Browsing by Author "W. Gregory Cope, Committee Co-Chair"

Filter results by typing the first few letters
Now showing 1 - 3 of 3
  • No Thumbnail Available
    Bioaccumulation of Platinum Group Metals in the Freshwater Mussel Elliptio Complanata
    (2009-04-15) Mays, Jason Warren; W. Gregory Cope, Committee Co-Chair; Thomas J. Kwak, Committee Co-Chair; Damian Shea, Committee Member
    ABSTRACT MAYS, JASON WARREN. Bioaccumulation of Platinum Group Metals in the Freshwater Mussel Elliptio complanata. (Under the direction of Thomas J. Kwak and W. Gregory Cope). The use of catalytic converters for automobile exhaust purification has led to emission and environmental contamination by the platinum group metals (PGM) platinum (Pt), palladium (Pd), and rhodium (Rh). In this study, a total of 37 sites were sampled throughout central North Carolina and were chosen based on availability of the freshwater mussel Elliptio complanata, varied geographic distribution, land use patterns, and vehicle traffic density. At each site, a sample of sediment and three adult E. complanata were collected from within 50-150 m both upstream and downstream of the road crossing. Mussel tissue and sediment samples were analyzed for concentrations of Pt, cadmium (Cd) and mercury (Hg). Related stream and local variables investigated included sediment total organic carbon, water chemistry, and estimated vehicle traffic density at the bridge. Landscape variables included human population density, land use, and density of transportation infrastructure. Pt concentrations in mussel tissue ranged 0.09-1.98 ng/g dry weight and 0.06-1.86 ng/g dry weight in sediment among sites. A biota sediment accumulation factor for Pt, calculated as the mean [tissue]/[soil], was 3.2, compared to 87 and 88 for Hg and Cd, respectively. Pt contamination of mussels and sediment at highway crossing sites were not significantly correlated with the amount of traffic crossing the specific structure. Rather, multiple regression modeling indicated a significant relation between Pt concentration in mussels at a site and the human population of the watershed. A 28-d laboratory test was conducted with waterborne Pt and Pd to determine toxicity, bioaccumulation, and to assess several potential biomarkers of exposure to Pt and Pd. Test mussels were exposed to five concentrations of an equal mixture of Pt and Pd salts, ranging from 0.05 to 500 μg/L of each metal, in a static renewal test. The 500 µg/L concentration resulted in high mortality (4 of 9 dead by day 12) of test mussels; all individuals in each of the other test concentrations survived to the end of the test. There were nine replicate mussels per treatment concentration, allowing three mussels from each treatment to be sampled on days 7, 14 and 28. Tissue and hemolymph were assessed for concentrations of Pt, Pd, sodium (Na+), calcium (Ca2+), potassium (K+), and chloride (Cl-) concentrations. Na+,K+-ATPase activity was assessed in gill tissue as a potential biomarker of exposure. Tissue concentrations of Pt ranged from 0.10 ng/g dry weight in controls to 34,486 ng/g dry weight in the 500 µg/L treatment, and Pd ranged from 0.06 ng/g dry weight in controls to 34,404 ng/g dry weight in the 500 µg/L treatment. Concentrations of Pt in hemolymph ranged from 0.08 ng/mL in controls to 50.1 ng/mL in the 500 µg/L treatment, and Pd ranged from 0.06 ng/mL in controls to 12.2 ng/mL in the 500 µg/L treatment. On day 28, Na+,K+-ATPase activity displayed a logarithmic trend (y=0.489ln(x)+2.054; R2=0.73) of increasing activity with increasing PGM exposure concentration; however, activity was only significantly increased (P<0.05) at 5.0 µg/L and 50 µg/L concentrations. High variation and weak correlation of Na+,K+-ATPase activity with Pt and Pd exposure concentration indicate that it may not be a suitable biomarker of PGM exposure. Hemolymph Ca2+ concentrations were increased on day 7 at the 50 µg/L concentration. Hemolymph Na+ levels were decreased on day 28 at the 5.0 µg/L and 50 µg/L concentrations. Cl- and K+ levels were decreased at the 50 µg/L concentration. Tissue Pt and Pd concentrations in mussels exposed to the lowest test concentration (0.05 µg/L) displayed tissue concentrations of Pt that were approximately six times greater than the maximum tissue concentrations measured in stream-sampled mussels. Hemolymph ion measurement does not appear to be sensitive enough to serve as a biomarker of PGM exposure at environmentally relevant exposure concentrations. Results from this study will provide resource managers with information on this emerging group of contaminants needed to perform risk assessments for transportation impacts to natural systems and to develop conservation, protection, and mitigation plans for this critically imperiled faunal group.
  • No Thumbnail Available
    Effects of Polycyclic Aromatic Hydrocarbon Exposure on Three Life Stages of Freshwater Mussels (Bivalvia: Unionidae)
    (2006-04-28) Humphries, LeRoy F; Arthur E. Bogan, Committee Member; W. Gregory Cope, Committee Co-Chair; Jay F. Levine, Committee Co-Chair
    Freshwater mussels (Bivalvia: Unionidae) are among the most threatened aquatic species in the world. One of the major issues implicated in this decline is water pollution. Polycyclic aromatic hydrocarbons (PAHs) are a suite of hydrophobic environmental pollutants common in terrestrial and aquatic ecosystems. These compounds are largely derived from petroleum related sources (e.g., gasoline, oil) and are of major concern from transportation-related runoff to aquatic systems due to the acute and chronic (e.g., mutagenic and carcinogenic) toxic properties of many members of this class. The effects of exposure to PAHs have been investigated in many species of bivalves; however, to date no comprehensive study of the effects of exposure to these compounds on all life stages of native freshwater mussels have been completed. The goals of this study therefore were to investigate the effects of exposure to PAHs on all life stages of freshwater mussels and to develop diagnostic tests that are rapid, accurate, inexpensive, and of minimal impact to the mussels. This study examined the acute (48 h) toxicity of PAHs to the glochidial (larval) and juvenile stages of mussels and the sub-acute (7 d) toxic effects on adult mussels. Additionally, the study examined the use of genetic damage as a biomarker of exposure of mussels to PAHs by utilizing the Comet assay to determine levels of DNA strand breakage following aqueous exposure. Finally, mussels were collected from areas of high and low environmental levels of PAHs and were analyzed to validate laboratory findings and to examine relations to previously obtained field PAH mussel, water and sediment measurements. We found that there were no acute toxic effects of PAHs on glochidia or juveniles of the two species of freshwater mussels examined, up to concentrations approaching water solubility, and well exceeding those commonly measured in the streams of North Carolina. Experiments with adult Elliptio complanata, both in the laboratory and from the field, indicated that genetic damage due to PAH exposure was likely present, however the results were highly variable and the potential for biological, ecological, and toxicological consequences were uncertain. Further development and improvement of assay methods may reduce this variation. Generally, mussels from streams with higher average daily traffic counts (ADTC) exhibited greater levels of genetic damage compared to mussels from streams with lower ADTC values. Data obtained from the laboratory study generally showed increasing DNA damage relative to increasing PAH concentration. Based on the data generated, however, PAHs are not likely contributing to acute toxicity of mussels in North Carolina streams, but the chronic, long-term pervasive effect of PAHs on native freshwater mussels remains uncertain.
  • No Thumbnail Available
    Modulation of Immune Function Parameters in Fish Caused by Sudden Environmental Changes
    (2005-03-06) Choi, Kyoungju; Craig Harms, Committee Member; Mac Law, Committee Co-Chair; W. Gregory Cope, Committee Co-Chair; Muquarrab Qureshi, Committee Member
    Three related projects were conducted using multiple tiered bioassays to determine the effects of acute changes in salinity, low oxygen saturation (hypoxia), or triamcinolone on immune function in teleost (bony) fish using the well characterized tilapia fish model. We hypothesized that sudden changes in the aquatic environment, specifically salinity and dissolved oxygen, would compromise immune function in teleost fish leading to alterations of cytokine expression, namely increase in TGF-β and decrease in IL-1β; suppression of phagocytosis; and adverse changes in plasma chemistry and hematology. Further, we hypothesized that these immune system changes would be similar to those caused by administration of triamcinolone. Our overall hypothesis was that the total immunocompromise caused by rapid environmental changes leads to increased susceptibility to diseases such as epizootic ulcerative syndrome (EUS). To model the rapid environmental changes often experienced by fish in North Carolina estuaries, tilapia (Oreochromis niloticus) were exposed under controlled laboratory conditions to either acute salinity changes, acute drop in dissolved oxygen, or intraperitoneal injection of triamcinolone (positive control). Tiered bioassays of increasing specificity for immune function were performed on tissue samples: Tier I, histopathology; Tier II, hematology, plasma biochemistry, and plasma cortisol; Tier III, phagocytosis of peripheral blood leukocytes (PBL), and mRNA expression of transforming growth factor-β (TGF-β) & interleukin-1β (IL-1β) splenic mononuclear cells using real time PCR. While histopathology was a useful tool for assessing overall health of the test fish, no remarkable lesions were found in that could be attributed to any of the three stressors. Triamcinolone administration (i.p., 10mg/kg) for 3 days induced lymphopenia, neutrophilia with overall leukopenia, and monocytosis. Hematocrit and circulatory red blood cell count did not change with triamcinolone administration nor with acute decrease in salinity. Increase in salinity (5-20 ppt) had no effects on any of the aforementioned parameters. Hypoxia induced lymphopenia and neutrophilia without change in monocytes and additionally inhibited values of PO2, SO2, total protein, and lipase in exposed fish. Decrease in salinity (20-5 ppt) did not affect plasma cortisol levels, nor did triamcinolone administration or hypoxia treatment. Plasma protein level was not changed in response to decrease in salinity or triamcinolone administration. Triamcinolone administration suppressed phagocytosis of peripheral blood leukocytes (PBL) without a significant change in phagocytic index (P.I). Decrease in salinity elevated phagocytosis without change in P.I. in exposed tilapia. Increase in TGF-β transcription and decrease in IL-1β transcription with in vitro LPS stimulation were identified after triamcinolone administration. Acute decrease in salinity upregulated TGF-β transcription, whereas IL-1β transcription without in vitro LPS stimulation was not detectable in exposed fish. During hypoxia it was observed that changes in phagocytosis and TGF-β transcription were correlated negatively and that changes in IL-1β transcription and phagocytosis correlated positively. Taken together, these controlled laboratory experiments suggest that rapid changes in the aquatic environment can lead to increased disease susceptibility via compromise of the fish immune system. In these studies, this immunocompromise was especially evident in the modulation of the inflammatory mediators TGF-β and IL-1β, as well as in shifts in blood leukocyte distribution. It is likely that such perturbations of teleost immune system parameters have much wider implications, including in North Carolina estuaries.