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Selected AbstractsAssessing the impact of pollution on the Japaratuba river in Brazil using the Drosophila wing spot testENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2 2007Silmara de Moraes Pantaleão Abstract The Drosophila melanogaster somatic mutation and recombination test (SMART) was used to assess the genotoxicity of surface (S) and bottom (B) water and sediment samples collected from Sites 1 and 2 on the Japaratuba River (Sergipe, Brazil), an area impacted by a petrochemical industrial complex that indirectly discharges treated effluent (produced water) into the river. The genotoxicity tests were performed in standard (ST) cross and high bioactivation (HB) cross flies and were conducted on samples taken in March (dry season) and in July (rainy season) of 2003. Mutant spot frequencies found in treatments with unprocessed water and sediment samples from the test sites were compared with the frequencies observed for similar samples taken from a clean reference site (the Jacarecica River in Sergipe, Brazil) and those of negative (ultrapure water) controls. While samples from the Japaratuba River generally produced greater responses than those from the Jacarecica River, positive responses were detected for both the test and reference site samples. All the water samples collected in March 2003 were genotoxic. In July 2003, the positive responses were restricted to water samples collected from Sites 1 B and 2 S in the ST cross. The genotoxicity of the water samples was due to mitotic recombination, and the samples produced similar genotoxic responses in ST and HB flies. The spot frequencies found in the July water samples were considerably lower than those for the March water samples, suggesting a seasonal effect. The only sediment samples that were genotoxic were from Site 1 (March and July) and from the Jacarecica River (March). The genotoxins in these samples produced both somatic mutation (limited to the Site 1 sample in HB flies) and recombination. The results of this study indicate that samples from both the Japaratuba and Jacarecica Rivers were genotoxic, with the most consistently positive responses detected with Site 1 samples, the site closest to the putative pollution source. Environ. Mol. Mutagen. 48:, 2007. © 2007 Wiley-Liss, Inc. [source] Immunocompetence of bivalve hemocytes as evaluated by a miniaturized phagocytosis assayENVIRONMENTAL TOXICOLOGY, Issue 3 2002C. Blaise Abstract Immune function in bivalves can be adversely affected by long-term exposure to environmental contaminants. Investigating alterations in immunity can therefore yield relevant information about the relationship between exposure to environmental contaminants and susceptibility to infectious diseases. We have developed a rapid, cost-effective, and miniaturized immunocompetence assay to evaluate the phagocytic activity, viability, and concentration of hemocytes in freshwater and marine bivalves. Preliminary experiments were performed to optimize various aspects of the assay including 1) the time required for adherence of hemocytes to polystyrene microplate wells, 2) the time required for internalization of fluorescent bacteria, 3) the ratio of hemocytes to fluorescent bacteria in relation to phagocytosis, 4) hemolymph plasma requirements, and 5) the elimination of fluorescence from (noninternalized) bacteria adhering to the external surface of hemocytes. The results of these experiments showed the optimal adherence time for hemocytes in microplate wells to be 1 h, that phagocytosis required at least 2 h of contact with fluorescently labeled E. coli cells, that the number of fluorescent E. coli cells had a positive effect on phagocytic activity, that at least 2.5 million cells/mL were required to measure a significant intake, and that a linear increase in uptake of bacteria (R = 0.91; p < 0.01) could be obtained with concentrations of up to 1.3 × 106 hemocytes/mL. Afterward, the assay was used in two field studies to identify sites having the potential to affect the immunocompetence of bivalves. The first study was conducted on Mya arenaria clams collected at selected contaminated sites in the Saguenay River (Quebec, Canada), and the second examined Elliptio complanata freshwater bivalves that had been exposed to a municipal effluent plume in the St. Lawrence River (Quebec, Canada). In the Saguenay River field study a significant increase in phagocytosis was observed at sites closest to polluted areas. Phagocytotic activity varied over time and was highest during the warmest months (June, July, and August), closely paralleling the spawning period of Mya arenaria clams. In contrast, a drop in phagocytic activity was observed in Elliptio complanata mussels exposed to surface water 4 km downstream of a major municipal effluent plume, with a concomitant increase in the number of hemocytes in the hemolymph. It appears that both immunosuppressive and immunostimulative effects are likely to occur in the field and that responses will be influenced by the type and intensity of contaminants at play. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 160,169, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10047 [source] Molluscan shellfish biomarker study of the Quebec, Canada, Saguenay Fjord with the soft-shell clam, Mya arenariaENVIRONMENTAL TOXICOLOGY, Issue 3 2002C. Blaise Abstract A spatial and temporal survey of six sites in the Saguenay Fjord and of one adjacent site in the St. Lawrence River estuary (Quebec, Canada) was undertaken to study the possible effects of anthropogenic contaminant input on soft-shell clam (Mya arenaria) populations. Bivalve sampling sites were selected because they reflected a range of areas representative of either no known (or apparent) pollution sources or of areas potentially influenced by different gradients and types of contamination sources. The most upstream site selected in the Saguenay Fjord, nearest to a highly populated and industrialized sector, and the most downstream site, near its mouth with the St. Lawrence River estuary, spanned a distance of some 70 km and encompassed the entire intertidal area suitable for Mya arenaria habitat. To measure effects in collected animals, we used a comprehensive battery of biomarkers composed of metallothionein-like proteins (MT), 7-ethoxyresorufin O-deethylase activity (EROD), DNA damage (DD), lipid peroxidation (LPO), vitellinlike proteins (Vn), phagocytosis (PHAG), nonspecific esterase (NspE) activity, and condition factor (weight-to-length ratio of clams). Vn, PHAG, DD, and NspE biomarkers were assayed in hemolymph (or hemocytes), whereas others (MT, EROD, LPO) were determined in the digestive gland. Whole-tissue metal content was also quantified in clams collected in the spatial survey. The spatial survey conducted in June 1997 showed significant effects at all sites, and principal component analysis indicated in addition that the more important responses were linked to the MT, LPO, and NspE biomarkers. Clams collected from sites closest to the upstream reaches of the fjord generally displayed higher levels of tissue metals (cadmium, manganese), as well as greater responses of NspE activity, MT, LPO, and PHAG. Animals collected from sites influenced by municipal wastewaters had higher levels of Vn, suggesting the presence of environmental estrogens. The results of the temporal survey (six monthly samplings of clams at three sites from May through October, 1997) showed that the bivalve reproductive cycle (vitellogenesis and spawning) can modulate the expression of several biomarkers. Vn levels, for example, were positively correlated with DD and EROD and negatively correlated with MT, suggesting that reproduction can influence the susceptibility of clams to some contaminants. Discrimination analysis over the 6 months of sampling revealed that the mean value of the discriminant function changed significantly over time, suggesting important changes in the relative contribution of each biomarker. In short, this study has provided evidence that clam populations in the Saguenay Fjord are impacted by multiple sources of contamination whose effects can be modulated by reproduction. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 170,186, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10048 [source] Genotoxicity in wood mice (Apodemus sylvaticus) along a pollution gradient: Exposure-, age-, and gender-related effectsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2006Jan Scheirs Abstract We investigated the effects of environmental pollution on genetic damage in wood mice (Apodemus sylvaticus) by means of the comet assay, with special attention to the role of age and gender as potential confounding variables. The present study was carried out at four sites along a pollution gradient in the vicinity of Antwerp (Belgium), with a nonferrous smelter as the main pollution source. We measured the concentration of heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Pb, and Zn) in mouse liver and kidney and the concentration of organochlorine compounds (polychlorinated biphenyls and 1,1-dichloro-2,2-bis(p -chlorophenyl)ethylene) in mouse muscle tissue to assess individual exposure. Cadmium exposure was very high at the sites closest to the smelter, and exposure to this metal decreased with increasing distance from the smelter. Exposure to the other pollutants was low to moderate at the different sites. Genetic damage was higher in mice from populations in the vicinity of the nonferrous smelter compared with that in the control populations. A significant increase in genetic damage with age was observed at the most polluted sites, but not at the control sites. Genetic damage was higher in male mice than in female mice at the most polluted site, but not at the other areas. Yet, no obvious relationship was found between individual pollutant levels and individual genetic damage levels. We conclude that the comet assay can be used to compare genotoxicity at the population level if the confounding variables of gender and age are taken into account. However, its use for individual health risk assessment remains questionable. [source] Changes in population biology of two succulent shrubs along a grazing gradientJOURNAL OF APPLIED ECOLOGY, Issue 4 2003Corinna Riginos Summary 1Heavy livestock grazing in Namaqualand, South Africa, is threatening the region's unique diversity of succulent shrubs. This is especially true in the communally managed lands, where grazing is centred around fixed enclosures (stockposts) in which animals stay overnight. In this study we set out to determine the effects of a semi-permanent stockpost on the composition of the surrounding vegetation and the mechanisms by which grazing limits the persistence of leaf-succulent shrub populations. 2We used the grazing gradient created by a stockpost to examine the impacts of grazing on vegetation composition and changes in mortality, reproductive output and seedling establishment for the leaf-succulent species Ruschia robusta and Cheiridopsis denticulata. 3Vegetation composition was found to change from a community dominated by the unpalatable shrub Galenia africana at high grazing intensities to a community dominated by the palatable leaf-succulent shrub R. robusta at lower grazing intensities. 4Mortality of the leaf-succulents R. robusta and C. denticulata was high at the sites closest to the stockpost, while fruit production and seedling germination were substantially reduced over distances of 800 m and 2 km for the two species, respectively. Seedling establishment was not limited by either grazing or microsite availability. Thus reduction in reproductive output is the greatest impact of heavy grazing on these two species. 5Synthesis and applications. This study demonstrates that marked zonation in vegetation composition and population biology can develop around a fixed stockpost and that the greatest impact of grazing on the two leaf-succulent species studied is the suppression of flower and fruit production. Consistent suppression of reproductive output could have long-term consequences for the persistence of succulent shrub populations in the heavily grazed communal lands of Namaqualand. We recommend that (i) herders should be encouraged to relocate their stockposts regularly to prevent the development of centres of degradation, and (ii) areas should be relieved periodically of all grazing pressure to allow for successful seed set of native shrubs. [source] Modeling the effects of El Niño, density-dependence, and disturbance on harbor seal (Phoca vitulina) counts in Drakes Estero, California: 1997,2007MARINE MAMMAL SCIENCE, Issue 1 2009Benjamin H. Becker Abstract Harbor seal (Phoca vitulina) haul-out site use may be affected by natural or anthropogenic factors. Here, we use an 11-yr (1997,2007) study of a seal colony located near a mariculture operation in Drakes Estero, California, to test for natural (El Niño-Southern Oscillation (ENSO), density-dependence, long-term trends) and anthropogenic (disturbance or displacement related to oyster production activities) factors that may influence the use of haul-out subsites. Annual mariculture related seal disturbance rates increased significantly with increases in oyster harvest (rs= 0.55). Using generalized linear models (GLMs) ranked by best fit and Akaike's Information Criteria, ENSO and oyster production (as a proxy for disturbance/displacement) best explained the patterns of seal use at all three subsites near the mariculture operations, with effects being stronger at the two subsites closest to operations. Conversely, density-dependence and linear trend effects poorly explained the counts at these subsites. We conclude that a combination of ENSO and mariculture activities best explain the patterns of seal haul-out use during the breeding/pupping season at the seal haul-out sites closest to oyster activities. [source] | ||||||||||