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Can Sediment Total Organic Carbon and Grain Size Be Used to Diagnose Organic Enrichment in Estuaries
Citation:
PELLETIER, M. C., D. E. CAMPBELL, KAY T. HO, R. M. BURGESS, C. T. AUDETTE, AND N. E. DETENBECK. Can Sediment Total Organic Carbon and Grain Size Be Used to Diagnose Organic Enrichment in Estuaries. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 30(3):538-547, (2011).
Impact/Purpose:
Eutrophication (i.e., nutrient enrichment, organic enrichment and oxygen depletion) is one of the most common sources of impairment in 303(d) listed waters in the United States and can cause adverse effects to the benthos. However, water column variables tend to be spatially and temporally variable, while sediment measures may be more stable and act to integrate responses over space and time. Sediment organic carbon content has been used as an indicator of enrichment in sediments and is thought to reflect eutrophic conditions. However, anthropogenic contaminants often co-occur with elevated levels of organic carbon. In this paper we investigated the utility of the relationship between organic carbon and sediment grain size as an indicator of eutrophication using data from the US EPA’s Environmental Monitoring and Assessment Program. Contaminant analysis and toxicity tests showed no compelling evidence that the benthic community impairment observed in enriched sites was due to anthropogenic contaminants. The data supported the hypothesis that sites designated as enriched were eutrophied. Dissolved oxygen levels were reduced at enriched sites, while chlorophyll a and nutrients were higher at enriched sites. This suggests that the relationship of organic carbon to grain size in sediments can be used to diagnose eutrophication.
Description:
Eutrophication (i.e., nutrient enrichment, organic enrichment and oxygen depletion) is one of the most common sources of impairment in 303(d) listed waters in the United States. While eutrophication can eventually cause adverse effects to the benthos, it may be hard to diagnose. Sediment organic carbon content has been used as an indicator of enrichment in sediments but the amount of surface area available for carbon adsorption must be considered. We investigated the utility of the relationship between organic carbon and sediment grain size as an indicator of eutrophication. Data from the US EPA’s Environmental Monitoring and Assessment Program was used to test this relationship. However, anthropogenic contaminants are also capable of causing adverse effects to the benthos and often co-occur with elevated levels of organic carbon. Contaminant analysis and toxicity tests showed no compelling evidence that the benthic community impairment observed in enriched sites was due to anthropogenic contaminants. Although there was variability in response reflecting the variance in the water column factors (i.e., dissolved oxygen, chlorophyll a and nutrients) and limited sample sizes, the data supported the hypothesis that sites designated as enriched were eutrophied. Dissolved oxygen levels were reduced at enriched sites, while chlorophyll a and nutrients were higher at enriched sites. This suggests that the relationship of organic carbon to grain size can be used to diagnose eutrophication.