USGS Science⌕ Search

Geology topics

C. L. Brown

Publications and source records attributed to C. L. Brown.

At least 19 recordsLinked to original sources
USGS2008

Enzymatic and histopathologic biomarkers as indicators of contaminant exposure and effect in Asian clam ( Potamocorbula amurensis )

Enzymatic and histopathologic alterations of the digestive gland, gill, gonad, and kidney were studied in Asian clam (Potamocorbula amurensis) in April, 1997 from each of four United States Geological Survey (USGS) stations in the San Francisco Estuary. Stations were selected based on differing body burdens of metallic contaminants in clams (Stn 4.1>6.1>8.1>12.5) observed over 7 years. Because no pristine sites are known within the estuary and because no laboratory-reared stocks of P. amurensis were available, clams from station 12.5 served as reference animals. Histopathologic analysis revealed no lesions in clams collected from station 12.5. Mild digestive gland atrophy and moderate distal kidney tubular vacuolation were seen in clams collected from station 8.1. Mild digestive gland atrophy, moderate kidney tubular atrophy, and moderate gill inflammation were seen in clams collected from station 6.1. Lesions found only in clams from station 4.1 were: (1) severe inflammation and moderate atrophy of primary ducts and diverticula, and decreased numbers of heterophagosomes and heterolysosomes in diverticula of the digestive gland; (2) severe gill inflammation; (3) severe kidney tubular atrophy; (4) severe ovarian and testicular inflammation and necrosis (5) decreased numbers of mature ova; and (6) decreased number of glycogen storage cells in the ovary and testis. Localization of specific enzymes including adenosine triphosphatase (ATP), acid phosphatase (ACP), alkaline phosphatase (ALKP), gamma-glutamyl transpeptidase (GGT), and glucose-6-phosphate dehydrogenase (G6PDH) was performed and correlated, in serial sections with glycogen (PAS) and haematoxylin and eosin stains. Enzymatic analysis revealed: (1) increased digestive diverticula ATP in stations 6.1 and 4.1; (2) decreased digestive diverticula ACP in stations 6.1 and 4.1 and proximal kidney tubular ACP deficiency in station 4.1; (3) no ALKP differences among stations; (4) increased distal kidney tubular GGT at station 12.5 and decreased distal kidney tubular GGT at station 4.1; (5) decreased digestive diverticula G6PDH G6PDH in all stations except 12.5 and decreased proximal kidney tubular G6PDH in stations 8.1 and 6.1. It is possible that other anthropogenic and natural stressors may have affected the results in this study. However, the prevalence and increased severity of lesions in clams with highest metal body burden suggests a contaminant- associated etiology. Enzymatic and histopathologic biomarker alterations identified in this study were positively correlated with the metal body burden. Clams with the higher prevalence of diseases and enzyme alterations also showed a lower condition index and glycogen content in the month when histopathological assessment was performed. Further study will seek to develop enzymatic and histopathologic biomarkers for use in controlled laboratory conditions to help validate the field study.

Biomarkers↗
USGS2003

Influence of salinity on the localization of Na+/K +-ATPase, Na+/K+/2Cl- cotransporter (NKCC) and CFTR anion channel in chloride cells of the Hawaiian goby (Stenogobius hawaiiensis)

Na+/K+-ATPase, Na+/K+/2Cl- cotransporter (NKCC) and cystic fibrosis transmembrane conductance regulator (CFTR) are the three major transport proteins thought to be involved in chloride secretion in teleost fish. If this is the case, the levels of these transporters should be high in chloride cells of seawater-acclimated fish. We therefore examined the influence of salinity on immunolocalization of Na +/K+-ATPase, NKCC and CFTR in the gills of the Hawaiian goby (Stenogobius hawaiiensis). Fish were acclimated to freshwater and 20??? and 30??? seawater for 10 days. Na+/K +-ATPase and NKCC were localized specifically to chloride cells and stained throughout most of the cell except for the nucleus and the most apical region, indicating a basolateral/tubular distribution. All Na+/K +-ATPase-positive chloride cells were also positive for NKCC in all salinities. Salinity caused a slight increase in chloride cell number and size and a slight decrease in staining intensity for Na+/K +-ATPase and NKCC, but the basic pattern of localization was not altered. Gill Na+/K+-ATPase activity was also not affected by salinity. CFTR was localized to the apical surface of chloride cells, and only cells staining positive for Na+/K+-ATPase were CFTR-positive. CFTR-positive cells greatly increased in number (5-fold), area stained (53%) and intensity (29%) after seawater acclimation. In freshwater, CFTR immunoreactivity was light and occurred over a broad apical surface on chloride cells, whereas in seawater there was intense immunoreactivity around the apical pit (which was often punctate in appearance) and a light subapical staining. The results indicate that Na+/K +-ATPase, NKCC and CFTR are all present in chloride cells and support current models that all three are responsible for chloride secretion by chloride cells of teleost fish.

Journal of Experimental Biology↗
USGS2000

Influence of acid volatile sulfides and metal concentrations on metal partitioning in contaminated sediments

The influence of acid volatile sulfide (AVS) on the partitioning of Cd, Ni, and Zn in porewater (PW) and sediment as reactive metals (SEM, simultaneously extracted metals) was investigated in laboratory microcosms. Two spiking procedures were compared, and the effects of vertical geochemical gradients and infaunal activity were evaluated. Sediments were spiked with a Cd−Ni−Zn mixture (0.06, 3, 7.5 μmol/g, respectively) containing four levels of AVS (0.5, 7.5, 15, 35 μmol/g). The results were compared to sediments spiked with four levels of Cd−Ni−Zn mixtures at one AVS concentration (7.5 μmol/g). A vertical redox gradient was generated in each treatment by an 18-d incubation with an oxidized water column. [AVS] in the surface sediments decreased by 65−95% due to oxidation during incubation; initial [AVS] was maintained at 0.5−7.5 cm depth. PW metal concentrations were correlated with [SEM − AVS] among all data. But PW metal concentrations were variable, causing the distribution coefficient, Kd pw (the ratio of [SEM] to PW metal concentrations) to vary by 2−3 orders of magnitude at a given [SEM − AVS]. One reason for the variability was that vertical profiles in PW metal concentrations appeared to be influenced by diffusion as well as [SEM − AVS]. The presence of animals appeared to enhance the diffusion of at least Zn. The generalization that PW metal concentrations are controlled by [SEM − AVS] is subject to some important qualifications if vertical gradients are complicated, metal concentrations vary, or equilibration times differ.

Environmental Science & Technology↗
USGS2000

Linkage of bioaccumulation and biological effects to changes in pollutant loads in south San Francisco Bay

The developed world has invested billions of dollars in waste treatment since the 1970s; however, changes in ecological or biological responses are rarely associated with reductions in metal pollutants. Here we present a novel, 23-yr time series of environmental change from a San Francisco Bay mudflat located 1 km from the discharge of a suburban domestic sewage treatment plant. Samples of surface sediment, the bioindicator Macoma balthica , and metals loading data were used to establish links between discharge, bioaccumulation, and effects. Mean annual Ag concentrations in M. balthica were 106 μg/g in 1978 and 3.67 μg/g in 1998. Concentrations of Cu declined from 287 μg/g in 1980 to a minimum of 24 μg/g in 1991. Declining Cu bioaccumulation was strongly correlated with decreasing Cu loads from the plant between 1977 and 1998. Relationships with bioaccumulation and total annual precipitation suggested that inputs from nonpoint sources were most important in controlling Zn bioavailability during the same period. Ecoepidemiological criteria were used to associate failed gamete production in M. balthica to a metals-enriched environment. Reproduction persistently failed between the mid-1970s and mid-1980s; it recovered after metal contamination declined. Other potential environmental causes such as food availability, sediment chemistry, or seasonal salinity fluctuations were not related to the timing of the change in reproductive capability. The results establish an associative link, suggesting that it is important to further investigate the chemical interference of Cu and/or Ag with invertebrate reproduction at relatively moderate levels of environmental contamination.

California↗
USGS1995

Use of the euryhaline bivalve Potamocorbula amurensis as a biosentinel species to assess trace metal contamination in San Francisco Bay

Potamocorbula amurensis was assessed as a biosentinel species in San Francisco Bay, California, USA. Uptake of metal in both the laboratory and field showed that P. amurensis was sufficiently responsive to Ag, Cd, Cr, Ni and V to detect environmental differences in exposure. It was less suitable as an indicator of Cu and Zn contamination. Concentration factors for P. amurensis were: Ag, 386000; Cd, 50200; Cr, 36600; Cu, 12200; Ni, 5200; and Zn, 115500. Samples were collected from 6 stations throughout the bay at near-monthly intervals from January 1991 to March 1992. Variability within a collection was influenced by gut content and animal size. Other sources of variability were time [coefficient of variation (CV) = 10 to 21%], small-scale spatial variability (within 3 km, CV = 10 to 25%), and large-scale spatial variability (CV = 3.3 to 12.4%). Depuration for 48 h was necessary to mitigate bias from gut content. Precision was improved by analyzing large numbers of individuals (60 to 120) separated into several (5 to 14) composites at each collection and by determining, from regression, the mean and variance for samples with significant correlations between metal concentration and shell length. Repeated monthly sampling increased the accuracy of long-term site characterizations. Temporal variability was small because of drought. The grand means of the concentrations of Ag, Cd, Cr, Ni, and V in the tissues of P. amurensis at each station for the 15 mo period revealed persistent contamination from industrialized Suisun Bay to the mouth of San Francisco Bay. Demonstration of responsiveness, precision and accuracy should be a prerequisite for the optimal use of biosentinels.

California↗