Browsing by Author "Farris, Jerry L."
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- Cellulolytic responses to heavy metal accumulation in Corbicula fluminea and Mudalia dilatataFarris, Jerry L. (Virginia Tech, 1986-03-05)Cellulolytic responses of the Asiatic clam, Corbicula fluminea and a snail, Mudalia dilatata, to selected constituents of power plant effluents (i.e., zinc, cadmium, acidic and alkaline pH, individually and paired) were investigated in 30-day exposures. Exposures were conducted in both laboratory and field-oriented artificial streams and then validated in the river receiving system of a power plant. Cellulolytic activity was reduced by laboratory and field exposures to cadmium and zinc at all levels tested from 0.012 to 0.10 mg cadmium/L and generally at 0.025 to 1.0 mg zinc/L. Clams detected acute lethal levels of metal and used valve closure as an avoidance mechanism for 14 days. Snails, however, did not effectively avoid exposures and were more sensitive to acute stress during all exposures. These behavioral responses were corroborated by both cellulolytic activity and metal accumulation. Measurements of cellulolytic activity for both test species in laboratory exposures differed from those in field artificial streams. Reduced enzyme activity in controls by day 30 was attributed to artificially induced stress associated with the laboratory environment. This factor precluded any analysis of laboratory responses for periods of exposure longer than 20 days as well as recovery analysis. Field oriented artificial streams provided a sufficient environment to adequately assess long-term stress and recovery as measured by cellulolytic activity and metal accumulation in both clams and snails. Enzyme activity responded to metal exposure with respect to both degree and duration of exposure. Cadmium and zinc combined exposures caused significantly reduced cellulolytic activity at the same concentration as those for cadmium alone. Reduced enzyme activity caused by cadmium and zinc addition at levels that were not detectable suggested that the cellulolytic index was sensitive to sublethal stressors. This was supported by metal uptake patterns in clams and snails. Cellulolytic activity responded to zinc addition at alkaline and acidic pH in a manner that supported pH optima for cellulases and bioavailability of metals. Effects seen in macroinvertebrate assemblages (diversity, richness, and similarity) were compared with cellulolytic activity of caged Corbicula from a site specific power plant discharge. Enzyme activity inhibition was the most sensitive indicator measured. Reductions in cellulolytic activity at stations monitored for total zine content were consistent with effects seen at comparable exposures to zine in field-located artificial streams. A zine concentration of 0.05 mg/L consistently caused the first significant reductions in cellulolytic activity. This concentration is comparable to the U.S. Environmental Protection Agency's Water Quality Criteria value (0.047 mg/L zinc) for protection of aquatic life.
- Control strategies for the zebra mussel, Dreissena polymorpha, and the Asian clam, Corbicula fluminea: comparative stress responses and nontarget impactBidwell, Joseph R. (Virginia Tech, 1993-09-04)The studies described herein focused on the use of intermittent halogenation to control biofouling of water intake systems by the zebra mussel, Dreissena polymorpha, the comparative response of zebra mussels and the Asian clam, Corbicula fluminea, to a surfactant -based chemical control agent, the nontarget impact associated with the control agent, and the use of the Asian clam as a biomonitor of the control agent. Effects of intermittent (2-4 hr/day) treatments with chlorine or bromine at levels of 0.5 and 1.0 mg/L (total residual oxidant) upon settling of zebra mussel veligers were examined in studies conducted in a field laboratory on western Lake Erie. Veliger densities in the water column at the field site peaked at 530/L, while mussel densities on settling monitors reached 147,083/m² over the course of the study period. Zebra mussel settling in test systems treated with the halogens was reduced by as much as 91 % in comparison with controls, although mussel densities of up to 6,044/m² still occurred. Treated mussels which remained settled had growth rates similar to controls, and reached 2-4 mm length over 30 days. The intermittent halogen treatments had no significant impact on either adult zebra mussels or Asian clams. The studies indicate that while the treatment regimes may reduce zebra mussel densities within intake systems, the threat of eventual fouling due to cumulative settling remains.
- Development of a three-trophic level toxicity test utilizing an alga (Chlorella vulgaris), rotifer (Brachinous calyciflorus), and fish (Pimephales promelas)Dobbs, Michael G. (Virginia Tech, 1994-05-05)In this research a test system was developed that is designed as a tool to evaluate the potential hazard of chemicals to aquatic ecosystems. The system developed is a linear three-trophic level food chain consisting of an alga (Ch/ore/la vulgaris), rotifer (Brachionus calyciflorus), and fish (Pimephales promelas). The chemostat design used for the lower two trophic levels was crucial in being able to supply the top trophic level with sufficient food on a continuous basis. The system was initially evaluated using copper (Cu) and selenium (Se) as toxicants. In the copper experiments, results of a 7 day three-trophic level toxicity test were compared with a series of single species tests. The LOEC was 31.5 µg/L based on a temporary impairment of the algal population growth, with a corresponding NOEC of 16.2 µg/L. The algal population at all initially impaired treatment levels demonstrated recovery to control levels by the end of the test. Single species tests with the same species showed impairment at treatment concentrations lower than the corresponding value from the three-trophic level test. The difference in sensitivity is attributable to the fact that most of the Cu in the single species tests was in the dissolved form (approximately 80 %), whereas in the trophic level test most of the Cu was not ( < 15 % dissolved Cu). The three-trophic level Se experiment lasted for 25 days, with both short-term and long-term impacts evident. At the algal trophic level, growth was not impaired on a daily basis at any of the exposure levels (110.3, 207.7, and 396.1 µg/L Se). However, algal densities were slightly reduced at the 207. 7 and 396.1 µg Sell treatments, although not significantly different when the data was pooled across days. Rotifer populations were impaired at these same levels by day 4, and succumbed to the Se by day 7. Fathead minnow growth was also impaired at these two concentrations by day 7. In addition, sub lethal impairment of rotifer and fish growth was evident at the 110.3 pg/L level after day 20 indicating a more subtle trophic impact. Bioconcentration factors ranged between 100 and 1000 µg/L and were found to be dependent on the species, treatment, and day.
- Distribution and life history of the endangered James Spinymussel, pieurobema collina (bivalvia: unionidae)Hove, Mark Curtis (Virginia Tech, 1990-05-05)Distribution of the James spinymussel (Pleurobema collina) and aspects of its life history were studied from June 1987 to October 1989. Field and laboratory observations were used to determine gravidity and glochidial release periods, fish host requirements, age class structure, growth characteristics, and juvenile survival. Stream surveys conducted at 243 sites in 20 counties revealed new populations of this species in three subdrainages (Catawba Creek, Pedlar River, and Mechums River), of the James River, greatly expanding its known range. Female P. collina were gravid from late May through early August 1988 and 1989 in Craig Creek, Virginia, and the South Fork Potts Creek, West Virginia. Glochidia were released from late June through early July in the South Fork Potts Creek, at mean water temperatures between 21 and 25 °C, and discharges between 0.013 and 0.050 m l/sec. Field observations and laboratory tests confirmed that cyprinids serve as fish hosts for P. collina glochidia. Glochidia of the James spinymussel were identified on the common shiner (Notropis cornutus), rosyside dace (Clinostomus funduloides), bluehead chub (Nocomis leptocephalus), pumpkinseed (Lepomis gibbosus), and fantail darter (Etheostoma flabellare) in the South Fork Potts Creek. Eleven fish families were tested for suitability as fish hosts in the laboratory, but only the following 7 species served as hosts: bluehead chub (N. leptocephalus), rosyside dace (C. funduloides), satinfin shiner (N. analostanus), rosefin shiner (N. ardens), central stoneroller (Campostoma anomalum), blacknose dace (Rhinichthys atratulus), and mountain redbelly dace (Phoxinus oreas). Juvenile P. collina, fed a mixture of three green algae species in chambers with and without silt, lived 50 days. Juveniles in silt grew significantly faster than those not in silt after 18 days. Age and growth characteristics of adults were obtained by thin-sectioning valves collected in muskrat middens in Dicks and Johns creeks, Virginia. Ages ranged between 3 and 19 yr, and a strong year class was identified at age 11. Mean annual mortality rate was calculated to be 9.8%. As predicted by the von Bertalanffy growth equation, P. collina reaches a maximum length of 74.4 mm, and annual growth increments decrease from 7.04 mm/yr (age 1) to 0.88 mm/yr (age 19). As judged by qualitative surveys, current populations of P. collina in Craig Creek, Johns Creek, and the South Fork Potts Creek appear to be self-sustaining. Populations in Catawba and Patterson creeks appear to be small and are probably in jeopardy of being extirpated. The status of the James spiny mussel in Dicks Creek, Rocky Run, and Pedlar and Mechums rivers is unknown since these streams were not extensively surveyed.
- Impact zone delineation for biological assessment of power plant effluent effects on snail populations in the Clinch RiverReed, Donna K. (Virginia Tech, 1993)The impact of a power plant discharge (Clinch River Plant, CRP, Carbo, Virginia) on resident snail populations was assessed. In 1988, snail absence below the plant, was attributed to plant discharges rather than naturally occurring habitat limitations. Habitat limitations for the two dominant snail species, Leptoxis praerosa and Pleurocera unciale were defined before power plant impact was assessed. Eleven physicochemical parameters (i.e., flow rate, substrate type, silt accumulation, depth, water chemistry and food biomass parameters) were measured at selected sites and compared to snail density. Flow rate, substrate type and periphyton biomass were the most influential parameters in determining Leptoxis density; while periphyton biomass was the most influential for Pleurocera. Cluster analysis also linked Leptoxis density with river structure and flow. Other variables linked to Pleurocera density were flow rate, river structure and silt. Although Leptoxis is most prolific in riffle/shoal areas and Pleurocera in slower riffle-pool interfaces, these two ‘species often coexist. This research suggests that habitat partitioning between these two species is influenced most by flow rate. Greatest density of Leptoxis occurred at flow rates of 20-30 cm/sec. Frequency of occurrence was greatest at 20-100 cm/sec. Pleurocera occurred most frequently at flow rates of 20-30 cm/sec with greatest density at 25-45 cm/sec. Measurements of impact of the CRP effluent (i.e., toxicity, metals {mainly copper} bioaccumulation in aufwuchs and snails, and cellulase enzyme activity impairment) were summarized by using zone delineation. Habitat parameters were measured below plant discharges and upstream, and compared with water column Cu, snail tissue Cu and aufwuchs Cu measurements. Habitat selection was strongly influenced by effluent but the role of waterborne metals concentration and habitat alterations (e.g. periphyton changes and bioconcentration) was unclear. Feeding studies were conducted to estimate impact of aufwuchs bioconcentration of metals on snails. Leptoxis significantly bioconcentrated Cu when fed aufwuchs containing 564 (±269) ug Cu/g in artificial stream feeding studies, but no cellulase impairments were seen in these studies. No foodborne bioconcentration was found from aufwuchs containing up to 20,000 (±18,400) ug Zn/L. These results suggest that though foodborne uptake of Cu may occur, water column Cu concentrations may have to be an order of magnitude higher for impairment to occur through injestion than through waterborne exposures. Acute and chronic effects of both whole effluent and Cu on Leptoxis were measured in laboratory and artificial stream exposures. The 96-hr LC₅₀ was 95% effluent (containing 148 ug Cu/L)in flow-through exposures, but in Static stirred exposures, 100% effluent (105 ug Cu/L)was not toxic. The lowest-observable effect concentration (LOEC)from 30-day exposures was 10% effluent (22 ug Cu/L) causing cellulase activity impairment (70% of control activity) and bioconcentration (300 ug Cu/g). Constituents of effluent other than Cu were believed to contribute to impairment effects since no impairment was found in 30-day CuSO₄ dosings of up to 25 ug Cu/L. The LOEC for Cu from 30-day CuSO₄ dosings ranged from 17-35 ug/L and the no-observed effect concentration (NOEC)was 12 ug Cu/L. The EPA water quality criteria concentration (17 ug Cu/L)was questionable for Leptoxis in long-term exposures (114-day), causing enzyme impairment and mortality. Chronically toxic conditions to Leptoxis occurred on the left side of the river for 0.7 km downstream of discharge, where the water column contained 42 ug Cu/L, while acutely toxic conditions occurred in the immediate mixing zone. Artificial stream impairment tests were substantiated in the river except in lower reaches of the impairment zone (left side of river, 0.7-0.9 km below cooling tower discharge), where snail absence was attributed to periphyton Cu bioconcentration (242 ug Cu/g). Functional recovery (of enzyme activity) was found at the next acceptable habitat downstream (Station 14A), so the area of impact extended 0.9 km downstream of the discharge on the left side of the river. It was concluded that zone delineation by simultaneously evaluating structural and functional aspects of environmental change is a better approach to impact assessment than approaches that only use functional measurements.
- Macrohabitat factors affecting distribution patterns of freshwater mussels in the Clinch River (Virginia, Tennessee)Church, Gregory W. (Virginia Tech, 1997-10-09)Studies were conducted to determine the macrohabitat factors structuring high quality mussel habitat in the Clinch and Little rivers. In the first habitat study, 4 substratum variables, 7 channel morphology variables, and 3 stream and valley variables were compared between high and low mussel density aggregations from 6 study reaches. Wilcoxon rank-sum tests were conducted separately for all transects, unbraided (without islands) transects, and braided (anastomosing river channels with islands) transects. Stepwise discriminant analysis (SDA) was used in the first habitat study to identify variables which best differentiated high and low mussel density transect groups. Percent bedrock (PBR) (p>F=0.002), d50 particle size (p>F=0.03), and mean depth (MDEP) (p>F=0.11) were the most useful predictors (cumulative average squared canonical correlation (ASCC) = 0.30) when SDA was performed on all transects (n = 66). The ASCC values improved substantially when unbraided and braided transects were analyzed separately. PBR (p>F=0.0001), d84 particle size (p>F=0.05), MDEP (p>F=0.03), and direction of streamflow (DIR) (p>F=0.05) were selected by SDA (cumulative ASCC = 0.52) for unbraided transects (n = 43), and proximity to floodplain (PROX) (p>F=0.0008) and PBR (p>F=0.005) were selected by SDA (cumulative ASCC = 0.61) for braided transects (n = 23). In the second habitat study, 14 habitat variables were compared between high and low quality mussel sites documented in a TVA survey (1986). The variables PBR (p>F=0.0001), d84 (p>F=0.0001), DIR (p>F=0.09), and valley floor width (VFW) (p>F=0.05) were selected by SDA (cumulative ASCC = 0.69) when all sites were included in the analysis; and PBR (p>F=0.0095), d84 (p>F=0.004), d50 (p>F=0.15), and DIR (p>F=0.07) were selected (cumulative ASCC = 0.62) when only unbraided sites were included in the analysis. Mussels were associated with areas of smaller mean particle size with low exposed bedrock in the channel cross-section. Site location patterns for the entire TVA data set (n = 141 sites) were examined for patterns relative to streamflow direction. The greatest frequency of high quality unbraided sites occurred where the river flows in the direction of geologic dip. High quality braided sites occurred where the river flows along the line of geologic strike. The orientation of bedrock ledges relative to direction of streamflow seemingly determines the long-term stability of mussel habitat in unbraided reaches by retaining streambed alluvium during high discharge events.
- Sensitivity of early life stages of freshwater mussels (Bivalvia: Unionidae) to copperJacobson, Peter James (Virginia Tech, 1990-05-05)Four life stages of freshwater mussels were tested for their sensitivity to copper and a metal-containing effluent. This permitted an assessment of the variability in sensitivity among the life stages in order to identify those stages most threatened in the wild from copper exposure. Glochidia, while held within the marsupia of the adult, the released or isolated glochidia, the encysted glochidia, and the gravid mussel were tested. Little effect on glochidia was detected following 30- day artificial stream exposures of gravid adults to 19.1 ug Cu/L and an effluent containing an average of 23.9 ug Cu/L. Isolated glochidia were killed by copper concentrations ranging from 20-80 ug/L in 24-hour exposures, with sensitivity increasing with hardness and temperature. Encysted glochidia were resistant to exposures up to 400 ug Cu/L. No significant effect on metamorphosis to the stage was detected. This is likely due to the encapsulation of the glochidium by the host fish. Juvenile mussels reduced their activity during 24-hour exposures to copper concentrations as low as 17 to 24 ug/L and concentrations of 30 to 42 ug/L caused mortality. Juvenile mussels and glochidia within the marsupia are probably the two most sensitive stages in the life cycle of the freshwater mussel. Copper pollution will have its greatest impact in the summer, during periods of high water temperature and low flow.