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1.
Zhaoqing Yang Taiping Wang Tarang Khangaonkar Stephen Breithaupt 《Environmental Fluid Mechanics》2012,12(1):63-80
The interactions of physical processes between estuaries and upstream river floodplains are of great importance to the fish
habitats and ecosystems in coastal regions. Traditionally, a hydraulic analysis of floodplains has used one- or two-dimensional
models. While this approach may be sufficient for planning the engineering design for flood protection, it is inadequate when
floodwaters inundate the floodplain in a complex manner. Similarly, typical estuarine and coastal modeling studies do not
consider the effect of upstream river floodplains because of the technical challenge of modeling wetting and drying processes
in floodplains and higher bottom elevations in the upstream river domain. While various multi-scale model frameworks have
been proposed for modeling the coastal oceans, estuaries, and rivers with a combination of different models, this paper presents
a modeling approach for simulating the hydrodynamics in the estuary and river floodplains, which provides a smooth transition
between the two regimes using an unstructured-grid, coastal ocean model. This approach was applied to the Skagit River estuary
and its upstream river floodplain of Puget Sound along the northwest coast of North America. The model was calibrated with
observed data for water levels and velocities under low-flow and high-flood conditions. This study successfully demonstrated
that a three-dimensional estuarine and coastal ocean model with an unstructured-grid framework and wetting-drying capability
can be extended much further upstream to simulate the inundation processes and the dynamic interactions between the estuarine
and river floodplain regimes. 相似文献
2.
We tested for unintended mercury contamination problems associated with estuarine floodplain restoration projects of the Louisiana coastal zone, USA. Barataria Bay and Breton Sound are two neighboring deltaic estuaries that were isolated by levees from the Mississippi River about 100 years ago. These estuaries recently have been reconnected to the nutrient-rich Mississippi River, starting major river diversion (input) flows in 1991 for Breton Sound and in 2004 for Barataria Bay. We collected > 2100 fish over five years from 20 stations in these estuaries to test two hypotheses about Hg bioaccumulation: (H1) Background Hg bioaccumulation in fish would be highest in low-salinity upper reaches of estuaries, and (H2) recent river inputs to these upper estuarine areas would increase Hg bioaccumulation in fish food webs. For H1, we surveyed fish Hg concentrations at several stations along a salinity gradient in Barataria Bay in 2003-2004, a time when this estuary lacked strong river inputs. Results showed that average Hg concentrations in fish communities were lowest (150 ng/g dry mass) in higher salinity areas and -2.4x higher (350 ng/g) in low-salinity oligohaline and freshwater upper reaches of the estuary. For H2, we tested for enhanced Hg bioaccumulation following diversion onset in both estuaries. Fish communities from Breton Sound that had long-term (> 10 years) diversion inputs had -1.7x higher average Hg contents of 610 ng/g Hg vs. 350 ng/g background values. Shorter-term diversion inputs over 2-3 years in upper Barataria Bay did not result in strong Hg enrichments or stable C isotope increases seen in Breton Sound, even though N and S stable-isotope values indicated strong river inputs in both estuaries. It may be that epiphyte communities on abundant submerged aquatic vegetation (SAV) are important hotspots for Hg cycling in these estuaries, and observed lesser development of these epiphyte communities in upper Barataria Bay during the first years of diversion inputs may account for the lessened Hg bioaccumulation in fish. A management consideration from this study is that river restoration projects may unintentionally fertilize SAV and epiphyte-based food webs, leading to higher Hg bioaccumulation in river-impacted floodplains and their food webs. 相似文献
3.
John F. Paul K. John Scott A. Fred Holland Steven B. Weisberg J. Kevin Summers Andrew Robertson 《Chemistry and Ecology》2013,29(1-4):93-116
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. 相似文献
4.
John F. Paul K. John Scott A. Fred Holland Steven B. Weisberg J. Kevin Summers Andrew Robertson 《Chemistry and Ecology》1992,7(1):93-116
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. 相似文献
5.
Climate change is increasing the need to characterise the vulnerability of coastal landscapes to coastal and flood hazards that result in erosion and inundation. Indices, such as the Coastal Vulnerability Index (CVI), have emerged as useful tools with which coastal managers can prioritise areas for further detailed assessment of vulnerability, risk, resilience and adaptation options. Approaches, such as the use of an index, efficiently characterise the vulnerability of linear, one-dimensional coastal features such as coastlines; however, they do not capture variability in coastal processes affecting more complex, non-linear features, such as estuaries, or interactive effects of coastal processes between linear (e.g. coastlines) and non-linear (e.g. estuaries) landforms. We present an approach that uses geomorphology to indicate biophysical vulnerability of estuaries to coastal and flood hazards. The approach is applied to the South Coast of NSW; a wave-dominated coastline of approximately 400 km length that contains more than 100 estuaries. We demonstrate the simplicity of the approach and its utility in identifying areas requiring higher resolution assessments. Although this approach does not include socio-economic factors, we demonstrate the capacity to incorporate socio-economic components of vulnerability using regional land use mapping. We infer that the most vulnerable estuaries are characterised by large catchment areas, broad estuarine valleys, mature stages of infill, or entrances oriented towards the prevailing wave direction. The area below 15 m elevation was identified as a robust indicator of the total area of vulnerability within a catchment. This approach can be applied to one-dimensional and more complex two-dimensional landscapes, such as estuaries; integrates varying sea-level rise projections; and incorporates a wider range of hazards that operate in the coastal zone. 相似文献
6.
Conservation of coastal lands reduces non-point source pollution loads into oceans and estuaries, retains natural areas and
saves ecological communities from disappearance and change. A recent agreement for protection of Long Island Sound waters
in New York and Connecticut established 30 environmental and management goals. One of them is establishment of a listing of
existing undeveloped properties and their prioritization for natural resource conservation and outdoor recreation. The optimal
prioritization approach poses strong constraints and methodological challenges on selection of data for analysis, assignment
of a priority score to each property unit and the assessment of this assignment. To be a practical tool, the prioritization
model should be reproducible and include a mechanism for evaluation of obtained prioritization scenarios. Presented study
uses Geographic Information System (GIS) to assign conservation priority scores to unprotected and undeveloped parcels greater
than five acres in size within New York’s Long Island Sound coastal area. The method combines spatial multi-criteria analysis
and statistical methods. The results of this project include identification and prioritization of more than 700 undeveloped
properties on New York coast. The most important finding of GIS analysis was the discovery of clusters of vacant parcels that
together form large areas available for future conservation. These results offer new conservation tools and strategies to
coastal managers and government in New York State. 相似文献
7.
To improve the present national and local sustainable planning capability for the coastal zone a GI application for the Italian
Coastal Susceptibility Assessment was planned within an institutional agreement between ENEA and the Land Defence Service
of the Italian Ministry of Environment. Taking into account previous European actions a suitable methodology to assess, in
a quantitative way, the susceptibility of beaches to be eroded has been set up.
The methodology balances the coastline trend as evaluated for a defined time period with the present coastal areas morphology
and land use, this in order to derive a value that expresses the evolutionary process in terms of probability of the loss
of goods within the ‘Homogeneous Coastal Tracts’.
The trend in the movement of the sea-land line has been used asgeo-indicator of a complex dynamic balance that refers both to marine and inland systems, and a vector GI application was built and locally
applied in southern Italian coastal areas.
The present shoreline position and some other information describing the intrinsic beach morphologies, and having significance
for the coastal erosion hazard assessment, have been derived from the national 1∶10.000 ortho-images of the National Cartographic
Reference System provided by the Italian Ministry of Environment. The illustrated GI application— CoSTAT—keeps the nominal
scale of all data collected or produced. In this analysis the coastal dune presence is analysed as factor limiting coastal
erosion susceptibility. Applying a matrix calculation a quantitative evaluation of erosion susceptibility degree was achieved
and plans were made to develop new information for a suitable use of Italian coastal areas.
The work describes the methodology, the conceptual frame-work and the results of a local application. 相似文献
8.
David E. Jennings Joseph D. DiBattista Kristine L. Stump Nigel E. Hussey Bryan R. Franks R. Dean Grubbs Samuel H. Gruber 《Journal of Coastal Conservation》2012,16(3):405-428
Coastal biodiversity is threatened worldwide by both direct and indirect anthropogenic activities. To more effectively manage and protect coastal biodiversity, accurate assessments of genetic, species, and ecosystem level diversity are required. We present the results from an assessment of the aquatic species diversity of a small (3?km2), shallow, mangrove-fringed Bahamian lagoon (the North Sound) subject to ongoing anthropogenic development. The assessment was conducted through a collation of field observations and data in published literature. We found that eight angiosperm species, 30 macroalgal species, and 370 animal species (including 95 fishes, 69 arthropods, 56 birds, and 45 mollusks) were documented within the lagoon. At least 11 of these species are of conservation concern, such as the critically endangered smalltooth sawfish (Pristis pectinata) and hawksbill turtle (Eretmochelys imbricata). Comparisons of community similarity indicated that the North Sound has a relatively distinct fauna and flora, but available data suggest that the species found there are most similar to those found in nearby habitats in Cuba. The lagoon forms a key nursery habitat for many species, including lemon sharks (Negaprion brevirostris), Caribbean spiny lobsters (Panulirus argus), and queen conch (Strombas gigas). Recently, the lagoon was included as part of a new marine protected area (MPA), but much of the habitat has already experienced considerable anthropogenic disturbance and the MPA boundaries have yet to be established. We have therefore analyzed the lagoon biodiversity and expect the data presented here to serve as a baseline for future comparisons. 相似文献
9.
Margarida Cardoso da Silva António Carmona Rodrigues 《Journal of Coastal Conservation》2004,10(1):13-24
The need for a better management of estuaries requires an environmental characterization following a methodology that allows
the comparison of distinct estuarine systems and the assessment of their evolution. The peculiar characteristics of estuaries,
in particular their intrinsic variability, make this characterization difficult and there is no commonly accepted general
methodology available. The approach followed in freshwater ecosystems is generally based on the concept of environmental indicators,
but such a concept has not been developed for estuaries. Indeed, a different approach is needed here, due to the spatial heterogeneity
and the different time scales associated with the processes that control water quality.
This paper presents a proposal for a methodology that starts with observed values and uses a procedure to integrate these
values in time and space in order to calculatesignificant values, upon whichnormalized indicators are built which take into account criteria based either on legal, scientific or heuristic concentration limits. A normalization
is carried out in two steps: (1) application of a mathematical operator to theignificant values, (2) transformation using the concept ofpenalty curves. This methodology may be complemented with the definition ofquality classes, particularly appealing and useful, as tools to communicate with decision makers and the public in general.
Water quality data pertaining to the Tejo estuary are used to test the methodology. 相似文献
10.
NICHOLAS J. GOTELLI ANNE CHAO ROBERT K. COLWELL WEN‐HAN HWANG GARY R. GRAVES 《Conservation biology》2012,26(1):47-56
Abstract: Assessing species survival status is an essential component of conservation programs. We devised a new statistical method for estimating the probability of species persistence from the temporal sequence of collection dates of museum specimens. To complement this approach, we developed quantitative stopping rules for terminating the search for missing or allegedly extinct species. These stopping rules are based on survey data for counts of co‐occurring species that are encountered in the search for a target species. We illustrate both these methods with a case study of the Ivory‐billed Woodpecker (Campephilus principalis), long assumed to have become extinct in the United States in the 1950s, but reportedly rediscovered in 2004. We analyzed the temporal pattern of the collection dates of 239 geo‐referenced museum specimens collected throughout the southeastern United States from 1853 to 1932 and estimated the probability of persistence in 2011 as <6.4 × 10?5, with a probable extinction date no later than 1980. From an analysis of avian census data (counts of individuals) at 4 sites where searches for the woodpecker were conducted since 2004, we estimated that at most 1–3 undetected species may remain in 3 sites (one each in Louisiana, Mississippi, Florida). At a fourth site on the Congaree River (South Carolina), no singletons (species represented by one observation) remained after 15,500 counts of individual birds, indicating that the number of species already recorded (56) is unlikely to increase with additional survey effort. Collectively, these results suggest there is virtually no chance the Ivory‐billed Woodpecker is currently extant within its historical range in the southeastern United States. The results also suggest conservation resources devoted to its rediscovery and recovery could be better allocated to other species. The methods we describe for estimating species extinction dates and the probability of persistence are generally applicable to other species for which sufficient museum collections and field census results are available. 相似文献
11.
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. 相似文献
12.
Winter mortality has been hypothesized to select for large body size in young-of-the-year (YOY) fishes, yet substantiation of winter mortality and its cause(s) are available for few estuarine or marine species. We examined seasonal length distributions of wild populations of four common marine species, black sea bass (Centropristis striata), tautog (Tautoga onitis), cunner (Tautogolabrus adspersus), and smallmouth flounder (Etropus microstomus), and mortality (i.e., frequency of death), growth, and behavior of their YOY in the laboratory at ambient winter temperatures (mean 7°C, range 2-13°C) during a 135-day period (December 1992 through mid-April 1993) to establish potential causes of their mortality in the field. Young-of-the-year black sea bass experienced 100% mortality when water temperatures decreased to 2-3°C in February, emphasizing the importance of winter emigration from estuaries in this southern species. The low mortality of two labrid species, YOY tautog (14%) and YOY cunner (3%), was consistent with their northern distribution and year-round occurrence in estuarine and nearshore coastal waters. Laboratory mortality of YOY smallmouth flounder (33%) was higher for small (<35 mm total length) fish, suggesting that this small species may experience high winter mortality in estuaries and nearshore coastal waters. Seasonal differences in fish length result potentially from several mechanisms (e.g., mortality and/or migration) that are difficult to assess, but our laboratory experiments suggest that seasonal temperature changes cause size-specific mortality of YOY smallmouth flounder and offshore migration of YOY black sea bass. 相似文献
13.
Estimating soil salinity in different landscapes of the Yellow River Delta through Landsat OLI/TIRS and ETM+ Data 总被引:2,自引:0,他引:2
Soil salinization has increasingly become a serious issue in coastal zone due to global climate changes and human disturbances. Assessment of soil salinity, especially at the landscape scale, is critical to coastal management and restoration. Two data from OLI/TIRS and ETM+ sensors of Landsat satellite were used to compare their ability to invert the spatial pattern of soil salinity in both farmland and salt marsh landscapes in the Yellow River Delta, China, respectively. The results showed that the in situ electrical conductivity (EC a ) of soil, representing soil salinity, were closely related with spectral parameters and salinity indices calculated by the remote sensing data. The results of multiple regression models have showed that nearly all the spectral parameters and salinity indices calculated by OLI/TRIS data were more sensitive to soil salinity than those by ETM+ data. Therefore, the models based on OLI/TIRS data are superior to those on ETM+ data in estimating the spatial pattern of soil salinity in farmland and salt marsh landscapes. Our results were very helpful to evaluate the levels of soil salinization in the Yellow River Delta. 相似文献
14.
Abstract: Nonmarket valuation research has produced economic value estimates for a variety of threatened, endangered, and rare species around the world. Although over 40 value estimates exist, it is often difficult to compare values from different studies due to variations in study design, implementation, and modeling specifications. We conducted a stated‐preference choice experiment to estimate the value of recovering or downlisting 8 threatened and endangered marine species in the United States: loggerhead sea turtle (Caretta caretta), leatherback sea turtle (Dermochelys coriacea), North Atlantic right whale (Eubalaena glacialis), North Pacific right whale (Eubalaena japonica), upper Willamette River Chinook salmon (Oncorhynchus tshawytscha), Puget Sound Chinook salmon (Oncorhynchus tshawytscha), Hawaiian monk seals (Monachus schauinslandi), and smalltooth sawfish (Pristis pectinata). In May 2009, we surveyed a random sample of U.S. households. We collected data from 8476 households and estimated willingness to pay for recovering and downlisting the 8 species from these data. Respondents were willing to pay for recovering and downlisting threatened and endangered marine taxa. Willingness‐to‐pay values ranged from $40/household for recovering Puget Sound Chinook salmon to $73/household for recovering the North Pacific right whale. Statistical comparisons among willingness‐to‐pay values suggest that some taxa are more economically valuable than others, which suggests that the U.S. public's willingness to pay for recovery may vary by species. 相似文献
15.
Linda Harris Stephen Holness Ronel Nel Amanda T. Lombard David Schoeman 《Journal of Coastal Conservation》2013,17(1):143-154
The Benguela Current Large Marine Ecosystem off southwest Africa is a regionally valued system because of its biological productivity, which supports high biomass throughout the foodweb, and a rich diversity of habitats and species. However, the region is exposed to numerous anthropogenic pressures that are likely to escalate under future economic growth. In response, the Benguela Current Commission called for a spatial biodiversity assessment (BCC-SBA) to identify conservation priorities, including potential areas for marine protected areas. The systematic conservation-planning approach to this assessment requires a fine-scale map of coastal habitats, which was not previously available for the region. Our aim was to undertake this mapping, within tight logistic and resource limitations. We used a previously derived methodology for mapping the distribution of coastal habitats from aerial imagery. The Benguela coast is approximately 5,047 km long. Half of this extent is sandy beach, a third is rocky and mixed shores, 13 % comprises lagoonal features, and the remainder (4 %) comprises estuaries and offshore islands. The distribution and extent of these coastal habitats differs substantially alongshore (i.e. with latitude), with conditions ranging north–south from hot, humid mangrove-lined lagoons, to hyper-arid coastal desert sandy beaches. Patterns in regional geology, climate and oceanography are proposed as the main drivers of spatial heterogeneity in coastal habitat types. The resulting ecological and socio-economic wealth requires proactive protection (supported through the BCC-SBA, for example), to ensure sustainable utilization of the rich natural resources, and persistence of these resources for the benefit of current and future generations. 相似文献
16.
Angel Pérez-Ruzafa Concepción Marcos Isabel María Pérez-Ruzafa María Pérez-Marcos 《Journal of Coastal Conservation》2011,15(3):369-392
The European Water Framework Directive (WFD) establishes a well differentiated typology of water bodies on the basis of scientific
and biological criteria. For coastal waters, such criteria have long been established, while for transitional waters they
are still under discussion. One of the difficulties when applying the WFD to coastal lagoons is to include them in only one
of these categories, and while there is no doubt about the nature of estuaries as transitional waters, there is some controversy
concerning lagoons. To what extent, reference conditions may be similar for estuaries and lagoons, or whether features common
to all coastal lagoons are more important for differentiating them from other water bodies than the fact that there is (or
is not) any fresh water influence, is something that remains unclear and is discussed in this work. Coastal lagoons and estuaries
form part of a continuum between continental and marine aquatic ecosystems. Shelter, strong boundaries or gradients with adjacent
ecosystems, anomalies in salinity regarding freshwater or marine ecosystems, shallowness, etc. all contribute to the high
biological productivity of estuaries and lagoons and determine common ecological guilds in the species inhabiting them. On
the other hand, fresh water influence, the spatial organization of gradients and environmental variability (longitudinal one-dimensional
gradients in estuaries versus complex patterns and three-dimensional heterogeneity in lagoons) constitute the main differences,
since these factors affect both the species composition and the dominance of certain ecological guilds and, probably, the
system’s complexity and homeostatic capability. In the context of the WFD, coastal lagoons and estuaries are closer to each
other than they are to continental or marine waters, and, on the basis of the shared features, they could be intercalibrated
and managed together. However, coastal lagoons cannot be considered transitional waters according to the present definition.
To assume that fresh water influence is an inherent characteristic to these ecosystems could lead to important changes in
the ecological organization and functioning of coastal lagoons where natural fresh water input is low or null. In our opinion,
the present day definition of transitional waters should be changed substituting the criterion of fresh water influence by
another based on common features, such as relative isolation and anomalies in salinity in water bodies with marine influence.
Otherwise, coastal lagoons should be considered a particularly characteristic type of water mass for establishing reference
conditions of ecological status. 相似文献
17.
Wenqian CAI Wei MENG Lusan LIU Kuixuan LIN 《Frontiers of Environmental Science & Engineering》2014,8(5):737-746
Based on biologic and environmental materials collected from coastal areas of Bohai Bay (China) in April, 2008, three biotic indices (AZTI's Marine Biotic Index (AMBI), Shannon-Wiener Index and W-statistic) were applied together to evaluate the ecological status of the sampling area. The results showed a clear spatial gradient from a worse ecological status in the near-shore areas (especially around Haihe and Jiyun River Estuaries) to a better status in the offshore areas. While all the three indices could assist decision makers in visualizing spatial changes of organic pollutants in Bohai Bay, two indices, i. e., AMBI and Shannon-Wiener index, were effective in distinguishing sites from Haihe River Estuary, Jiyun River Estuary and other area. However, W-statistic can't tell the differences between estuaries and other area. It would be explained that organic pollutants and/or other environ- mental stresses in Bohai Bay were not strong enough to reduce the size ofmacrozoobenthos, which may cause both of the abundance and biomass curves crossed. To our knowledge, this is the first time that several benthic indices were used to assess the benthic ecological status in Bohai Bay, which gave the similar results. Furthermore, there is indication that the ecological status is related to excess input of wastewater along main rivers and outlets. In a word, AMBI, Shannon-Wiener Index and W-statistic could be able to assess the benthic ecological status of Bohai Bay under the organic pollutants pressure. 相似文献
18.
Modeling estuarine-shelf exchanges in a deltaic estuary: Implications for coastal carbon budgets and hypoxia 总被引:1,自引:0,他引:1
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. 相似文献
19.
Sea ice offers a physical support to the growth of microalgae (epontic community). Almost all the studies on ice microflora in the Arctic and the Antarctic have been performed in waters of high salinities, and they generally reported a very high standing crop. From February through May 1978, 15 stations were sampled in the southeastern part of Hudson Bay (Manitounuk Sound), Quebec, Canada. The peculiar physical condition of the water bodies establishes a salinity gradient in the underlying waters from the mouth of the Great Whale River to the upper reaches of Manitounuk Sound, leading to a parallel gradient in the ice dynamics. The main goal of this study was to examine the effect of these gradients on the biomass and the taxonomic composition of the epontic community. Thus, there are two distinct gradients in the ice, one ruled by the surface-water salinity gradient controlling the ice thickness and the settlement efficiency, which triggers the biomass of the epontic community (higher standing crop in the upper reaches of Manitounuk Sound). In addition, the ice salinity gradient influences the taxonomic composition (lower number of microalgae taxa toward the mouth of the Great Whale River). Salinity of the underlying surface waters, following discriminant analyses of species-based clusters of observations, emerges as a major environmental variable controlling the distribution and abundance of species. In addition to adequate light intensity and nutrient supply, salinity of the underlying waters is therefore another limiting factor to the settlement and growth of an ice microflora. This factor is of great potential significance in coastal and esturine glacial waters. 相似文献
20.
《Ecological modelling》2005,187(4):513-523
Phytoplankton growth in estuaries is controlled by factors such as flushing, salinity tolerance, light, nutrients and grazing. Here, we show that biodiversity of estuarine phytoplankton is related to flushing, and illustrate this for some European estuaries.The implications for the definition of reference conditions for quality elements in estuaries of different types are examined, leading to the conclusion that constraints on the number of estuarine and coastal types that may be defined for management purposes require that quality classes take into account natural variability within types, in order to be ecologically meaningful. We develop a screening model to predict the growth rate required for a phytoplankton species to be present under different flushing conditions and apply it to estuaries in the EU and US to show how changes in physical forcing may alter biodiversity. Additional results are presented on the consequences for eutrophication, showing that changes in residence time may interact with species-specific nutrient uptake rates to cause shifts in species composition, potentially leading to effects such as harmful algal blooms.We discuss applications for integrated coastal zone management, and propose an approach to normalization of estuarine phytoplankton composition as regards species numbers. 相似文献