina, Diplodonta sp. - Tellina sp.; una comunidad de agua salobre, C. salebrosa - N. squamosa y una comunidad de extensión amplia, S. squamata - H. similis. La distribución de la especies macrozoobentónica de estuario parece ser controlada principalmente por la salinidad y el gradiente observados en composición. La dominancia de especies en las partes marina y salobre del estuario del Río de Itanhaém es similar a la de otros hábitats mixohalinos de la costa del sudeste brasileño.

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Naik, Richita, Jesly Araujo, Anil Pratihary, Siby Kurian et S. W. A. Naqvi. « Sedimentary sulphate reduction and organic matter mineralization across salinity gradient of the Mandovi Estuary, West coast of India ». Estuarine, Coastal and Shelf Science 221 (mai 2019) : 21–29. http://dx.doi.org/10.1016/j.ecss.2019.03.005.

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Amisi, Joel, Cosmas Munga, Nina Wambiji et Edward Kimani. « Assessment of vertical and horizontal distribution of meiobenthos along a salinity gradient in the Tana and Sabaki Estuaries, north coast Kenya ». Western Indian Ocean Journal of Marine Science 21, n^o 1 (23 août 2022) : 77–89. http://dx.doi.org/10.4314/wiojms.v21i1.6.

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Meiobenthos respond to variability in salinity gradients in estuarine habitats and are thus suitable organisms for ecological studies. The vertical and horizontal distribution of the meiofauna community structure of two major estuaries (Sabaki and Tana) on the north coast of Kenya were compared. The aim was to draw a meiofaunal dataset inventory of the two estuaries and to examine how salinity gradient, seasonality and sediment characteristics influence their structure. Replicate samples were collected from three sampling stations along the salinity gradient of each river estuary. A total of 3,556 individuals belonging to 26 taxa were recorded. Based on seasons and across stations, the upper surface (0-5 cm) layer recorded the highest meiobenthic density (90 ± 42 ind.10 cm-2), followed by 46 ± 23 ind.10 cm-2 (5-10 cm) and 30 ± 8 ind.10 cm-2 in the deepest sediment layer (10-15 cm) studied. The southeast monsoon season recorded the highest mean density (160 ± 22 ind.10 cm-2) compared to the northeast monsoon season (22 ± 12 ind.10 cm-2) for both estuaries. Results of the non-Metric Multidimensional Scaling technique revealed distinct seasonal composition in meiobenthos but not between the estuaries. Results of the 2-way ANOSIM test confirmed no significant differences in meiobenthic composition between the estuaries (p = 0.712). However, seasonal difference was significant (p = 0.001) with higher densities for nematoda (166 ± 99 ind.10 cm-2 and 56 ± 29 ind.10 cm-2) recorded in Tana and Sabaki, respectively during the southeast monsoon season. At least 7 taxa out of a total of 26 were present in both estuaries. Salinity gradient, season and sediment depth were found to influence the meiobenthic densities and taxa composition.

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Milano, Stefania, Bernd R. Schöne et Igor Gutiérrez-Zugasti. « Oxygen and carbon stable isotopes of Mytilus galloprovincialis Lamarck, 1819 shells as environmental and provenance proxies ». Holocene 30, n^o 1 (31 juillet 2019) : 65–76. http://dx.doi.org/10.1177/0959683619865595.

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Mollusc shell stable isotopes are commonly used to reconstruct past environmental conditions. However, despite being abundant components of natural and anthropogenic fossil accumulations, the geochemical composition of mussel shells ( Mytilus spp.) has rarely received attention in palaeoenvironmental studies. This study tests the suitability of oxygen isotopes (δ18Os) of Mytilus galloprovincialis as palaeothermometer. For 1 year, mussels and water samples were collected twice a month from Berria Beach, in Northern Spain. The geochemical data of the shells indicate that water temperatures can be reconstructed with an average offset of 1.2 ± 0.7°C with respect to the measured values. Furthermore, no prolonged shell growth cessations are observed. These results validate M. galloprovincialis as reliable recorders of seasonal water temperature fluctuations, supporting their use in palaeoenvironmental studies. In addition, further shell and water collections were carried out in the upper and lower areas of a nearby estuary. The geochemical analyses of these shells were aimed to test whether oxygen and carbon stable isotopes (δ13Cs) may be used as novel proxies to identify the shell provenance at local scale. The results show that the δ18Os versus δ13Cs correlation direction varies along the coast–upper estuary geographical gradient, suggesting it to be a potential new proxy to distinguish between marine and estuarine mussel specimens.

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Daverat, F., J. Tomas, M. Lahaye, M. Palmer et P. Elie. « Tracking continental habitat shifts of eels using otolith Sr/Ca ratios : validation and application to the coastal, estuarine and riverine eels of the Gironde - Garonne - Dordogne watershed ». Marine and Freshwater Research 56, n^o 5 (2005) : 619. http://dx.doi.org/10.1071/mf04175.

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To enable a relevant interpretation of otolith strontium : calcium (Sr/Ca) variations in terms of habitat shifts of eels, the Sr/Ca-salinity relationship in eel otoliths was validated. Downstream and upstream migrations of young eels were reproduced in the laboratory by transferring groups of fish every 2 months between aquaria filled with water coming from the Dordogne river (salinity = 0), the upper Gironde estuary (salinity = 5), the lower Gironde estuary (salinity = 25) and the coast (salinity = 30), which represented the salinity gradient observed in the Gironde–Garonne–Dordogne watershed. Ontogenetic changes in otolith Sr/Ca were assessed in two groups of control fish that were kept in one of either two constant salinities (fresh water or seawater). X-ray electron microprobe (wavelength dispersive spectrometry, WDS) analyses of Sr/Ca ratios in the otoliths showed that the change of aquarium was recorded as a Sr/Ca increase (downstream migration) or a Sr/Ca decrease (upstream migration). No ontogenetic effect was detected in otoliths of control fish outside glass eel marks in either group of fish. The electron microprobe (WDS) analysis of the Sr/Ca life (transected in several otoliths of eels caught in the Gironde–Garonne–Dordogne watershed) showed that some of them were migrant eels that had experienced one major habitat shift during their continental life.

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Colombano, DD, AD Manfree, TA O’Rear, JR Durand et PB Moyle. « Estuarine-terrestrial habitat gradients enhance nursery function for resident and transient fishes in the San Francisco Estuary ». Marine Ecology Progress Series 637 (5 mars 2020) : 141–57. http://dx.doi.org/10.3354/meps13238.

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Nursery functions of US West Coast drowned river valley estuaries are not well understood. Using long-term fish-monitoring data (1995-2017) in Suisun Marsh, San Francisco Estuary, California, USA, we examined spatial and temporal trends in abundance and apparent growth of fishes with diverse life-history types. Focal species were Sacramento splittail Pogonichthys macrolepidotus, striped bass Morone saxatilis, tule perch Hysterocarpus traski, and starry flounder Platichthys stellatus, which collectively represented 55% of total catch (n = 140092). We identified keystone habitat patches that functioned as nursery hotspots during the peak young-of-the-year recruitment window. Deep, flow-through sloughs close to the open estuary were important nursery habitats for the marine transient starry flounder. In contrast, splittail and striped bass mostly migrated through such corridors to rear in shallow, dead-end sloughs bisecting tidal marsh plains, managed tidal ponds, and uplands. Tule perch were concentrated in shallow, interior sloughs, reflecting their resident life-history type and adaptations to variable conditions in a small home range. Interactions among freshwater flows and stationary habitat features (e.g. channel depth, land-to-open-water ratio) were related to fish abundance; however, species and age classes differed in their relationships to these interactions, suggesting a mechanism for habitat partitioning in space and time. Overall, we inferred that habitat connectivity—longitudinal, lateral, and vertical—along the estuarine-terrestrial gradient was a driver of fish species diversity and productivity. Consideration of seascape-landscape dynamics across multiple spatial and temporal scales in estuaries should help maintain or increase fish populations and ecological resilience in the face of rising sea levels and other environmental stressors.

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Laruelle, Goulven Gildas, Nicolas Goossens, Sandra Arndt, Wei-Jun Cai et Pierre Regnier. « Air–water CO<sub>2</sub> ; evasion from US East Coast estuaries ». Biogeosciences 14, n^o 9 (15 mai 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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Cheng, Jiao, Nan Zhang et Zhongli Sha. « Nuclear microsatellites reveal population genetic structuring and fine-scale pattern of hybridization in the Japanese mantis shrimp Oratosquilla oratoria ». PeerJ 8 (5 novembre 2020) : e10270. http://dx.doi.org/10.7717/peerj.10270.

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The interplay between historical and contemporary processes can produce complex patterns of genetic differentiation in the marine realm. Recent mitochondrial and nuclear sequence analyses revealed cryptic speciation in the Japanese mantis shrimp Oratosquilla oratoria. Herein, we applied nuclear microsatellite markers to examine patterns and causes of genetic differentiation in this morphotaxon. Population structure analyses revealed two genetically divergent and geographically structured clades in O. oratoria, one dominating the temperate zone of the Northwestern (NW) Pacific and the other occurring in the subtropical and tropical waters where are influenced by the Kuroshio Current. Two sympatric zones, one around the Changjiang Estuary in China coast and the other in the northern Japan Sea, were demonstrated to be hybrid zones where introgressive hybridization occurred asymmetrically. The interaction between historical climate shifts and contemporary factors (e.g., freshwater discharge, temperature gradient and isolation by distance) may contribute to the present-day genetic architecture in the Japanese mantis shrimp. Range shift induced by climate changes and oceanographic factors may promote hybridization and gene flow between the O. oratoria complex. Our results provide insights into the interacting mechanisms that give rise to diversification and speciation of coastal species in the NW Pacific.

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Gaspar, Felipe Lima, Barbara Ramos Pinheiro, Carlos Esteban Delgado Noriega, Moacyr Araujo, Nathalie Lefèvre et Manuel de Jesus Flores Montes. « Alkalinity, inorganic carbon and CO2 flux variability during extreme rainfall years (2010-2011) in two polluted tropical estuaries NE Brazil ». Brazilian Journal of Oceanography 66, n^o 1 (mars 2018) : 115–30. http://dx.doi.org/10.1590/s1679-87592018149406601.

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Abstract The susceptibility of coastal environments to shifts in the biogeochemical cycles of carbon and nutrients driven by anthropogenic pressure and climate change is a real challenge for the scientific community. This paper evaluated the effects of an extreme rainfall event over the nutrients and carbonate parameters in two polluted tropical estuaries. Surface water samples were taken seasonally along a salinity gradient in the Capibaribe and Barra de Jangadas estuaries in order to investigate the spatial and seasonal variability of dissolved nutrients, chlorophyll-a, dissolved oxygen, total alkalinity, inorganic carbon, partial pressure of CO2 (pCO2) and CO2 fluxes. The increased riverine influence caused by the fluvial flooding during the extremely rainy season augmented the nitrogen concentrations in the plumes, which also presented reduced salinity, alkalinity and dissolved oxygen values. In the Capibaribe plume it has also shifted the mean CO2 flux value of - 4.01 mmolC m-2 d-1 during the dry season, to a positive mean flux of + 5.7 mmolC m-2 d-1 during the rainy season. Within the estuaries the BOD5,20 and dissolved phosphorus values were higher during the dry season (p<0.0001), they showed positive correlation with the phytoplanktonic blooms that reached a chl-a value of 85 mg m-3 in the Capibaribe. The high alkalinity found in both estuaries, with mean values between dry and wet seasons respectively from 1808 to 1373 µmol kg-1 in the Capibaribe estuary and 1616 to 1058 µmol kg-1 in Barra de Jangadas estuary, may act as a buffer to the process of coastal acidification due to eutrophication. The increased rivers discharge lead to a greater transport of organic matter and nutrients to the coast, decreasing the oxygen availability and shifting the metabolic status of the estuarine plume to heterotrophic, whereas increased the water quality within the estuaries due the flushing promoted by the extreme rainfall event.

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de Sieyes, Nicholas R., Todd L. Russell, Kendra I. Brown, Sanjay K. Mohanty et Alexandria B. Boehm. « Transport of enterococci and F+ coliphage through the saturated zone of the beach aquifer ». Journal of Water and Health 14, n^o 1 (22 juin 2015) : 26–38. http://dx.doi.org/10.2166/wh.2015.290.

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Coastal groundwater has been implicated as a source of microbial pollution to recreational beaches. However, there is little work investigating the transport of fecal microbes through beach aquifers where waters of variable salinity are present. In this study, the potential for fecal indicator organisms enterococci (ENT) and F+ coliphage to be transported through marine beach aquifers was investigated. Native sediment and groundwaters were collected from the fresh and saline sections of the subterranean estuary at three beaches along the California coast where coastal communities utilize septic systems for wastewater treatment. Groundwaters were seeded with sewage and removal of F+ coliphage and ENT by the sediments during saturated flow was tested in laboratory column experiments. Removal varied significantly between beach and organism. F+ coliphage was removed to a greater extent than ENT, and removal was greater in saline sediments and groundwater than fresh. At one of the three beaches, a field experiment was conducted to investigate the attenuation of F+ coliphage and ENT down gradient of a septic leach field. ENT were detected up to 24 m from the leach field. The column study and field observations together suggest ENT can be mobile within native aquifer sediments and groundwater under certain conditions.

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Fatela, Francisco, João Moreno et M. Cristina Cabral. « Salinity and water temperature assessment of the tidal marshes from the W Portuguese coast, as an ecological tool to palaeoenvironmental reconstructions based on Foraminifera and Ostracoda assemblages ». Estudos do Quaternário / Quaternary Studies, n^o 14 (22 juin 2016) : 73–81. http://dx.doi.org/10.30893/eq.v0i14.124.

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A seasonal study of temperature and salinity of estuarine and sediment interstitial water of tidal marshes was undertaken along three estuaries of W Portuguese coast (Minho, Tejo and Mira).The climatic N-S transition from wet Atlantic to Mediterranean features appear clearly imprinted in the distribution of tidal marsh assemblages, like foraminifera and ostracoda, mainly reflecting the water salinity gradient control.The Minho low estuary tidal marsh tends to be flooded by estuarine water ranging from 0.5‰ to 32‰ in each tide cycle, even during dry seasons. However, the marsh hydrological balance sustains a more stable environment where the salinity of interstitial water measurements yielded 8‰ to 16‰. In contrast the Tejo and Mira salt marsh flooding waters record a narrow range between 33‰ and 36‰, in spring, and between 29‰ and 36‰ in autumn. The climatic control of evaporation/ precipitation balance produces an enhanced salinity of marsh interstitial water, that can reach hypersaline conditions, with maximum records of 53‰ in Tejo and 48‰ in Mira lower estuaries.These environmental differences along the W Portuguese coast are recorded by the tidal marsh assemblages, namely foraminifera and ostracoda. In the low salinity Caminha salt marsh, living foraminifera are essentially composed by the agglutinated species Haplophragmoides manilaensis, Miliammina fusca, Pseudothurammina limnetis Psammosphaera sp. and Trochamminita salsa. The modern ostracoda assemblage includes Leptochytere baltica, Leptochytere psammophila, Leptocythere sp. A and Tuberoloxoconcha sp.1. In the Tejo and Mira salt marsh Ammonia beccarii, Ammonia tepida, Haynesina germanica, Jadammina macrescens, Trochammina inflata, are the dominant foraminifera and Loxoconcha malcomsoni, Terrestricythere cf. elisabethae, Tuberoloxoconcha cf. atlantica and Xestoleberis labiata prevail as well as many other more marine ostracoda species, such as Basslerites teres and Leptocythere fabaeformis.This study highlights that the knowledge of driven ecological parameters of modern assemblages (usually preserved in fossil record), is fundamental to support reliable paleoclimatic and palaeoenvironmental reconstructions.

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Fouet, Marie P. A., David Singer, Alexandra Coynel, Swann Héliot, Hélène Howa, Julie Lalande, Aurélia Mouret, Magali Schweizer, Guillaume Tcherkez et Frans J. Jorissen. « Foraminiferal Distribution in Two Estuarine Intertidal Mudflats of the French Atlantic Coast : Testing the Marine Influence Index ». Water 14, n^o 4 (18 février 2022) : 645. http://dx.doi.org/10.3390/w14040645.

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This study focuses on the foraminiferal distribution on intertidal mudflats of two contrasted estuaries (Auray and Vie) along the French Atlantic coast. In both estuaries, the foraminiferal communities are dominated by Haynesina germanica and the Ammonia tepida group. Stations located near the outlets show a high diversity and abundance of species of the genus Elphidium. Stations in the inner estuary show a higher proportion of agglutinated species (Ammotium salsum, Ammobaculites agglutinans). Multivariate statistical analysis suggests that the distance to the sea and the percentage of fine sediment (<63 µm) are the two main parameters explaining the foraminiferal distribution. Chemical analyses of the sediment show that the two studied estuaries are not affected by major anthropogenic pollution, so that the faunas should mainly reflect the natural controlling parameters. Three indices of environmental quality commonly used in coastal areas show counter-intuitive differences between stations, suggesting that these indices may be less reliable for use in intertidal estuarine mudflats. The newly developed Marine Influence Index (MII) integrates three major ecological factors: the position of the sampling point on the salinity gradient, the emergence time at low tide and the relative importance of fresh water discharge. In our dataset, MII shows significant correlations with the controlling environmental parameters (distance to the sea, percentage grains < 63 µm), as well as with the foraminiferal patterns (PCA axis 1, species richness, percentage of Elphidium spp. and Quinqueloculina spp.). These results suggest that the MII explains a substantial part of the faunal variability on estuarine intertidal mudflats, and can be used to detect deviations from the natural distribution patterns in response to anthropogenic pollution.

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Kruglov, G. G., N. N. Linkevich et O. V. Nemerovets. « Filtration Bypassing Retaining Hydraulic Structures ». Science & ; Technique 19, n^o 3 (5 juin 2020) : 252–57. http://dx.doi.org/10.21122/2227-1031-2020-19-3-252-257.

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Concrete dams that are part of river waterworks are integrated with earthworks or with banks using coastal abutments. If the soil of cost or earthen dam is permeable, then in the zone of contiguity water filtration occurs around the coastal abutment. Calculation of filtration bypassing the coastal abutment at specified water levels in the upper and lower pools is performed with the aim of constructing an encircling curve of depression and determining a gradient of filtration flow that controls the filtration strength of the soil beyond the abutment. This problem has no theoretical solutions – in view of its complexity, approximate calculation methods have been developed for individual calculation schemes. For the case when the soil behind the coastal abutment is homogeneous and isotropic, groundwater inflow from the coast is absent or insignificant and can be neglected, and the coastal abutment is located on a water bed and approximate methods by V. P. Nedrigi and R. R. Chugaeva are proposed in the paper. The experience of surveying a number of Belarusian hydropower stations has shown that the absence of a justified prediction pertaining to the position of groundwater levels beyond the estuary leads to a decrease in the strength and stability of the coastal abutment and its possible destruction. An experimental verification of the approximate method for calculation filtration bypassing the coastal abutment developed by R. R. Chugaev has been carried out in laboratory conditions. According to the obtained experience a depression curve encircling the abutment has been constructed which show good agreement between experimental and calculated data that allows to use this method for reasonable design of coastal abutment structures ensuring their reliable operation.

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Daviray, Maxime, Emmanuelle Geslin, Nils Risgaard-Petersen, Vincent V. Scholz, Marie Fouet et Edouard Metzger. « Potential impacts of cable bacteria activity on hard-shelled benthic foraminifera : implications for their interpretation as bioindicators or paleoproxies ». Biogeosciences 21, n^o 4 (20 février 2024) : 911–28. http://dx.doi.org/10.5194/bg-21-911-2024.

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Abstract. Hard-shelled foraminifera are protists able to build a calcareous or agglutinated shell (called a “test”). Here we study the impact of sediment acidification on calcareous test preservation. For this study, sediment cores were sampled in the macrotidal Auray estuary located on the French Atlantic coast. Living and dead foraminifera were quantified until 5 cm depth and discriminated using the Cell-Tracker™ Green vital marker. The pH and oxygen profiles combined with quantitative polymerase chain reaction (qPCR) suggested that cable bacteria were most likely to cause the acidifying process. Cable bacteria (CB) are filamentous bacteria coupling sulfide oxidation to oxygen reduction over centimetre distances, generating a strong pH gradient within the first few centimetres of the sediment that could affect the microhabitats occupied by benthic foraminifera. On two different intertidal mudflats, volumetric filament densities have been estimated. They were comparable to those observed in the literature for coastal environments, with 7.4 ± 0.4 and 74.4 ± 5.0 m cm−3 per bulk sediment, respectively. Highly contrasting sediment acidification (from low to very intense) was described from 1.0 to 2.4 ΔpH. This seems to lead to various dissolution stages of the foraminiferal calcareous test from intact to fully dissolved tests revealing the organic lining. The dissolution scale is based on observations of living Ammonia spp. and Haynesina germanica specimens under a scanning electronic microscope. Furthermore, dead foraminiferal assemblages showed a strong calcareous test loss and an organic lining accumulation throughout depth under low pH, hampering the test preservation in deep sediment. These changes in both living and dead foraminiferal assemblages suggest that cable bacteria must be considered in ecological monitoring and historical studies using foraminifera as bioindicators and paleoenvironmental proxies.

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Zhao, Chenyu, Nan Wang, Yang Ding, Dehai Song, Junmin Li, Mengqi Li, Lingling Zhou, Hang Yu, Yanyu Chen et Xianwen Bao. « Numerical Study on the Formation Mechanism of Plume Bulge in the Pearl River Estuary under the Influence of River Discharge ». Water 16, n^o 9 (2 mai 2024) : 1296. http://dx.doi.org/10.3390/w16091296.

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Previous studies have investigated the characteristics and influencing factors of plume bulge in the Pearl River Estuary (PRE) using observations and numerical simulations. However, the understanding of how river discharge affects plume bulge is not consistent, and the response mechanism of plume bulge to changes in river discharge has not been revealed in detail. In this study, a three-dimensional hydrodynamic Finite-Volume Coastal Ocean Model (FVCOM) is constructed, and five experiments were set to characterize the horizontal and vertical distribution of the plume bulge outside the PRE under different river discharge conditions during spring tide. The physical mechanisms of plume bulge generation and its response mechanisms to river discharge were discussed through standardized analysis and momentum diagnostic analysis. The results indicate that the plume bulge is sensitive to changes in river discharge. When the river discharge is relatively low (e.g., less than 11,720 m3/s observed in the dry season), the bulge cannot be formed. Conversely, when the river discharge is relatively high (e.g., exceeding 23,440 m3/s observed in flood season), the bulge is more significant. The plume bulge is formed by the anticyclonic flow resulting from the action of the Coriolis force on the strongly mixed river plume. The bulge remains stable under the combined effects of barotropic force, baroclinic gradient force, and Coriolis force. The reduction of river discharge weakens the mixing of freshwater and seawater, resulting in the reduction of both the volume and momentum of the river plume, and the balance between advective diffusion and Coriolis forces are altered, resulting in the plume, which is originally flushed out from the Lantau Channel, not being able to maintain the anticyclonic structure and instead floating out along the coast of the western side of the PRE, with the disappearance of the plume bulge. Due to the significant influence of plume bulges on the physical and biogeochemical interactions between estuaries and terrestrial environments, studying the physical mechanisms behind the formation of plume bulges is crucial.

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Mukherjee, S., E. A. Mohammad et R. H. Worden. « Satellite data interpretation of causes and controls on groundwater-seawater flow directions, Merseyside, UK : implications for assessing saline intrusions ». Hydrology and Earth System Sciences Discussions 2, n^o 3 (9 juin 2005) : 887–916. http://dx.doi.org/10.5194/hessd-2-887-2005.

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Abstract. Groundwater in the Triassic Sherwood Sandstone aquifer, Liverpool, UK, has locally elevated chloride concentrations (~4000 mg/l) in parts of the coastal region although there is freshwater right up to the coast line in other areas. The aquifer is cut my numerous faults with vertical displacements of as much 300 m. SPOT satellite data have been used for the Merseyside area of Liverpool. The satellite data revealed and confirmed the location of some of the main faults since the fault zones of the aquifer have low permeability (due to grain crushing, cataclasis, and clay smearing). Where fault zones outcrop at the surface, below the well-developed regolith, there is locally elevated soil water and thus anomalous vegetation patterns in comparison to unfaulted and highly porous aquifer. The ability to identify fault zones by this satellite-based method strongly suggests that they are at least partially sealing, sub-vertical features in the aquifer. Digitally enhanced and processed satellite data were used to define the relative proportions of sand and clay in the near-coastal (inter-tidal) part of the Mersey estuary. Sand-dominated sediment has higher pixel values in comparison with clay deposits in the near infrared spectral region (NIR). Where open and weathered fault rocks crop out at the surface near the intertidal zone, water movement in these potential surface water conduits is limited where the intertidal zone is clay-dominated since clay will plug the conduit. Where these weathered and open fault-rocks crop out against sand-dominated parts of the coastline, fresh water outflux into the seawater has been imaged using the satellite data. Furthermore, the high and low chloride concentration parts of the aquifer are separated by major, sub-vertical fault zones and have allowed a very steep water table gradient to remain in the aquifer.

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Krask, Julie L., Tracy L. Buck, Robert P. Dunn et Erik M. Smith. « Increasing tidal inundation corresponds to rising porewater nutrient concentrations in a southeastern U.S. salt marsh ». PLOS ONE 17, n^o 11 (28 novembre 2022) : e0278215. http://dx.doi.org/10.1371/journal.pone.0278215.

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Salt marshes are ecologically and economically important features of coastal environments that are vulnerable to sea level rise, the rate of which has accelerated in recent decades along the southeastern US Atlantic coast. Increased flooding frequency and duration across the marsh platform is predicted to impact vegetation community structure and overall marsh persistence, but the effect of changing inundation patterns on biogeochemical processes in marsh sediments remains largely unexplored. As part of a long-term monitoring effort to assess how marshes are responding to sea level rise in North Inlet estuary (South Carolina, USA), we collected data on porewater nutrient concentrations from a series of permanent monitoring plots across multiple transects spanning the marsh elevation gradient during the growing season from 2009 to 2019. Additionally, we calculated time inundated for each plot using local water level data and high-resolution elevation measurements to assess the change in time flooded at each plot. Our results indicate that both NH4 and PO4 nutrient concentrations have increased in most permanent plots over the 11-year study period and that nutrient concentrations are higher with increasing proximity to the creek. Spatial patterns in nutrient increases through time are coincident with considerable increases in tidal inundation observed over the marsh platform. Across plots located in the low marsh, porewater NH4 and PO4 concentrations have risen at average rates of 8.96 μM/year and 0.86 μM/year, respectively, and have reached rates as high as 27.25 μM/year and 3.13 μM/year. We suggest that increased inundation time due to rising sea level has altered biogeochemical conditions influencing nutrient availability in marsh porewater, resulting in increases that likely have relevance for larger scale nutrient cycles as well as marsh ecosystem stability and function.

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Alves, Ana Sofia, Helena Adão, Joana Patrício, João Magalhães Neto, Maria José Costa et João Carlos Marques. « Spatial distribution of subtidal meiobenthos along estuarine gradients in two southern European estuaries (Portugal) ». Journal of the Marine Biological Association of the United Kingdom 89, n^o 8 (13 juillet 2009) : 1529–40. http://dx.doi.org/10.1017/s0025315409000691.

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The spatial variation in abundance and composition of subtidal meiobenthos communities was studied in two Portuguese estuaries under distinct degrees of anthropogenic pressure. Samples were collected from 20 sampling stations along both estuarine gradients from freshwater (<0.5) to euhaline areas (>30). Of these stations 11 were located in the Mondego estuary, a system exposed to high anthropogenic stress, and 9 in the Mira estuary, a naturally stressed system located inside the Natural Park ‘Costa Vicentina’ (south-western coast of Portugal).Total meiobenthos density was higher in the Mira estuary and in both estuaries the community was dominated by nematodes. Among the twelve taxa identified in the Mira estuary, Harpacticoid copepods and Polychaeta were the second and the third most abundant groups respectively. In the Mondego estuary, Polychaeta was the second while Harpacticoid copepods was the third most abundant group in the thirteen total taxa recorded.Estuarine gradients of salinity, particles size and water nutrients were clearly detected in both estuaries and there was significant spatial heterogeneity in abundance and composition of the subtidal meiobenthos communities along these environmental gradients. Accordingly, three distinct sections were identified in both estuaries: (i) freshwater sections, where total density, and density of nematodes and Harpacticoid copepods reached minimum values; (ii) oligohaline and mesohaline sections, where the total density was low and diversity was poor; and (iii) polyhaline and euhaline sections, where both total density and diversity reached the highest values.The similar spatial distribution of meiobenthos assemblages in both estuaries suggests that natural stressors may be the major factors controlling the physicochemical conditions that determine meiobenthos community patterns. The mesoscale variability of subtidal meiobenthos density and composition within estuaries (in the order of kilometres) seems to be more important than the variability between estuaries (at the scale of hundreds of kilometres), a common feature in intertidal systems. From the management point of view, these results, based on higher taxa resolution, represent an obvious constraint to the applicability of ecological quality evaluation tools.

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Ellis, Kathryn K., Timothy Callahan, Dianne I. Greenfield, Denise Sanger, Joshua Robinson et Martin Jones. « Measuring and Modeling Flow Rates in Tidal Creeks : A Case Study from the Central Coast of South Carolina ». Journal of South Carolina Water Resources, n^o 4 (1 juin 2017) : 21–39. http://dx.doi.org/10.34068/jscwr.04.03.

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The purpose of this study was to collect site- and condition-specific hydrology data to better understand the water flow dynamics of tidal creeks and terrestrial runoff from surrounding watersheds. In this paper, we developed mathematical models of tidal creek flow (discharge) in relation to time during a tidal cycle and also estimated terrestrial runoff volume from design storms to compare to tidal creek volumes. Currently, limited data are available about how discharge in tidal creeks behaves as a function of stage or the time of tide (i.e., rising or falling tide) for estuaries in the southeastern United States, so this information fills an existing knowledge gap. Ultimately, findings from this study will be used to inform managers about numeric nutrient criteria (nitrogen-N and phosphorus-P) when it is combined with biological response (e.g., phytoplankton assemblages) data from a concurrent study. We studied four tidal creek sites, two in the Ashepoo-Combahee-Edisto (ACE) Basin and two in the Charleston Harbor system. We used ArcGIS to delineate two different watersheds for each study site, to classify the surrounding land cover using the NOAA Coastal Change Analysis Program (C-CAP) data, and to analyze the soils using the NRCS Soil Survey Geographic database (SSURGO). The size of the U.S. Geological Survey’s Elevation Derivatives for National Application (EDNA) watersheds varied from 778 to 2,582 ha; smaller geographic watersheds were delineated for all sites (except Wimbee) for stormwater modeling purposes. The two sites in Charleston Harbor were within the first-order Horlbeck Creek and the second-order Bulls Creek areas. The ACE Basin sites were within the third-order Big Bay Creek and the fourth-order Wimbee Creek areas. We measured the stage and discharge in each creek with an acoustic Doppler current profiler (ADCP) unit for multiple tide conditions over a 2-year period (2015–2016) with the goal of encompassing as large of a range of tide stage and discharge data measurements as possible. The Stormwater Runoff Modeling System (SWARM) was also used to estimate the potential water entering the creeks from the land surface; this volume was very small relative to the tide water volume except for the more-developed Bulls Creek watershed. The results show that the peak discharge occurred on the ebb tide and that the duration of the flood tide spanned a longer period of time; both of these observations are consistent with traits associated with an ebb-dominated tidal creek system. The tidal inflow and outflow (flood and ebb tides, respectively) showed an asymmetrical pattern with respect to stage and discharge; peak discharge during the flood (rising) tide occurred at a higher stage than for the peak discharge during the ebb (falling) tide. This is not an unexpected result, as the water on an ebb tide is moving down gradient funneled through the creek channel toward the coast. Furthermore, water moving with the rising flood tide must overcome frictional losses due to the marsh bank and vegetation; i.e., the peak discharge can only happen when the water has risen above these impediments. We infer from the flow dynamics data that faster water velocities during ebb tide imply that more erosive energy could transport a larger mass of suspended solids and associated nutrients (e.g., orthophosphate) from the estuary to the coastal ocean. However, the discharge and runoff modeling indicate that land-based flux was important in the developed Bulls Creek watershed, but not at the larger and less-developed Big Bay Creek watershed. At Big Bay Creek, the relatively large tidal discharge volume compared to the smaller potential runoff generated within the watershed indicates that the creek could potentially dilute terrestrial runoff contaminants. Smaller, more-urbanized tidal wetland systems may not benefit from such dilution effects and thus are vulnerable to increased runoff from adjacent developed landscapes.

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Zhang, Junjue, et Fenzhen Su. « Spatial Pattern of Construction Land Distribution in Bays along the Coast of Vietnam ». ISPRS International Journal of Geo-Information 9, n^o 12 (26 novembre 2020) : 707. http://dx.doi.org/10.3390/ijgi9120707.

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Current studies of urban spatial morphology have rarely focused on the particularity of coastal cities, such as sea–land gradient features and bay types. In this paper, we provide a method to analyze the spatial and vertical distribution of construction land in the bay area and discuss the influence of bay type on the distribution characteristics. Landscape indexes and a clustering algorithm were used to identify the spatial pattern of construction land distribution. Strip division was used to analyze the landscape features of construction land in the sea–land direction. We established eight large bays in Vietnam as the study area. According to the formation and geomorphology of the bay, the eight bays were divided into five types: delta bay, lagoon bay, structural bay, bedrock erosion-stacking bay and estuary bay. The construction land data were generated from Landsat images captured in 1988 and 2015 or so. The study effectively identified five spatial patterns of construction land distribution in bays without prior knowledge. Danang Bay (a bedrock erosion-stacking bay) had a typical high intensity-high concentration pattern, and Hai Loc Bay (a delta bay) had a typical high intensity-low concentration pattern. In the sea–land gradient, the proportions of construction land in the 0–2 km zone were greatest. In Danang Bay, the proportion generally decreased in the sea–land direction; while in Hai Loc Bay, the proportion increased.

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Tuchkovenko, Yu S., D. V. Kushnir, V. A. Ovcharuk, A. V. Sokolov et V. N. Komorin. « Characteristics of Black Sea dispersion of freshened and polluted transitional waters from the Dnipro-Bug estuary after destruction of the Kakhovka Reservoir dam ». Ukrainian hydrometeorological journal, n^o 32 (27 décembre 2023) : 95–114. http://dx.doi.org/10.31481/uhmj.32.2023.07.

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This study examines the characteristics of distribution of large volumes of freshened and polluted transitional waters from the Dnipro-Bug estuary across the northwestern part of the Black Sea (NWBS) that was caused by destruction of the Kakhovka HPP dam in June 2023. From June 6, 2023 to June 12, 2023 14.4 km³ of water were discharged from the Kakhovka Reservoir into the Dnipro-Bug estuary and subsequently into the sea. This volume constitutes 27% of the total annual average natural runoff of the Dnipro River (53.5 km³). During the initial days following the dam destruction water flow through the breach amounted to 40-50 thousand m³/s. The water carried a variety of pollutants into the sea that were present in the water of the Kakhovka Reservoir, in its bottom sediments, and also washed off from the flooded territories of the lower Dnipro area (more than 2000 hectares). The analysis of the distribution characteristics was conducted using satellite images of the sea surface color and chlorophyll a concentrations, as well as the results of hydrodynamic modeling with application of the 3-D variant of a numerical hydrodynamic model Delft3D-Flow Flexible Mesh. It was established that the plume of freshened and polluted water initially spread across the Dnipro-Bug estuarine region of the NWBS and then moved towards the sea coast of Odesa reaching it on June 9-10, 2023. Subsequently, the plume began to spread along the western sea coast and reached the Tuzlivski Limans area on June 14, 2023. After this the narrow plume of dispersed water along the sea coast began to dilute when moving towards the open sea in the form of "tongues" that had formed over the sea bottom elevations. The modeling of dispersion of a conservative neutral buoyancy admixture serving as a marker of pollution spread with the transitional waters from the Dnipro-Bug estuary showed that reduction in pollution levels took place solely due to hydrodynamic dilution (up to 60% in Odesa District of the NWBS and up to 30% in the Danube-Dniester interfluve area of the river water pollution level observed in Kherson). The identified characteristics were determined based on the water circulation process that formed in the Dnipro-Bug estuarine area under the influence of significant sea level gradients resulting from the inflow of large volumes of freshened transitional waters through the estuary and the Kinburn Strait during the first days, and then followed by the density currents formed at the hydrofront between the transformed river water and surrounding sea. The influence of wind conditions manifested itself in the form of spread across the NWBS of the plume of dispersed transitional water from the Dnipro-Bug estuary and the hydrofront's position and configuration. Though wind-induced currents were not dominant, they still influenced the water dynamics and distribution of concentrations of admixtures, for instance, chlorophyll a, within the freshened plume that was outlined by the hydrofront. They also promoted penetration along the coastal shallow area of transformed river water towards Odesa.

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Torruella, Alfredo J. « HYDRODYNAMICS OF THE CONDADO LAGOON ». Coastal Engineering Proceedings 1, n^o 33 (15 décembre 2012) : 36. http://dx.doi.org/10.9753/icce.v33.posters.36.

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The San Juan Bay Estuary Program and the Corporation for the Conservation of the San Juan Bay Estuary, intends to develop a cost-effective and environmentally acceptable plan for water quality improvement and seagrass restoration in the Condado Lagoon. One of the principal challenges associated with this Project is evaluating options for dredge material sources (borrow sites), transport, and placement in the Condado Lagoon to achieve the ecological restoration goal. A potential borrow site has been identified in the northwestern side of San Juan Bay near La Esperanza Peninsula. The accretion of sediment near the Peninsula has inhibited tidal flushing to this area from San Juan Bay. The implementation of this Project would support the beneficial use initiative by dredging the shoaling material at La Esperanza Peninsula and filling the artificial depressions in Condado Lagoon to improve water circulation at both the dredge and fill sites; as well as providing habitat for epibenthic growth in the Lagoon. In March 2011, Tetra Tech performed baseline investigations in Condado Lagoon, Puerto Rico in support of the San Juan Bay Estuary Program’s Water Quality Improvement and Seagrass Restoration Project. Field investigations included a bathymetric (multibeam) survey, benthic community data collection and sediment sampling. The results of the surveys were used to characterize benthic habitats in the Lagoon and to assist in evaluating alternatives for restoring the Lagoon to a gradient that supports a diverse epibenthic assemblage of Lagoon and estuarine species, specifically seagrass communities. In addition to the above mentioned investigations, Caribbean Oceanography Group deployed GPS-tracked lagrangian drifters in the lagoon in order to gather current data for the calibration of a hydrodynamic model of the Condado Lagoon. The intent of the multibeam survey was to map the existing depths and bathymetric features within Condado Lagoon, with an emphasis on detailing the extents of seven artificial depressions. The results of the survey determined a minimum depth of 0.8 m and maximum depth of 10.4 m (2.6 to 34.1 ft) in the Lagoon. Maximum depths were recorded in the center of the dredge holes, which are located in the center and eastern end of the Lagoon. The results of the multibeam survey were also used to support depth-based in situ data collection of the benthic community. The results of the benthic survey indicate a regional separation in benthic community diversity and abundance. The south-central and southeastern sides of the Lagoon support low to no biotic cover. This is contrary to the biotic diversity and abundance at the western, north-central and northeastern sides of the Lagoon. The benthic data also showed a segregation of benthic community assemblages between three depth ranges (shallow 1.8 to 2.4 m [6.0 to 8.0 ft]; mid (2.7 to 5.8 m [9 to 19 ft]); and deep 6.1 to 9.1 m [20 to 30 ft]). The benthic community in the mid depth range supports the greatest diversity and abundance of organisms. The areas with little to no biotic cover correspond to the dredged areas of the Condado Lagoon. Typical of low energy environments, finer grained sediments are located in the central and eastern regions of the Lagoon. Grain size analyses reported coarse material at the La Esperanza Peninsula sample site and the western end of Condado Lagoon, which are indicative of currents and regular water exchange in these locations. Organic content decreases from west to east in the Lagoon which supports the observations of lower benthic cover in the south-central and southeastern Lagoon compared to the western region. Based on the 2011 baseline investigations, H. decipiens was determined to be the most prevalent seagrass species in the Lagoon, followed by T. testudinum. Fill volume calculations based solely on the bathymetric survey results, estimate between 132,211 and 488,719 cy of fill material needed to support a water depth gradient (2.7 to 5.8 m [9.0 to 19.0 ft]) conducive to H. decipiens and T. testudinum growth in the central and eastern portions of the Lagoon. More specifically, the baseline results suggest a preferred depth of 4.05 m (13.3 ft) for H. decipiens, which would require between approximately 317,629 and 336,504 cy of fill material to restore a portion of the Lagoon. Caribbean Oceanography Group (with the support of Tetra Tech) has modeled the circulation within the Lagoon using the Environmental Fluid Dynamics Code (EFDC) hydrodynamic model. Modeling results reveal a complex circulation within the Condado Lagoon that is largely wind driven. A statistical analysis of the wind record for NOAA’s U.S. Coast Guard Station ID 9755371, located at the western end of the model domain was carried out, and 70%, 80%, 90%, 95% and 98% exceedance levels were determined. Model results show that under the 98% wind speed exceedance scenario, two of the examined locations within the dredged area of the lagoon experience a shear stress large enough to trigger a minimum sand grain diameter requirement for stability through the Shields relation. The locations and their minimum sand grain diameters are: A-2 with 0.46 mm and A-3 with 0.21 mm. These grain sizes correspond to Medium Sand and Fine Sand, respectively (after Wentworth (1922)). Evaluation of the direction of the shear at the above mentioned locations reveals that a portion of the material eroded from location A-2 (the medium sand) will be deposited at location A-3, and the rest (the fine sand) will be deposited at some combination of locations A-4, A-5, A-6 and A-7. Likewise the material originally eroded from location A-3 (fine sand) will be deposited at some combination of locations A-4, A-5, A-6 and A-7. Therefore, any unstable material placed at locations A-2 and A-3 will merely be shifted to another location within the fill area with a lower shear stress where it will become stable. Therefore the requirements for fill stability in the Condado Lagoon in terms of grain size are: 1) In order to remain stable under a 98% exceedance wind event, fill at location A-2 should be composed of sand with a grain diameter greater than 0.46 mm. In other words, Medium to Coarse sand should be used to fill location A-2. 2) In order to remain stable under a 98% exceedance wind event, fill at location A-3 should be composed of sand with a grain diameter greater than 0.21 mm. In other words, Fine to Medium sand should be used to fill location A-3. Of note is the finding that any material too fine to remain stable at either A-2 or A-3 will be deposited at some combination of the remaining fill locations, and thus will not be lost from the fill area, nor will it be unstable and cause problems elsewhere in the lagoon. It should be kept in mind that the lower exceedance levels (95% or less) did not present any minimum sand grain size requirements for stability. For those cases, sand fill of any grain size remains stable. Likewise, a higher exceedance level than 98% would require coarser fill at A-2 and A-3 than that discussed above. In either case, however, the eroded material would remain within the fill area, being deposited the downstream at a more sheltered location

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da Silva, Leiliane Souza, Danielle Viveiros Cavalcante-Braga, Caio Brito Lourenço, Ralf Schwamborn et Jussara Moretto Martinelli-Lemos. « Factors affecting the seasonal variability of planktonic shrimps (Dendrobranchiata) along an estuary–ocean gradient on the Amazon continental shelf ». Journal of the Marine Biological Association of the United Kingdom 101, n^o 2 (mars 2021) : 331–42. http://dx.doi.org/10.1017/s0025315421000308.

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AbstractDendrobranchiata shrimp taxonomic composition and spatial and temporal distribution on the Amazon continental shelf (ACS) were investigated along a transect between the sources of the Amazon and Pará Rivers, encompassing an extension of ~250 km towards the continental slope. Plankton was collected with oblique trawls (200 μm mesh size), and nine taxa were found; 59.4% were larvae (mysis or decapodid stages) and 40.6% were juveniles or adults. Acetes was negatively related to chlorophyll-a and temperature, and Luciferidae were positively correlated with months. This study provides novel information on the density distribution of dendrobranchiate shrimps, thus helping to pave the way to characterize a large-scale, hugely relevant area that is poorly studied. As in other tropical coastal areas, there is here an increase in number of taxa with increased distance from the coast. Luciferidae, Solenoceridae and Penaeidae were the most frequent families whereas Sicyoniidae and Sergestidae had the lowest frequency of occurrence nearer the slope. Despite the low larval density of penaeid shrimps, their presence in all months and at all sampling sites along the ACS proves the importance of this area for shrimps with socioeconomic relevance, as well as its importance as a nursery and growth habitat for dendrobranchiate shrimps.

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Cavalcanti, Lisana F., Marco V. J. Cutrim, Caio B. Lourenço, Ana Karoline D. S. Sá, Amanda L. L. Oliveira et Andrea C. G. de Azevedo-Cutrim. « Patterns of phytoplankton structure in response to environmental gradients in a macrotidal estuary of the Equatorial Margin (Atlantic coast, Brazil) ». Estuarine, Coastal and Shelf Science 245 (octobre 2020) : 106969. http://dx.doi.org/10.1016/j.ecss.2020.106969.

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Chougule, V. A., J. B. Sapkale et V. S. Pawar-Patil. « RUSLE and SDR model for erosional risk assessment and sediment yield estimation of Achara basin, western coast, India ». Disaster Advances 14, n^o 7 (25 juin 2021) : 19–31. http://dx.doi.org/10.25303/147da1921.

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The phenomenon of accelerated soil erosion, the resulting of irresponsible land use practices and human interference bring considerable changes within the Achara basin. The high rate of soil erosion deteriorates the fertility of the soil and consequently reduces crop productivity. Accumulation of transported soil at the lower part of the basin creates a severe problem of sedimentation within the channel and affects the hydraulic characteristics. The estimated potential sediment yield has been derived by using an integrated RUSLE model accompanied remote sensing database in geospatial environment. The result reveals the estimated average annual soil loss for the watershed as 18.81 t ha-1 year-1 . Sediment Delivery Ratio (SDR) fluctuates from 0.01 to 0.627. It has shown remarkably low for almost all parts of the basin, except steep slope and lower part of the watershed depending on the channel gradient of the major river. The junctions of the main channels are more susceptible to accumulate the sediment (> 4 t ha-1 year-1 ) within the basin. The lowermost portion of the basin receives a massive amount of sediment which ranges between 0.01 to 127 t ha-1 year-1 causing sedimentation within the estuary. The attempted work focuses on assessment of the erosional risk and sedimentation issue of Achara basin. The applied model will be helpful in the disaster management planning of such kind of coastal basins in Maharashtra.

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Rimper, Joice, Richardus Kaswadji, Bambang Widigdo, Nawangsari Sugiri et Inneke Rumengan. « DISTRIBUTION OF MONOGONONT ROTIFERS, Branchionus spp IN NORTH SULAWESI ». Marine Research in Indonesia 32, n^o 2 (12 mai 2018) : 103–8. http://dx.doi.org/10.14203/mri.v32i2.443.

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In order to characterize the distribution pattern of rotifers Brachionus spp. in North Sulawesi, sample collections have been conducted at four locations, two at east coast and other two at west coast of North Sulawesi peninsula, which are connected to Maluku and Sulawesi Seas, respectively. At each location, a 40 p.m mesh size plankton net with a 0.3 m opening diameter was horizontally towed at three sites to represent coastal water, estuary and brachkiswater pond. Sampling periods were in January and August 2005 to represent west monsoon and east monsoon, respectively. Each sampling was performed twice a day during high and low tide. Some environmental factors were also measured in situ during the sampling. Three species of Brachionus were found during the survey, Brachionus rotundiformis, B. caudatus and B. quadridentatus. Their abundances were significantly different, both between locations and sampling sites. However, among the similar habitat such as between Manembo-nembo and Minanga brachkishwater ponds, B. rotundiforms abundance was not significantly different. This species was the most abundant compared to the other two species, in average 1984,4 ind/m3, while the other species was as low as 26,1 ind/m3 and 212,9 ind/m3 for B. caudatus and B. quadridentatus, respectively. The abundance of rotifers in northern areas connected to Molluccas Sea is higher compared to those in the southern areas connected to Sulawesi Sea. Distribution of B. caudatus is very similar to those of B. rotundiformis, while B. quadridentatus appears to have its specific pattern. Results of this study suggest that the abundance and species composition of the rotifers reflect trophic status of the aquatic ecosystem in the area. It is still awaiting future studies to elaborate the impacts of the trophic gradients in horizontal distribution of rotifers. Therefore, it is necessary to conduct a long term monitoring with emphasis on the structure of rotifer assemblages in a variety of sites subjected to environmental perturbations, including anthropogenic contaminant inputs.

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Mama, Anselme Crépin, Gisele Flodore Youbouni Ghepdeu, Olivia Fossi Tankoua, Manfred Desire Bonga, Willy Karol Abouga Bodo, Thérésa Irma Mandeng, François Désiré Owona Edoa, Noel Chuye Tangko et Jules Rémi Ngoupayou Ndam. « Effects of the tide on the temporal and spatial physicochemical structure of the Kienké river estuary (South Atlantic Coast of Cameroon, Kribi) and its phytoplankton ». Oceanological and Hydrobiological Studies 52, n^o 1 (18 mars 2023) : 20–40. http://dx.doi.org/10.26881/oahs-2023.1.02.

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The present work aimed to understand the physicochemical and phytoplanktonic structure of the Kienke estuary water in the urban area of Kribi town in relation to human activities and fluvial or oceanic influences. Field investigations and laboratory work were devoted to the sampling and measurement of some physicochemical and biological parameters, specific treatments and classical statistics (descriptive, multidimensional) of variables. Estuary water is characterised by an instability and spatiotemporal variations in its physicochemical parameters. The most sensitive parameters are as follows: a temperature ranging between 22.6°C and 31°C under the influence of atmospheric variations, electrical conductivity and salinity that are relatively high (0.22 < C. E < 49.70 mS cm-1; avg =16.56 mS cm-1; 0 < Sal < 29.32 PSU; avg = 11.51 PSU), and a pH that is overall acidic to basic (6 < pH < 8.86; avg = 7.75 ± 0.82). The nutrients variation (ammonium, nitrite, nitrate and orthophosphate) is very low in space and time, with a longitudinal distribution controlled by tidal flows, river flows and the biological pump. For the 64 samples collected, 167 phytoplankton taxa were identified. The most abundant (36.36%) were Chrysophyta Division, followed by Chlorophyta. Species richness is marked by brackish water taxa. According to this structure and the combination of both gradients, mineratilisation and organic matter enrichment is of a physicochemical typology, and the biotypology is hydrotypologically dependent.

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Morales-Ramírez, Álvaro, Marco Corrales-Ugalde, Octavio Esquivel-Garrote, Allan Carrillo Baltodano, Karina Rodríguez-Sáenz et Carolina Sheridan. « Estudios de zooplancton marino en Costa Rica : una revisión y perspectivas a futuro ». Revista de Biología Tropical 66, n^o 1-1 (10 mai 2018) : 24. http://dx.doi.org/10.15517/rbt.v66i1.33258.

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This review summarizes marine zooplankton research performed in the Costa Rican Pacific and Caribbean coasts and at Isla del Coco National Park. Composition, abundance, biomass, distribution and some ecological features of the zooplankton for each system is discussed. Pacific coastal zooplankton composition has been described in Bahía Salinas and Bahía Culebra. The local oceanography of these bays is heavily influenced by the Papagayo wind jet, which produces seasonal coastal upwelling and most likely drives the seasonal changes in zooplankton abundance and biomass. Copepods and ostracods were the dominant taxonomic groups throughout the year with a strong seasonality, furthermore 53 hydromedusae species has been found, where Liriope tetraphylla (Chamisso & Eysenhardt, 1821), Solmundella bitentaculata (Quoy & Gaimard, 1833) and Aglaura hemistoma (Péron & Lesueur, 1810), were the most abundant species. Zooplankton herbivory rates at Gulf of Nicoya estuary was estimated over 50 % removal of primary production. This is a typical value for tropical productive environments. Copepods numerically dominated zooplankton community from the Gulf of Nicoya. Other dominant taxa includes merozooplanktonic decapod larvae and ichthyoplankton. Biomass is high and there are strong crossshelf gradients in the Gulf. Zooplankton collected in the southern Pacific coast (close to Isla del Caño) is also dominated by copepods, while Bahía Coronado has a mixed zooplankton composition of oceanic and coastal transition waters. In Golfo Dulce, zooplankton is highly diverse and dominated by copepods, appendicularians, and ostracods. About 35 % of daily primary production is consumed by microzooplankton, and zooplankton adapt to anomalous conditions of El Niño-Southern Oscillation (ENSO). Coco´s Island, and other oceanic islands in the Eastern Tropical Pacific are “hot spot” of zooplankton diversity, where > 160 zooplankton species have been reported (predominantly copepods). The biomass is dominated by mesozooplankton, and new species records for the Eastern Tropical Pacific have been found in this insular ecosystem. In the other hand, early works of 1980 carried out at Caribbean coast (Cahuita National Park), show a considerably low zooplankton diversity and abundance while research at the end of the 2000 decade recognized a significant increase in zooplankton diversity, specially fish larvae. Recent zooplankton studies have added six new copepod species and several new records of species from different taxonomic groups such as appendicularians, amphipods, chaetognats, euphausiids, gastropods, and polychaetes. Future work should focus on monthly long-term monitoring programs to investigate the effects of ocean acidification and the trophic dynamics associated with fisheries. Alike, longterm studies are needed to see trends of change in planktonic communities, especially comparing areas under human activity in the coastal zone (tourism, port, urban development) with protected areas as targets for study. An increase of sampling efforts must be done in the relatively understudied Northern Caribbean coast.

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Paleček, Dragana, Stefania Milano, Igor Gutiérrez-Zugasti et Sahra Talamo. « Stable isotopes in the shell organic matrix for (paleo)environmental reconstructions ». Communications Chemistry 7, n^o 1 (18 janvier 2024). http://dx.doi.org/10.1038/s42004-023-01076-0.

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AbstractStable isotope ratios of mollusc shell carbonates have long been used to reconstruct past environmental conditions. Although shells also contain organics, they are seldom used in (paleo)climatic studies. Here, we extract the acid-soluble and insoluble fractions of the organic matrix of modern Mytilus galloprovincialis shells from three sites along a coast–to-upper-estuary environmental gradient to measure their hydrogen (δ2H) and oxygen (δ18O) isotope compositions. Both organic fractions showed isotopic signatures significantly different from those of carbonate and water at each site, indicating the involvement of different fractionation mechanisms. The soluble fraction showed gradual differences in isotope values along the gradient, while the insoluble fraction showed δ2H-δ18O correlation regressions subparallel to the Global and Local Meteoric Water Lines. These results showed the great potential of the shell organic matrix stable isotopes as possible (paleo)environmental proxies, stimulating further research to better define the fractionation mechanisms involved.

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Hu, Xinping, Hongming Yao, Melissa R. McCutcheon, Larissa Dias, Cory J. Staryk, Michael S. Wetz et Paul A. Montagna. « Aragonite saturation states in estuaries along a climate gradient in the northwestern Gulf of Mexico ». Frontiers in Environmental Science 10 (10 octobre 2022). http://dx.doi.org/10.3389/fenvs.2022.951256.

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In the northwestern Gulf of Mexico (nwGOM), the coastal climate shifts abruptly from the humid northeast to the semiarid southwest within a narrow latitudinal range. The climate effect plays an important role in controlling freshwater discharge into the shallow estuaries in this region. In addition to diminishing freshwater runoff down the coast, evaporation also increases substantially. Hence, these estuaries show increasing salinity along the coastline due to the large difference in freshwater inflow balance (river runoff and precipitation minus evaporation and diversion). However, this spatial gradient can be disrupted by intense storm events as a copious amount of precipitation leads to river flooding, which can cause temporary freshening of these systems in extreme cases, in addition to freshwater-induced ephemeral stratification. We examined estuarine water aragonite saturation state (Ωarag) data collected between 2014 and 2018, covering a period of contrasting hydrological conditions, from the initial drought to multiple flooding events, including a brief period that was influenced by a category 4 hurricane. Based on freshwater availability, these estuaries exhibited a diminishing Ωarag fluctuation from the most freshwater enriched Guadalupe Estuary to the most freshwater-starved Nueces Estuary. While Ωarag values were usually much higher than the threshold level (Ωarag = 1), brief freshwater discharge events and subsequent low oxygen levels in the lower water column led to episodic corrosive conditions. Based on previously obtained Ωarag temporal trends and Ωarag values obtained in this study, we estimated the time of emergence (ToE) for Ωarag. Not only did estuaries show decreasing ToE with diminishing freshwater availability but the sub-embayments of individual estuaries that had a less freshwater influence also had shorter ToE. This spatial pattern suggests that planning coastal restoration efforts, especially for shellfish organisms, should emphasize areas with longer ToE.

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Barroeta, Ziortza, Ibon Uriarte, Arantza Iriarte et Fernando Villate. « Intraregional variability of exotic and native zooplankton in Basque coast estuaries (inner Bay of Biscay) : effect of secondary dispersion, estuary features and regional environmental gradients ». Hydrobiologia, 29 septembre 2023. http://dx.doi.org/10.1007/s10750-023-05363-8.

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AbstractThe zooplankton of five estuaries of the Basque coast (southeast Bay of Biscay) was surveyed in summer 2019 to check the intraregional spread of exotic species and analyse the cross-estuary differences in brackish and neritic communities related to the arrival of exotic species and the summertime geographic gradient of water temperature. Results revealed that all the studied estuaries have been colonized by Oithona davisae but not by Acartia tonsa and Pseudodiaptomus marinus. Environmental constraints due to estuarine hydrological features partly explained such differences, and the role of secondary spread opportunities remained less clear. Cross-estuary differences in the brackish community mainly reflected changes in the dominance of the native species Acartia bifilosa relative to different exotic copepod species. The neritic holoplankton differed in the contribution of thermophilic species in agreement with the thermal west–east increase of surface water temperature in the inner Bay of Biscay in summer. The detection of large numbers of larvae of the exotic crab Rhithropanopeus harrisii only in one of the estuaries highlighted the role of exotic benthic species in enhancing intraregional differences in estuarine meroplankton. Differences in the dominance of neritic or brackish species as a function of salinity and distance from coastline were also explored.

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Sibaja-Cordero, Jeffrey A., et Silvia Echeverría-Sáenz. « Polychaetes associated with decaying wood in Térraba mangrove, South Pacific, Costa Rica ». Revista de Biología Tropical, 3 février 2016, 61–74. http://dx.doi.org/10.15517/rbt.v63i1.23096.

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The present study shows spatial patterns in the faunal assemblage of decaying wood and sediments, with emphasis on the polychaetes. The survey was executed across a salinity gradient in a tropical mangrove estuary of Costa Rica. To capture the organisms we analyzed decomposing logs found in the Térraba mangrove and sediment samples were taken with a corer in the sand bottom. Seven different phyla were found in the sediment samples. Of the 192 individuals found in the sediment samples, 18 were polychaetes belonging to nine families and 11 species. Analyses of decaying wood resulted in 2 564 individuals distributed in five phyla. Polychaetes accounted for 429 individuals belonging to eight families and 16 species. Although, polychaetes were more abundant in decaying wood, and their diversity was lower. The abundance of polychaetes in decaying wood was negatively correlated with the number of individuals of Mollusca, Hexapoda and Crustacea. A change in the composition of polychaetes in decaying wood was found along the salinity gradient of this estuarine zone. Dissimilarities in the composition of benthic fauna in decaying wood and sediments in the Térraba mangrove showed that biodiversity was increased by the microhabitats inside the mangrove forest. Finally, several genera or species of polychaetes are new records for Costa Rica and the Central American Pacific Coast.

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Torres, Angela EC, Marlon C. França, Fernando A. Borges da Silva, Jorge HA Morales, Marcelo CL Cohen, Luiz CR Pessenda et Kita Macario. « A 1500-year multi-proxy record of subtropical mangrove dynamics in relation to sea level and climate changes on Babitonga Bay, Southern Brazil ». Holocene, 17 janvier 2024. http://dx.doi.org/10.1177/09596836231219491.

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Climatic changes and sea level variations have had a significant impact on the mangroves along the Brazilian coast during the Holocene. The present study focused on understanding the specific factors that have determined the establishment and expansion of mangroves in a subtropical estuary of southern Brazil (Babitonga Bay, State of Santa Catarina-SC), as well as their response to climate change and sea level variations during the late-Holocene. In this study, we carried out sedimentary analysis, palynology, and radiocarbon dating (C-14) to paleoenvironmental reconstruction of the last 1500 cal. year BP. Three facies associations were identified, indicating a progradational succession where a tidal flat was developed at the margin of the estuary. During the first phase, between at least 1440 and ±1286 cal. year BP, the area was characterized by a subtidal environment. The presence of Laguncularia pollen grains since ± 1390 cal. year BP indicated favorable conditions for mangrove establishment in proximity to the study site. Subsequently, around ± 1286 cal. year BP, the tidal flat developed, reaching the present-day shoreline, facilitated by the relative sea level drop. Avicennia trees were established on the tidal flat since ± 1273 cal. year BP, and the establishment of Rhizophora trees occurred in the most recent decades. This mangrove succession developed in Babitonga Bay following a temperature gradient, associated with low-temperature tolerance, and likely its establishment is associated with a temperature increase during the late-Holocene, that caused a migration of the southern limit of the mangrove in the subtropical zone to higher latitudes. Furthermore, the relatively slow expansion of mangroves upstream of Babitonga Bay also may have been controlled by the suitable salinity and substrate conditions, which were favored by the relative sea-level fall during the late-Holocene.

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Silva, Marcelo H. L., Audálio R. Torres Júnior, Antonio C. L. Castro, James W. J. Azevedo, Cássia F. C. Ferreira, Rayssa L. Cardoso, Jorge L. S. Nunes et Raimunda N. F. Carvalho-Neta. « Fish assemblage structure in a port region of the Amazonic coast ». Iheringia. Série Zoologia 108 (11 juin 2018). http://dx.doi.org/10.1590/1678-4766e2018018.

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ABSTRACT: The fish assemblage structure in a port area in São Marcos Bay (Amazonic coast) was evaluated based on the spatial and temporal distributions to identify potential changes in response to anthropic pressure increases associated with industrial and port activities in region. The samples were taken between March 2011 and November 2015. The ichthyofauna was represented by a total of 56 species, distributed in 15 orders and 29 families. Captures were dominated by Genyatremus luteus (Bloch, 1790), but Sciades proops (Valenciennes, 1840) was the most representative in terms of biomass. Seasonal distributions of fish assemblage did not reveal significant differences. However, there was a difference between catch sites, abundance, biomass and Shannon diversity index was higher in the Site 1 and evenness in Site 4. The analysis NMDS and the test ANOSIM between months and between sampling sites, based on species composition, revealed a seasonal differentiation associated with the rainy and drought months, as well as spatial differentiation, in function of a depth gradient and hydrodynamics, resulting from greater distance from mangrove areas. The low diversity recorded may be a reflection of port activities that historically occur in the area investigated. However, there was still a maintenance of regional diversity throughout the period under analysis. Thus, temporal and spatial scales become important for the detection and understanding of fish biodiversity in an Amazonian estuary, reflecting, the importance of mangroves for the maintenance of the ichthyofaunistic diversity in the area. In this context, the present study may subsidize possible conservation projects in the area since information of this nature is almost non-existent for estuarine fish from the Maranhão Amazon.

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