Polycyclic aromatic hydrocarbon contamination in South Carolina salt marsh-tidal creek systems: relationships among sediments, biota, and watershed land use.

Sediments and biota from 11 tidal creeks were sampled and classified into forested, suburban, and urban/industrial watershed land-use categories. Total PAH levels ( summation operatorPAH(16)) in sediments were significantly higher in urban/industrialized creeks (5,795 +/- 1,173 ng/g) compared to suburban (793 +/- 131 ng/g) and forested (238 +/- 34 ng/g) creeks. No differences in summation operatorPAH(16) levels among land-use classifications were found for either oligochaetes (Monopylephorus rubroniveus) or grass shrimp (Palaemonetes pugio). However, summation operatorPAH(16) levels in grass shrimp were related to sediment summation operatorPAH(16) levels and summation operatorPAH(16) levels in oligochaetes and grass shrimp eggs were related to impervious cover in the watershed. Diagnostic ratios suggest that the primary sources of PAH in suburban and urban/industrialized creeks are pyrogenic. Carcinogenic PAH contents of sediments and biota were related to impervious cover. While human exposures to these sediment-associated carcinogens were not assessed, levels of several carcinogenic PAHs in sediments of urban/industrial tidal creeks were above the levels that represent an increased cancer risk in humans.

Effects of changing land use on the microbial water quality of tidal creeks.

Population growth along the southeastern United States coast has precipitated the conversion of forested watersheds to suburban and urban ones. This study sampled creeks representing forested, suburban, and urban watersheds along a longitudinal gradient for indicators of water quality, including traditional indicator bacteria (fecal coliforms and enterococci) and alternative viral indicators (male-specific and somatic coliphages). Tested microorganisms were generally distributed with highest concentrations in creek headwaters and in more developed watersheds. The headwaters also showed the strongest predictive relationship between indicator concentrations and urbanization as measured by impervious cover. A seasonal pattern was observed for indicator bacteria but not for indicator viruses. Coliphage typing indicated the likely source of contamination was nonhuman. Results suggest that headwater creeks can serve as sentinel habitat, signaling early warning of public health concerns from land-based anthropogenic activities. This study also implies the potential to eventually forecast indicator concentrations under land use change scenarios.

Development of a data management framework in support of southeastern tidal creek research.

The NOAA Center of Excellence for Oceans and Human Health Initiative (OHHI) at the Hollings Marine Laboratory (HML) is developing a data management framework that supports an integrated research program across scientific disciplines. The primary focus of the database is to support environmental research focused on tidal creek watershed systems. Specifically, the current data holdings include physical water quality parameters, nutrients, pathogens, chemical contaminants, benthic and nekton species abundances and human dimensions data from Georgia, North Carolina and South Carolina dating to 1994. These data are not from a single long-term research project but are derived from several state and federal research programs and integrated into a common database model to support current research being conducted under the OHHI program at HML. The Tidal Creek database was developed with the intent to support a well documented and open system, thus metadata elements from common metadata standards including the Dublin Core ISO 15836:2003 and Federal Geographic Data Committee (FGDC-STD-001-1998) are components of the database model. The result is a semantic database framework with descriptive ancillary data at the record level including methods, investigator names, date, locations and other descriptive elements. The primary users of the database are project personnel to meet analytical needs. The database is also available through a number of web-based applications that are designed to give users the necessary information to evaluate and access data. In addition, data can be accessed with Open Geospatial Consortium (OGC) standards, and species records and abundances are being made available to the Ocean Biogeographic Information System (OBIS). Overall, the Tidal Creek database summarizes the response of tidal creeks and watersheds to coastal development, and serves as a repository for environmental, demographic, and socioeconomic data in the Southeast.

Comparative tolerance of two estuarine annelids to fluoranthene under normoxic and moderately hypoxic conditions.

The tolerance of the oligochaete Monopylephorus rubroniveus and the polychaete Streblospio benedicti to sediment-associated fluoranthene was characterized under normoxic (>80% dissolved oxygen saturation) and moderately hypoxic ( approximately 50% dissolved oxygen saturation) conditions. Under both conditions, M. rubroniveus was highly tolerant of fluoranthene. Streblospio benedicti was considerably less tolerant of fluoranthene compared with M. rubroniveus. In addition, S. benedicti was less tolerant to fluoranthene under moderately hypoxic conditions, although no differences in sensitivity between the two oxygen conditions were observed based upon median lethal tissue residues. Bioaccumulation factors were higher for S. benedicti exposed to moderate hypoxia, suggesting that behavioral adaptations to compensate for the lower dissolved oxygen increased its bioaccumulation of fluoranthene. The results of the present laboratory study demonstrate that (1). changes in annelid tolerance to fluoranthene under varying oxygen conditions is a species-dependent phenomenon and (2). the differential tolerance of these two annelids to these combined stressors is consistent with their relative abundances in the field.

Evaluation of the impacts of dock structures and land use on tidal creek ecosystems in South Carolina estuarine environments.

Tidal creeks and their associated salt marshes are the primary link between uplands and estuaries in the southeastern region. They are also critical nursery and feeding grounds. In addition, the uplands surrounding creeks are preferred sites for homebuilding because of their natural beauty and the ability to access the estuary from a personal dock structure. The objective of this study was to evaluate the cumulative impacts of docks on tidal creek nursery habitats for both small and large tidal creeks. The number of docks was associated with the amount of impervious cover in both small and large creeks. The presence of docks had little measurable effect on sediment metal concentrations at the scale of small and large creeks. In small and large creeks, sediment polycyclic aromatic hydrocarbon (PAH) concentrations were related to the human activity in the upland that includes the presence of docks at the scale of small and large creeks. Some impacts on the benthic community were associated with docks and human activity in small creeks but not in large creeks. Suburban development may reduce fish and crustacean abundances, but the dock may potentially mediate the development effect. Individually, the harm to the marine environment resulting from dock shading, chrominated copper arsenate leachates, and PAH contamination was small at the scale of tidal creeks. However, impacts from dock structures could not be separated from anthropogenic watershed-scale effects. These results demonstrate that suburban development with its accompanying dock construction does represent a major source of environmental degradation to tidal creeks and associated salt marsh habitats.

Cumulative impacts of dock shading on Spartina alterniflora in South Carolina estuaries.

Salt marshes dominated by Spartina alterniflora and the associated networks of tidal creeks that drain them are characteristic geographical features of southeastern estuaries, important nursery habitat areas, and preferred sites for residential development. As the size of the coastal population increases, so has the number of requests for dock permits. With each new request for a dock permit, public concerns about the cumulative environmental impacts of dock proliferation on the coastal environment have increased. The objective of this particular study was to evaluate the impacts of shading by dock structures on stem densities of S. alterniflora in South Carolina coastal marshes. Shading impacts under individual docks were extrapolated to the tidal creek (local), county, and statewide scales. Dock structures were sampled both under and next to the walkway in the Charleston Harbor area of South Carolina. The density of S. alterniflora under docks was significantly lower than that which occurred next to the docks (i.e., 5 m away) for the short-form, tall-form, and both forms combined. We estimated that shading effects from dock structures in South Carolina decreased the stem density of S. alterniflora by 71%. Dock shading effects were small when evaluated from the perspective of the amount of marsh that occurs within specific tidal creeks (0.03-0.72%), in coastal counties at a maximum dock length (0.01-0.98%), or statewide (0.01-0.13%) at a maximum dock length. However, approximately 7,000 docks have been permitted over the last decade, resulting in a loss of salt marsh equivalent to 60 ha.

Bioaccumulation and toxicity of fluoranthene in the estuarine oligochaete Monopylephorus rubroniveus.

The tolerance of the estuarine oligochaete Monopylephorus rubroniveus to fluoranthene was characterized both in the presence and absence of ultraviolet (UV) radiation. Using waterborne exposures, the 72-h median lethal concentration (LC(50)) and median lethal dose (LD(50)) were 0.7 (95% CI, 0.4-0.8) microg/L and 8.0 (5.6-9.6) microg/g worm dry weight, respectively, in the presence of UV radiation [UV-A=64.7+/-1.0 mu W/cm(2) (mean+/-standard deviation)]. In the absence of UV radiation, little mortality was observed, even at the water solubility limits of fluoranthene (120.4 microg/L). Mean bioconcentration factors across all treatments was 10,893+/-2828. Using sediment exposures, little mortality was observed following 10 days at concentrations as high as 3912 microg fluoranthene/g sediment dry weight in both the presence of UV radiation (UV-A=108.4+/-1.3 mu W/cm(2)) and its absence. Bioaccumulation of sediment-associated fluoranthene was comparatively high and varied little among the five sediment treatments. The results of the present study demonstrate that M. rubroniveus is (1) sensitive to waterborne fluoranthene in the presence of UV radiation and (2) highly tolerant of fluoranthene in the presence of sediment, despite the ability to bioaccumulate fluoranthene to comparatively high levels. These findings suggest that those environmental factors which could potentially increase their exposure to UV radiation need to be considered when assessing the overall risk of fluoranthene to M. rubroniveus.