Study of the dynamics of estuarine and coastal waters using remote sensing: the Tinto-Odiel estuary,SW Spain

This paper deals with the application of satellite images to characterize some aspects of the circulation dynamics of the Tinto-Odiel estuary using turbidity patterns as ‘natural tracers’. 15 images (Landsat TM and Spot HRV) were processed to provide synoptic, instantaneous views of the circulation patterns under different environmental conditions. In addition, a comparison was made between results of oceanographic field work, using biplanes and fluorescent tracers, and satellite image turbidity patterns used as ‘ground truth’ data for specific hydroclimatic situations. This approach allowed (1) the identification and mapping of dynamic processes of interest during a theoretical tidal cycle, (2) the elaboration of additional information on the ‘flow schemes’ at the mouth of the estuary with improved spatial and temporal resolution, and (3) the supply of basic data to improve the knowledge of exchange processes between estuarine and coastal waters. The results of this study are considered to be useful for the management of the estuarine system.     

Study of the dynamics of estuarine and coastal waters using remote sensing: the Tinto-Odiel estuary, SW Spain

This paper deals with the application of satellite images to characterize some aspects of the circulation dynamics of the Tinto-Odiel estuary using turbidity patterns as ‘natural tracers’. 15 images (Landsat TM and Spot HRV) were processed to provide synoptic, instantaneous views of the circulation patterns under different environmental conditions. In addition, a comparison was made between results of oceanographic field work, using biplanes and fluorescent tracers, and satellite image turbidity patterns used as ‘ground truth’ data for specific hydroclimatic situations. This approach allowed (1) the identification and mapping of dynamic processes of interest during a theoretical tidal cycle, (2) the elaboration of additional information on the ‘flow schemes’ at the mouth of the estuary with improved spatial and temporal resolution, and (3) the supply of basic data to improve the knowledge of exchange processes between estuarine and coastal waters. The results of this study are considered to be useful for the management of the estuarine system.     

Spatial segregation amongst goby species within an Australian estuary,with a comparison of the diets and salinity tolerance of the two most abundant species

The present study was undertaken to determine whether the various species of gobies that are found within the large Swan Estuary in south-western Australia are segregated within that system, and to attempt to determine the basis for any differences in their spatial distributions. The Swan Estuary comprises a long entrance channel (lower estuary), two wide basins (middle estuary) and the saline reaches of the tributary rivers (upper estuary). A total of 26232 gobies, representing seven species, was collected using a 3 mm-mesh seine net at 15 sites throughout this estuary on at least one occasion monthly over seven consecutive seasons between September 1983 and March 1985. Favonigobius lateralis and Pseudogobius olorum contributed 47.0 and 47.8%, respectively, to the total catch of gobies at all sites. The densities of each species at each site were used to determine the relative contribution of each species to the gobiid fauna at each of the sites in the lower, middle and upper estuary. Comparisons of these data with those published on the distribution and abundance of gobiid larvae confirmed that F. lateralis, which was found predominantly in the lower estuary, is a marine species that spawns in high salinities near the estuary mouth or in inshore coastal waters. In contrast, the life cycle of P. olorum and Papillogobius punctatus are typically completed within the saline reaches of the upper estuary, and that of Arenigobius bifrenatus within both this region and parts of the middle estuary where the substrate is particularly soft. Afurcagobius suppositus also spawns in this area, as well as in fresh water. Tridentiger trigonocephalus, represented by only eight individuals, is an introduced, marine species that was found mainly in the lower estuary. A single representative of the marine species Callogobius depressus was caught. The relatively low numbers of gobies caught in the middle estuary, where they contributed only about 3.5% to the total number of all gobies at all sites, may represent an aversion to the presence of rougher waters in the large basins. Circumstantial evidence suggests that the sandy substrate and consistently high salinities found in the lower estuary are preferred by F. lateralis, whereas the silty surface to the substrate and lower salinities of the upper estuary are preferred by Pseudogobius olorum. Densities of three of the four most abundant species were higher in either spring or summer than in winter, reflecting the influx of 0 + recruits, and possibly also the tendency for species in estuaries to congregate in the shallows during the warmer periods of the year. F. lateralis fed mainly on polychaetes and crustaceans, whereas P. olorum ingested predominantly algae, reflecting differences in mouth morphology and feeding behaviour, rather than the type of food available.     

The Estuarine Component of the Us E.P.A.'S Environmental Monitoring and Assessment Program

The US Environmental Protection Agency's Office of Research and Development has initiated the Environmental Monitoring and Assessment Program (EMAP) to monitor status and trends in the condition of the nation's near coastal waters, forests, wetlands, agro-ecosystems, surface waters, deserts and rangelands. the programme is also intended to evaluate the effectiveness of Agency policies at protecting ecological resources occurring in these systems. Monitoring data collected for all ecosystems will be integrated for regional and national status and trends assessments. the near coastal component of EMAP consists of estuaries, coastal waters, and the Great Lakes. Near coastal ecosystems have been regionalized and classified, and an integrated sampling strategy has been developed. EPA and NOAA have agreed to coordinate and, to the extent possible, integrate the near coastal component of EMAP with the NOAA National Status and Trends Program. A demonstration project was conducted in estuaries of the mid-Atlantic region (Chesapeake Bay to Cape Cod) in the summer of 1990. in 1991, monitoring continued in mid-Atlantic estuaries and was initiated in estuaries of a portion of the Gulf of Mexico. Preliminary results indicate: there are no insurmountable logistical problems with sampling on a regional scale; several of the selected indicators are practical and sensitive on the regional scale; and an efficient effort in future years will provide valuable information on condition of estuarine resources at regional scales.     

The Estuarine Component of the Us E.P.A.'S Environmental Monitoring and Assessment Program

The US Environmental Protection Agency's Office of Research and Development has initiated the Environmental Monitoring and Assessment Program (EMAP) to monitor status and trends in the condition of the nation's near coastal waters, forests, wetlands, agro-ecosystems, surface waters, deserts and rangelands. the programme is also intended to evaluate the effectiveness of Agency policies at protecting ecological resources occurring in these systems. Monitoring data collected for all ecosystems will be integrated for regional and national status and trends assessments. the near coastal component of EMAP consists of estuaries, coastal waters, and the Great Lakes. Near coastal ecosystems have been regionalized and classified, and an integrated sampling strategy has been developed. EPA and NOAA have agreed to coordinate and, to the extent possible, integrate the near coastal component of EMAP with the NOAA National Status and Trends Program. A demonstration project was conducted in estuaries of the mid-Atlantic region (Chesapeake Bay to Cape Cod) in the summer of 1990. in 1991, monitoring continued in mid-Atlantic estuaries and was initiated in estuaries of a portion of the Gulf of Mexico. Preliminary results indicate: there are no insurmountable logistical problems with sampling on a regional scale; several of the selected indicators are practical and sensitive on the regional scale; and an efficient effort in future years will provide valuable information on condition of estuarine resources at regional scales.     

Dissolved nutrient dynamics along the southwest coastal waters of India during northeast monsoon: a case study

Dissolved nutrients, Chl-a and primary productivity were measured from seven transects along the coastal waters of the southeastern Arabian Sea during northeast monsoon. Ten major estuaries were chosen to study the influence of estuarine discharge on the nutrient dynamics in the coastal waters. The mean water discharge of the estuaries in the north (64.8?±?18?×?10⁵?m³?d^?1) was found to be higher than those in the south (30.6?±?21.4?×?10⁵?m³?d^?1), whereas the nutrient concentrations were found to be higher in the estuaries of the south. The results from the offshore waters were discussed in accordance with the depth contour classification, that is, shelf (depth?≤?30?m) and slope waters (depth?≥?30?m). Our results suggest that the estuarine discharge plays a major role in the nutrient distribution in near shore shelf waters, whereas in shelf and slope waters, it was mainly controlled by in situ biological processes. The inorganic form of N to P ratios were found to be higher than Redfield ratio in slope waters when compared with shelf waters, suggesting that PO₄^3? (<0.15?µmol?L^?1) is a limiting nutrient for primary production. The multivariate statistical analysis revealed that the nutrient dynamics in the coastal waters was controlled by both biological and physical processes.     

Age structure,growth, and morphometric variations in the Atlantic surf clam,Spisula solidissima,from estuarine and inshore waters

The surf clam, Spisula solidissima (Dillwyn), population in the estuarine waters of Long Island Sound, New York, USA, was characterized in 1984 and again in 1988 by an age structure restricted to just two age-classes, and an apparent lifespan of only about 10 yr. In the inshore coastal waters off Fire Island, New York, a wide age range from 2 to 22 yr old was present. The age structure at Long Beach, New York, a third geographic region which is coastal but influenced by the Hudson River estuary, was similar to Long Island Sound. Juvenile surf clams grew at similar rates in all three geographic regions. However, adults from the Long Island Sound population grew significantly slower and reached an asymptotic maximum size which was 37% smaller than Fire Island adults. Long Beach adults had intermediate growth rates and maximum sizes. The shells of Long Island Sound clams were also 25% thinner than those from the other two regions. Density dependent effects on growth, evaluated over abundances ranging from 0.5 to 294 ind. m^–2, were present but were too small to account for observed regional differences. Results suggest that adult surf clams may be physiologically stressed by the reduced salinity and more extreme temperatures found in estuarine waters.     

Horizontal transport,mixing and retention in a large,shallow estuary: Río de la Plata

We use field data and a high-resolution three-dimensional (3D) hydrodynamic numerical model to investigate the horizontal transport and dispersion characteristics in the upper reaches of the shallow Río de la Plata estuary, located between the Argentinean and Uruguayan coasts, with the objective of relating the mixing characteristics to the likelihood of algal bloom formation. The 3D hydrodynamic model was validated with an extensive field experiment including both, synoptic profiling and in situ data, and then used to quantify the geographic variability of the local residence time and rate of dispersion. We show that during a high inflow regime, the aquatic environment near the Uruguayan coast, stretching almost to the middle of the estuary, had short residence time and horizontal dispersion coefficient of around 77 \(\mathrm {m}^{2}\,\mathrm {s}^{-1}\) , compared to the conditions along the Argentinean coastal regime where the residence time was much longer and the dispersion coefficient (40 \(\mathrm {m}^{2}\,\mathrm {s}^{-1}\) ) much smaller, making the Argentinian coastal margin more susceptible for algae blooms.     

Nutrients of the Cochin Backwater in relation to environmental characteristics

The nutrient distribution of the Cochin Backwater was studied at 6 stations throughout the year. The depth profiles of phosphorus (inorganic and organic), nitrogen (nitrate and nitrite) and silicon, showed a marked seasonal rhythm, induced by the local precipitation and land runoff. Changes in other environmental features such as temperature, salinity, dissolved oxygen, pH and alkalinity were small during the premonsoon period when the system remains marine-dominated, and large during the monsoon period when the estuary becomes freshwater-dominated. Seasonal changes in the hydrographical conditions of the adjoining coastal waters of the Arabian Sea which influence the backwater system have been discussed.     

Phytoplankton production modelling in three marine ecosystems—static versus dynamic approach

Phytoplankton productivity is usually determined from water samples incubated at a number of irradiance levels during several hours. The resultant productivity-irradiance (P–E) curves are then used to estimate local and/or global phytoplankton production. However, there is growing evidence that these curves, referred as static, underestimate phytoplankton photosynthesis to a great deal, by assuming a stable response to light over the incubation period. One of the drawbacks of static P–E curves is the overestimation of photoinhibition.In this work, three one-dimensional vertically resolved models were developed as simply as possible, to investigate differences between static and dynamic phytoplankton productivity in three marine ecosystems: a turbid estuary, a coastal area and an open ocean ecosystem. The results show that, when photoinhibition development time is considered (dynamic model), the primary production estimates are always higher than when calculated with the static model. The quantitative importance of these differences varies with the type of ecosystem and it appears to be more important in coastal areas and estuaries (from 21 to 72%) than in oceanic waters (10%). Thus, these results suggest that primary production estimates, obtained under the assumption of a static behaviour response to light, may underestimate the real values of global phytoplankton primary production. Calculations suggest that the quantitative importance of this underestimation may be larger than the global missing carbon sink.     

Habitat related growth and reproductive investment in estuarine waters,illustrated for the tellinid bivalve <Emphasis Type="Italic">Macoma balthica</Emphasis> (L.) in the western Dutch Wadden Sea

In estuarine areas, bivalve species can be found in a variety of environments, where they experience large differences in environmental conditions. In the present paper, the importance of different habitats (intertidal, subtidal and adjacent coastal waters) for the persistence of the population was evaluated for the bivalve Macoma balthica (L.) in the western Dutch Wadden Sea estuary. Intra-specific variation in growth and reproductive output were followed during the year and related to local abiotic conditions. Significant differences in growth and reproductive investment were found between locations. Young individuals were mostly found in the intertidal area, where growth in terms of somatic mass was good. These areas were not favourable for adult individuals, since growth in shell length was low and many individuals did not reproduce. In the subtidal, where the highest densities were found, somatic and gonadal mass indices were low. Coastal areas had the lowest densities and showed high growth in terms of shell length and body mass. The habitat with the highest reproductive effort per individual was not the most important habitat in terms of reproductive output due to differences in density and in size of the habitat type. For M. balthica, the subtidal habitat contributed the most to the reproductive output of the western Dutch Wadden Sea population although the highest reproductive output per individual was in the coastal area.     

Life history strategy of a southern European population of brown shrimp (Crangon crangon L.): evidence for latitudinal changes in growth phenology and population dynamics

This study provides a comprehensive examination of the life cycle dynamics of the brown shrimp (Crangon crangon L.) in the Mondego estuary, Portugal, a habitat located near the southern edge of the range of this species in European waters. The phenology of all life stages was documented (from the occurrence of ovigerous females, developing embryos, planktonic larvae and benthic post-larvae), and migration patterns of larvae into and out of the estuary were examined. Temperature-dependent functions of egg and larval development were combined with data on field abundance to predict the timing and magnitude of occurrence of larvae and recruits. Compared to brown shrimp at higher latitudes, southern conspecifics grow slower, mature earlier and have smaller brood sizes, and larvae have a more protracted settlement period. The Mondego estuary, besides acting as nursery area, is a dynamic platform for C. crangon to use in different stages, sizes and seasons.     

Optical remote sensing of coastal plumes and run-off in the Mediterranean region

Sea surface colour data, derived from the Coastal Zone Colour Scanner (CZCS) archive, have been used to assess the space/time variability of coastal plumes and run-off in the Mediterranean Sea. A time series of 2645 scenes, collected by the CZCS from 1979 to 1985, was processed to apply sensor calibration algorithms, correct for atmospheric contamination, and derive chlorophyll-like pigment concentration. Individual images, remapped on a 1-km² pixel grid, were generated for each available day, and then mean values calculated pixel by pixel to form monthly, seasonal and annual composites. The results obtained must be taken with caution, due to the CZCS limitations in the quantitative assessment of bio-optical pigments when high concentrations of dissolved organics or suspended sediments are present, e.g. along littorals or within plumes. Marked differences appear in the distribution of water constituents between coastal zones and open sea, northern and southern near-coastal areas, western and eastern sub-basins. The oligotrophic character of the basin contrasts with areas of high concentration related to river plumes—Ebro (Ebre), Po, Rhone, Nile—, coastal run-off patterns, and persistent mesoscale features (e.g. coastal filaments and eddies). Seasonal variability appears to be high, with higher concentrations occurring over most of the basin in the cold season, when climatic conditions are favourable to coastal run-off and vertical mixing. Atmospheric forcing (wind and rainfall over continental margins) could play an important role in establishing the observed space/time distribution of water constituents. The impact of continental interactions (fluvial and coastal run-off), or that of exchanges between coastal zone and open sea, could have paramount influence on the biogeochemical fluxes in the entire basin.     

Modeling estuarine-shelf exchanges in a deltaic estuary: Implications for coastal carbon budgets and hypoxia

The export of wetland-derived materials to the coastal ocean (i.e., the “Outwelling” hypothesis) has received considerable attention over the past several decades. While a number of studies have shown that estuaries export appreciable amounts of nutrients and carbon, few studies have attempted to estimate the importance of estuarine sources for the coastal carbon budgets in river-dominated coastal ecosystems. A novel tidal prism model was developed to examine estuarine-shelf exchanges in the Barataria estuary, a deltaic estuary located in the north-central Gulf of Mexico. This estuary has been the site of a massive wetland loss, and it has been hypothesized that carbon export from the eroding coastal wetlands supports the development of a large hypoxic zone in the coastal Gulf of Mexico. The model results show that the Barataria estuary receives nitrogen through the tidal passes and releases carbon to the coastal ocean. The mean calculated tidal water discharge of 6930 m³ s⁻¹ is equivalent to about 43% of the lower Mississippi River discharge. The annual total organic carbon (TOC) export is 109 million kg, or 57 gC m² yr⁻¹ when prorated to the total water area of the estuary. This carbon export is equivalent to a loss of 0.5 m of wetland soil horizon over an area of 8.4 km², and accounts for about 34% of the observed annual wetland loss in the estuary between 1978 and 2000. Compared to the lower Mississippi River, the Barataria estuary appears to be a very small source of TOC for the northern Gulf of Mexico (2.7% of riverine TOC), and is unlikely to have a significant influence on the development of the Gulf's hypoxia.     

The fish fauna of a seasonally closed Australian estuary. Is the prevalence of estuarine-spawning species high?

The fish at sites located throughout the large, seasonally closed Wilson Inlet, on the southern coast of Western Australia, were sampled bimonthly between September 1987 and April 1989. Seine nets were used to sample nearshore shallow waters, while gill nets were employed in slightly more offshore and deeper waters. Twenty species were recorded in the shallows, of which the three species of atherinid and the three species of goby comprised >97% of the total catch. In terms of number of individuals, the 27 species recorded in gill nets in the deeper waters were dominated by Cnidoglanis macrocephalus and Platycephalus speculator, and to a lesser extent Engraulis australis, Aldrichetta forsteri, Sillaginodes punctata and Arripis georgianus. Fifty-five percent of the species recorded in the nearshore shallow waters and 18% of those in offshore deeper waters spawn within Wilson Inlet; these species contributed 98.5 and 63.0%, respectively, to the total catches in those waters. Classification and ordination showed that the composition of the fauna in the shallows was similar at all sites throughout the large basin and did not change conspicuously with season. However, the composition of catches taken in offshore waters differed between the lower part of the basin and the middle and upper regions of the basin, which in turn differed from those in the saline reaches of a tributary river. The four diagnostic species of the lower estuary were all marine species, while the three diagnostic species in the river included a marine species (Mugil cephalus) that often penetrates far upstream in other systems, and a species which was confined to the rivers (Acanthopagrus butcheri). The composition of the fish fauna in the offshore waters of the lower estuary between the middle of spring and middle of autumn was different in 1987/1988 (when the estuary mouth was open for only the first two months of that period) from that in 1988/1989 (when the mouth was open for the whole of that period). This difference is related to the greater number of marine species that were retained in the first of these years, when the estuary was open to the ocean for only a short period. The greater retention of marine species in 1987/1988 than in 1988/1989 probably reflects a far lower level of freshwater flusing and/or a less marked decline in salinity.     

Seasonal changes in the structure of an intertidal community

Quantitative (0.25 m²) samples of macrofaunal (>1.0 mm) invertebrates were taken in each season from one habitat of an intertidal sandbar in the North Inlet estuary near Georgetown, South Carolina, USA. During all seasons the community inhabiting the sample site was numerically dominated by two species of haustoriid amphipods (Acanthohaustorius millsi and Pseudohaustorius caroliniensis). Seasonal changes at the community level were clearly controlled by the population dynamics of the numerically dominant species, and qualitative information on life histories was important to the interpretation of analyses' results.This work was supported by the Environmental Technology Center of Martin Marietta Corporation and the Belle W. Baruch Institute for Marine Biology and Coastal Research. It is Contribution No. 138 of the Belle W. Baruch Institute for Marine Biology and Coastal research.     

An analysis of the developmental differences in Borneo’s Southeastern and Northwestern Coastal Zones

In this research, Landsat TM images were used to extract the land use information for Borneo’s coastal zones (0 to 35 km) during three time periods (1990, 2000, and 2010). Then, in combination with the DEM and shoreline types, the developmental differences under the influences of the geographical boundaries of the Borneo coastal zones were examined from such perspectives as the spatial distribution characteristics of the land development, sea-land gradient variation characteristics, and comparative analyses of the different regions. The results indicated that the geographic boundaries, as well as the different countries, had great influences on the development of the coastal zones. The regions with the most active development in Borneo’s coastal zones were mainly located in the estuary bay, onshore with land on both sides, and the near-shore alluvial plain with DEM?<?50 m. The northwestern coast zone showed relatively flat topography, and was close to an important international waterway. Therefore, the development in this area was found to be more intense than in the southeastern coastal zone, and which was characterized by a long developmental history. On one side of the geographical boundary, the development was also found to differ among the different countries. Malaysia was observed to be dominated by industrial plantations. Meanwhile, the industrial plantations, agriculture, and aquaculture in Indonesia were significantly increased, which was closely linked with the national economic policies. Furthermore, the development of Borneo’s coastal zones has led to vegetation degradation towards a constant inland development, plantation enlargements, agricultural development, and cleared and burnt areas, which have resulted in the land use transfer of 22,000 km² of forest land within the 0 to 35 km range.     

Modeling the impact of natural and anthropogenic nutrient sources on phytoplankton dynamics in a shallow coastal domain, Western Australia

The influence of different nutrient sources on the seasonal variation of nutrients and phytoplankton was assessed in the northern area of the Perth coastal margin, south–western Australia. This nearshore area is shallow, semi-enclosed by submerged reefs, oligotrophic, nitrogen-limited and receives sewage effluent via submerged outfalls. Analysis of 14 year of field observations showed seasonal variability in the concentration of dissolved inorganic nitrogen and phytoplankton biomass, measured as chlorophyll-a. For 2007–2008, we quantified dissolved inorganic nitrogen inputs from the main nutrient sources: superficial runoff, groundwater, wastewater treatment plant effluent, atmospheric deposition and exchange with surrounding coastal waters. We validated a three-dimensional hydrodynamic-ecological model and then used it to assess nutrient-phytoplankton dynamics. The model reproduced the temporal and spatial variations of nitrate and chlorophyll-a satisfactorily. Such variations were highly influenced by exchange through the open boundaries driven by the wind field. An alongshore (south–north) flow dominated the flux through the domain, with dissolved inorganic nitrogen annual mean net-exportation. Further, when compared with the input of runoff, the contributions from atmospheric-deposition, groundwater and wastewater effluent to the domain’s inorganic nitrogen annual balance were one, two and three orders of magnitude higher, respectively. Inputs through exchange with offshore waters were considerably larger than previous estimates. When the offshore boundary was forced with remote-sensed derived data, the simulated chlorophyll-a results were closer to the field measurements. Our comprehensive analysis demonstrates the strong influence that the atmosphere–water surface interactions and the offshore dynamics have on the nearshore ecosystem. The results suggest that any additional nutrient removal at the local wastewater treatment plant is not likely to extensively affect the seasonal variations of nutrients and chlorophyll-a. The approach used proved useful for improving the understanding of the coastal ecosystem.     

An integrated river basin-coast-sea modelling scenario for nitrogen management in coastal waters

Linked river basin and coastal water models were applied to analyse the effects of an optimal nitrogen management scenario in the Oder/Odra river basin on water quality in the Oder (Szczecin) Lagoon and the Pomeranian Bay (Baltic Sea). This scenario would reduce nitrogen loads into the coastal waters by about 35%, a level which is similar to the load of the late 1960’s. During summer the primary production and algae biomass in the Oder estuary is limited by nitrogen, which makes a nitrogen management reasonable. The comparison of the late 1960’s and the mid 1990’s shows that an optimal nitrogen management has positive effects on coastal water quality and algae biomass. However, this realistic nitrogen reduction scenario would not ensure a good coastal water quality according to the European Water Framework Directive. A good water quality in the river will not be sufficient to ensure a good water quality in the lagoon. Nitrogen load reductions bear the risk of increased potentially toxic, blue-green algae blooms, especially in the Baltic coastal sea. However, to reach water quality improvements in lagoons and inner coastal waters, nitrogen cuts are necessary. A mere focus on phosphorus is not sufficient.