No description available.

No description available.

No description available.

Contaminants introduced in solution to coastal waters eventually accumulate in sediment. Pollution by these contaminants is only evident when biological effects occur. Geochemical procedures lack the ability to identify biological effects of pollution. Biological methods (i.e. community structure analyses and/or bioassays) are currently the best available techniques for pollution assessment. Standardised and locally relevant protocols for pollution assessment are lacking in many developing countries, including South Africa. This study aims to develop a sediment toxicity testing protocol using an amphipod species endemic to South Africa, Grandidierella lignorum. Initial research focussed on establishing ranges of physico-chemical parameters (i.e. salinity, temperature, sediment grain size and organic matter content) within which sediment toxicity tests should be performed. The sensitivity of the amphipod was then determined by exposing the amphipod to cadmium, copper and zinc at various salinities. Lastly, the amphipod was exposed to effluents (to test the amphipod’s sensitivity in water only tests) and whole sediment (to tests the amphipod’s sensitivity to solid phase material). G. lignorum tolerates salinities between 0 and 56, but prefers salinities between 7 and 42. Preferred salinity range is modified by temperature, with salinity of 42 becoming less tolerable. Salinities between 7 and 35 are most preferred at 10-25°C. G. lignorum prefers fine- (27.48±12.13%), medium- (25.11±12.99%) and coarse-grained sand (21.45±8.02%). Sediment with low (≤2%) organic matter content is most preferable, regardless of sediment grain size or type of organic matter (protein-rich vs. carbohydrate-rich). Cadmium toxicity decreased with increasing salinity (LC₅₀: 0.34 ± 0.17 mg l⁻¹ (salinity of 7), 0.73 ± 0.05 mg l⁻¹ (salinity of 21) and 1.08 ± 0.49 mg l⁻¹ (salinity of 35)). Zinc toxicity increased with decreasing salinity (1.56 ± 0.33 mg l⁻¹ at a salinity of 21 to 0.99 ± 0.13 mg l⁻¹ at a salinity of 7) and with increasing salinity (from salinity of 21 to 0.82 ± 0.19 mg l⁻¹ at a salinity of 35). Copper toxicity did not differ significantly with salinity and ranged between 0.72 ± 0.18 mg l⁻¹ (salinity of 35) and 0.89 ± 0.24 mg l⁻¹ (salinity of 21). Toxicity testing using Grandidierella lignorum should be performed in coarse- to fine-grained sediment at salinities of 7 - 35, at 10 – 25°C. Amphipods do not need to be fed during toxicity testing. A control chart using cadmium as a reference toxicant was established to determine the acceptability of toxicity results. Toxicity test results should be accepted when cadmium toxicity falls between 0.49 and 4.02 mg l⁻¹. The amphipod responded consistently to effluents and was able to discriminate polluted and unpolluted sediment in Durban Bay. Recommendations for refining the effluent and sediment toxicity test are suggested. / Ph.D. University of KwaZulu-Natal, Durban 2013.

No description available.

Concentrations of selenium (Se), manganese (Mn), zinc (Zn), cadmium (Cd), lead (Pb) and arsenic (As) were measured in the water column, sediment and biota, in conjunction with selected physicochemical data, from representative wetland types at a mining site within Salt Lake County, Utah, USA. The selected field sites included Oolitic Pond (lentic) and Lee Creek (lotic), which are moderately contaminated brackish, alkaline aquatic wetlands managed by a copper mining industry. These fishless wetlands are located in a geographic region that poses risk to migratory shorebird populations from dietary Se. A spatial sampling study demonstrated the extent of variation in total Se concentration within the wetlands. With the exception of the sediment compartment, Se concentration did not differ significantly along the 2-mile length of Lee Creek or within the Pond. The differences in sediment total Se concentrations between the Creek East and West segments characterize lower Lee Creek as having two segments distinguished by unique processes that influence the sediment Se accumulation profiles. Se accumulation trends were observed temporally over 3-years (2000 to 2002) and over two seasons (spring and autumn). Total Se body burden in benthic invertebrates was more clearly associated with sediment/detritus Se concentrations than with surface water concentrations. Three invertebrate groups dominated the aquatic invertebrates assemblage in the lotic and lentic benthos; primary consumers (Chironomidae, Diptera), generalist feeders (Hemiptera) and predators (Odonata). The chironomid larvae accumulated 1.3 to 39 times the trace metal concentrations of the Hemiptera or odonate taxa, independent of trace metal type (essential or non-essential) or wetland occupation. Organism-specific factors, such as habitat selection and preferential feeding habits, were proposed to influence benthic invertebrate accumulation profiles by modifying trace metal exposure. Mixed diets, trophic omnivory and the complexity of wetland biogeochemistry limit the power of stable nitrogen fractionation signatures to define benthic food web relationships. Wetland site-specific processes impacted Se accumulating efficiency, with trace metal concentrations from 4 to 7 times greater within the lentic benthic system than the lotic. The fractionation of the natural abundant stable carbon isotopes revealed the importance of sedimentary and detrital organic carbon as dietary sources for the benthic food web. Sediment organic content was not significantly associated with sediment, or invertebrate, Se accumulation profiles. Ecological risk assessments based on sound understanding of metal chemistry and the interactions between the sediment matrix and benthic organisms are necessary to provide tools for environmental management. / Graduation date: 2005