Siga este enlace para ver otros tipos de publicaciones sobre el tema: Processus estuaire.
Artículos de revistas sobre el tema "Processus estuaire"
Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros
Consulte los 50 mejores artículos de revistas para su investigación sobre el tema "Processus estuaire".
Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.
También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.
Explore artículos de revistas sobre una amplia variedad de disciplinas y organice su bibliografía correctamente.
1
Drapeau, Georges y Rémy Morin. "Contribution des vagues au transport des sédiments littoraux dans la région de Trois-Pistoles, estuaire du Saint-Laurent, Québec". Géographie physique et Quaternaire 35, n.º 2 (1 de febrero de 2011): 245–51. http://dx.doi.org/10.7202/1000441ar.
Texto completoResumen
Dans la région de Trois-Pistoles, l’action des vagues est moins importante en raison de la prédominance que prennent le glaciel et la marée dans le transport des sédiments littoraux de cette région. La disparité et le mauvais triage des sédiments de surface montrent que plusieurs processus sédimentologiques contribuent à la répartition des sédiments récents. L’influence de la marée dont le marnage atteint 5 m et celle des glaces flottantes dont l’activité dure environ 100 jours par année sont des processus relativement bien connus. L’analyse de l’action des vagues est basée sur le modèle de mise en mouvement des sédiments mis au point par KOMAR et MILLER (1975) en utilisant les données de vagues enregistrées au large de Trois-Pistoles. L’action prédominante des vagues consiste davantage à brasser les sédiments qu’à les trier à cause du balancement de la marée. La formation de nombreuses flèches dans la région montre cependant que les vagues d’intensité plus forte réparties sur de longues périodes contribuent à la construction des formes d’accumulation dans la région. Le rôle que jouent les vagues à l’interface entre les sédiments récents et les argiles de la mer de Goldthwait reste à déterminer.
2
Dionne, Jean-Claude. "Données quantitatives sur les cailloux à la surface du couvert glaciel, estuaire du Saint-Laurent". Géographie physique et Quaternaire 47, n.º 2 (23 de noviembre de 2007): 181–92. http://dx.doi.org/10.7202/032947ar.
Texto completoResumen
RÉSUMÉ À plusieurs endroits, le couvert glaciel des rivages de l'estuaire du Saint-Laurent contient des débris grossiers. Un relevé des cailloux à la surface de la glace a été fait dans quatre sites. On y a mesuré plus de 300 cailloux pesant entre un kilo et une tonne. Dans les sites étudiés, les cailloux de petite taille (1 à 20 kg) prédominent avec 60 %; les cailloux de 20 à 50 kg comptent pour 25 %; les autres ont un poids supérieur à 50 kg. Dans trois des sites étudiés, la débâcle est survenue le lendemain des observations. Les cailloux à la surface de la glace ont donc été évacués au large et vers l'aval sur des distances qui ont pu atteindre 30 km avant d'être délestés. La puissance des vagues et la vélocité des courants étant relativement modestes sur les estrans du Saint-Laurent estuarien, une grande partie des sédiments grossiers excède leur compétence; les matériaux au-dessus de 10 cm sont donc exclusivement déplacés par les glaces. Le relevé des cailloux à la surface du couvert glaciel renseigne utilement sur la charge sédimentaire des glaces et aide à quantifier le processus.
3
Brodeur, Denis y Michel Allard. "Les plates-formes littorales de l’île aux Coudres, moyen estuaire du Saint-Laurent, Québec". Géographie physique et Quaternaire 37, n.º 2 (29 de noviembre de 2007): 179–95. http://dx.doi.org/10.7202/032513ar.
Texto completoResumen
RÉSUMÉ De larges plates-formes littorales ceinturent l'île aux Coudres, dans le moyen estuaire du Saint-Laurent. Le substrat rocheux est constitué de microgrès et de schistes à forts pendages. L'environnement océanographique est caractérisé par un régime marégraphique semi-diurne macrotidal, des eaux saumâtres, de forts courants de marée généralement parallèles aux rivages, et des vagues relativement importantes du sud-ouest et du nord-est suivant l'axe du Saint-Laurent. Une saison glacielle de 4 mois environ permet le développement d'un pied de glace en hiver. Des profils topographiques levés tout autour de l'île ont permis de mettre en évidence certains faits: 1) les plates-formes les moins exposées, du côté nord, sont étroites, en pente forte, relativement élevées et contiguës à une falaise rocheuse parfois vive; il semble qu'elles résultent d'un recul, sous l'action des agents littoraux, de l'escarpement rocheux correspondant au front des nappes appalachiennes; 2) les plates-formes des deux extrémités exposées de l'île accusent un degré de destruction plus avancé que les autres; 3) des niveaux préférentiels d'aplanissement sont décelables statistiquement et peuvent être corrélés avec des modes dans la courbe de distribution de la fréquence des niveaux d'eau. Les plates-formes de l'île aux Coudres évoluent sous les conditions hydrodynamiques actuelles, mais il s'agit de paléoformes rajeunies qui correspondraient à la surface Micmac. La cryoclastrie, l'érosion glacielle et l'altération superficielle des formations schisteuses et microgréseuses sont considérées comme des agents majeurs dans les processus d'érosion en relation avec les marées.
4
Dinauer, Ashley y Alfonso Mucci. "Spatial variability in surface-water <i>p</i>CO<sub>2</sub> and gas exchange in the world's largest semi-enclosed estuarine system: St. Lawrence Estuary (Canada)". Biogeosciences 14, n.º 13 (6 de julio de 2017): 3221–37. http://dx.doi.org/10.5194/bg-14-3221-2017.
Texto completoResumen
Abstract. The incomplete spatial coverage of CO2 partial pressure (pCO2) measurements across estuary types represents a significant knowledge gap in current regional- and global-scale estimates of estuarine CO2 emissions. Given the limited research on CO2 dynamics in large estuaries and bay systems, as well as the sources of error in the calculation of pCO2 (carbonic acid dissociation constants, organic alkalinity), estimates of air–sea CO2 fluxes in estuaries are subject to large uncertainties. The Estuary and Gulf of St. Lawrence (EGSL) at the lower limit of the subarctic region in eastern Canada is the world's largest estuarine system, and is characterized by an exceptional richness in environmental diversity. It is among the world's most intensively studied estuaries, yet there are no published data on its surface-water pCO2 distribution. To fill this data gap, a comprehensive dataset was compiled from direct and indirect measurements of carbonate system parameters in the surface waters of the EGSL during the spring or summer of 2003–2016. The calculated surface-water pCO2 ranged from 435 to 765 µatm in the shallow partially mixed upper estuary, 139–578 µatm in the deep stratified lower estuary, and 207–478 µatm along the Laurentian Channel in the Gulf of St. Lawrence. Overall, at the time of sampling, the St. Lawrence Estuary served as a very weak source of CO2 to the atmosphere, with an area-averaged CO2 degassing flux of 0.98 to 2.02 mmol C m−2 d−1 (0.36 to 0.74 mol C m−2 yr−1). A preliminary analysis revealed that respiration (upper estuary), photosynthesis (lower estuary), and temperature (Gulf of St. Lawrence) controlled the spatial variability in surface-water pCO2. Whereas we used the dissociation constants of Cai and Wang (1998) to calculate estuarine pCO2, formulations recommended for best practices in open ocean environments may underestimate pCO2 at low salinities, while those of Millero (2010) may result in overestimates.
5
Gomes, Vando J. C., Nils E. Asp, Eduardo Siegle, José Diego Gomes, Ariane M. M. Silva, Andrea S. Ogston y Charles A. Nittrouer. "Suspended-Sediment Distribution Patterns in Tide-Dominated Estuaries on the Eastern Amazon Coast: Geomorphic Controls of Turbidity-Maxima Formation". Water 13, n.º 11 (1 de junio de 2021): 1568. http://dx.doi.org/10.3390/w13111568.
Texto completoResumen
In tide-dominated estuaries, maximum-turbidity zones (MTZs) are common and prominent features, characterized by a peak in suspended-sediment concentration (SSC) associated with estuarine processes. The Brazilian Amazon coast includes many estuaries, experiencing macrotidal conditions. MTZs are expected to occur and are crucial for sediment delivery to the longest continuous mangrove belt of the world. The area is under influence of the Amazon River plume (ARP), the main SSC source, as local rivers do not deliver substantial sediment supply. To assess the processes that allow the ARP to supply sediment to the estuaries and mangrove belt along the Amazon coast, the results from previous individual studies within five Amazon estuaries (Mocajuba, Taperaçu, Caeté, Urumajó and Gurupi) were compared with regards to SSC, salinity, morphology and tidal propagation. This comparison reinforces that these estuaries are subject to similar regional climate and tidal variations, but that their dynamics differ in terms of distance from the Amazon River mouth, importance of the local river sediment source, and morphology of the estuarine setting. The Urumajó, Caeté and Gurupi are hypersynchronous estuaries where perennial, classic MTZs are observed with SSC > 1 g·L−1. This type of estuary results in transport convergence and MTZ formation, which are suggested to be the main processes promoting mud accumulation in the Amazonian estuaries and therefore the main means of mud entrapment in the mangrove belt. The Mocajuba and the Taperaçu estuaries showed synchronous and hyposynchronous processes, respectively, and do not present classic MTZs. In these cases, the proximity to the ARP for the Mocajuba and highly connected tidal channels for the Taperaçu estuary, assure substantial mud supply into these estuaries. This study shows the strong dependence of the estuaries and mangrove belt on sediment supply from the ARP, helping to understand the fate of Amazon River sediments and providing insights into the mechanisms providing sediment to estuaries and mangroves around the world, especially under the influence of big rivers.
6
R., Anusiya y Sukumaran M. "Assessment of Seasonal Variation (2020 to 2021) in Physico-Chemical Parameters of Nandalar Estuary in East Coast of Tamil Nadu, India". International Journal of Zoological Investigations 08, special issue (2022): 254–58. http://dx.doi.org/10.33745/ijzi.2022.v08i0s.030.
Texto completoResumen
Estuaries are defined as the areas between rivers and the ocean that have unique ecological characteristics, a wealth of flora and fauna, and are essential to both biodiversity and hydrological processes. Aquatic ecosystems depend on their biological traits as well as their physical and chemical qualities. The objective of the current study was to identify seasonal variations in the physico-chemical parameters of Tamil Nadu's Nandalar Estuary. The physico-chemical characteristics of the Nandalar Estuary were recorded which have an impact on the estuarine environment. Future analyses of the ecological, biological, and cultural elements of estuarine species as well as the allowable limit of fisheries and aquatic life would benefit from preliminary data on the physico-chemical parameters in this Nandalar estuary area.
7
Schmidt, Sabine y Ibrahima Iris Diallo. "Hypoxia also occurs in small highly turbid estuaries: the example of the Charente (Bay of Biscay)". Biogeosciences 21, n.º 7 (10 de abril de 2024): 1785–800. http://dx.doi.org/10.5194/bg-21-1785-2024.
Texto completoResumen
Abstract. The French coast facing the Bay of Biscay (North-East Atlantic) is characterised by the presence of small macrotidal and turbid estuaries, including the Charente, which is geographically located between the two large estuaries of the Gironde and the Loire (south-west France). Multi-year, multi-site and high-frequency water quality surveys have shown that the Loire and, to a lesser extent, the Gironde suffer from summer hypoxia. These observations raised the question of the possible occurrence of hypoxia, particularly in one of these small estuaries, the Charente, which flows into the Bay of Marennes-Oléron, the first oyster-farming area in France. Unlike its two large neighbours, the Charente estuary is not continuously monitored, although it is subject to similar climatic changes and anthropogenic pressures, making it impossible to assess potential risks to the ecosystem. Here we present a first study of dissolved oxygen in the Charente estuary based on a combination of longitudinal studies along the estuary axis and instrumented sites to determine the intensity and spatial extent of deoxygenation. Temperature, dissolved oxygen and conductivity sensors were deployed at several sites during the summers of 2018, 2019 and 2020 to record temperature, salinity and dissolved oxygen every 15 min. The high-frequency dataset is compared with a long-term low-frequency dataset (1975–2022; 8–12 measurements per year) to determine whether or not there is a deterioration in the oxygenation of the Charente estuary. The high-frequency dataset shows a high variability in dissolved oxygen (DO) with a clear influence of the tidal cycle. During summer, DO concentrations are often below 5 mg L−1 and sometimes even below 2 mg L−1, indicating the presence of a summer estuarine oxygen minimum zone with an extension along the estuarine axis of about 20–25 km. Temperature is the main factor controlling DO in the Charente estuary, which limits preventive management strategies and, in the context of global warming, raises questions about the long-term suitability of estuarine conditions for the needs of the biological communities, particularly migratory fish.
8
Braat, Lisanne, Thijs van Kessel, Jasper R. F. W. Leuven y Maarten G. Kleinhans. "Effects of mud supply on large-scale estuary morphology and development over centuries to millennia". Earth Surface Dynamics 5, n.º 4 (9 de octubre de 2017): 617–52. http://dx.doi.org/10.5194/esurf-5-617-2017.
Texto completoResumen
Abstract. Alluvial river estuaries consist largely of sand but are typically flanked by mudflats and salt marshes. The analogy with meandering rivers that are kept narrower than braided rivers by cohesive floodplain formation raises the question of how large-scale estuarine morphology and the late Holocene development of estuaries are affected by cohesive sediment. In this study we combine sand and mud transport processes and study their interaction effects on morphologically modelled estuaries on centennial to millennial timescales. The numerical modelling package Delft3D was applied in 2-DH starting from an idealised convergent estuary. The mixed sediment was modelled with an active layer and storage module with fluxes predicted by the Partheniades–Krone relations for mud and Engelund–Hansen for sand. The model was subjected to a range of idealised boundary conditions of tidal range, river discharge, waves and mud input. The model results show that mud is predominantly stored in mudflats on the side of the estuary. Marine mud supply only influences the mouth of the estuary, whereas fluvial mud is distributed along the whole estuary. Coastal waves stir up mud and remove the tendency to form muddy coastlines and the formation of mudflats in the downstream part of the estuary. Widening continues in estuaries with only sand, while mud supply leads to a narrower constant width and reduced channel and bar dynamics. This self-confinement eventually leads to a dynamic equilibrium in which lateral channel migration and mudflat expansion are balanced on average. However, for higher mud concentrations, higher discharge and low tidal amplitude, the estuary narrows and fills to become a tidal delta.
9
Conroy, Ted, David A. Sutherland y David K. Ralston. "Estuarine Exchange Flow Variability in a Seasonal, Segmented Estuary". Journal of Physical Oceanography 50, n.º 3 (marzo de 2020): 595–613. http://dx.doi.org/10.1175/jpo-d-19-0108.1.
Texto completoResumen
AbstractSmall estuaries in Mediterranean climates display pronounced salinity variability at seasonal and event time scales. Here, we use a hydrodynamic model of the Coos Estuary, Oregon, to examine the seasonal variability of the salinity dynamics and estuarine exchange flow. The exchange flow is primarily driven by tidal processes, varying with the spring–neap cycle rather than discharge or the salinity gradient. The salinity distribution is rarely in equilibrium with discharge conditions because during the wet season the response time scale is longer than discharge events, while during low flow it is longer than the entire dry season. Consequently, the salt field is rarely fully adjusted to the forcing and common power-law relations between the salinity intrusion and discharge do not apply. Further complicating the salinity dynamics is the estuarine geometry that consists of multiple branching channel segments with distinct freshwater sources. These channel segments act as subestuaries that import both higher- and lower-salinity water and export intermediate salinities. Throughout the estuary, tidal dispersion scales with tidal velocity squared, and likely includes jet–sink flow at the mouth, lateral shear dispersion, and tidal trapping in branching channel segments inside the estuary. While the estuarine inflow is strongly correlated with tidal amplitude, the outflow, stratification, and total mixing in the estuary are dependent on the seasonal variation in river discharge, which is similar to estuaries that are dominated by subtidal exchange flow.
10
Kleinhans, Maarten G., Lonneke Roelofs, Steven A. H. Weisscher, Ivar R. Lokhorst y Lisanne Braat. "Estuarine morphodynamics and development modified by floodplain formation". Earth Surface Dynamics 10, n.º 2 (29 de abril de 2022): 367–81. http://dx.doi.org/10.5194/esurf-10-367-2022.
Texto completoResumen
Abstract. Rivers and estuaries are flanked by floodplains built by mud and vegetation. Floodplains affect channel dynamics and the overall system's pattern through apparent cohesion in the channel banks and through filling of accommodation space and hydraulic resistance. For rivers, effects of mud, vegetation and the combination are thought to stabilise the banks and narrow the channel. However, the thinness of estuarine floodplain, comprised of salt marsh and mudflats, compared to channel depth raises questions about the possible effects of floodplain as constraints on estuary dimensions. To test these effects, we created three estuaries in a tidal flume: one with recruitment events of two live vegetation species, one with mud and a control with neither. Both vegetation and mud reduced channel migration and bank erosion and stabilised channels and bars. Effects of vegetation include local flow velocity reduction and concentration of flow into the channels, while flow velocities remained higher over mudflats. On the other hand, the lower reach of the muddy estuary showed more reduced channel migration than the vegetated estuary. The main system-wide effect of mudflats and salt marsh is to reduce the tidal prism over time from upstream to downstream. The landward reach of the estuary narrows and fills progressively, particularly for the muddy estuary, which effectively shortens the tidally influenced reach and also reduces the tidal energy in the seaward reach and mouth area. As such, estuaries with sufficient sediment supply are limited in size by tidal prism reduction through floodplain formation.
11
Dijkstra, Yoeri M. y Henk M. Schuttelaars. "A Unifying Approach to Subtidal Salt Intrusion Modeling in Tidal Estuaries". Journal of Physical Oceanography 51, n.º 1 (enero de 2021): 147–67. http://dx.doi.org/10.1175/jpo-d-20-0006.1.
Texto completoResumen
AbstractThe salinity structure in estuaries is classically described in terms of the salinity structure as well mixed, partially mixed, or salt wedge. The existing knowledge about the processes that result in such salinity structures comes from highly idealized models that are restricted to either well-mixed and partially mixed cases or subtidal salt wedge estuaries. Hence, there is still little knowledge about the processes driving transitions between these different salinity structures and the estuarine parameters at which such a transition is found. As an important step toward a unified description of the dominant processes driving well-mixed, partially mixed, and salt wedge estuaries, a subtidal width-averaged model applicable to all these salinity structures is developed and systematically analyzed. Using our model, we identify four salinity regimes, resulting from different balances of dominant processes. It is shown that each regime is uniquely determined by two dimensionless parameters: an estuarine Froude and Rayleigh number, representing freshwater discharge and tidal mixing, respectively, resulting in a classification of the regimes in terms of these two parameters. Furthermore, analytical expressions to approximate the salt intrusion length in each regime are developed. These expressions are used to illustrate that the salt intrusion length in different regimes responds in a highly different manner to changes in depth and freshwater discharge. As one of the key results, we show that there are only very weak relations between the process-based regime of an estuary and the salt intrusion length and top–bottom stratification. This implies that the salinity structure of an estuary cannot be uniquely matched to a regime.
12
Moore-Maley, Benjamin L., Debby Ianson y Susan E. Allen. "The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river". Biogeosciences 15, n.º 12 (20 de junio de 2018): 3743–60. http://dx.doi.org/10.5194/bg-15-3743-2018.
Texto completoResumen
Abstract. Ocean acidification threatens to reduce pH and aragonite saturation state (ΩA) in estuaries, potentially damaging their ecosystems. However, the impact of highly variable river total alkalinity (TA) and dissolved inorganic carbon (DIC) on pH and ΩA in these estuaries is unknown. We assess the sensitivity of estuarine surface pH and ΩA to river TA and DIC using a coupled biogeochemical model of the Strait of Georgia on the Canadian Pacific coast and place the results in the context of global rivers. The productive Strait of Georgia estuary has a large, seasonally variable freshwater input from the glacially fed, undammed Fraser River. Analyzing TA observations from this river plume and pH from the river mouth, we find that the Fraser is moderately alkaline (TA 500–1000 µmol kg−1) but relatively DIC-rich. Model results show that estuarine pH and ΩA are sensitive to freshwater DIC and TA, but do not vary in synchrony except at high DIC : TA. The asynchrony occurs because increased freshwater TA is associated with increased DIC, which contributes to an increased estuarine DIC : TA and reduces pH, while the resulting higher carbonate ion concentration causes an increase in estuarine ΩA. When freshwater DIC : TA increases (beyond ∼ 1.1), the shifting chemistry causes a paucity of the carbonate ion that overwhelms the simple dilution/enhancement effect. At this high DIC : TA ratio, estuarine sensitivity to river chemistry increases overall. Furthermore, this increased sensitivity extends to reduced flow regimes that are expected in future. Modulating these negative impacts is the seasonal productivity in the estuary which draws down DIC and reduces the sensitivity of estuarine pH to increasing DIC during the summer season.
13
Austin, Timothy, Ana Vila-Concejo, Andrew Short y Roshanka Ranasinghe. "A Multi-Scale Conceptual Model of Flood-Tide Delta Morphodynamics in Micro-Tidal Estuaries". Geosciences 8, n.º 9 (29 de agosto de 2018): 324. http://dx.doi.org/10.3390/geosciences8090324.
Texto completoResumen
Wave and tide induced sediment transport pathways and rates govern the morphological evolution of estuarine systems. An understanding of the morphodynamics of these systems is required to maintain their commercial, biological and recreational value. The morphodynamics of Port Stephens estuary, a micro-tidal estuary located on a wave dominated southeast coast of Australia were investigated using bathymetric surveys and current velocity data from several locations over the estuary. This provided detailed insight into the rates and direction of movement for the main sedimentary features of the system, and how these features interact with the processes that drive their evolution. We used these findings to develop a conceptual model for estuarine morphodynamics that accounts for fair weather and storm conditions. Our model explains how sediment eroded from the estuarine beaches is trapped by the adjacent flood-tide delta. The model is applicable to fetch-limited estuaries that do not have offshore sources of sediment, where the tidal currents are weak in relation to the incident ocean waves, and that have a wide, stable entrance through which ocean waves can propagate into the estuary. The model is multi-scale in that it encapsulates both short-term and local process, and large scale evolution of an estuary; therefore, it represents a tool that may be used in developing sustainable estuary management strategies.
14
Le Vu, Hong y Ron Johnstone. "Anthropogenic Impacts on Biochemical Processes in a Tropical Estuarine Lagoon". International Journal of Engineering Technology and Sciences 5, n.º 2 (1 de agosto de 2018): 102–6. http://dx.doi.org/10.15282/ijets.v5i2.1401.
Texto completoResumen
Estuaries play an invaluable role in the transformation and cycling of materials as they move between land and sea; including anthropogenic materials. Increasingly, human land use is delivering material loads that risk overwhelming the normal functions that these ecosystems provide. In this context, the objective of this study is to assess key biogeochemical processes to understand the connections of anthropogenic activities on ecosystem performance in a tropical estuarine lagoon system. This research focuses on a case study area, Dong Ho lagoon in Vietnam, which exemplifies the anthropogenic impacts and management issues facing most of the Mekong coastline and other similar areas in Vietnam. Located at the south-western edge of the Mekong delta, the Dong Ho estuary is subject to material inputs from both local and more remote sources; making it vulnerable to degradation and functional loss. This paper summarises the key findings from an assessment of the Dong Ho estuarine functions and highlights potential risks it is currently facing.
15
Wei, Xi, Josette Garnier, Vincent Thieu, Paul Passy, Romain Le Gendre, Gilles Billen, Maia Akopian y Goulven Gildas Laruelle. "Nutrient transport and transformation in macrotidal estuaries of the French Atlantic coast: a modeling approach using the Carbon-Generic Estuarine Model". Biogeosciences 19, n.º 3 (15 de febrero de 2022): 931–55. http://dx.doi.org/10.5194/bg-19-931-2022.
Texto completoResumen
Abstract. Estuaries are key reactive ecosystems along the land–ocean aquatic continuum, with significant ecological and economic value. However, they have been facing strong morphological management changes and increased nutrient and contaminant inputs, possibly leading to ecological problems such as coastal eutrophication. Therefore, it is necessary to quantify the import and export fluxes of the estuaries, their retention capacity, and estuarine eutrophication potential. The 1-D Carbon-Generic Estuary Model (C-GEM) was used to simulate the transient hydrodynamics, transport, and biogeochemistry for estuaries with different sizes and morphologies along the French Atlantic coast during the period 2014–2016 using readily available geometric, hydraulic, and biogeochemical data. These simulations allowed us to evaluate the budgets of the main nutrients (phosphorus – P; nitrogen – N; silica – Si) and total organic carbon (TOC), and their imbalance, providing insights into their eutrophication potential. Cumulated average annual fluxes to the Atlantic coast from the seven estuaries studied were 9.6 kt P yr−1, 259 kt N yr−1, 304 kt Si yr−1, and 145 kt C yr−1. Retention rates varied depending on the estuarine residence times, ranging from 0 %–27 % and 0 %–34 % to 2 %–39 % and 8 %–96 % for total phosphorus (TP), total nitrogen (TN), dissolved silica (DSi), and TOC, respectively. Large-scale estuaries had higher retention rates than medium and small estuaries, which we interpreted in terms of estuarine residence times. As shown by the indicator of eutrophication potential (ICEP), there might be a risk of coastal eutrophication, i.e., the development of non-siliceous algae that is potentially harmful to the systems studied due to the excess TN over DSi. This study also demonstrates the ability of our model to be applied with a similar setup to several estuarine systems characterized by different sizes, geometries, and riverine loads.
16
Laruelle, Goulven Gildas, Nicolas Goossens, Sandra Arndt, Wei-Jun Cai y Pierre Regnier. "Air–water CO<sub>2</sub> evasion from US East Coast estuaries". Biogeosciences 14, n.º 9 (15 de mayo de 2017): 2441–68. http://dx.doi.org/10.5194/bg-14-2441-2017.
Texto completoResumen
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.
17
Leuven, Jasper R. F. W., Sanja Selaković y Maarten G. Kleinhans. "Morphology of bar-built estuaries: empirical relation between planform shape and depth distribution". Earth Surface Dynamics 6, n.º 3 (11 de septiembre de 2018): 763–78. http://dx.doi.org/10.5194/esurf-6-763-2018.
Texto completoResumen
Abstract. Fluvial–tidal transitions in estuaries are used as major shipping fairways and are characterised by complex bar and channel patterns with a large biodiversity. Habitat suitability assessment and the study of interactions between morphology and ecology therefore require bathymetric data. While imagery offers data of planform estuary dimensions, only for a few natural estuaries are bathymetries available. Here we study the empirical relation between along-channel planform geometry, obtained as the outline from imagery, and hypsometry, which characterises the distribution of along-channel and cross-channel bed levels. We fitted the original function of Strahler (1952) to bathymetric data along four natural estuaries. Comparison to planform estuary shape shows that hypsometry is concave at narrow sections with large channels, while complex bar morphology results in more convex hypsometry. We found an empirical relation between the hypsometric function shape and the degree to which the estuary width deviates from an ideal convergent estuary, which is calculated from river width and mouth width. This implies that the occurring bed-level distributions depend on inherited Holocene topography and lithology. Our new empirical function predicts hypsometry and along-channel variation in intertidal and subtidal width. A combination with the tidal amplitude allows for an estimate of inundation duration. The validation of the results on available bathymetry shows that predictions of intertidal and subtidal area are accurate within a factor of 2 for estuaries of different size and character. Locations with major human influence deviate from the general trends because dredging, dumping, land reclamation and other engineering measures cause local deviations from the expected bed-level distributions. The bathymetry predictor can be used to characterise and predict estuarine subtidal and intertidal morphology in data-poor environments.
18
Groeneveld, Johan C., Jorge Santos, Fiona MacKay y Cosmas N. Munga. "A regional assessment of seasonal-to-decadal changes in estuarine socio-ecological systems in the Western Indian Ocean". Western Indian Ocean Journal of Marine Science, n.º 1/2021 (23 de diciembre de 2021): 131–61. http://dx.doi.org/10.4314/wiojms.si2021.1.9.
Texto completoResumen
Estuarine socio-ecological systems (SES) in the Western Indian Ocean (WIO) region face mounting pressures from overexploitation, habitat degradation, impacts of climate change and governance inadequacies. A regional assessment of seasonal-to-decadal change in SES of three estuaries (Bons Sinais in Mozambique, Ruvu in Tanzania and Tana in Kenya) was undertaken along 2000 km of tropical coastline (3°-18°S), using a systems-oriented approach and information collected during the Estuarize-WIO project (2016-2019). All three estuaries were open and tidal, but differed along gradients of geomorphology, annual precipitation, exposure to tropical storms, drought, sea level rise, and rural to urban development. Despite physical differences, similar marine species, mangrove assemblages, seasonality in fish-based farming systems and cultivated crops, and fishing methods were apparent across the region. Key differences were related to the scale of anthropogenic disturbance, discerned from land use / land cover (LULC) change analysis, which showed decadal increases in developed-, cultivated- and grasslands, at the expense of wetlands and forests, and seasonal transformation of wetlands to agriculture and grasslands. The three estuaries represented a gradient along urban-production-conservation dimensions, brought about by rural to urban transformation, and by freshwater and sediment diversion for economic development in upstream catchment areas. Household surveys indicated strongly seasonal livelihood strategies, with highest diversity in peri-urban settings, and reliance on different combinations of ecosystem goods and services in coastal and upstream rural settings. Estuarine fisheriesranged from unselective, low trophic-level fisheries using fine-mesh nets at the urbanized and most-disturbed Bons Sinais Estuary, to a more complex organized fishery at the least-disturbed Tana. At Ruvu, fisheries and agriculture production exit the system to distant markets. The systems-oriented approach demonstrated that human-induced processes affected WIO estuaries and dependent livelihoods more deeply than inherent physical differences. A key conclusion is that research, management and governance will benefit from regional cooperation, given the similarities of the systems and the different levels of disturbance.
19
Carmona Rodrigues, A., M. Cardoso da Silva, A. Câmara, T. Faria Fernandes y J. Gomes Ferreira. "Dispersion Modelling for a Complex Estuary – The Case of the Tagus". Water Science and Technology 20, n.º 6-7 (1 de junio de 1988): 271–76. http://dx.doi.org/10.2166/wst.1988.0212.
Texto completoResumen
Estuarine dispersion models have been commonly used to define the pollutant loads permissible to achieve pre-defined water quality levels and improve our knowledge of estuarine phenomena. Those models for large estuaries with complex hydrodynamic and ecological processes usually have extremely high running times. This paper presents an approach based on the use of increasingly complex models, which attempts to circumvent the problem of initial lack of data, as well as to give some initial insight into the processes of the Tagus Estuary, within acceptable levels of precision. As a first stage, simple models were developed and applied to the estuary, one of the largest in Europe, with more than 300 sources of pollution and intensive use for recreation, fishing, and navigation. The computational exercises undertaken with these models were also used to accumulate information on the response of the Tagus Estuary to a number of forcing conditions. This information, synthesized in ‘if … then' rules, was integrated to form a data base on the estuary, which is currently being developed. The data base will organize existing information and, providing that learning mechanisms are included, it will also create new knowledge, as well as supplying the complex models under development with reasonable initial values.
20
Joesoef, Andrew, David L. Kirchman, Christopher K. Sommerfield y Wei-Jun Cai. "Seasonal variability of the inorganic carbon system in a large coastal plain estuary". Biogeosciences 14, n.º 21 (8 de noviembre de 2017): 4949–63. http://dx.doi.org/10.5194/bg-14-4949-2017.
Texto completoResumen
Abstract. Carbonate geochemistry research in large estuarine systems is limited. More work is needed to understand how changes in land-use activity influence watershed export of organic and inorganic carbon, acids, and nutrients to the coastal ocean. To investigate the seasonal variation of the inorganic carbon system in the Delaware Estuary, one of the largest estuaries along the US east coast, dissolved inorganic carbon (DIC), total alkalinity (TA), and pH were measured along the estuary from June 2013 to April 2015. In addition, DIC, TA, and pH were periodically measured from March to October 2015 in the nontidal freshwater Delaware, Schuylkill, and Christina rivers over a range of discharge conditions. There were strong negative relationships between river TA and discharge, suggesting that changes in HCO3− concentrations reflect dilution of weathering products in the drainage basin. The ratio of DIC to TA, an understudied but important property, was high (1.11) during high discharge and low (0.94) during low discharge, reflecting additional DIC input in the form of carbon dioxide (CO2), most likely from terrestrial organic matter decomposition, rather than bicarbonate (HCO3−) inputs due to drainage basin weathering processes. This is also a result of CO2 loss to the atmosphere due to rapid water transit during the wet season. Our data further show that elevated DIC in the Schuylkill River is substantially different than that in the Delaware River. Thus, tributary contributions must be considered when attributing estuarine DIC sources to the internal carbon cycle versus external processes such as drainage basin mineralogy, weathering intensity, and discharge patterns. Long-term records in the Delaware and Schuylkill rivers indicate shifts toward higher alkalinity in estuarine waters over time, as has been found in other estuaries worldwide. Annual DIC input flux to the estuary and export flux to the coastal ocean are estimated to be 15.7 ± 8.2 × 109 mol C yr−1 and 16.5 ± 10.6 × 109 mol C yr−1, respectively, while net DIC production within the estuary including inputs from intertidal marshes is estimated to be 5.1 × 109 mol C yr−1. The small difference between riverine input and export flux suggests that, in the case of the Delaware Estuary and perhaps other large coastal systems with long freshwater residence times, the majority of the DIC produced in the estuary by biological processes is exchanged with the atmosphere rather than exported to the sea.
21
Lange, Xaver y Hans Burchard. "The Relative Importance of Wind Straining and Gravitational Forcing in Driving Exchange Flows in Tidally Energetic Estuaries". Journal of Physical Oceanography 49, n.º 3 (marzo de 2019): 723–36. http://dx.doi.org/10.1175/jpo-d-18-0014.1.
Texto completoResumen
AbstractIn straight tidal estuaries, residual overturning circulation results mainly from a competition between gravitational forcing, wind forcing, and friction. To systematically investigate this for tidally energetic estuaries, the dynamics of estuarine cross sections is analyzed in terms of the relation between gravitational forcing, wind stress, and the strength of estuarine circulation. A system-dependent basic Wedderburn number is defined as the ratio between wind forcing and opposing gravitational forcing at which the estuarine circulation changes sign. An analytical steady-state solution for gravitationally and wind-driven exchange flow is constructed, where tidal mixing is parameterized by parabolic eddy viscosity. For this simple but fundamental situation, is calculated, meaning that the up-estuary wind forcing needs to be 15% of the gravitational forcing to invert estuarine circulation. In three steps, relevant physical processes are added to this basic state: (i) tidal dynamics are resolved by a prescribed semidiurnal tide, leading to caused by tidal straining; (ii) lateral circulation is added by introducing cross-channel bathymetry, smoothly increasing from 0.47 (flat bed) to 1.3 (parabolic bed) due to an increasing effect of lateral circulation on estuarine circulation; and (iii) full dynamics of a real tidally energetic inlet with highly variable forcing, where results from a two-dimensional linear regression.
22
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.
Texto completoResumen
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.
23
Hodgkin, Ernest P. y Patrick Hesp. "Estuaries to salt lakes: Holocene transformation of the estuarine ecosystems of south-western Australia". Marine and Freshwater Research 49, n.º 3 (1998): 183. http://dx.doi.org/10.1071/mf96109.
Texto completoResumen
When the estuaries of south-western Australia were first flooded by the Holocene marine transgression about 7000 years before present (BP), most were enclosed by limestone barrier dunes. Coastal sand drift built bars and flood-tide deltas in the narrow entrances, but until about 3500 years BP the estuaries remained tidal-dominated systems with a diverse marine–estuarine fauna. Now the bars/deltas so obstruct the small tides that estuary water is fresh in winter and marine to hypersaline in summer; the estuaries are river-flow-dominated systems and the ecosystems are characterised by a restricted euryhaline estuarine biota. Some estuaries are still permanently open, their bars/deltas never close, and some are seasonally open, their bars open with river flow in winter and close in summer. Other estuaries are normally closed, their bars remain closed for several years and break with episodic flood flow, or are permanently closed coastal salt lakes with bars that never or rarely break: they can become grossly hypersaline and may dry up altogether. An hypothesis to explain this Holocene transformation of the estuaries attributes it principally to sedimentary processes in an environment where river flow is highly seasonal, tides are microtidal, there was a fall in sea level, and there are differences in the volume and periodicity of flow and the degree of shelter to the entrances from the prevailing south-west winds and swell.
24
Hu, Wang, Yao y Jin. "A Case Study: Response Mechanics of Irregular Rotational Tidal Flows to Outlet Regulation in Yangtze Estuary". Water 11, n.º 7 (12 de julio de 2019): 1445. http://dx.doi.org/10.3390/w11071445.
Texto completoResumen
Responses of irregular rotational tidal flows to an outlet regulation (the Guyuan Sand (GYS) regulation) in the three-level branching Yangtze Estuary are studied by a high-resolution numerical model and theoretical analysis. The project is launched around GYS at the outlet of the North Branch of the Yangtze Estuary. The tidal flows around GYS are rotational and become irregular under the influences of the runoff-tide interactions, rapidly varying topographies and complex solid boundaries in coastal areas. Three designs of GYS regulation were studied, including various diversion dikes and new outlets of different widths. The regulation disturbs the irregular rotational flows around GYS, and further changes the estuarine tidal processes and the water exchange between different branches of the branching Yangtze Estuary. It was interesting to find that additional current and additional storage are formed along the North Branch when a southward outlet and the clockwise rotational flow met around GYS. This special phenomenon is named “guide effect” in this study. The guide effect, together with common resist effect (arising from the narrowed outlet channel), reshapes the estuarine tidal processes. Based on the simulation result and a theoretical analysis, response mechanics of irregular rotational tidal flows to the outlet regulation in complex branching estuaries are quantitatively studied.
25
Volta, C., G. G. Laruelle, S. Arndt y P. Regnier. "Linking biogeochemistry to hydro-geometrical variability in tidal estuaries: a generic modeling approach". Hydrology and Earth System Sciences Discussions 12, n.º 7 (1 de julio de 2015): 6351–435. http://dx.doi.org/10.5194/hessd-12-6351-2015.
Texto completoResumen
Abstract. This study applies the Carbon-Generic Estuary Model (C-GEM) modeling platform to simulate the estuarine biogeochemical dynamics – in particular the air-water CO2 exchange – in three idealized end-member systems covering the main features of tidal alluvial estuaries. C-GEM uses a generic biogeochemical reaction network and a unique set of model parameters extracted from a comprehensive literature survey to perform steady-state simulations representing average conditions for temperate estuaries worldwide. Climate and boundary conditions are extracted from published global databases (e.g. World Ocean Atlas, GLORICH) and catchment model outputs (GlobalNEWS2). The whole-system biogeochemical indicators Net Ecosystem Metabolism (NEM), C and N filtering capacities (FCTC and FCTN, respectively) and CO2 gas exchanges (FCO2) are calculated across the three end-member systems and are related to their main hydrodynamic and transport characteristics. A sensitivity analysis, which propagates the parameter uncertainties, is also carried out, followed by projections of changes in the biogeochemical indicators for the year 2050. Results show that the average C filtering capacities for baseline conditions are 40, 30 and 22% for the marine, mixed and riverine estuary, respectively. This translates into a first-order, global CO2 outgassing flux for tidal estuaries between 0.04 and 0.07 Pg C yr−1. N filtering capacities, calculated in similar fashion, range from 22% for the marine estuary to 18 and 15% for the mixed and the riverine estuary, respectively. Sensitivity analysis performed by varying the rate constants for aerobic degradation, denitrification and nitrification over the range of values reported in the literature significantly widens these ranges for both C and N. Simulations for the year 2050 indicate that all end-member estuaries will remain net heterotrophic and while the riverine and mixed systems will only marginally be affected by river load changes and increase in atmospheric pCO2, the marine estuary is likely to become a significant CO2 sink in its downstream section. In the decades to come, such change of behavior might strengthen the overall CO2 sink of the estuary-coastal ocean continuum.
26
Volta, C., S. Arndt, H. H. G. Savenije, G. G. Laruelle y P. Regnier. "C-GEM (v 1.0): a new, cost-efficient biogeochemical model for estuaries and its application to a funnel-shaped system". Geoscientific Model Development 7, n.º 4 (4 de julio de 2014): 1271–95. http://dx.doi.org/10.5194/gmd-7-1271-2014.
Texto completoResumen
Abstract. Reactive transport models (RTMs) are powerful tools for disentangling the complex process interplay that drives estuarine biogeochemical dynamics, for assessing the quantitative role of estuaries in global biogeochemical cycles and for predicting their response to anthropogenic disturbances (land-use change, climate change and water management). Nevertheless, the application of RTMs for a regional or global estimation of estuarine biogeochemical transformations and fluxes is generally compromised by their high computational and data demands. Here, we describe C-GEM (Carbon-Generic Estuary Model), a new one-dimensional, computationally efficient RTM that reduces data requirements by using a generic, theoretical framework based on the direct relationship between estuarine geometry and hydrodynamics. Despite its efficiency, it provides an accurate description of estuarine hydrodynamics, salt transport and biogeochemistry on the appropriate spatio–temporal scales. We provide a detailed description of the model, as well as a protocol for its set-up. The new model is then applied to the funnel-shaped Scheldt estuary (BE/NL), one of the best-surveyed estuarine systems in the world. Its performance is evaluated through comprehensive model–data and model–model comparisons. Model results show that C-GEM captures the dominant features of the biogeochemical cycling in the Scheldt estuary. Longitudinal steady-state profiles of oxygen, ammonium, nitrate and silica are generally in good agreement with measured data. In addition, simulated, system-wide integrated reaction rates of the main pelagic biogeochemical processes are comparable with those obtained using a high-resolved, two-dimensional RTM. A comparison of fully transient simulations results with those of a two-dimensional model shows that the estuarine net ecosystem metabolism (NEM) only differs by about 10%, while system-wide estimates of individual biogeochemical processes never diverge by more than 40%. A sensitivity analysis is carried out to assess the sensitivity of biogeochemical processes to uncertainties in parameter values. Results reveal that the geometric parameters LC (estuarine convergence length) and H (water depth), as well as the rate constant of organic matter degradation (kox) exert an important influence on the biogeochemical functioning of the estuary. The sensitivity results also show that, currently, the most important hurdle towards regional- or global-scale applications arises from the lack of an objective framework for sediment and biogeochemical process parameterization. They, therefore, emphasize the need for a global compilation of biogeochemical parameter values that can help identify common trends and possible relationships between parameters and controlling factors, such as climate, catchment characteristics and anthropic pressure.
27
Volta, C., S. Arndt, H. H. G. Savenije, G. G. Laruelle y P. Regnier. "C-GEM (v 1.0): a new, cost-efficient biogeochemical model for estuaries and its application to a funnel-shaped system". Geoscientific Model Development Discussions 6, n.º 4 (14 de noviembre de 2013): 5645–709. http://dx.doi.org/10.5194/gmdd-6-5645-2013.
Texto completoResumen
Abstract. The first part of this paper describes C-GEM (Carbon – Generic Estuary Model), a new, one-dimensional, generic reactive-transport model for the biogeochemical dynamics of carbon and associated bio-elements (N, P, Si) in estuaries. C-GEM is computationally efficient and reduces data-requirements by using an idealized representation of the estuarine geometry to quantitatively predict the dominant features of the estuarine hydrodynamics, salt transport and biogeochemistry. A protocol for the set-up of C-GEM for an estuarine system is also described. The second part of this paper presents, as a proof of concept, the application of C-GEM to the funnel-shaped Scheldt estuary (Belgium, the Netherlands), one of the best-surveyed system in the world. Steady-state and transient simulations are performed and the performance of C-GEM is evaluated through model-data and model-model comparison, using integrated measures of the estuarine biogeochemical functioning, such as system-wide estimates of the Net Ecosystem Metabolism (NEM). A sensitivity analysis is also carried out to identify model parameters that exert the most important control on biogeochemical processes and to assess the sensitivity of the NEM to uncertainties in parameter values. The paper ends by a short discussion of current model limitations with respect to local, regional and global scale applications.
28
Seriani, Robson, Lucas Buruaem Moreira, Denis Moledo de Souza Abessa, Laís D. Abujamara, Natashy S. B. de Carvalho, Luciane Alves Maranho, Aline A. Kirschbaum y Maria José T. Ranzani-Paiva. "Hematological analysis of Micropogonias Furnieri, Desmarest, 1823, Scianidae, from two estuaries of Baixada Santista, São paulo Brazil". Brazilian Journal of Oceanography 58, spe3 (junio de 2010): 87–92. http://dx.doi.org/10.1590/s1679-87592010000700011.
Texto completoResumen
Hematological alterations in fish are considered a useful tool to evaluate pathological processes resulting from the exposure to environmental pollutants. The whitemouth croaker Micropogonias furnieri is a common species in estuarine areas and potentially exposed to many contaminants. In the present study, the hematological characteristics of fish collected at two sites in Baixada Santista (Santos Estuarine System - SES, a polluted site; and the Estuary of Itanhaém River - EIR, unpolluted site) del was analysed. The following blood descriptors were analyzed: number of Erythrocytes (Er), Hematocrit (Ht), Hemoglobin (Hb), Mean Corpuscular Volume (MCV) and Mean Corpuscular Hemoglobin concentration (MCHC). Fish from SES exhibited significant lower levels of Ht and increase on MCHC and Hb. Such differences are likely related to the different contamination levels found in these estuaries.
29
Burchard, Hans. "A Universal Law of Estuarine Mixing". Journal of Physical Oceanography 50, n.º 1 (enero de 2020): 81–93. http://dx.doi.org/10.1175/jpo-d-19-0014.1.
Texto completoResumen
AbstractA universal law of estuarine mixing is derived here, combining the approaches of salinity coordinates, Knudsen relations, total exchange flow, mixing definition as salinity variance loss, and the mixing–exchange flow relation. As a result, the long-term average mixing within an estuarine volume bounded by the isohaline of salinity S amounts to M(S) = S2Qr, where Qr is the average river runoff into the estuary. Consequently, the mixing per salinity class is m(S) = ∂SM(S) = 2SQr, which can also be expressed as the product of the isohaline volume and the mixing averaged over the isohaline. The major differences between the new mixing law and the recently developed mixing relation based on the Knudsen relations are threefold: (i) it does not depend on internal dynamics of the estuary determining inflow and outflow salinities (universality), (ii) it is exactly derived from conservation laws (accuracy), and (iii) it calculates mixing per salinity class (locality). The universal mixing law is demonstrated by means of analytical stationary and one-dimensional and two-dimensional numerical test cases. Some possible consequences for the salinity distribution in real estuaries are briefly discussed. Since the mixing per salinity class only depends on the river runoff and the chosen salinity, and not on local processes at the isohaline, low-mixing estuaries must have large isohaline volumes and vice versa.
30
Silva, Janaina Barbosa da, Josiclêda Domiciano Galvíncio, Antonio Carlos De Barros Corrêa, Danielle Gomes da Silva y Célia Cristina Clemente Machado. "Classificação Geomorfológica dos Estuários do Estado de Pernambuco (Brasil) com Base em Imagens do LANDSAT 5/TM (Geomorphologic Classification of Estuaries of the State of Pernambuco (Brazil) Based on Landsat 5 TM Images)". Revista Brasileira de Geografia Física 4, n.º 1 (17 de julio de 2011): 118. http://dx.doi.org/10.26848/rbgf.v4i1.232689.
Texto completoResumen
O presente estudo visou classificar os quinze estuários do Estado de Pernambuco, adotando como base as características geomorfológicas. A base de dados utilizada para a classificação foram imagens de satélites do Landsat 5-TM. Foram realizadas análises visuais das imagens de satélite e posteriormente efetuados trabalhos de campo com o intuito de validar as interpretações realizadas. Na zona costeira pernambucana os estuários classificam-se como: Planície Costeira (vale inundado), Formado por Barras e por Outros Processos. As interações espaço-temporal dos processos ambientais durante o Quaternário foram de fundamental importância para a atual configuração das áreas estuarinas classificadas, tendo em vista que tectonismo, erosão e sedimentação recorrente das regressões e transgressões marinhas foram processos recursivos durante a formação dos estuários e que deixaram registros na paisagem. Foram definidos como planície costeira os estuários do Goiana/Megaó, Jaguaribe, Paratibe, Maracaípe, Sirinhaém e Formoso. Do tipo construído pro barra tem-se o Timbó, Beberibe, Jaboatão/Pirapama, Mamucabas/Ilhetas e Una. Estuários tipo ria são os de Itapessoca e Canal de Santa Cruz, enquanto os de laguna costeira são o Ipojuca e o Capibaribe. Palavras-chave: Estuários, Zona Costeira Pernambucana, Quaternário Geomorphologic Classification of Estuaries of the State of Pernambuco (Brazil) Based on Landsat 5 TM Images ABSTRACT This study aimed to classify the fifteen estuaries of the State of Pernambuco-Brazil, using as base the geomorphological characteristics. The database used for the classification were satellite images of Landsat-5 TM. Were performed visual analysis of satellite images and were later made field work to validate the interpretations made. In the coastal zone of Pernambuco are found three classifications of estuaries: coastal plain (the flood plain), formed by bars and other processes. The space-time interactions of environmental processes during the Quaternary were of fundamental importance to the current configuration of estuarine areas classified in order to tectonics, erosion and sedimentation of the applicant marine transgressions and regressions were recursive processes during the formation of estuaries and left records in the landscape. Were defined as the coastal plain estuaries of Goiana/Megaó, Jaguaribe, Paratibe, Olinda, Sirinhaém and Formoso. Type built by bar has the Timbó, Beberibe, Jaboatão/Pirapama, Mamucaba/Ilhetas and Una. Estuaries are the kind of laughed Itapessoca and Channel and Santa Cruz, while the coastal lagoon and are Ipojuca and Capibaribe. Key-words: Estuary, coastal Pernambuco, quaternary
31
Schulz, Gesa, Tina Sanders, Yoana G. Voynova, Hermann W. Bange y Kirstin Dähnke. "Seasonal variability of nitrous oxide concentrations and emissions in a temperate estuary". Biogeosciences 20, n.º 15 (7 de agosto de 2023): 3229–47. http://dx.doi.org/10.5194/bg-20-3229-2023.
Texto completoResumen
Abstract. Nitrous oxide (N2O) is a greenhouse gas, with a global warming potential 298 times that of carbon dioxide. Estuaries can be sources of N2O, but their emission estimates have significant uncertainties due to limited data availability and high spatiotemporal variability. We investigated the spatial and seasonal variability of dissolved N2O and its emissions along the Elbe Estuary (Germany), a well-mixed temperate estuary with high nutrient loading from agriculture. During nine research cruises performed between 2017 and 2022, we measured dissolved N2O concentrations, as well as dissolved nutrient and oxygen concentrations along the estuary, and calculated N2O saturations, flux densities, and emissions. We found that the estuary was a year-round source of N2O, with the highest emissions in winter when dissolved inorganic nitrogen (DIN) loads and wind speeds are high. However, in spring and summer, N2O saturations and emissions did not decrease alongside lower riverine nitrogen loads, suggesting that estuarine in situ N2O production is an important source of N2O. We identified two hotspot areas of N2O production: the Port of Hamburg, a major port region, and the mesohaline estuary near the maximum turbidity zone (MTZ). N2O production was fueled by the decomposition of riverine organic matter in the Hamburg Port and by marine organic matter in the MTZ. A comparison with previous measurements in the Elbe Estuary revealed that N2O saturation did not decrease alongside the decrease in DIN concentrations after a significant improvement of water quality in the 1990s that allowed for phytoplankton growth to re-establish in the river and estuary. The overarching control of phytoplankton growth on organic matter and, subsequently, on N2O production highlights the fact that eutrophication and elevated agricultural nutrient input can increase N2O emissions in estuaries.
32
Wang, Chongyang, Li Wang, Danni Wang, Dan Li, Chenghu Zhou, Hao Jiang, Qiong Zheng et al. "Turbidity maximum zone index: a novel model for remote extraction of the turbidity maximum zone in different estuaries". Geoscientific Model Development 14, n.º 11 (11 de noviembre de 2021): 6833–46. http://dx.doi.org/10.5194/gmd-14-6833-2021.
Texto completoResumen
Abstract. An efficient recognition and extraction of the estuarine turbidity maximum zone (TMZ) is important for studying terrestrial hydrological processes. Although many studies relevant to the TMZ have been conducted worldwide, the extraction methods and criteria used to describe the TMZ vary significantly both spatially and temporally. To improve the applicability of the methods adopted in previous studies and to develop a novel model to accurately extract the TMZ in multiple estuaries and different seasons from remote-sensing imageries, this study estimated the total suspended solid (TSS) and chlorophyll a (Chl a) concentrations in three estuaries. These were the Pearl River estuary (PRE), the Hanjiang River estuary (HRE), and the Moyangjiang River estuary (MRE) of Guangdong Province, China. The spatial distribution characteristics of the TSS and Chl a concentrations were analyzed. A nearly opposite association was found between the TSS and Chl a concentrations in the three estuaries, particularly in the PRE. The regions with high (low) TSS concentrations had relatively low (high) Chl a concentrations and, therefore, a turbidity maximum zone index (TMZI), defined as the ratio of the difference and sum of the logarithmic transformation of the TSS and Chl a concentrations, was firstly proposed. By calculating the TMZI values in the PRE on 20 November 2004 (low-flow season), it was found that the criterion TMZI>0.2 could be used to identify the TMZs of the PRE effectively. The TMZ extraction results were generally consistent with the visual-interpretation results. The area-based accuracy measures showed that the quality (Q) of the extraction reached 0.8429. The same criterion was applied in the PRE on 18 October 2015 (high-flow season), and high accuracy and consistency across seasons were observed (Q=0.8171). The western shoal of the PRE was the main distribution area of TMZs. Extracting TMZs by the newly proposed index performed well in different estuaries and on different dates (HRE on 13 August 2008 in the high-flow season and MRE on 6 December 2013 in the low-flow season). Compared to the previous fixed threshold of TSS or turbidity methods, extracting the TMZ using the TMZI had higher accuracy and better applicability (Q: 0.1046–0.4770 vs. 0.8171–0.8429). Evidently, this unified TMZI is potentially an optimized method for the global monitoring and extraction of TMZs of estuaries from different satellite remote-sensing imageries. It can be used to help the understanding of the spatial and temporal variation in TMZs and estuarine processes at regional and global scales as well as improve the management and sustainable development of regional society and the natural environment.
33
Youm, Cheikh Ibrahima, Adama Gueye, Elena García-Villalba, Mbemba F. Doumbouya, Ibrahima-Sory Sow, Elhadji Sow y Juan A. Morales. "Lithofacies and Sediment Sequences of a Microtidal, Wave-Dominated Tropical Estuary in Somone Lagoon (Senegal, West Africa)". Coasts 4, n.º 2 (5 de abril de 2024): 306–22. http://dx.doi.org/10.3390/coasts4020016.
Texto completoResumen
Estuary sedimentary sequences have been the focus of several papers in the last decades; however, the majority these papers were centered in mesotidal and macrotidal estuaries of the middle latitudes. This present paper studies, from a sedimentological point of view, the infilling of a microtidal, wave-dominated tropical estuary, where wide tidal flats, mangroves and sabkhas are developed. Somone Lagoon is a Senegalese protected environment, very rich from an ecological point of view and with a definitive touristic vocation. For this work, 14 piston cores were studied. Additionally, the grain size, calcium carbonate and organic matter contents of 61 sediment samples vertically distributed in these cores were analyzed. The distribution of facies and the vertical sequences of sediments show the influence of the tropical seasonal fluctuations of fluvial sediment supply and evaporation processes. A high degree of bioturbation and an elevated organic content can be interpreted as the result of a high capacity of retention of the organic material into the estuary influenced by the weak tidal currents typical of a microtidal regime. These processes, acting since the last Holocene invasion of sea level, caused an advanced state of infilling of this estuarine system where both flood tidal deltas and bay head deltas prograde above the fine facies of the central domain of the estuary.
34
Hughes, Brent B., Kerstin Wasson, M. Tim Tinker, Susan L. Williams, Lilian P. Carswell, Katharyn E. Boyer, Michael W. Beck et al. "Species recovery and recolonization of past habitats: lessons for science and conservation from sea otters in estuaries". PeerJ 7 (10 de diciembre de 2019): e8100. http://dx.doi.org/10.7717/peerj.8100.
Texto completoResumen
Recovering species are often limited to much smaller areas than they historically occupied. Conservation planning for the recovering species is often based on this limited range, which may simply be an artifact of where the surviving population persisted. Southern sea otters (Enhydra lutris nereis) were hunted nearly to extinction but recovered from a small remnant population on a remote stretch of the California outer coast, where most of their recovery has occurred. However, studies of recently-recolonized estuaries have revealed that estuaries can provide southern sea otters with high quality habitats featuring shallow waters, high production and ample food, limited predators, and protected haul-out opportunities. Moreover, sea otters can have strong effects on estuarine ecosystems, fostering seagrass resilience through their consumption of invertebrate prey. Using a combination of literature reviews, population modeling, and prey surveys we explored the former estuarine habitats outside the current southern sea otter range to determine if these estuarine habitats can support healthy sea otter populations. We found the majority of studies and conservation efforts have focused on populations in exposed, rocky coastal habitats. Yet historical evidence indicates that sea otters were also formerly ubiquitous in estuaries. Our habitat-specific population growth model for California’s largest estuary—San Francisco Bay—determined that it alone can support about 6,600 sea otters, more than double the 2018 California population. Prey surveys in estuaries currently with (Elkhorn Slough and Morro Bay) and without (San Francisco Bay and Drakes Estero) sea otters indicated that the availability of prey, especially crabs, is sufficient to support healthy sea otter populations. Combining historical evidence with our results, we show that conservation practitioners could consider former estuarine habitats as targets for sea otter and ecosystem restoration. This study reveals the importance of understanding how recovering species interact with all the ecosystems they historically occupied, both for improved conservation of the recovering species and for successful restoration of ecosystem functions and processes.
35
Gallop, Shari L., Karin R. Bryan, David P. Hamilton, Melissa Foley y John L. Largier. "ECOENGINEERING FRESHWATER FLOWS FOR ESTUARY HYDROLOGICAL STATE". Coastal Engineering Proceedings, n.º 37 (1 de septiembre de 2023): 17. http://dx.doi.org/10.9753/icce.v37.management.17.
Texto completoResumen
The quantity, quality and timing of freshwater inflow into estuaries is critical to support estuarine ecosystem health. However, most estuaries are affected by upstream manipulation of freshwater inflows. Coinciding with the United Nations Decade of Restoration (2021–2030), there is great interest in re-creating functional estuarine ecosystems, including by modifying the physio-chemical characteristics with the premise that a functional ecosystem will follow (ecoengineering). To restore estuarine ecology, the physical processes of the system must first be conductive to supporting the re-establishment and sustenance of biota. These physical processes are generally under-monitored and often not used as a measure of restoration success. We explore ecoengineering to restore freshwater inflows to estuaries, focused on hydrological state. We use the Pressure—State—Response (PSR) framework to set the context for this review.
36
Lokhorst, Ivar R., Lisanne Braat, Jasper R. F. W. Leuven, Anne W. Baar, Mijke van Oorschot, Sanja Selaković y Maarten G. Kleinhans. "Morphological effects of vegetation on the tidal–fluvial transition in Holocene estuaries". Earth Surface Dynamics 6, n.º 4 (9 de octubre de 2018): 883–901. http://dx.doi.org/10.5194/esurf-6-883-2018.
Texto completoResumen
Abstract. Vegetation enhances bank stability and sedimentation to such an extent that it can modify river patterns, but how these processes manifest themselves in full-scale estuarine settings is poorly understood. On the one hand, tidal flats accrete faster in the presence of vegetation, reducing the flood storage and ebb dominance over time. On the other hand flow-focusing effects of a tidal floodplain elevated by mud and vegetation could lead to channel concentration and incision. Here we study isolated and combined effects of mud and tidal marsh vegetation on estuary dimensions. A 2-D hydromorphodynamic estuary model was developed, which was coupled to a vegetation model and used to simulate 100 years of morphological development. Vegetation settlement, growth and mortality were determined by the hydromorphodynamics. Eco-engineering effects of vegetation on the physical system are here limited to hydraulic resistance, which affects erosion and sedimentation pattern through the flow field. We investigated how vegetation, combined with mud, affects the average elevation of tidal flats and controls the system-scale planform. Modelling with vegetation only results in a pattern with the largest vegetation extent in the mixed-energy zone of the estuary, which is generally shallower. Here vegetation can cover more than 50 % of the estuary width while it remains below 10 %–20 % in the outer, tide-dominated zone. This modelled distribution of vegetation along the estuary shows general agreement with trends in natural estuaries observed by aerial image analysis. Without mud, the modelled vegetation has a limited effect on morphology, again peaking in the mixed-energy zone. Numerical modelling with mud only shows that the presence of mud leads to stabilisation and accretion of the intertidal area and a slight infill of the mixed-energy zone. Combined modelling of mud and vegetation leads to mutual enhancement with mud causing new colonisation areas and vegetation stabilising the mud. This occurs in particular in a zone previously described as the bedload convergence zone. While vegetation focusses the flow into the channels such that mud sedimentation in intertidal side channels is prevented on a timescale of decades, the filling of intertidal area and the resulting reduction in tidal prism may cause the infilling of estuaries over centuries.
37
Keeley, Annika T. H., Alexander K. Fremier, Pascale A. L. Goertler, Patrick R. Huber, Anna M. Sturrock, Samuel M. Bashevkin, Blake A. Barbaree et al. "Governing Ecological Connectivity in Cross-Scale Dependent Systems". BioScience 72, n.º 4 (25 de enero de 2022): 372–86. http://dx.doi.org/10.1093/biosci/biab140.
Texto completoResumen
Abstract Ecosystem management and governance of cross-scale dependent systems require integrating knowledge about ecological connectivity in its multiple forms and scales. Although scientists, managers, and policymakers are increasingly recognizing the importance of connectivity, governmental organizations may not be currently equipped to manage ecosystems with strong cross-boundary dependencies. Managing the different aspects of connectivity requires building social connectivity to increase the flow of information, as well as the capacity to coordinate planning, funding, and actions among both formal and informal governance bodies. We use estuaries in particular the San Francisco Estuary, in California, in the United States, as examples of cross-scale dependent systems affected by many intertwined aspects of connectivity. We describe the different types of estuarine connectivity observed in both natural and human-affected states and discuss the human dimensions of restoring beneficial physical and ecological processes. Finally, we provide recommendations for policy, practice, and research on how to restore functional connectivity to estuaries.
38
Yin, Xiao Ling, Dong Lin Bai y Li Cheng Li. "The Response of Salinity in Dry Season to Vertical Circulation in the Modaomen Estuary of the Pearl River, China". Advanced Materials Research 518-523 (mayo de 2012): 4574–77. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.4574.
Texto completoResumen
In recent years, salt intrusion in estuaries of the Pearl River has become a serious problem for local water supply in dry season. Water level, circulation and salinity around mouth of the Modaomen estuary in spring and neap were examined respectively through field measurements. The results indicated that mild water level process reinforced baroclinic action to cause notable circulation downstream, which was more durable in neap. And, the current in lower layer was generally faster than that in upper layer during the neap circulation. These two probably resulted in higher bottom salinity in neap than in spring within the upper mouth, which was on the contrary to the lower mouth as well as the open coastal sea nearby. The activity of observed salt wedge by tidal force within the lower mouth contributed to local salinity variation. Thus, the saline processes and distributions in the estuary mouth depended on cooperation of estuarine circulation and tidal driving in the absence of river flow and wind.
39
Hwan Hwang, Jin, Dong Hyeon Kim y Bo-Kyung Kim. "Advanced flow simulations of estuarine water resources responding to changes in societal demands". IOP Conference Series: Earth and Environmental Science 1313, n.º 1 (1 de marzo de 2024): 012015. http://dx.doi.org/10.1088/1755-1315/1313/1/012015.
Texto completoResumen
Abstract Water resources of rivers and estuaries have traditionally been managed for local societal demands, including municipal, agricultural, and industrial usages, as well as for transportation as navigational channels. However, as societal demands have changed including urban expansion, economic growth, cultural transition, etc., the land uses also should be changed, and the civil necessities of water have been diversified, and this has raised concerns about the ecology, environment, and water quality issues. This study attempted to address three water resource management issues in South Korean rivers and estuaries, which occurred recently due to the changes in societal demands for water and explained how the most advanced scientific research techniques had been applied. The main issues were 1) agricultural water security and ecological environment restoration in Nakdong River Estuary, 2) water and soil quality degradation due to industrial effluents in Hyeongsan River Estuary, and 3) utilization of rivers as waterways and water quality and ecology issues in the ARA waterway. To find solutions to conflicts of water resources, the series of numerical simulations validated by the field observations allowed 1) assessments of the impact and extent of salt intrusion upon the opening of estuary dam gates, 2) estuarine physical processes to investigate the influence of industrial effluent, and 3) analysis water quality variations resulting from changes in the function of artificial channels. These analyses are expected to provide appropriate and science-based strategies of regional water management.
40
Bruce, L. C., P. L. M. Cook, I. Teakle y M. R. Hipsey. "Controls on oxygen dynamics in a riverine salt-wedge estuary – a three-dimensional model of the Yarra River estuary, Australia". Hydrology and Earth System Sciences Discussions 10, n.º 7 (26 de julio de 2013): 9799–845. http://dx.doi.org/10.5194/hessd-10-9799-2013.
Texto completoResumen
Abstract. Oxygen depletion in estuarine waters is an important factor governing water quality and ecological health. A complex and dynamic balance of physical and biogeochemical factors drive the extent and persistence of hypoxia and anoxia making it difficult to predict. An increased understanding of the effect of changing flow regimes and temperature on patterns of estuarine oxygen depletion is required to support ongoing management. Coupled physical and biogeochemical models have been applied to study the interaction of physical processes and seasonal hypoxia, however, application to riverine estuaries with tight curvature and more sporadic periods of oxygen depletion is rare. In this study we apply a finite volume 3-D hydrodynamic-biogeochemical model (TUFLOW-FV–FABM) to the Yarra River estuary, Australia, in order to predict the extent of salt-wedge intrusion and consequent patterns of oxygen depletion. The predictive capacity of the model was evaluated using a series of model verification metrics and the results evaluated to determine the dominant mechanisms affecting salt-wedge position and the extent and persistence of anoxia and hypoxia. Measures of model fit indicated that the model reasonably captured the strength of stratification and the position and extent of the salt wedge (r2 ~ 0.74). The extent of the salt wedge intrusion was controlled by riverine flow and the strength of stratification or mixing dominated by topographical features corresponding to areas of tight curvature ("horseshoe" bends). The model predicted that the extent of anoxic waters generally mimicked the extent of the salt wedge (r2 ~ 0.65) increasing during periods of low flow and reduced following episodic high flow events. The results showed two sporadically isolated "hot spots" of anoxia, the first downstream of the horseshoe bend and the second downstream of a sill. Simulated oxygen concentrations indicated that whilst a threshold salt wedge intrusion was a requirement of oxygen depletion, temperature was critical in determining the extent of hypoxia and anoxia in the estuary. These findings highlight the importance of how seasonal changes in flow events and environmental flow management can impact on estuarine oxygen depletion in a warming climate. This study provides an improved understanding of the controls on hypoxia and anoxia in riverine estuaries, which is essential to support improved prediction of nutrient dynamics and ecological heath.
41
Hewageegana, Viyaktha Hithaishi, Maitane Olabarrieta y Jose M. Gonzalez-Ondina. "Main Physical Processes Affecting the Residence Times of a Micro-Tidal Estuary". Journal of Marine Science and Engineering 11, n.º 7 (30 de junio de 2023): 1333. http://dx.doi.org/10.3390/jmse11071333.
Texto completoResumen
Residence time is an important parameter linked to the water quality in an estuary. In this paper, we identify and analyze the main processes that affect the residence time of the Caloosahatchee River Estuary, a micro-tidal and mixed diurnal-semidiurnal estuary located in western Florida. Multiyear validated hydrodynamic hindcast results were coupled with an offline particle tracking model to compute the residence time of the estuary, which showed a strong seasonality driven by the river discharge. The residence time reduced with increasing river flow. The wind velocity and direction also affected the residence time. The influence of the wind was dependent on the magnitude of the river discharge. In general, upstream-directed wind increased residence time, while downstream-directed wind decreased residence time. Downstream wind during the dry period reduced residence time on average by a week. Processes such as water density gradient-induced circulation and particle buoyancy also influenced the residence time of the estuary. The outcomes of this study can be used to better understand the influence of the main physical processes affecting the residence time at other similar estuaries and to help in the management of the estuaries to improve their water quality.
42
Silva, Alex Evaristo da, Pedro Smith Menandro, Kleverson Alencastre Do Nascimento, Valéria Da S. Quaresma y Alex C. Bastos. "INTERPRETATION OF SEDIMENTARY PROCESSES USING ECHO-CHARACTER DISTRIBUTION: CASE STUDY OF PIRAQUÊ-AÇU AND PIRAQUÊ-MIRIM ESTUARINE SYSTEM, ARACRUZ – ES (BRAZIL)". Revista Brasileira de Geofísica 32, n.º 2 (1 de junio de 2014): 301. http://dx.doi.org/10.22564/rbgf.v32i2.484.
Texto completoResumen
ABSTRACT. This research aimed to map distinct types of echo-character in order to recognize estuarine sedimentary processes along the Piraquê-Açu System, in Aracruz, Espírito Santo State, Brazil. Echo-character mapping was undertaken using high frequency sub-bottom profiling data. Four echo-character (EC1, EC2, EC3,EC4) patterns were recognized by combining sub-bottom and surficial sedimentological data. These EC patterns defined three distinct areas within the system that arecharacterized by the predominance of a specific echo-character and a seabed type: i) estuarine mouth, where sand beds with low penetration prevail; ii) a transitionzone, where sandy-muddy andmuddy-sandy beds are associated with a high penetration echo-character; and, iii) the rivers/estuary Piraquê-Ac¸u and Piraquê-Mirim withsandy-muddy and muddy beds with high penetration echo pattern. The interpretation showed that the association of EC and surficial sediment may represent modernsedimentary processes within the estuary. Three sedimentary processes were recognized: a) marine dominated processes showing sand transport by tidal currents;b) estuarine processes with fine sediment input, resuspension and deposition; and c) erosive estuarine processes or scour lags, exposing possibly relict deposits.Keywords: estuarine sedimentation, shallow geophysics, sub-bottom profiler. RESUMO. Esse estudo busca reconhecer os tipos de ecocaráter existentes para o melhor entendimento dos processos sedimentares do sistema estuarino do Piraquê-Açu e Piraquê-Mirim, localizado no município de Aracruz, Espírito Santo. O reconhecimento e o mapeamento dos tipos de ecocaráter foram realizados a partir deregistros de perfilador de subfundo de alta frequência. Através da associação dos dados geofísicos com dados sedimentológicos foram reconhecidos e definidos quatropadrões de ecocarácteres (EC1, EC2, EC3, EC4) associados a tipos de fundo distintos. A distribuição espacial dos tipos de eco permitiu a divisão do estuário em três áreas distintas que diferem pela predominância de diferentes tipos de ecocaráter e sedimento: i) A foz do sistema estuarino, interpretada como região de domiâancia marinha, onde predomina o fundo arenoso e a baixa penetração do sinal; ii) A zona de confluência, onde predomina sedimentos areno-lamosos a lamo-arenosos compenetração do sinal acústico; iii) Os braços Piraquê-Açu e Piraquê-Mirim de predomínio de fundo areno-lamoso a lamoso, com penetração do sinal. Estas áreas estão associadas a distintos processos sedimentares, sendo eles: a) processos marinhos com transporte de sedimentos arenosos por correntes de maré (foz do sistema até a confluência dos braços); b) processos estuarinos com aporte, resuspensão e deposição de sedimentos finos, típicos da região interna do sistema; e c) processosestuarinos erosivos ou de ravinamento, ocorrendo localmente nos braços.Palavras-chave: sedimentação estuarina, geofísica rasa, perfilador de subfundo
43
Mendes, Joana, Rui Ruela, Ana Picado, João Pedro Pinheiro, Américo Soares Ribeiro, Humberto Pereira y João Miguel Dias. "Modeling Dynamic Processes of Mondego Estuary and Óbidos Lagoon Using Delft3D". Journal of Marine Science and Engineering 9, n.º 1 (15 de enero de 2021): 91. http://dx.doi.org/10.3390/jmse9010091.
Texto completoResumen
Estuarine systems currently face increasing pressure due to population growth, rapid economic development, and the effect of climate change, which threatens the deterioration of their water quality. This study uses an open-source model of high transferability (Delft3D), to investigate the physics and water quality dynamics, spatial variability, and interrelation of two estuarine systems of the Portuguese west coast: Mondego Estuary and Óbidos Lagoon. In this context, the Delft3D was successfully implemented and validated for both systems through model-observation comparisons and further explored using realistically forced and process-oriented experiments. Model results show (1) high accuracy to predict the local hydrodynamics and fair accuracy to predict the transport and water quality of both systems; (2) the importance of the local geomorphology and estuary dimensions in the tidal propagation and asymmetry; (3) Mondego Estuary (except for the south arm) has a higher water volume exchange with the adjacent ocean when compared to Óbidos Lagoon, resulting from the highest fluvial discharge that contributes to a better water renewal; (4) the dissolved oxygen (DO) varies with water temperature and salinity differently for both systems. On the one hand, for Mondego Estuary during winter the DO levels mainly fluctuate with salinity. On the other hand, for Óbidos Lagoon, DO distribution is determined by both water temperature and salinity. During summer, the high residence time and water temperature limit the DO levels in both systems. The high transferability and superior stability of Delft3D make this model a foundation for realistic simulation and research of distinct estuarine systems, giving support to their maintenance and restoration.
44
Hsieh, Tung-Chou, Yan Ding, Keh-Chia Yeh y Ren-Kai Jhong. "Investigation of Morphological Changes in the Tamsui River Estuary Using an Integrated Coastal and Estuarine Processes Model". Water 12, n.º 4 (10 de abril de 2020): 1084. http://dx.doi.org/10.3390/w12041084.
Texto completoResumen
This study is to investigate morphological changes in the Tamsui River Estuary in Taiwan driven by multiple physical processes, such as river flows, tides, waves, and storm surges, and then to study the impacts of sediment flushing operated at the Shihmen reservoir upstream on the river estuary. An integrated coastal and estuarine processes model (CCHE2D-Coast) (Center for Computational Hydroscience and Engineering Two-Dimensional-Coast) was validated by simulating these physical processes in the estuary driven by three historical typhoons in 2008. The site-specifically validated model was then applied to simulate morphological changes in the estuary in response to reservoir sediment flush scenarios from the upstream. For the impact assessment of sediment flushing, a synthetic hydrological event was designed by including a historical typhoon and a typical monsoon. It was found that during the typhoon, the sediments will be mostly deposited in the estuarine river reach of Tamsui and the Wazihwei sandy beach. During the monsoon period, most of the sediments tend to be deposited in the second fishing port of Tamsui, the northern breakwater, and the estuary, while the Wazihwei sandy beach in the river mouth would be scoured by backflow. Simulations of the complex flow fields and morphological changes will facilitate the best practice of sediment management in the coastal and estuarine regions.
45
Dähnke, Kirstin, Tina Sanders, Yoana Voynova y Scott D. Wankel. "Nitrogen isotopes reveal a particulate-matter-driven biogeochemical reactor in a temperate estuary". Biogeosciences 19, n.º 24 (21 de diciembre de 2022): 5879–91. http://dx.doi.org/10.5194/bg-19-5879-2022.
Texto completoResumen
Abstract. Estuaries and rivers are important biogeochemical reactors that act to modify the loads and composition of nutrients in the coastal zone. In a case study during July 2013, we sampled an 80 km transect along the Elbe Estuary under low-oxygen conditions. To better elucidate specific mechanisms of estuarine nitrogen processing, we tracked the evolution of the stable isotopic composition of nitrate, nitrite, particulate matter, and ammonium through the water column. This approach allowed assessment of the in situ isotope effects of ammonium and nitrite oxidation and of remineralization at the reach scale. The isotope effects of nitrite oxidation and ammonium oxidation were consistent with pure-culture assessments. We found that the nitrogen budget of the Elbe Estuary is governed by settling, resuspension, and remineralization of particulate matter, and we further used our stable isotope data to evaluate sources and sinks of nitrogen in the Elbe Estuary via an isotope mass-balance approach. We find that the reactivity of particulate matter, through its remineralization in the estuary, is the main control on the isotope dynamics of inorganic nitrogen species. Moreover, while underscoring this role of particulate matter delivery and reactivity, the isotope mass balance also indicated additional sinks of reactive nitrogen, such as possible denitrification of water column nitrate in the intensively dredged and deep Hamburg Harbor region.
46
Adams, Janine Barbara y Lara Van Niekerk. "Ten Principles to Determine Environmental Flow Requirements for Temporarily Closed Estuaries". Water 12, n.º 7 (8 de julio de 2020): 1944. http://dx.doi.org/10.3390/w12071944.
Texto completoResumen
Temporarily closed estuaries require seasonal opening to tidal flows to maintain normalecological processes. Each estuary has specific environmental flow (EFlow) requirements basedon the relationship between freshwater inflow, coastal dynamics, rate of sandbar formation,and the open/closed state of the mouth. Key abiotic processes and ecosystem services linkedto mouth state were highlighted. We reviewed completed EFlow requirement studies for temporarilyclosed estuaries in South Africa and found that the formulation of these requirements shouldconsider the timing and magnitude of flows in relation to the morphology of an estuary, its mouthstructure, catchment size, and climate. We identified ten key principles that could be adapted tosimilar systems in equivalent climatic settings. Principle 1 recognizes that each estuary is unique interms of its EFlow requirements because size, scale, and sensitivity of core elements to freshwaterinflow are specific for each system; EFlows cannot be extrapolated from one estuary to another.Principle 2 highlights the importance of baseflows in keeping an estuary mouth open because a smallreduction in flow can cause the mouth to close and alter essential ecological processes. Principle 3outlines the role of floods in resetting natural processes by flushing out large volumes of sedimentand establishing the equilibrium between erosion and sedimentation. Principle 4 emphasizes the needfor open mouth conditions to allow regular tidal flushing that maintains water quality throughreducing retention times and preventing the onset of eutrophic conditions. Principle 5 advisesartificial breaching to be practiced with caution because execution at low water levels encouragessedimentation that reduces the scouring eect of flushing. Principle 6 holds that elevated inflowvolumes from wastewater treatment works or agricultural return flows can increase the frequency ofmouth opening and cause ecological instability. Principle 7 states that water released from dams tosupply the environmental flow cannot mimic the natural flow regime. Principle 8 specifies the needfor short- and long-term data to increase the confidence levels of EFlow assessments, with data tobe collected during the open and closed mouth states. Principle 9 advocates the implementation ofa monitoring program to track the achievement of EFlow objectives as part of a strategic adaptivemanagement cycle. Finally, Principle 10 recommends the adoption of a holistic catchment-to-coastmanagement approach underpinned by collaboration with regulatory authorities and stakeholdersacross a range of sectors. These principles can be used to guide the formulation and managementof EFlows, an essential strategy that links the maintenance of estuarine ecological integrity withsocial well-being.
47
Bengani, R. y M. Gadhia. "APPRAISING THE WATER POLLUTION INDEX OF AN ESTUARIAL ENVIRONMENT". International Journal of Engineering Applied Sciences and Technology 7, n.º 4 (1 de agosto de 2022): 131–37. http://dx.doi.org/10.33564/ijeast.2022.v07i04.018.
Texto completoResumen
The WPI is an important tool to summarize a large number of water quality data into simple terms which is one of the most effective ways to interrelate information on water quality trends. The information generated can help to guide policy makers on effective restoration, conservation and management of water resources. In this technique the weightage for various water quality parameters is assigned to be inversely proportional to the recommended standards for the corresponding parameters. Estuaries represent productive aquatic habitats and are characterized by dynamic biogeochemical processes. Water quality loss in estuaries is, therefore, one of the worst forms of water pollution. For the analysis of water parameters, the water samples were collected and preserved in pre-rinsed plastic bottles at monthly intervals during June 2011–May 2013 for the period of two years from the Dumas vicinity of Tapi estuary. Temperature and pH were analyzed in situ and other parameters were analyzed as per standard references. The WPI in the studied area in the first year ranged between 1.2334 to 7.8266 whereas it varied from 1.797 to 6.439 in second year of the study. The higher value of WPI was observed during the month of December and January in the first year and in the month of December in the second year indicating high polluted nature of the estuary. The overall study revealed the polluted nature of the water ranging from mild to severe during different months in the studied area. It was observed that estuarine environment was polluted by the impact of anthropogenic as well as industrial activities. This study is important as understanding the ecological status of the estuarine habitats is imperative for successful environmental management and sustainable development.
48
Xue, D., P. Boeckx y Z. Wang. "Nitrate sources and dynamics in a salinized river and estuary – a δ<sup>15</sup>N–NO<sub>3</sub><sup>−</sup> and δ<sup>18</sup>O–NO<sub>3</sub><sup>−</sup> isotope approach". Biogeosciences 11, n.º 20 (31 de octubre de 2014): 5957–67. http://dx.doi.org/10.5194/bg-11-5957-2014.
Texto completoResumen
Abstract. To trace NO3− sources and assess NO3− dynamics in salinized rivers and estuaries, three rivers (Haihe River: HH River, Chaobaixin River: CB River and Jiyun River: JY River) and two estuaries (HH Estuary and CJ Estuary) along the Bohai Bay (China) have been selected to determine dissolved inorganic nitrogen (DIN: NH4+, NO2− and NO3−. Upstream of the HH River, NO3− was removed 30.9 ± 22.1% by denitrification, resulting from effects of the floodgate: limiting water exchange with downstream and prolonging water residence time to remove NO3−. Downstream of the HH River NO3− was removed 2.5 ± 13.3% by NO3− turnover processes. Conversely, NO3− was increased 36.6 ± 25.2% by external N source addition in the CB River and 34.6 ± 35.1% by in-stream nitrification in the JY River. The HH and CY Estuaries behaved mostly conservatively excluding the sewage input in the CJ Estuary. Hydrodynamics in estuaries has been changed by the ongoing reclamation projects, aggravating the loss of the attenuation function of NO3− in the estuary.
49
Pennino, Michael J., Sujay S. Kaushal, Sudhir N. Murthy, Joel D. Blomquist, Jeff C. Cornwell y Lora A. Harris. "Sources and transformations of anthropogenic nitrogen along an urban river–estuarine continuum". Biogeosciences 13, n.º 22 (18 de noviembre de 2016): 6211–28. http://dx.doi.org/10.5194/bg-13-6211-2016.
Texto completoResumen
Abstract. Urbanization has altered the fate and transport of anthropogenic nitrogen (N) in rivers and estuaries globally. This study evaluates the capacity of an urbanizing river–estuarine continuum to transform N inputs from the world's largest advanced (e.g., phosphorus and biological N removal) wastewater treatment facility. Effluent samples and surface water were collected monthly along the Potomac River estuary from Washington D.C. to the Chesapeake Bay over a distance of 150 km. In conjunction with box model mass balances, nitrate stable isotopes and mixing models were used to trace the fate of urban wastewater nitrate. Nitrate concentrations and δ15N-NO3− values were higher down-estuary from the Blue Plains wastewater outfall in Washington D.C. (2.25 ± 0.62 mg L−1 and 25.7 ± 2.9 ‰, respectively) compared to upper-estuary concentrations (1.0 ± 0.2 mg L−1 and 9.3 ± 1.4 ‰, respectively). Nitrate concentration then decreased rapidly within 30 km down-estuary (to 0.8 ± 0.2 mg L−1), corresponding to an increase in organic nitrogen and dissolved organic carbon, suggesting biotic uptake and organic transformation. TN loads declined down-estuary (from an annual average of 48 000 ± 5000 kg day−1 at the sewage treatment plant outfall to 23 000 ± 13 000 kg day−1 at the estuary mouth), with the greatest percentage decrease during summer and fall. Annually, there was a 70 ± 31 % loss in wastewater NO3− along the estuary, and 28 ± 6 % of urban wastewater TN inputs were exported to the Chesapeake Bay, with the greatest contribution of wastewater TN loads during the spring. Our results suggest that biological transformations along the urban river–estuary continuum can significantly transform wastewater N inputs from major cities globally, and more work is necessary to evaluate the potential of organic nitrogen and carbon to contribute to eutrophication and hypoxia.
50
Carmichael, Ruth H., William Walton y Heidi Clark. "Bivalve-enhanced nitrogen removal from coastal estuaries". Canadian Journal of Fisheries and Aquatic Sciences 69, n.º 7 (julio de 2012): 1131–49. http://dx.doi.org/10.1139/f2012-057.
Texto completoResumen
Interest in use of bivalves to remediate estuarine eutrophication has increased in recent years. High variation among data sets, substantial focus on particle removal, and insufficient links to anthropogenic nitrogen (N) sources encouraged this empirical examination of N removal by bivalves from estuaries receiving different N loads. We determined the capacity of the oyster Crassostrea virginica to remove N by comparing N assimilated into tissues with anthropogenic N from land or available in phytoplankton. Oyster growth yielded 0.2–0.4 g N in tissues and depended on estuary-specific conditions. δ15N values confirmed that N in oyster tissues derived from local anthropogenic sources. At representative restoration and aquaculture conditions (≤400 oysters·m–2 at 0.5%–1.0% of estuary area), estimated N removal was ≤15% of land-derived loads and <1% of phytoplankton N. N removal via biogeochemical processes was negligible during grow-out, but became important after oysters attained harvestable size. This study explicitly demonstrates that oysters assimilated land-derived N, but suggests that bivalve bioremediation consider trade-offs between intensity of planting, ecological effects, and available space.