This research is designed to test how sublethal exposure to copper affects tadpole predator-escape behavior and how quickly tadpoles recover. After exposure, tadpoles were separated. Escape behavior was recorded for two-thirds of exposed tadpoles while one-third of the exposed population was measured weekly to determine growth and recovery. Control tadpoles were consumed within 15 minutes whereas those exposed to higher concentrations were consumed at a slower rate, which does not support the hypotheses. Although the rate of predation was lower, tadpoles exposed to higher Cu concentrations were on average, 1.47 cm in total body length. Those exposed to 0.93 mg/L averaged 0.86 cm. After being placed into clean water, treatment tadpoles recovered after 20 days.

Multi-walled carbon nanotube aggregates can be suspended in the aqueous phase by natural organic matter. These aggregates are ingested by filter feeding zooplankton. Ingested aggregates result in decreased growth and decreased reproduction. These effects may be caused by reduction in energy input from normal feeding behavior. pH alters natural organic matter structure through changes in electrostatic repulsion. Altered natural organic matter structure changes multi-walled carbon nanotube aggregate size. This size variation with variation in pH is significant, but not large enough a change in size to alter toxicity, as the aggregate size range remains well within the particle size selection of the organisms.

Includes bibliographical references (p. B1-B24)

4-nonylphenol (NP), a surfactant degradation product, is an unregulated, ubiquitous aquatic contaminant and endocrine disruptor, for which aquatic life criteria are currently under development by U.S. EPA. The effects of NP on estuarine amphipods and chinook salmon fry were investigated, and this dissertation reports research into the impacts of NP bioaccumulation on the amphipods and resultant endocrine disruption of their juvenile salmon predators. Sensitivity to, and bioaccumulation of, NP by benthic amphipods were quantified. Factors affecting the bioavailability of NP to three species of amphipod (Eohaustorius estuarius, Grandidierella japonica, and Corophium salmonis) were determined in contaminated sediments. Standard bioassay techniques were modified to determine toxicity and bioaccumulation, with varying amounts and differing nutritional qualities of sedimentary organic carbon. �����C-Ring-labeled NP was used as a tracer in the experiments to quantify amphipod exposures. NP was acutely toxic to Eohaustorius estuarius from aqueous exposures, mean (+/-SD) LC50=227 ��g/L +/- 56, 1 h mean reburial EC50=138 +/- 36. The predicted LC50 for NP (202 ��g/L) from an amphipod-derived structure-activity relationship was not significantly different (p>0.05) from our empirically derived LC50 (227 ��g/L). All three amphipod species accumulated significant NP body burdens. Accumulation was inversely proportional to the total amount of organic carbon, but it did not differ between types of organic matter. Calculated accumulation factors indicated that amphipods could be an important and previously unrecognized source of NP to higher trophic levels. Plasma vitellogenin (Vtg) was quantified in juvenile chinook salmon following dietary exposure to NP contaminated amphipods and aqueous exposure to multiple NP concentrations. Fry that had fed upon contaminated amphipods did not have significantly greater Vtg levels than controls; however, Vtg was detected in 30 percent of fry. NP aqueous concentrations at 60 and 240 ��g/L significantly induced Vtg in fry following 5 d exposures. The 240 ��g/L aquatic NP treatment fry had comparable levels of Vtg to the positive control treatment in which fry were injected 17B-estradiol. These results indicate that amphipods are potential vectors of sediment NP to higher trophic levels within the water column, including juvenile chinook salmon. / Graduation date: 2003

Zebra mussels (Dreissena polymorpha) have invaded a great proportion of the waters of the eastern part of North America. This mollusk may be a useful sentinel species for bioaccumulation of heavy metals and organic contaminants in aquatic ecosystems. The zebra mussel's capacity to bioaccumulate cadmium at environmentally relevant exposure and to sequester metals in metal-binding proteins, metallothioneins, was investigated. Elevated (relative to control) concentrations of Cd$ sp{2+}$ were detected in Dreissena exposed to $ ge$2 $ mu$g Cd/liter suggesting that zebra mussels cannot regulate Cd$ sp{2+}$ of trace exposure concentration. More than 85% of the measured Cd$ sp{2+}$ was bound to metallothioneins. / Lesser scaup (Aythya affinis) was assessed as a model species for potential impacts of zebra mussels on higher trophic levels. The feasibility of incubating and rearing scaup in semi-natural conditions was evaluated. A series of biomarkers was assessed in 3 groups of scaup fed a contaminant-free diet or diets containing zebra mussels from the St-Lawrence River or Lake Erie. / Lesser scaup proved to be a suitable species to raise in captivity providing daily water misting through out incubation and strict hygiene conditions during brooding. A hatching success of 89% was achieved. Appropriate housing, feeding and bathing conditions yielded low (3%) post-hatching mortality. / Phagocytosis and respiratory burst activities of heterophils of scaup were suppressed after 6 weeks of feeding on zebra mussels, compared to the control group. These two heterophilic functions were negatively correlated with the incidence of pododermatitis (bacterial feet infection), suggesting a suppression of the non specific immunity. Increased liver/body mass ratio and decreased hepatic vitamin A (retinol and retinyl palmitate) concentrations were observed in scaups fed zebra mussels. Lipid accumulation and glycogen overload were found in the livers of scaups fed mussels from the St-Lawrence River and the Lake Erie groups, respectively. These immunological, biochemical and histopathological biomarkers show promise for monitoring "early" injury and may help in the understanding of health impairment of different species of waterfowl exposed to xenobiotics via contaminated food sources.

This research investigated the effects of waterborne zinc (Zn) on the interactions between guppies, Poecilia reticulata (Peters), and Gyrodactylus turnbulli Harris, 1986, a monogenean parasite of its skin and fins. The first objective was to determine if sublethal concentrations of waterborne Zn (up to 240 mug/L added to artificial freshwater) exerted a concentration-dependent effect on the population dynamics of Gyrodactylus on isolated guppies. Whereas survival of uninfected fish was unaffected, mortality of infected fish increased linearly with increasing Zn concentration. In addition, the improved parasite population growth at concentrations up to 120 mug Zn/I suggested either that the elevated Zn promotes survival and/or reproduction of the parasite, or impairs host defense mechanisms. Analysis of lifetime survival and reproduction of individual parasites on and off the fish revealed Zn toxicity to the parasite as survival of detached parasites decreased linearly with increasing Zn concentration and parasite survival on the host was also lower at the highest Zn concentrations. Also, all morphological parameters decreased linearly in response both to increasing concentration and duration of exposure to waterborne Zn. The guppy epidermis responded rapidly to both infection and waterborne Zn, and the cumulative effects of these combined stressors were synergistic for epidermal thickness and mucous cell numbers, but antagonistic in terms of mucin composition. Both Zn and infection induced mucous production, but at elevated Zn concentrations and/or at high parasite burdens, the capacity for continued mucous production was apparently exceeded. I hypothesize that this condition is favorable for parasite survival because of the impaired host response; but unfavorable for host survival because of the high numbers of pathogenic parasites and the inability to control entry of Zn into host tissues. In conclusion, sublethal concentrations of waterborne Zn are more detrimental to the infected host than to the parasite.

M.Sc. (Aquatic Health) / The North West Province is mineral rich and known for its extensive mining and agricultural activities. These activities drain organic and inorganic pollutants in our waterways, possibly resulting in reduced water quality in dams. Organic and inorganic pollutants such as nutrients, organochlorine pesticides and metals may be present in unacceptable levels possibly affecting fish as well as human health. The North West dams are known for their high nutrient loads and are mostly classified as hypertrophic. In order to better understand the possible effects of the combined pollutant loads on fish health and edibility of fish, (1) a fish health assessment and (2) a human health risk assessment should be conducted. The fish health assessment and the human health risk assessment form an important role in the establishment of water quality standards or/and guidelines for acceptable levels of safe consumption of fish respectively. The aim of this study was to determine (1) if Oreochromis mossambicus from the Klipvoor -, Roodekopjes - and Vaalkop Dams show adverse effects and (2) if consumed, pose a human health risk. The results were compared to the reference site, the Marico-Bosveld Dam.

Please read the abstract on p1 of the document 00dissertation / Dissertation (M Inst Agrar (Sustainable Insect Management))--University of Pretoria, 2007. / Zoology and Entomology / M Inst Agrar / unrestricted

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