Fluoride pollution in French rivers and estuaries

Fluoride concentrations have been determined in major French rivers and estuaries. The unpolluted estuary in the Loire has been compared with the Seine, Gironde and Charente where important discharges occur. Natural dissolved concentration can be multiplied by a factor of 30. Particulate fluorine concentration reach almost 2000 ppm in the Seine estuary. The percentage between free and complexed dissolved fluoride is not affected by the anthropic discharge. The present French rivers discharge of fluoride is 700% higher than the pristine value. At a global scale, dissolved fluoride has probably increased by 25% compared with the natural situation.     

Pb,Zn, Cs,Sc and rare earth elements as tracers of the Loire and Gironde particles on the Biscay shelf (SW France)

The western Atlantic continental margin of the Bay of Biscay is characterised by a combined macro-tidal and a high energy environment. These conditions are responsible for the essentially sandy sedimentary cover along with well-defined fine deposit zones observed on the shelf. The main continental sources are the Loire, Gironde and Adour Rivers. It is estimated that 2.4 to 2.5 million tons of fine sediments are supplied annually to the ocean from these rivers of the French Atlantic coast. The Gironde and the Loire contribute with 84 % and the Gironde with 60 % of this amount. Previous studies of the distribution of the clay mineral assemblages and of oligo-elements have distinguished two provinces (north and south Biscay areas) according to these riverine sources. The use of an inductively coupled plasma-mass spectrometry (ICP-MS) technique allowed us to analyse both heavy metals and rare earth elements (REE), thus permitting an effective characterisation of continental sources. On the basis of these results, it has been possible to better identify the respective contributions of the Loire and the Gironde Rivers to the fine-grained sedimentation on the inner shelf.     

Fish composition and assemblage structure in three Eastern English Channel macrotidal estuaries: A comparison with other French estuaries

This study has analysed for the first time fish composition and assemblage structures of three small macrotidal estuaries of the Eastern English Channel (EEC) and has explored the influences of 19 biotic and abiotic variables on the fish assemblages. Fish from Canche, Authie and Somme estuaries were collected during spring (June 2006 and May 2007) and autumn (September 2006) along the estuarine gradients using a 1.5 m beam trawl. Using identical sampling protocols, the study also analysed and compared for the first time taxonomic and functional aspects of the fish assemblages in 15 estuaries located along the Atlantic and English Channel coasts. SIMPER analysis showed high similarities in fish assemblages in the three EEC estuaries and during either spring or autumn periods. However, intra-estuary similarities were relatively low, indicating that fish assemblage structures (species richnesses or abundances) were more variable within the estuary (salinity gradient) than between estuaries and/or seasons (spring vs autumn). Although numerous environmental variables were included in the study, only 47% of the variability observed in the fish distribution was explained. Fish spatial variations in the EEC estuaries are mostly driven by abiotic variables as opposed to biological interactions. As indicated by CCA, salinity and muddy sediments were the two most important factors structuring the fish assemblages. The macrobenthos being very abundant in the EEC estuaries (580–1121 ind. m⁻²), the availability of potential prey is probably not a limiting factor in the utilization of estuaries by fish. Contrary to the majority of French estuaries dominated by estuarine species (ES), the fish assemblages of the EEC estuaries are clearly dominated by marine migrant (MM) species (65% on average) with high abundance of juveniles (mostly young-of-the-year). Cluster and SIMPROF's analyses distinguished the functional structure of the 15 estuarine fish assemblages into different clusters. The three EEC estuaries form a similar group with the largest French estuaries (Seine, Loire and Gironde). The latters were characterized by higher MM/ES ratio compared to the other French estuaries. Freshwater flow and tidal range were the main factors associated with this group of estuaries. The results of the present study do not indicate that anthropogenic impacts (chemical contamination) on estuaries affect their ecological functioning as described by the fish ecological guilds. It is suggested that the guild approach may not be useful to provide valuable information on the ecological status of estuaries.     

渤海3个河口区底栖硅藻群落的时空变化特征

底栖硅藻是河口泥滩系统中的重要初级生产者,其群落结构的时空变化可显著影响到河口底栖动物生产力。本研究选取渤海区域的大辽河口、汉沽河口和黄河口为研究对象,分析了泥滩中底栖硅藻群落结构的季节变化特征(2014?2016年)与空间差异,并探讨了环境因素的影响作用。结果表明,3个河口区底栖硅藻多样性和生物量高峰均出现在秋季,优势种存在显著季节演替特征;在空间上,大辽河口和汉沽河口的底栖硅藻生物量显著高于黄河口。底栖硅藻群落结构与多种环境因子的相关性分析表明,温度和营养盐浓度变化对底栖硅藻群落的季节性特征影响显著;河口沉积物的粒径、潮差与径流量可能是造成底栖硅藻群落空间差异的重要因素,黄河口较低的底栖硅藻生物量显著受限于较粗的沉积物粒径和显著的磷限制。     

Implications of Colorado river (Texas, USA) freshwater inflow to benthic ecosystem dynamics: A modeling study

Estuaries are defined by mixing of freshwater from rivers and saltwater from seas. Water resource development can reduce river flows to the coast, but it is difficult to predict effects on estuaries. The Lavaca-Colorado Estuary is a major estuarine system along the Texas coast that provides major economic benefit to the region by supporting a variety of agricultural, residential, industrial, and recreational functions. New water projects could divert freshwater from Matagorda Bay. So, what environmental effects could result from further changes to inflow patterns in the Matagorda Bay system? To answer this question, a bioenergetic model, calibrated using a long-term dataset of benthic biomass, was run to investigate dynamics of macrobenthic biomass related to salinity regimes in the estuary. The model simulation results were interpreted to assess the role of freshwater inflow in controlling benthic productivity. Simulations, based on calibrated parameters (1988–1999), were run for a long-term period from 1988 to 2005. The model performance was found to be promising with the best percent root mean square (RMS) difference being 63% and worst being 92%. Sensitivity tests for the benthic responses to changes in salinity show that, in general, when salinity increased with decreasing nutrient concentrations, deposit feeder biomass increased while suspension feeder biomass decreased. Estuary-wide comparison predicts that reducing freshwater inflow may cause the upper and lower bay communities to respond in different ways. Reduced inflow to Lavaca Bay would result in decreasing benthic biomass; whereas, in Matagorda Bay, biomass would increase. Also, functional diversity would decrease in both bays with decreasing inflow. These effects are probably due to the benthic community acclimating to different salinity regimes, or more (or less) salt tolerant species populating the area. It is concluded that freshwater inflow plays an important role in maintaining the observed character of estuarine productivity through the combined effects of the frequency, duration, timing, and magnitude of inflow, particularly during droughts or low-flow periods.     

我国典型潮间带底栖硅藻群落空间分布特征

底栖硅藻是河口、泥质海滩生态系统的重要生物类群,其数量与分布变化直接或间接地影响到多种海洋生物的饵料供给、海鸟的生存与迁徙。通过对我国从南到北14个典型潮间带表层沉积物中底栖硅藻的分析,共鉴定出硅藻153种,其物种多样性（Shannon-Weaver 指数范围:1.61~4.39）与生物量（范围:0.09×103 ~ 10×103个/g,干质量）在空间上存在显著差异;聚类分析与相似性分析检验（r=0.738,P=0.1%< 0.01）表明,14个调查区域的硅藻群落在空间上可分为4个大的组合,分别对应着渤、黄、东、南海4个区域,吻合了我国近海浮游植物的地理分布特征。与环境因素的相关性分析表明,底栖硅藻群落的物种多样性与生物量受沉积物类型与盐度的影响显著,泥质区域更有利于硅藻的保存,而生物多样性在泥砂质低盐区域相对较高。此外,底栖硅藻生物量与表层沉积物中TOC含量表现出显著正相关性;δ13C数值的空间变化范围为-25‰~-20‰,指示了有机质陆海混合的特征,其中,涧河河口、黄河口、大沽河口、苏北浅滩区域,δ13C数值明显偏正,表明底栖硅藻可能是这些区域沉积物中有机碳的重要贡献者。     

The concept of an estuary: A definition that incorporates systems which can become closed to the ocean and hypersaline

The majority of the definitions of estuaries have been based on the characteristics of estuaries in temperate regions of the northern hemisphere. As previously pointed out (Day, 1980), such definitions do not take into account such features as periodic closure of their mouths and hypersaline conditions during dry periods, which characterise many estuaries in southern Africa and south-western Australia. There is also ambiguity as to whether an estuary sensu stricto must be fed by a river. The following definition was developed to encompass the main characteristics of all estuaries: An estuary is a partially enclosed coastal body of water that is either permanently or periodically open to the sea and which receives at least periodic discharge from a river(s), and thus, while its salinity is typically less than that of natural sea water and varies temporally and along its length, it can become hypersaline in regions when evaporative water loss is high and freshwater and tidal inputs are negligible. Estuaries are thus regarded as unique ecosystems, which, in the case of fishes, for example, are occupied by species that collectively represent a particular suite of guilds.     

A comparative study of mercury contamination in the Tagus estuary (Portugal) and major French estuaries (Gironde,Loire, Rhône)

Concentrations of mercury were determined for the waters, suspended matter and sediments of the Tagus and of major French estuaries.The Tagus estuary is one of the most contaminated by mercury derived from the outfalls of a chloralkali plant and from other industrial sources. In deposited sediments the median level, 1·0 μg Hg g^?1, is twenty times higher than the natural background and Hg contents depend on the sediment grain-size, age and the distance from waste-outfalls. Suspended matter is more regularly and highly contaminated (median value: 4·5 μg Hg g^?1). In the French estuaries Hg levels in the suspended material decrease with salinity due to dilution and/or remobilization processes. In June 1982, in the Loire estuary, high values of Hg are observed in the middle estuary and attributed to urban and industrial sources.In the Tagus estuary, the general distribution of total dissolved Hg confirms the contamination: it increases seaward from 10 ng 1^?1 in the river to 80 ng 1^?1 in the estuary outlet. The dissolved Hg is almost totally organic in the river, inorganic in the middle estuary due to inorganic Hg effluents and again organic in the lower estuary. This variation is related to the dissolved organic carbon values. The dissolved Hg levels in the Loire Estuary (5–300 ng 1^?1) are much higher than in the Gironde estuary (3–6 ng 1^?1) and of the same order as those observed in the Tagus estuary.     

Do river discharge rates drive the overall functioning of the pelagic ecosystem over the continental shelf of the Bay of Biscay (NE Atlantic)? A comparison of two contrasting years with special reference to anchovy (<Emphasis Type="Italic">Engraulis encrasicolus</Emphasis> L.) nutritional state

In the 2000 and 2001 springtime periods, mesozooplankton samples were systematically taken during research cruises devoted to the study of the distribution and abundance of small pelagic fishes in the French part of the Bay of Biscay, NE Atlantic, continental shelf. Simultaneous activities of three enzymes were measured in these mesozooplankton samples, to characterize the main features of ecosystem function at a regional scale. The aim was to assess assimilation rates of carbohydrates, through pyruvate kinase activity, and protein, through trypsin activity, by the mesozooplankton community and the resulting overall productivity, through aspartate transcarbamylase activity. The highest influence on the pelagic environment was the strong difference in the freshwater outflow rates from the two main large rivers, the Loire and the Gironde, which was principally responsible for the inter-annual fluctuations of the nutrients in the Bay. This overall influence of river flow results in a characteristic pattern of sea-surface salinity, which was reflected by the phytoplankton biomass distribution. Mesozooplankton enzyme activities showed high variations between the two years. The contrast in the dynamics of the pelagic food web processes between the two consecutive years, with higher activity in 2001, affected the nutritional condition of the zooplanktivorous breeding anchovy Engraulis encrasicolus.     

Multi-bioindicator study of a small estuary in Vendée (France)

Surficial sediment (about 5 mm) was scraped off in 15 stations selected in the Vie Estuary, a small estuary on the French Atlantic coast. The samples, prepared using the suitable methods, were used for comparing the behaviour of periphytic algae, sporopollinic and other palynologic material, ostracoda and foraminifera for proposing a synthetic evaluation of the information provided by each of them. Dinoflagellate cysts, which are found in an almost monospecific assemblage in low-salinity water, are dispersed by tidal currents, but the location of tintinnids in only the lower reaches shows a limited inward transport. Sporopollinic material is clearly related to the adjacent vegetation, indicating a local origin, and then little influence of transport on the microbenthos, even if fragments of freshwater crustaceans and of Pediastrum alga are found down to the mouth in the sporopollinic deposits. This limited transport of microbenthos allows the use of periphytic algae, benthic ostracoda and benthic foraminifera as indicators of local environmental conditions. It was then possible to determine the extent of marine influence in the estuary, to discriminate between the main channel and adjacent basins, and between different stages of evolution of the basins, from a recently dug basin to a eutrophicated one.     

New Eulerian-Lagrangian Method for Salinity Calculation

A difference scheme in curvilinear coordinates is put forward for calculation of salinity in estuaries and coastal waters, which is based on Eulerian-Lagrangian method. It combines first-order and second-order Lagrangian interpolation to reduce numerical dispersion and oscillation. And the length of the curvilinear grid is also considered in the interpolation. Then the scheme is used in estuary, coast and ocean model, and several numerical experiments for the Yangtze Estuary and the Hangzhou Bay are conducted to test it. These experiments show that it is suitable for simulations of salinity in estuaries and coastal waters with the models using curvilinear coordinates.     

La dispersion des apports de la Gironde sur le plateau continental. Données in situ,satellitales et numériques

Coastal waters are generally a product of mixing between continental and oceanic originated water masses. Near river mouth areas, as in the Gironde estuary, oceanic waters are modified by the influence of freshwater discharge that introduces suspended and dissolved substances, including pollutants. Within PNOC (Programme National d'Oceanographie Côtière) our objective is to determine the extent of the influence of the Gironde estuary on to the Aquitanian continental shelf. Several cruises for collecting hydrological data have been carried out in this area. The data of every cruise were coupled with a NOAA-11 satellite passage. The recorded images have been analysed and were compared with the results given by a 3D mathematical model. The interaction among different dynamical factors (density, wind-driven and tidal circulation) controls the mixing and the transport of low salinity waters.     

Sensitivity to stress of the estuarine bivalve Macoma balthica from areas between the Netherlands and its southern limits (Gironde)

Variation in the sensitivity to stress of Macoma balthica was measured in several French and Dutch estuaries. For adult and juvenile Macoma balthica exposed to copper under conditions of starvation, differences in mortality rate, condition, glycogen, burrowing rate and copper content were assessed. No significant differences were observed between adults and juveniles; the influence of treatment and origin was always evident. Animals from the most southern estuaries, Loire and Gironde, near to the species's southern limit of distribution, showed, in the field, the strongest deviations for the ecophysiological traits measured, and were in the experiments the most sensitive to stress.     

Nitrogen and phosphorus species in the coastal and shelf waters of Southeastern North Carolina, Mid-Atlantic U.S. coast

The diversity of small-scale wetlands, high salinity tidal creeks, salt marshes, estuaries, and a wide and shallow shelf with the Gulf Stream close to the break makes the coastal zone of south-eastern North Carolina (U.S.) a natural laboratory for the study of the cycling of nitrogen (N) and phosphorus (P) in coastal and shelf waters. We assessed the summer concentrations, forms, and ratios for each N (total dissolved N, nitrate + nitrite, ammonium and dissolved organic N) and P (total dissolved P, o-phosphate and dissolved organic P) pool as these nutrients travel from tidal creeks, salt marshes and two large estuaries to Long and Onslow Bays. Additionally, we measured ancillary physical (temperature, salinity and turbidity) and chemical (dissolved oxygen, chlorophyll a and pH) water properties. Highest concentrations of all individual N and P compounds were found in the upper parts of each tributary and were attributed to loads from agricultural and urban sources to the coastal watersheds, continuing downstream to receiving estuaries. In all areas, dissolved organic N and P species were predominant constituents of the total dissolved N and P pools (64–97% and 56–93%, respectively). The lower parts of estuaries and surface shelf waters were characterized by oceanic surface values, indicating removal of N and P downstream in all tributaries. The different watershed and hydrological characteristics also determined the different speciation of N and P pools in each estuary. Despite a high level of anthropogenic pressure on the uppermost coastal waters, there is self-regulation in this coastal ecosystem with respect to human perturbations; i.e. significant amounts of the N and P load are retained within estuarine and nearshore waters without reaching the shelf.     

Investigation and comparison of one-dimensional (1-D) analytical models prediction for salt intrusion condition in two selected estuaries

Abstract

In this paper, two analytical models used worldwide to assess salinity variation in alluvial estuaries are applied to the Ashtamudi estuary, a Ramsar site, southwest coast of India; and Bouregreg estuary, in northwest part of Morocco. The estuaries’ bathymetry is described by an exponential function. Both models are quite similar and use a predictive equation for the dispersion in the estuary mouth (D₀). The major difference between the two models is the use of the constant value of K?=?0.5 for the Van der Burgh coefficient (K) and the introduction of the correction factor ζ, which is a function of damping (δ) and shape (γ). The performance of these two models was evaluated by comparing their results with field measurements; this revealed that both analytical models apply well to both the estimation of salinity distribution and the prediction of salt intrusion in the Ashtamudi and Bouregreg estuaries (Ashtamudi: RMSE = 0.60–1.22 ppt; Bouregreg: RMSE = 0.92–2.71 ppt). One model agrees more with the field measurements of salinity distribution along the estuaries axis; the second underestimate and overestimate some values of salinity distribution along the estuaries. Possibly, the constant value of K?=?0.5 for the Van der Burgh coefficient (K) has applicability limits for the estuaries under tidal conditions. The specifying of the parameterization may be a field of research.     

Seawater Intrusion in Semi-Closed Convergent Estuaries (Case Study of Moroccan Atlantic Estuaries): Application of Salinity Analytical Models

Salinity is an important parameter influencing the water quality of estuaries, and can constitute a serious problem to society due to the need for freshwater for industry and agriculture. Therefore, the determination of salt intrusion length in estuaries is a challenge for managers as well as scientists in this field. The managers tend to use simple and reliable tools for salinity variation. Although 2-D and 3-D numerical models are common tools for the prediction of salinity intrusion now, analytical models of salinity variation are much more efficient, and also require minimal sets of river data. In this paper, two analytical solutions, Brockway and Savenije used worldwide to assess longitudinal salinity variation in alluvial estuaries, are applied to the Moroccan Atlantic semi-closed estuaries, i.e., Sebou and Loukkos. The solutions are derived from salt convection-dispersion equations, with different assumptions for the dispersion coefficient. The estuaries' bathymetry is described by an exponential function. The performance of these two solutions was evaluated by comparing their results with field-measured salinity data. The Brockway model's salinity predictions performs well to observations especially in downstream reaches of the two estuaries (Sebou: R² = 0.95, root mean square error [RMSE] = 1.50‰, normalized root mean square error [NRMSE] = 3.45‰; Loukkos: R² = 0.95, RMSE = 1.13‰, NRMSE = 3.01‰), while the Savenije model outperformed the Brockway's model and is better to predict salt intrusion length and salinity variation along the two estuaries (Sebou: R² = 0.97, RMSE = 1.15‰, NRMSE = 2.85‰; Loukkos: R² = 0.98, RMSE = 0.95‰, NRMSE = 1.94‰). This revealed that both analytical solutions apply well to the estimation of salinity variation and the prediction of salt intrusion in these two estuaries.     

Spatial variability of nitrogen isotope ratios of particulate material from Northwest Atlantic continental shelf waters

Human encroachment on the coastal zone has led to concern about the impact of anthropogenic nitrogen (N) on estuarine and continental shelf waters. Western North Atlantic watershed budgets suggest that the export of human-derived N from estuaries to shelf waters off the east coast of the US may be significant; however, models based on water inputs and estimates of upwelling of deepwater nutrients to surface waters of the mid-Atlantic bight indicate that estuarine N may be a relatively minor component of the overall shelf N budget. Stable N isotope ratios could provide a means to assess the relative input of anthropogenic N to shelf waters, particularly since dissolved N from human sources has elevated δ¹⁵N values (range: 7–30‰). We collected particulate material from surface shelf waters off the US east coast from 2000 to 2005 at near-shore sample sites proximal to the mouth of six estuaries and corresponding sites farther offshore. Near-shore (mean 33.7 km from estuary mouth) δ¹⁵N values ranged from 5.5 to 7.7‰ Offshore values (mean 92.4 km from estuary mouth) were consistently lower than near-shore sites (average 4.7 ± 1.0‰ versus 6.8 ± 1.1‰), suggesting different N sources to near and offshore stations. Near-shore regions are often more productive, as mean monthly chlorophyll-a concentrations from the sea-viewing wide field-of-view sensor (SeaWiFS) were significantly higher at near-shore sites near the mouth of three of the six estuaries. A mass balance using a concentration-dependent mixing model with chlorophyll-a concentrations as a surrogate for dissolved inorganic nitrogen can account for all of the nitrogen at near-shore sites south of Cape Cod with estuarine nitrogen estimated to contribute 45–85% of the nitrogen to the near-shore surface particulate material. Our results support the hypothesis that estuarine nitrogen is influencing continental shelf ecosystems, and also provide preliminary evidence of the spatial extent of its influence on shelf waters in the mid-Atlantic bight.     

Hydrological characterisation of Ria de Aveiro,Portugal, in early summer

The hydrological features of Ria de Aveiro, a coastal lagoon on the northwest Atlantic coast of Portugal, were investigated in two sampling surveys carried out between 3/6 and 24/6/97 and between 29/6 and 7/7/97, respectively. There was a significant freshwater inflow into the lagoon during the first survey, especially in the first days, due to the recent rainfalls. Records concerning water level, salinity, temperature and current velocity were performed at several stations located along the four main channels of the lagoon. The type of tide at the mouth was determined and was observed that astronomical tide is the main forcing agent driving water circulation in Ria de Aveiro. The tide at the mouth is semidiurnal and the tidal wave propagation in the lagoon has the characteristics of a damped progressive wave. Typical estuarine longitudinal salinity and temperature gradients connected with the distance to the mouth were identified, whereas vertical and transverse gradients were found unimportant, except in the frontal zone between oceanic and fresh water masses. According to the results, even though Ria de Aveiro should be considered as vertically homogeneous, some channels may reveal characteristics of a partially mixed estuary, depending on the freshwater input.     

Effect of Salinity and Currents on Sea Level Variation Along the Indian Coast: A Numerical Study

The process of upwelling/sinking and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. Further,precipitation and monsoonal floods, apart from the marine meteorological parameters, are expected to influence the sea level fluctuations along the coast. This study comprises determining the sea level from the various parameters together with the pure wind stress forcing, which is compared with the observed cycle. However, it is found that there is considerable difference between the computations and observations. This suggests that the sea level is dependent not just on the local forcing alone, but also on the induced background circulation as well. For example, the sea level changes along the east coast of India, particularly the northern region, are more sensitive to freshwater discharge from various rivers joining the Bay of Bengal. This is due to more frequently occurring pre- and postmonsoon cyclonic storms and the associated surges in the Bay of Bengal as compared to the Arabian Sea. Hence the salinity effects are particularly important in the coastal waters off the east coast of India during monsoon months (June-September). For the west coast of India, however, it is expected that the large-scale coastal circulation may play a role in determining sea level changes in addition to other forcings. The salinity effects are negligible along the west coast in the absence of any major river systems that join the Arabian Sea. The local advection currents caused by the offshore directed freshwater discharge from various estuaries joining the coastal bay also seemed to influence the sea level. In order to elucidate the essential dynamics involved and to study the effect of the remote forcing, a three-dimensional baroclinic, nonlinear numerical model is used with appropriate open boundary conditions. The local effect of the current has been incorporated in the west coast model by means of opening a channel at Cochin through which the rainwater is carried away to the model ocean. The low saline plume, cascading from north along the east cost of India, has been incorporated in the east coast model through a proper forcing applied at the northern boundary of the model. With the inclusion of these remote forcings in the models, the disagreement between the simulations and the observations is minimized.     

Effect of Salinity and Currents on Sea Level Variation Along the Indian Coast: A Numerical Study

The process of upwelling/sinking and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. Further,precipitation and monsoonal floods, apart from the marine meteorological parameters, are expected to influence the sea level fluctuations along the coast. This study comprises determining the sea level from the various parameters together with the pure wind stress forcing, which is compared with the observed cycle. However, it is found that there is considerable difference between the computations and observations. This suggests that the sea level is dependent not just on the local forcing alone, but also on the induced background circulation as well. For example, the sea level changes along the east coast of India, particularly the northern region, are more sensitive to freshwater discharge from various rivers joining the Bay of Bengal. This is due to more frequently occurring pre- and postmonsoon cyclonic storms and the associated surges in the Bay of Bengal as compared to the Arabian Sea. Hence the salinity effects are particularly important in the coastal waters off the east coast of India during monsoon months (June-September). For the west coast of India, however, it is expected that the large-scale coastal circulation may play a role in determining sea level changes in addition to other forcings. The salinity effects are negligible along the west coast in the absence of any major river systems that join the Arabian Sea. The local advection currents caused by the offshore directed freshwater discharge from various estuaries joining the coastal bay also seemed to influence the sea level. In order to elucidate the essential dynamics involved and to study the effect of the remote forcing, a three-dimensional baroclinic, nonlinear numerical model is used with appropriate open boundary conditions. The local effect of the current has been incorporated in the west coast model by means of opening a channel at Cochin through which the rainwater is carried away to the model ocean. The low saline plume, cascading from north along the east cost of India, has been incorporated in the east coast model through a proper forcing applied at the northern boundary of the model. With the inclusion of these remote forcings in the models, the disagreement between the simulations and the observations is minimized.