Doctoral Dissertations

Date of Award

5-1989

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Ecology and Evolutionary Biology

Major Professor

Richard J. Strange

Committee Members

John F. McCarthy, Barbara J. Walton, Walter R. F

Abstract

The uptake of contaminants by diffusion across fish gills may be altered by changes in the contaminant's physicochemical form or changes in fish respiration. This study investigated the effects of changes in contaminant uptake due to absorption to humic acid and changes in fish respiration, induced by altering respiratory demand via an acute change in temperature and by altering the diffusional capacity of the gill membrane by exposure to chlorine. In each experimental design the uptake of selected polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyl congeners (PCBs) by the gills of rainbow trout, salmo gairdneri (Richardson) were measured simultaneously with measurements of fish respiratory functions using a fish metabolic chamber.

Binding to humic acid (HA) reduced the bioavailability of benzo[a]pyrene (BaP) and 2,2',5,5'-tetrachlorobiphenyl (TCB). A 1:1 correlation was found between reductions in the percentage of BaP or TCB that was freely dissolved (not bound to HA) and reductions in uptake of the contaminant by trout gills. These results imply that only the freely dissolved BeiP or TCB was available for uptake.

Eight to 24-h exposure to chlorine resulted in damage to gill lamellae. Reducticais in the uptake efficiencies of oxygen and three PCB congeners in chlorine-exposed trout were hypothesized to result from the chlorine-induced damage to the gill membrane. However, increases in ventilatory functions compensated for the lowered uptake efficiencies and resulted in no net change in either oxygen or PCB uptake.

An acute decrease in temperature resulted in reduced respiration and uptake of oxygen and BaP, TCB, and napthalene (NAP) by trout. Reductions in uptake efficiencies were hypothesized to result from temperature-induced reductions in the permeability of the gill membrane. Reductions in ventilatory functions and oxygen consumption were attributed to a reduced metabolic demand at the lower temperature. These results indicate that physiological and environmental factors can have a direct modulating effect on the diffusion of contaminants across the gill membrane. The quantitative relationships between sorption and bioavailability and fish respiration and contaminant uptake found in these experiments can be used to improve models of contaminant uptake in the natural environment.

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