Grantee Research Project Results
Final Report: Validation of Sediment Quality Criteria in Southeastern Estuaries
EPA Grant Number: R826201Title: Validation of Sediment Quality Criteria in Southeastern Estuaries
Investigators: Ringwood, Amy Huffman
Institution: South Carolina Department of Natural Resources , Marine Resources Research Institute
EPA Project Officer: Aja, Hayley
Project Period: December 1, 1997 through November 30, 2000 (Extended to November 30, 2001)
Project Amount: $449,794
RFA: Contaminated Sediments (1997) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Hazardous Waste/Remediation , Land and Waste Management
Objective:
Validation of models for establishing sediment quality criteria requires concurrent assessments of a variety of physicochemical parameters and biological effects. Therefore, multidisciplinary studies were conducted to evaluate the various parameters and models for estimating potential biological effects due to metal contamination in southeastern estuaries. These studies were used to evaluate the relationships between sediment and water parameters, biological responses of infaunal and epifaunal bivalves (laboratory and in situ toxicity assays and in situ bioaccumulation and toxicity studies), and benthic community assessments for metal contaminated sediments. These data then were used to evaluate various assessment approaches based on integrated analyses (e.g., equilibrium partitioning, interstitial water toxicity, apparent effects threshold, sediment quality triad; and individual parameters such as sediment metal concentrations, sediment grain size, organic composition, salinity, pH, and dissolved oxygen [DO] conditions of associated bottom waters), for predicting metal toxicity and bioaccumulation in bivalves and benthic communities. These approaches and results provide valuable insights for developing sediment quality criteria so that integrated assessment strategies can be appropriately applied and interpreted to reduce long-term chronic adverse effects on estuarine systems.
Summary/Accomplishments (Outputs/Outcomes):
This multiyear study yielded valuable data for evaluating relationships between environmental factors and bioavailability of metals to benthic invertebrates. Oysters and clams were used as the primary model systems for studying how sediment characteristics (e.g., acid volatile sulfide [AVS], total organic carbon [TOC]) and overlying water column conditions (e.g., salinity, pH, DO) could affect bioaccumulation and physiological responses. The data also were used to evaluate sediment quality models (e.g., sediment quality triad, interstitial water toxicity unit [IWTU]). These studies revealed some very interesting species-specific differences as well as similarities, new insights regarding relationships between natural habitat factors (such as salinity and pH), physiological responses, and important findings regarding metal bioavailability and physiological effects. Summary maps show that sediment quality triad components (sediment contaminants, 7-day laboratory clam toxicity, benthic community) plus a fourth indicator, 7-day in situ clam toxicity, were generated. When there is high concordance between all of the components, our ability to designate a site as reference or degraded is very good.. There were sites that were not so readily categorized that could represent some level of degradation (anthropogenic or natural) and it would be important to further investigate these areas to determine if there are management strategies that can be used to improve habitat conditions before the effects are more serious or irreversible. A more extended tabular summary of the various exposure variables and biological response variables also was produced as an expanded weight of evidence approach. In general, degraded sites tend to have higher sediment metal concentrations, higher oyster tissue metal concentrations, adverse effects on clam and oyster growth, and degraded benthic communities. When adverse effects on growth or benthic communities occur with little evidence of metal contaminants in sediments or tissues, it may be deduced that other factors are responsible. In the case of reference sites, this may be due to natural stressors or the presence of contaminants not measured; in the case of degraded sites, other contaminants such as polycyclic aromatic hydrocarbons and pesticides may be responsible for the observed effects. Overall, the data indicated that AVS equilibrium partitioning or IWTU approaches are very poor predictors of adverse effects or bioaccumulation.
Some of the most significant generalizations from this work are described in the following paragraphs. In situ toxicity tests and assessments generally were more sensitive as indicators of contaminant exposures than laboratory assays. Salinity and pH were important determinants of clam growth in situ under nonpolluted conditions, but oyster growth was not as affected by natural environmental factors, and both oysters and clams showed a strong tendency to bioaccumulate Zn and Cu at concentrations that were related to total sediment levels and SEM. Zn tissue concentrations generally were much higher than all of the other metals and comprised approximately 90 percent of the total tissue metals.
Porewater metal concentrations generally were lower than the 7-day clam growth EC50 values (derived from aqueous exposures), and the IWTU model did not reliably predict the potential for toxicity or bioaccumulation. Although there was evidence that factors such as AVS and TOC could modulate metal bioavailability, the AVS model (e.g., only metal concentrations in excess of AVS would be bioavailable) consistently failed to predict observed accumulation of metals. The Zn and Cu tissue concentrations in oysters were significantly related to salinity regimes. This reflects, in part, the tendency for high pollution levels in lower salinity areas, and also is believed to reflect the importance of salinity regimes to metal bioavailability. Physiological responses (growth and condition index) of oysters and clams were significantly related to tissue metals levels (Zn, Cu, and Ni). Physiological responses were more variable at low metal concentrations, but when critical toxic thresholds were exceeded, the physiological condition declined in a highly significant dose-dependent manner that was characterized by low variation.
Although current effects range-low (ERL) values for Cu and Zn may be sufficiently protective for oysters, the results indicate the potential for adverse effects on clams at much lower concentrations. Benthic community analyses (e.g., the Benthic Index of Biological Integrity [B-IBI], etc.) indicated a tendency for degraded conditions at the more polluted sites during both winter and summer seasons. There were significant correlations between sediment Zn and Cu levels and the B-IBI and significant relationships between oyster tissue Zn and Cu levels and the B-IBI. Finally, integrated assessments based on models such as the sediment quality triad and more extended weight-of-evidence approaches continue to be valuable for identifying contaminant-stressed habitats. These studies further illustrate the value of improving the efficacy of these approaches with in situ assessments based on physiological and bioaccumulation responses.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
Other project views: | All 20 publications | 5 publications in selected types | All 4 journal articles |
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Type | Citation | ||
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Keppler CJ, Ringwood AH. Effects of metal exposures on juvenile clams, Mercenaria mercenaria. Bulletin of Environmental Contamination and Toxicology 2002;68(1):43-48. |
R826201 (2001) R826201 (Final) |
not available |
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Ringwood AH, Keppler CJ. Comparative in situ and laboratory sediment bioassays with juvenile Mercenaria mercenaria. Environmental Toxicology and Chemistry 2002;21(8):1651-1657. |
R826201 (2001) R826201 (Final) |
not available |
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Ringwood AH, Hoguet J, Keppler C. Seasonal variation in lysosomal destabilization in oysters, Crassostrea virginica. Marine Environmental Research 2002;54(3-5):793-797. |
R826201 (Final) |
not available |
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Ringwood AH, Keppler CJ. Water quality variation and clam growth: Is pH really a non-issue in estuaries? Estuaries 2002;25(5):901-907. |
R826201 (2001) R826201 (Final) |
not available |
Supplemental Keywords:
integrated assessment, metals, environmental chemistry, Southeast, ecological affects, bioavailability, marine, estuary, indicators., RFA, Scientific Discipline, Waste, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Contaminated Sediments, Environmental Chemistry, Geochemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, Ecological Effects - Environmental Exposure & Risk, Southeast, Ecological Risk Assessment, Ecology and Ecosystems, Ecological Indicators, ecological exposure, risk assessment, estuaries, validation of models, sediment porewater parameters, Southeastern Estuaries, benthic biota, bioavailability, contaminated sediment, Ammonia, sediment, sediment quality survey, sediment quality criteria, water quality, ecology assessment models, metal contamination, marine ecosytems, pysicochemical parametersProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.