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1.
A benthic index of biotic integrity was developed for use in estuaries of the mid-Atlantic region of the United States (Delaware Bay estuary through Albemarle-Pamlico Sound). The index was developed for the Mid-Atlantic Integrated Assessment Program (MAIA) of the U.S. Environmental Protection Agency using procedures similar to those applied previously in Chesapeake Bay and southeastern estuaries, and was based on sampling in July through early October. Data from seven federal and state sampling programs were used to categorize sites as degraded or non-degraded based on dissolved oxygen, sediment contaminant, and sediment toxicity criteria. Various metrics of benthic community structure and function that distinguished between degraded and reference (non-degraded) sites were selected for each of five major habitat types defined by classification analysis of assemblages. Each metric was scored according to thresholds established on the distribution of values at reference sites, so that sites with low scoring metrics would be expected to show signs of degradation. For each habitat, metrics that correctly classified at least 50% of the degraded sites in the calibration data set were selected whenever possible to derive the index. The final index integrated the average score of the combination of metrics that performed best according to several criteria. Selected metrics included measures of productivity (abundance), diversity (number of taxa, Shannon-Wiener diversity, percent dominance), species composition and life history (percent abundance of pollution-indicative taxa, percent abundance of pollution-sensitive taxa, percent abundance of Bivalvia, Tanypodinae-Chironomidae abundance ratio), and trophic composition (percent abundance of deep-deposit feeders). The index correctly classified 82% of all sites in an independent data set. Classification efficiencies of sites were higher in the mesohaline and polyhaline habitats (81–92%) than in the oligohaline (71%) and the tidal freshwater (61%). Although application of the index to low salinity habitats should be done with caution, the MAIA index appeared to be quite reliable with a high likelihood of correctly identifying both degraded and non-degraded conditions. The index is expected to be of great utility in regional assessments as a tool for evaluating the integrity of benthic assemblages and tracking their condition over time.  相似文献   

2.
Compared to benthic and water-column invertebrate assemblages, considerably less is known about terrestrial arthropods inhabiting estuarine wetlands despite their importance to tidal wetland biodiversity and productivity. We also need to know more about how human modification of estuaries, including efforts to restore estuarine wetlands, affects these assemblages. To address this knowledge gap, we assembled data from multiple studies on terrestrial arthropod assemblages from 87 intertidal wetland sites in 13 estuaries along the west coast of North America. Arthropods were sampled between 1998 and 2013 with fallout traps deployed in wetlands for 1 to 3 days at a time. We describe patterns in the abundance and taxonomic composition of terrestrial arthropods and evaluate the relative ability of natural and anthropogenic factors to explain variation in abundance and composition. Arthropod abundance was highly variable. Vegetation assemblage, precipitation, and temperature best explained variation in arthropod abundance, while river discharge, latitude, and developed and agricultural land cover surrounding sampling sites were less important. Arthropod abundance rapidly achieved levels of reference wetlands after the restoration of tidal influence to leveed wetlands, regardless of surrounding land cover. However, arthropod assemblage composition was affected by the amount of developed land cover as well as restoration age. These results suggest that restoration of tidal influence to leveed wetlands can rapidly restore some components of estuarine wetland ecosystems but that recovery of other components will take longer and may depend on the extent of anthropogenic modification in the surrounding landscape.  相似文献   

3.
Hydrologists have long been concerned with the interface of groundwater flow into estuaries, but not until the end of the last century did other disciplines realize the major role played by groundwater transport of nutrients to estuaries. Mass balance and stable isotopic data suggest that land-derived NO3, NH4, and dissolved organic N do enter estuaries in amounts likely to affect the function of the receiving ecosystem. Because of increasing human occupancy of the coastal zone, the nutrient loads borne by groundwater have increased in recent decades, in spite of substantial interception of nutrients within the land and aquifer components of watersheds. Groundwater-borne nutrient loads have increased the N content of receiving estuaries, increased phytoplankton and macroalgal production and biomass, decreased the area of seagrasses, and created a cascade of associated ecological changes. This linkage between land use and eutrophication of estuaries occurs in spite of mechanisms, including uptake of land-derived N by riparian vegetation and fringing wetlands, “unloading” by rapid water removal, and direct N inputs to estuaries, that tend to uncouple the effects of land use on receiving estuaries. It can be expected that as human activity on coastal watersheds continues to increase, the role of groundwater-borne nutrients to the receiving estuary will also increase.  相似文献   

4.
Macrobenthic community indices were examined for their ability to characterize the influence of shoreline alteration and watershed land use in nearshore estuarine environments of the Chesapeake Bay, U.S.A. Twenty-three watersheds were surveyed in 2002 and 2003 for nearshore macrobenthic assemblages, environmental parameters (i.e., dissolved oxygen, pH, total suspended solids, salinity, and sediment composition), shoreline condition, and land use. Two indices of macrobenthic biological integrity, benthic index of biological integrity in the nearshore (B-IBIN) and abundance biomass comparison (W-value), were evaluated for associations with environmental and shoreline condition, and riparian and watershed land use. Comparisons between nearshore measures of the B-IBI with offshore values (>2 m; Chesapeake Bay benthic index of biological integrity [B-IBICB]) were conducted to assess the ability of the index to reflect land use patterns at near and far proximities to shore. Nearshore macrobenthic communities were represented by a total of 94 species (mean number of species =9.2 ± 0.4 sample−1), and were dominated by the phyla Arthropoda, Annelida, and Mollusca. Temporal variability in environmental conditions and macrobenthic abundance and biomass may be attributable to the notable increase in precipitation in 2003 that led to nutrient influxes and algal blooms. For the biotic indices applied in the nearshore, the highest scores were associated with forested watersheds (W-value, B-IBIN). Ecological thresholds were identified with nonparametric change-point analysis, which indicated a significant reduction in B-IBIN and W-value scores when the amount of developed shoreline exceeded 10% and developed watershed exceeded 12%, respectively.  相似文献   

5.
By applying discriminant analysis to benthic macroinvertebrate data, we have developed an indicator of benthic condition for northern Gulf of Mexico estuaries. The data used were collected by the United states Environmental Protection Agency’s Environmental Monitoring and Assessment Program (EMAP) in the Louisianian Province from 1991 to 1994. This benthic index represents a linear combination of the following weighted parameters: the proportion of expected species diversity, the mean abundance of tubificid oligochaetes, the percent of total abundance represented by capitellid polychaetes, the percent of total abundance represented by bivalve mollusks, and the percent of total abundance represented by amphipods. We successfully validated and retrospectively applied the benthic index to all of the benthic data collected by EMAP in the Louisianian Province. This benthic index was also calculated for independent data collected from Pensacola Bay, Florida, in order to demonstrate its flexibility and applicability to different estuarine systems within the same biogeographic region. The benthic index is a useful and valid indicator of estuarine condition that is intended to provide environmental managers with a simple tool for assessing the health of benthic macroinvertebrate communities.  相似文献   

6.
Development and validation of an estuarine biotic integrity index   总被引：1，自引：0，他引：1  
We tested hypotheses about how estuarine fish assemblages respond to habitat degradation and then integrated these responses into an overall index, the Estuarine Biotic Integrity Index (EBI), which summarized observed changes. Fish assemblages (based on trawl catches) and habitat quality were measured monthly or biweekly at nine sites in two estuaries from March 1988 to June 1990. Submerged aquatic vegetation habitats were classified as low or medium quality based on year-round measurements of chemical and physical characteristics (phytoplankton blooms; macroalgae; dissolved oxygen; nutrients; dredged channels). We tested 15 metrics and selected 8 for inclusion in the EBI: total number of species, dominance, fish abundance (number or biomass), number of nursery species, number of estuarine spawning species, number of resident species, proportion of benthic-associated fishes, and proportion abnormal or diseased. Fish assemblages in low-quality sites had lower number of species, density, biomass, and dominance compared with medium-quality sites. Fish abundance peaked in July and August, and was lowest in January to March. The seasonal cycle in low-quality sites was damped compared with medium-quality sites. Abundances of fishes using estuaries as a spawning and nursery area and of benthic species were lower in low-quality sites compared to medium-quality sites. The individual metrics and the overall index correlated with habitat degradation. The EBI based on biomass did not do better than the EBI based on number, indicating that the extra effort to obtain biomass may not be warranted. We suggest the EBI is a useful indicator of estuarine ecosystem status because it reflects the relationship between anthropogenic alterations in estuarine ecosystems and the status of higher trophic levels.  相似文献   

7.
To use bioassessments to help diagnose or identify the specific environmental stressors affecting estuaries, we need a better understanding of the relationships among sediment chemistry guidelines, ambient toxicity tests, and community metrics. However, this relationship is not simple because metrics generally assess the responses at the community level of biological organization whereas sediment guidelines and ambient toxicity tests generally assess or are based on the responses at the organism level. The relationship may be further complicated by the influence of other chemical and physical variables that affect the bioavailability and toxicity of chemical contaminants in the environment. Between 1990 and 1993, the U.S. Environmental Protection Agency (USEPA) conducted an Environmental Monitoring and Assessment Program (EMAP) survey of estuarine sites in the Virginian Province of the eastern United States. The surveys collected data on benthic assemblages, physical and chemical habitat characteristics, and sediment chemistry and toxicity. We characterized these estuarine sites as affected by sediment contamination based on the exceedence of sediment guidelines or on ambient sediment toxicity tests (i.e., 10-day Ampelisca abdita survival). Then, benthic invertebrate metrics were compared among affected and unaffected sites to identify metrics sensitive to the contamination. A number of benthic invertebrate metrics differed between groups of sites segregated using the organism-level measures whereas other metrics did not. The difference among metrics appears to depend on the sensitivity of the individual metrics to the stressor gradient represented by metals or persistent organic toxics in sediments because the insensitive metrics do not effectively quantify the changes in the benthic invertebrate assemblage associated with these stressors. The significant relationships suggest that a relationship exists between the organism-level effects assessed by chemistry or ambient toxicity tests and the community-level effects assessed by community metrics and that the organism-level effects are predictive, to some extent, of community-level effects.  相似文献   

8.
Spatial patterns of estuarine biota suggest that some nearshore ecosystems are functionally linked to interacting processes of the ocean, watershed, and coastal geomorphology. The classification of estuaries can therefore provide important information for distribution studies of nearshore biodiversity. However, many existing classifications are too coarse-scaled to resolve subtle environmental differences that may significantly alter biological structure. We developed an objective three-tier spatially nested classification, then conducted a case study in the Alexander Archipelago of Southeast Alaska, USA, and tested the statistical association of observed biota to changes in estuarine classes. At level 1, the coarsest scale (100–1000’s km2), we used patterns of sea surface temperature and salinity to identify marine domains. At level 2, within each marine domain, fjordal land masses were subdivided into coastal watersheds (10–100’s km2), and 17 estuary classes were identified based on similar marine exposure, river discharge, glacier volume, and snow accumulation. At level 3, the finest scale (1–10’s km2), homogeneous nearshore (depths <10 m) segments were characterized by one of 35 benthic habitat types of the ShoreZone mapping system. The aerial ShoreZone surveys and imagery also provided spatially comprehensive inventories of 19 benthic taxa. These were combined with six anadromous species for a relative measure of estuarine biodiversity. Results suggest that (1) estuaries with similar environmental attributes have similar biological communities, and (2) relative biodiversity increases predictably with increasing habitat complexity, marine exposure, and decreasing freshwater. These results have important implications for the management of ecologically sensitive estuaries.  相似文献   

9.
Activities of man in rivers and their watersheds have altered enormously the timing, magnitude, and nature of inputs of materials to estuaries. Despite an awareness of large-scale, long-term changes in river-estuarine watersheds, we do not fully understand the consequences to estuarine ecosystems of these activities. Deforestation, urbanization, and agriculturalization have changed the timing and nature of material inputs to estuaries. Conversion of land from forest to almost any other land use promotes overland flow of storm runoff; increases the timing, rate and magnitude of runoff; and increases sediment, organic matter, and inorganic nutrient export. It has been estimated that total organic carbon levels in rivers have increased by a factor of 3–5 over natural levels. Man’s activities have also changed the magnitude of particulate organic carbon relative to dissolved organic carbon export and the lability of the organic matter. Historically, rivers and streams had different features than they do today. Two of man’s activities that have had pronounced effects on the timing and quality of river water are channelization and damming. Agricultural drainage systems, channelized and deepened streams, and leveeing and prevention of overbank flooding have had the combined effect of increasing the amplitude and rate of storm runoff, increasing sediment load, increasing nutrient delivery downstream, and decreasing riparian wetland productivity. Dams on the other hand have altered natural discharge patterns and altered the downstream transfer of sediments, organic matter, and nutrients. Patterns of estuarine community metabolism are sensitive to variations, in the timing, magnitude, and quality of material inputs from watersheds. The autotrophic-heterotrophic nature of an estuary is determined by three primary factors: the ratio of inorganic to organic matter inputs, water residence time, and the overall lability of allochthonous organic matter inputs. A simulation model is used to explore the effects of man’s activities in watersheds on the spatial patterns of production and respiration in a generalized estuarine system. Examined are the effects of variations in the ratios of inorganic and organic nitrogen loading, the residence time of water in the estuary, the degradability of allochthonous organic matter, and the ratio of dissolved to particulate organic matter inputs. Simulations suggest that the autotrophic-heterotrophic balance in estuaries is more sensitive to variations in organic matter loading than inorganic nutrient loading. Water residence time and flocculation-sedimentation of organic matter are two physical factors that most effect simulated spatial patterns of metabolism in estuaries.  相似文献   

10.
We demonstrate that land reclamation in estuaries is resulting in very large-scale loss of intertidal area and disconnection of stored sediment with the water column. This process is not just causing loss of estuarine ecosystem services, it is also having a major deleterious impact on the ability of estuaries to retain nutrients and trace metals. The global scale of loss of estuarine wetlands and subtidal sediments has reached the point where the impact of this loss of estuarine retention is likely to be affecting coastal seas worldwide and possibly global element cycles.  相似文献   

11.
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12.
Organisms and chemicals preserved in sediment cores from the Chesapeake estuary in mid-Atlantic USA are consistent with a precolonial landscape covered with a diversity of forests and marshes, large and small. During the past 300 years, many of the wetlands have been drained, and the landscape was converted to agricultural fields and urban and suburban development. During this time, sources of nitrogen have diversified, and loadings have increased. Since precolonial time, the mesohaline estuary has become increasingly eutrophic and anoxic. Estuaries and coastal regions throughout the world have experienced similar conditions in their recent history. These changes are recorded in Chesapeake sediment cores by increases in ragweed pollen, dry taxa, sedimentation rates, nitrogen influxes, and a major change in estuarine autotrophs from benthic to planktonic. In many areas, attempts to reverse estuarine eutrophication and anoxia have centered on restoring streams and riparian areas and reducing fertilizer use on agricultural lands. However, data from soils and historical reports and the paleoecological record suggest that to reduce the effects of modern nitrogen inputs, it may be necessary to locate and enhance denitrifying areas throughout the watershed.  相似文献   

13.
The invasion of North American tidal marshes byPhragmites australis, or common reed, is a large-scale ecological problem that has been primarily studied at small spatial scales. Previous local-scale studies have provided evidence that the expansion ofPhragmites is facilitated by disturbance and increased nitrogen (N) associated with agricultural and urban-suburban (developed) land uses along wetland-upland borders. We tested the generality of previous findings across a larger spatial scale and wider range of environmental conditions in Chesapeake Bay, the largest estuarine ecosystem in the USA. We sampled 90 tidal wetlands nested within 30 distinct subestuarine watersheds and examined the relationship between land use andPhragmites abundance and foliar N, an indicator of nitrogen availability. We estimated land use adjacent to wetland borders and within subestuary watersheds and explored the importance of spatial proximity by weighting land use by its distance from the wetland border or subestuary shoreline, respectively. Regression tree and changepoint analyses revealed thatPhragmites abundance sharply increased in almost every wetland where development adjacent to borders exceeded 15%. Where development was <15% but natural land cover at the near the subestuary shoreline was low (<∼35%),Phragmites was abundant, suggesting that wetlands in highly modified watersheds also were susceptible to invasion, regardless of land use adjacent to wetlands.Phragmites foliar N was markedly elevated in watersheds with >14–22% shoreline development, the same level of development that corresponded to high levels of invasion. Our results suggest that development near wetlands is at least partially responsible for patterns of invasion across Chesapeake Bay. Larger-scale phenomena, such as nitrogen pollution at the watershed-subestuary scale, also may be facilitating invasion. Urbanization near coastlines appears to play an important role in the invasion success ofPhragmites in coastal wetlands of Chesapeake Bay and probably much of eastern North America.  相似文献   

14.
The continued urbanization of coastal watersheds can influence the quality of water that enters rivers and estuaries. Intelligent management of aquatic resources will require the capability to quantitatively assess and evaluate the impacts of alterations in surface waters that result from changes in patterns of land use. An aquatic ecosystem model was developed and linked to an empirical landscape model to estimate ecological risks posed by nutrients and potentially toxic trace elements (copper [Cu], cadmium [Cd], arsenic [As]) in the Patuxent River, Maryland. The empirical landscape model translated reductions in croplands within the Patuxent River watershed into corresponding changes in nitrate estimated to enter the river. Trace element concentrations were increased in relation to urbanization associated with the loss of agricultural lands in the watershed. The aquatic ecosystem model used the altered inputs of nutrients and trace elements to estimate changes in the annual production dynamics of selected producer and consumer populations within the Patuxent River. The models were implemented for four mainstem locations that defined a transect from the upper freshwater portion of the river to downstream estuarine locations. Ecological impacts were estimated for 4 hypothetical changes in land use that consisted of 10%, 7.5%, 5%, and 2.5% watershed coverage by cropland. Impacts were estimated as the probability (risk) of different magnitudes of increases or decreases in total annual production of populations representative of freshwater and estuarine food webs in the Patuxent River.  相似文献   

15.
Fringing marshes are important but often overlooked components of estuarine systems. Due to their relatively small size and large edge to area ratio, they are particularly vulnerable to impacts from adjacent upland development. Because current shoreland zoning policies aim to limit activities in upland buffer zones directly next to coastal habitats, we tested for relationships between the extent of development in a 100-m buffer adjacent to fringing salt marshes and the structure of marsh plants, benthic invertebrates, and nekton communities. We also wanted to determine useful metrics for monitoring fringing marshes that are exposed to shoreline development. We sampled 18 fringing salt marshes in two estuaries along the coast of southern Maine. The percent of shoreline developed in 100-m buffers around each site ranged from 0 to 91 %. Several variables correlated with the percent of shoreline developed, including one plant diversity metric (Evenness), two nekton metrics (Fundulus heteroclitus %biomass and Carcinus maenas %biomass), and several benthic invertebrate metrics (nematode and insect/dipteran larvae densities in the high marsh zone) (p?<?0.05). Carcinus maenas, a recent invader to the area, comprised 30–97 % of the nekton biomass collected at the 18 sites and was inversely correlated with Fundulus %biomass. None of these biotic metrics correlated with the other abiotic marsh attributes we measured, including porewater salinity, marsh site width, and distance of the site to the mouth of the river. In all, between 25 and 48 % of the variance in the individual metrics we identified was accounted for by the extent of development in the 100-m buffer zone. Results from this study add to our understanding of fringing salt marshes and the impacts of shoreline development to these habitats and point to metrics that may be useful in monitoring these impacts.  相似文献   

16.
Long-term interdisciplinary studies of the Rhode River estuary and its watershed in the mid-Atlantic coastal plain of North America have measured fluxes of nitrogen and phosphorus fractions through the hydrologically-linked ecosystems of this landscape. These ecosystems are upland forest, cropland, and pasture; streamside riparian forests; floodplain swamps; tidal brackish marshes and mudflats; and an estuarine embayment. Croplands discharged far more nitrogen per hectare in runoff than did forests and pastures. However, riparian deciduous hardwood forest bordering the cropland removed over 80 percent of the nitrate and total phosphorus in overland flows and about 85 percent of the nitrate in shallow groundwater drainage from cropland. Nevertheless, nutrient discharges from riparian forests downslope from croplands still exceeded discharges from pastures and other forests. The atomic ratio of nitrogen to phosphorus discharged from the watersheds into the estuary was about 9 for total nutrients and 6 for inorganic nutrient fractions. Such a low N:P ratio would promote nitrogen rather than phosphorus limitation of phytoplankton growth in the estuary. Estuarine tidal marshes trapped particulate nutrients and released dissolved nutrients. Subtidal mudflats in the upper estuary trapped particulate P, released dissolved phosphate, and consumed nitrate. This resulted in a decrease in the ratio of dissolved inorganic N:P in the estuary. However, the upper estuary was a major sink for total phosphorus due to sediment accretion in the subtidal area. Bulk precipitation accounted for 31 percent of the total nongaseous nitrogen influx to the landscape, while farming accounted for 69 percent. Forty-six percent of the total non-gaseous nitrogen influx was removed as farm products, 53 percent either accumulated in the watershed or was lost in gaseous forms, and 1 percent entered the Rhode River. Of the total phosphorus influx to the landscape, 7 percent was from bulk precipitation and 93 percent was from farming. Forty-five percent of the total phosphorus influx was removed as farm products, 48 percent accumulated in the watershed, and 7 percent entered the Rhode River. These nitrogen and phosphorus discharges into the Rhode River, although a small fraction of total loadings to the watershed, were large enough to cause seriously overenriched conditions in the upper estuary.  相似文献   

17.
A benthic index of environmental condition of Gulf of Mexico estuaries   总被引：1，自引：0，他引：1  
An index was developed for estuarine macrobenthos in the Gulf of Mexico that discriminated between areas with degraded environmental conditions and areas with undegraded or reference conditions. Test sites were identified as degraded or reference based on criteria for dissolved oxygen levels, sediment toxicity tests, and sediment contamination. Discriminant analysis was used to identify a suite of measures of benthic community composition and diversity that would most successfully distinguish degraded from undegraded sites. The resultant benthic index was composed of a linear combination of three factors: the Shannon-Wiener diversity index, the proportion of total benthic abundance as tubificid oligochaetes, and the proportion of total benthic abundance as bivalve molluscs. This index was used to evaluate the spatial patterns of degraded benthic resources in the Gulf of Mexico.  相似文献   

18.
Tropical estuaries are increasingly altered by inputs from watersheds subject to widespread deforestation, as well as by globally driven hydrodynamic changes in adjoining seas. To assess contributions of C4 and C3 plants (from pasture and forest vegetation cover, respectively) to particulates exported from Pacific Panama watersheds, we measured δ13C and δ15N in suspended particulate matter (SPM) within eight mangrove estuaries whose watersheds differed in degree of conversion from forest to pasture land cover. These measurements also allowed evaluation of down-estuary transformations and the relative marine influence on transport and exchanges of particles between land, estuary, and sea. Imprint of watershed mosaic was detectable in δ13C of SPM within upper reaches of estuaries but disappeared down-estuary. Detectably heavier δ13C suggested that C4 plants contributed to SPM in upper reaches of estuaries. δ13C signatures were sufficiently sensitive to reveal presence of a small, but still detectable, contribution by C4 grasses to SPM. Influence of heavier marine-derived sources increased down-estuary, erasing terrestrial imprints. δ13C and δ15N in SPM, and in mangrove species present, became enriched down-estuary, likely from increased inputs of particulates bearing heavier signatures from upwelled waters. In this tropical Pacific region, estuarine particulates are subject to increasing shifts in land cover as deforestation increases, and to global-scale changes in hydrodynamic forcing of upwelled waters.  相似文献   

19.
Nitrogen (N) loading to estuaries has become a major concern for coastal planners. As urban development on coastal watershed continues, estuaries and bays are becoming more eutrophic, and cascading effects are being felt at every trophic level. Managers and stakeholders need to have a suite of effective management tools that can be applied to coastal watersheds to minimize the effects of eutrophication. We applied an N loading model and an estuarine loading model to examine the effectiveness of a suite of potential management options that could be implemented in Waquoit Bay, Cape Cod, Massachusetts. This estuarine system is a case study in which we can explore the relative potential effectiveness of decreasing inputs from wastewater and fertilizer-derived N, diverting nitrogenous runoff from impervious surfaces, altering zoning ordinances, preserving forested tracts of land as well as freshwater and saltwater wetlands, harvesting macroalgae, dredging estuary channels, and exterminating waterfowl. From a combination of simulation results, assessment of the magnitude of loads from different sources, and through different land covers, and the additional consideration of feasibility we identified management options with high, intermediate, and low potential effectiveness. Improvement of septic system performance, use of zoning regulations, preservation of forested tracts and freshwater bodies, and conservation of salt marshes emerged as the most promising avenues to manage N loads in our system. Installation of wastewater treatment plants, controlling fertilizer use, and harvesting macroalgae would potentially have intermediate success. Diversion of runoff from impervious surfaces, dredging, and extermination of waterfowl show little promise at reducing N loads. These conclusions potentially set priorities for decision-makers charged with the management of Waquoit Bay. The same procedures applied to another watershed-estuary system with different land covers and different estuarine features may differ. Evaluation studies like this need to be done for any particular site, since the watershed-estuary coupling and the loads delivered to the receiving estuary could differ. The Waquoit Bay case study provides an example of a protocol that leads to identification of the most promising management options.  相似文献   

20.
We applied an index of estuarine biotic integrity (EBI) to 36 sites in 16 estuaries on Cape Cod and in Buzzards Bay, Massachusetts, U.S. Two estuaries were sampled in 6 years, from 1988–1999 (Waquoit and Buttermilk Bays), and a total of 14 others in Buzzards Bay were sampled in 1993, 1996, and 1998. Habitats at each site were classified as either low or medium quality by density and biomass of submerged rooted vegetation (eelgrass). The EBI and its metrics (fish abundance, biomass, total species, species dominance, life history, and proportion by life zone) were successful in classifying habitat quality. Greatest success and least bias of the EBI and its metrics in classifying habitat quality occurred when eelgrass habitats were least degraded. The EBI tracked habitat degradation over time in Waquoit and Buttermilk Bays. Average EBI values in medium-quality habitats of Buzzards Bay estuaries during 1996 and 1998 were less than expected based on earlier EBI values from Waquoit and Buttermilk Bays, suggesting that many of these sites are in transition from medium to low quality. Our results indicate that the EBI is sensitive to habitat quality change, and further suggest that low-quality habitats may approach a stable fish community structure that is well reflected by the EBI. The relationship of the EBI to an independent measure of water quality demonstrated inherent time lags between the degradation and improvement of water quality, fish habitat, and response of the fish community.  相似文献   

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