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1995 Carolinian Province Statistical Summary
Environmental Quality of Estuaries of the Carolinian Province:
1995 Annual Statistical Summary
Hyland, J.L., L. Balthis, C.T. Hackney, G. McRae, A. H. Ringwood, T.R. Snoots, R.F. Van Dolah and T.L. Wade.
1998. NOAA Technical Memorandum NOS ORCA 123. NOAA/NOS Office of Ocean Resources Conservation and Assessment, Silver Spring, MD.
View the document (164 pp, 1.2 Mb, about PDF)
Abstract
A study was conducted to assess the environmental condition of estuaries in the EMAP Carolinian Province (Cape Henry, VA St. Lucie Inlet, FL). A total of 87 randomly located stations was sampled from July 5 September 14, 1995 in accordance with a probabilistic sampling design. Wherever possible, synoptic measures were made of: (1) general habitat condition (depth, physical properties of water, sediment grain-size, organic carbon content), (2) pollution exposure (sediment contaminant concentrations, sediment toxicity, low dissolved oxygen conditions in the water column, ammonia and sulfide in sediment porewater), (3) biotic conditions (diversity and abundance of macroinfauna and demersal biota, pathological disorders in demersal biota), and (4) aesthetic quality (presence of anthropogenic debris, visible oil, noxious sediment odor, water clarity). Percentages of degraded vs. undegraded estuarine area were estimated based on these various environmental indicators. The data also were compared to results of a related EMAP survey conducted in 1994 in this same region as part of a multi-year monitoring effort.
High concentrations of contaminants in sediments were found at 25 of 86 sites with samplable substrates, representing 30% of the province area. The 1994 estimate of contaminated area was much less (12%). PCBs and pesticides (lindane, dieldrin, and DDT and derivatives) were the most dominant sediment contaminants over the two-year period. Analysis of chemical contaminants also was conducted on edible tissues of spot, croaker, blue crab, and penaeid shrimp obtained from a subset of 14 stations throughout the province, including sites where high levels of sediment contamination had been found. All measured analytes in these samples were below corresponding FDA tissue guidelines -- i.e., Action Levels for PCBs, pesticides, and mercury and Levels of Concern in shellfish for five additional metals (arsenic, cadmium, chromium, lead, and nickel).
About 82% of the province area, represented by 76 of the 87 stations, showed some evidence of environmental disturbance based on any one biotic, exposure, or aesthetic indicator. However, co- occurrences of adverse biological and exposure conditions were found in a much smaller proportion of the province -- 29% (represented by 20 stations). Over half of these sites (12) were in North Carolina, as were most degraded sites during the previous 1994 survey. The majority of these sites were characterized by degraded infaunal assemblages accompanied by high sediment contamination and/or sediment toxicity based on Mercenaria (seed clam) and Microtox assays.
Selected data on sediment contamination, sediment toxicity, and macroinfaunal composition (from both years) also were examined to evaluate conditions of Carolinian Province estuaries from the perspective of sediment quality. Each year a sizable portion of the province -- 36% in 1994 and 51% in 1995 -- showed some evidence of either degraded benthic assemblages, contaminated sediment in excess of reported bioeffect guidelines, or high sediment toxicity (significant toxicity in > 50% of assays at a station). Yet, co-occurrences of a degraded benthos and adverse exposure conditions (sediment contamination and/or toxicity) were much less extensive. Such conditions were found at 16 of 82 stations with samplable substrates in 1994 (representing 17% of the province area) and 17 of 86 stations in 1995 (25% of province). Only four sites in 1994 (5% of province) and three sites in 1995 (7% of province) had degraded infauna accompanied by both sediment contamination and toxicity (defined as above) suggesting that strong contaminant-induced effects on the benthos, based on such combined weight-of-evidence, are perhaps limited to a fairly small percentage of estuarine area province-wide.
The broad-scale sampling design of EMAP was not intended to support detailed characterizations of potential pollutant impacts within individual estuarine systems. Thus, some estuaries classified as undegraded may have degraded areas outside the immediate vicinity of the randomly sampled sites. Such localized impacts (not accounted for in the above estimates) were detected in this study at additional nonrandom supplemental sites sampled near anticipated contaminant sources. A strength of the EMAP probability-based sampling design, however, is its ability to support unbiased estimates of ecological condition with known confidence at regional scales. Further sampling in the Carolinian Province should improve the accuracy of these estimates and provide a basis for beginning to assess how the overall quality of these estuaries is changing with time.