R. Scott Carr

Bio: R. Scott Carr is an academic researcher from Texas A&M University. The author has contributed to research in topics: Bay & Estuary. The author has an hindex of 8, co-authored 11 publications receiving 1145 citations.

Development and evaluation of sediment quality guidelines for Florida coastal waters.

Abstract: The weight-of-evidence approach to the development of sediment quality guidelines (SQGs) was modified to support the derivation of biological effects-based SQGs for Florida coastal waters. Numerical SQGs were derived for 34 substances, including nine trace metals, 13 individual polycyclic aromatic hydrocarbons (PAHs), three groups of PAHs, total polychlorinated biphenyls (PCBs), seven pesticides and one phthalate ester. For each substance, a threshold effects level (TEL) and a probable effects level (PEL) was calculated. These two values defined three ranges of chemical concentrations, including those that were (1) rarely, (2) occasionally or (3) frequently associated with adverse effects. The SQGs were then evaluated to determine their degree of agreement with other guidelines (an indicator of comparability) and the percent incidence of adverse effects within each concentration range (an indicator of reliability). The guidelines also were used to classify (using a dichotomous system: toxic, with one or more exceedances of the PELs or non-toxic, with no exceedances of the TELs) sediment samples collected from various locations in Florida and the Gulf of Mexico. The accuracy of these predictions was then evaluated using the results of the biological tests that were performed on the same sediment samples. The resultant SQGs were demonstrated to provide practical, reliable and predictive tools for assessing sediment quality in Florida and elsewhere in the southeastern portion of the United States.

Sediment quality triad assessment survey of the Galveston Bay, Texas system.

Abstract: To characterize the quality of sediments at key sites in the Galveston Bay Estuary, sediment samples were collected concurrently for chemical and physical analyses, toxicity testing and an assessment of benthic community structure. Significant toxicity, as determined by the sea urchin (Arbacia punetulata) pore water embryological development assay, was observed at 12 of the 24 sites investigated in this study. No toxicity was observed at any of the sites with the amphipod (Grandidierella japonica) solid-phase test. There were a number of sites with elevated levels of trace metals and petroleum hydrocarbons. The chemistry, toxicity and benthic data were ranked by station and a scaled rank sum was calculated to facilitate comparisons among the stations. Five sites exhibited strong evidence of contaminant-induced degradation, while 15 stations showed no evidence of contaminant-induced degradation. At eight additional sites the sediment quality triad (SQT) data indicated that unmeasured chemicals or conditions were stressing the system. Contaminant impacts could be reduced or eliminated by alternative regulatory and management practices, including the restriction of produced water discharges into coastal estuaries and the use of dredge material disposal practices that minimize the reintroduction of sediment-associated contaminants to the bays.

Histopathologic and Biochemical Responses in Arctic Marine Bivalve Molluscs Exposed to Experimentally Spilled Oil

Abstract: Following two experimental spills of chemically dispersed and undispersed crude oil in shallow bays on the northwest coast of Baffin Island, Canadian Arctic, the bivalve molluscs Myu truncutu and Mucomu culcureu accumulated significant amounts of petroleum hydrocarbons in bays receiving dispersed oil and in those receiving crude oil alone (Boehm et al., 1987). Following the spills, Myu released accumulated hydrocarbons more rapidly than Mucomu. Specimens of Myu truncutu and Mucomu culcureu for histopathologic examination were collected immediately before, immediately after and one year after the experimental oil spills. Immediately after the spill there was an increased incidence of gill and digestive tract necrosis in Myu from the bays receiving chemically dispersed oil (Bays 7, 9 and 10). This was accompanied by an increase in the number of mucus cells in the digestive tract epithelium. After one year a few clams had granulocytomas throughout the tissues. Three clams from Bay 1 1 (receiving oil alone) collected one year after the spill had invasive neoplasias (probably cancer). One clam collected from Bay 7 immediately after the spill had a similar lesion. There were few lesions in Mucomu from Bays 7 and 9 immediately after orne year after the spill. One year after the spill, animals from Bay 1 1 had a high incidence of vacuolization of the digestive tubule epithelium. The incidence of parasitism and hemocytic infiltration also was higher in Mucomu from Bay 11 than from the other bays. One specimen had a blood neoplasm. Clams Myu truncutu were collected for biochemical analysis immediately before, immediately after and about two weeks after the simulated oil spills. Concentrations in the clam tissues of glucose, glycogen, trehalose, total lipid and free amino acids were measured. Concentrations and ratios of free amino acids in adductor muscles were the most useful indices of pollutant stress. The results of the biochemical analyses indicate that Myu from the four bays were not severely stressed by either dispersed oil or oil alone. Immediately after the spill, clams from the two major dispersed oil bays, and particularly Bay0, appeared to be more severely stressed than clams from Bay 11. After two weeks, clams from the dispersed oil bays were nearly normal, while those from the bay receiving oil alone appeared stressed. These results seem to corroborate results from analytical chemistry and histopathology: that the acute effects of dispersed oil are greater than those of undispersed oil, but effects of undispersed oil on infaunal molluscs develop more slowly and persist longer than those from dispersed oil.

Magnitude and extent of chemical contamination and toxicity in sediments of Biscayne Bay and vicinity

Abstract: The toxicity of sediments in Biscayne Bay and many adjoining tributaries was determined as part of a bioeffects assessments program managed by NOAA’s National Status and Trends Program. The objectives of the survey were to determine: (1) the incidence and degree of toxicity of sediments throughout the study area; (2) the spatial patterns (or gradients) in chemical contamination and toxicity, if any, throughout the study area; (3) the spatial extent of chemical contamination and toxicity; and (4) the statistical relationships between measures of toxicity and concentrations of chemicals in the sediments. The survey was designed to characterize sediment quality throughout the greater Biscayne Bay area. Surficial sediment samples were collected during 1995 and 1996 from 226 randomly-chosen locations throughout nine major regions. Laboratory toxicity tests were performed as indicators of potential ecotoxicological effects in sediments. A battery of tests was performed to generate information from different phases (components) of the sediments. Tests were selected to represent a range in toxicological endpoints from acute to chronic sublethal responses. Toxicological tests were conducted to measure: reduced survival of adult amphipods exposed to solid-phase sediments; impaired fertilization success and abnormal morphological development in gametes and embryos, respectively, of sea urchins exposed to pore waters; reduced metabolic activity of a marine bioluminescent bacteria exposed to organic solvent extracts; induction of a cytochrome P-450 reporter gene system in exposures to solvent extracts; and reduced reproductive success in marine copepods exposed to solid-phase sediments. Contamination and toxicity were most severe in several peripheral canals and tributaries, including the lower Miami River, adjoining the main axis of the bay. In the open basins of the bay, chemical concentrations and toxicity generally were higher in areas north of the Rickenbacker Causeway than south of it. Sediments from the main basins of the bay generally were less toxic than those from the adjoining tributaries and canals. The different toxicity tests, however, indicated differences in severity, incidence, spatial patterns, and spatial extent in toxicity. The most sensitive test among those performed on all samples, a bioassay of normal morphological development of sea urchin embryos, indicated toxicity was pervasive throughout the entire study area. The least sensitive test, an acute bioassay performed with a benthic amphipod, indicated toxicity was restricted to a very small percentage of the area. Both the degree and spatial extent of chemical contamination and toxicity in this study area were similar to or less severe than those observed in many other areas in the U.S. The spatial extent of toxicity in all four tests performed throughout the bay were comparable to the “national averages” calculated by NOAA from previous surveys conducted in a similar manner. Several trace metals occurred in concentrations in excess of those expected in reference sediments. Mixtures of substances, including pesticides, petroleum constituents, trace metals, and ammonia, were associated statistically with the measures of toxicity. Substances most elevated in concentration relative to numerical guidelines and associated with toxicity included polychlorinated biphenyls, DDT pesticides, polynuclear aromatic hydrocarbons, hexachloro cyclohexanes, lead, and mercury. These (and other) substances occurred in concentrations greater than effects-based guidelines in the samples that were most toxic in one or more of the tests. (PDF contains 180 pages)

Magnitude and extent of sediment toxicity in selected estuaries of South Carolina and Georgia

Abstract: Toxic chemicals can enter the marine environment through numerous routes: stormwater runoff, industrial point source discharges, municipal wastewater discharges, atmospheric deposition, accidental spills, illegal dumping, pesticide applications and agricultural practices. Once they enter a receiving system, toxicants often become bound to suspended particles and increase in density sufficiently to sink to the bottom. Sediments are one of the major repositories of contaminants in aquatic envronments. Furthermore, if they become sufficiently contaminated sediments can act as sources of toxicants to important biota. Sediment quality data are direct indicators of the health of coastal aquatic habitats. Sediment quality investigations conducted by the National Oceanic and Atmospheric Administration (NOAA) and others have indicated that toxic chemicals are found in the sediments and biota of some estuaries in South Carolina and Georgia (NOAA, 1992). This report documents the toxicity of sediments collected within five selected estuaries: Savannah River, Winyah Bay, Charleston Harbor, St. Simons Sound, and Leadenwah Creek (Figure 1). (PDF contains 292 pages)

Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems.

Abstract: Numerical sediment quality guidelines (SQGs) for freshwater ecosystems have previously been developed using a variety of approaches. Each approach has certain advantages and limitations which influence their application in the sediment quality assessment process. In an effort to focus on the agreement among these various published SQGs, consensus-based SQGs were developed for 28 chemicals of concern in freshwater sediments (i.e., metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and pesticides). For each contaminant of concern, two SQGs were developed from the published SQGs, including a threshold effect concentration (TEC) and a probable effect concentration (PEC). The resultant SQGs for each chemical were evaluated for reliability using matching sediment chemistry and toxicity data from field studies conducted throughout the United States. The results of this evaluation indicated that most of the TECs (i.e., 21 of 28) provide an accurate basis for predicting the absence of sediment toxicity. Similarly, most of the PECs (i.e., 16 of 28) provide an accurate basis for predicting sediment toxicity. Mean PEC quotients were calculated to evaluate the combined effects of multiple contaminants in sediment. Results of the evaluation indicate that the incidence of toxicity is highly correlated to the mean PEC quotient (R(2) = 0.98 for 347 samples). It was concluded that the consensus-based SQGs provide a reliable basis for assessing sediment quality conditions in freshwater ecosystems.

Predicting toxicity in marine sediments with numerical sediment quality guidelines

Abstract: .-Mat~hing'syno~tically collected chemical and laboratory bioassay data (n = 1.068) were compiled from analyses of surficial sediment samples collecred during 1990 to 1993 to evaluate the predictive ability of sediment quality guidelines (SQGs). specifically, effects range-low (ERL). effects range-median (ERM). threshold effects level (TELL and probable eifects level (PEL) values. Dam were acquired from surveys of sediment quality periomed in estuaries along the Atlantic. Pacific. and Gulf of hlexico coasts. Samples were classified as either nontoxic (p > 0.05 re!ative to controls). marginally toxic @ < 0.05 only). or highly toxic @ < 0.05 and response greater than minimum significant difference :elalive to controls). This analysis indic-red that. when nor exceeded. [he ERLs and TELs were highly predictive of nontoxicity. The percenrages of samples that were highly toxic generally increased with increasing numbers of guidelines (panicularly the EX.\.ls and PELS) that were exceeded. Also. the incidence of toxicity increased with increases in concentntions of mixtures of chemicals normalized to (divided by) the SQGs. The ERhls and PELs indicated high predictive ability in samples in which many substances exceeded these concentrations. Suggestions are provided on the uses of these estimates of the predictive ability oi sediment ~uidelines.

Recommended Uses of Empirically Derived, Sediment Quality Guidelines for Marine and Estuarine Ecosystems

Abstract: Sediment quality guidelines (SQGs), based upon empirical analyses of matching chemical and biological data, have been developed for many potentially toxic substances. The predictive abilities and recommended applications of two sets of guidelines, ERLs/ERMs and TELs/PELs, are discussed in this paper. The SQGs were intended as informal (i.e., non-regulatory) benchmarks to aid in the interpretation of chemical data. Low-range values (i.e., ERLs or TELs) were intended as concentrations below which adverse effects upon sediment-dwelling fauna would be expected only infrequently. In contrast, the ERMs and PELs represent chemical concentrations above which adverse effects are likely to occur. Evaluations of the reliability and predictive ability of the SQGs indicate they can be used effectively to assess the quality of soft, aqueous, sedimentary deposits. Specifically, the SQGs can be used to classify sediment samples with regard to their potential for toxicity, to identify contaminants of concern, and to prior...