The purpose of this work was to determine if environmentally-relevant concentrations of chlorpyrifos and copper, two commonly detected chemicals in Western surface waters, can negatively impact the biological health of salmonids. Both compounds are highly neurotoxic to fish, but each with distinct biological target sites and mechanisms of action. We used common biochemical and physiological indicators of toxicity, and correlated these effects with potentially significant behavioral alterations. For chlorpyrifos, the mechanism of toxic action is the inhibition of acetylcholinesterase (AChE) throughout the peripheral and central nervous system. Here, we conducted biochemical assays of AChE activity in brain and muscle tissues after exposing steelhead trout (Oncorhynchus mykiss) and coho salmon (0. kisutch) to chlorpyrifos for 96 hours. We then correlated the AChE inhibition with behavioral impairment in swimming and feeding activities. In juvenile steelhead and coho exposed to 0.6-2.5 ��g/L chlorpyrifos, AChE activity was inhibited between ~10-65%. This biochemical indicator was significantly correlated with changes in behavioral patterns. Spontaneous swimming rates were reduced ~30-80% in the exposed fish, and strikes at food items (brine shrimp) were reduced ~10-70%. For copper and some other neurotoxicants, the olfactory nervous system is a sensitive target site in fish. The highly-developed olfactory system in salmonids is particularly susceptible to toxic insult by dissolved chemicals since receptor neurons are in direct contact with the aquatic environment. Here, we used electrophysiological techniques to record odor-evoked responses from the sensory epithelium and the olfactory bulb as direct measures of olfactory function in juvenile coho salmon. In fish exposed to copper, chlorpyrifos, or esfenvalerate for 7 days, field potentials recorded from the sensory epithelium and the olfactory bulb showed reduced or obscured olfactory responses to two classes of odorants, which activate non-overlapping populations of receptor neurons. To determine if this reduced sensory input can subsequently alter or diminish olfactory-mediated predator avoidance behaviors, paired physiological and behavioral tests were conducted on juvenile coho exposed to copper. In fish exposed to 2-20 ��g/L copper for 3 hours, olfactory sensitivity was reduced by ~50-9O%. When these fish were presented with a predatory alarm cue (conspecific skin extract), fish with reduced olfactory function increasingly failed to exhibit antipredator behavior. In the following experiments, we show that chlorpyrifos and copper can impair the biochemical and physiological biology of salmonids at environmentally-relevant concentrations, and that these sublethal effects can alter potentially important behavioral patterns. / Graduation date: 2004

Graduation date: 2002

Thesis (MTech (Chemical Engineering))--Peninsula Technikon, Cape Town, 2003 / The monitoring of pesticide contamination in surface and groundwater is an essential aspect of an assessment of the potential environmental and health impacts of widespread pesticide use. Previous research in three Western Cape farming areas found consistent (37% to 69% of samples) pesticide contamination of rural water sources. However, despite the need, monitoring of pesticides in water is not done due to lack of analytical capacity and the cost of analysis in South Africa. The Solid Phase Microextraction (SPME) sampling method has been developed over the last decade as a replacement for solvent-based analyte extraction procedures. The method utilizes a short, thin, solid rod of fused silica coated with an absorbent polymer. The fibre is exposed to the pesticide contaminated water sample under vigorous agitation. The pesticide is absorbed into the polymer coating; the mass absorbed depends on the partition coefficient of the pesticide between the sample phase and the polymeric coating, the exposure time and factors such as agitation rate, the diffusivity of the analyte in water and the polymeric coating, and the volume and thickness of the coating. After absorption, the fibre is directly inserted into the Gas Chromatograph (GC) injection port for analysis. For extraction from a stirred solution a fibre will have a boundary region where the solution moves slowly near the fibre surface and faster further away until the analyte is practically perfectly mixed in the bulk solution by convection. The boundary region may be modelled as a layer of stationary solution surrounded by perfectly mixed solution.