Water pH and aluminum chemistry in the gill micro-environment of rainbow trout during acid and aluminum exposures |
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Authors: | Richard C Playle Chris M Wood |
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Institution: | (1) Department of Biology, McMaster University, L8S 4K1 Hamilton, Ontario, Canada |
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Abstract: | Summary Rainbow trout (Salmo gairdneri) were exposed to acidic soft water (pHin4.2–6.3) in the presence (93 g·l–1) or absence of Al. Fish were fitted with latex masks and opercular catheters to measure ventilation
, pH changes at the gills, O2 consumption
, ammonia excretion
, and Al extraction. During 2–3-h exposures,
was generally higher in Al-exposed fish over the pHin range 4.7–6.3. Alkalinization of expired water was about 0.3 pH units less in Al-exposed fish than in acid-only exposed fish at pHin 4.5–5.2, an effect attributable to both increased
and to buffering by Al. During 44-h exposures to pHin 5.2 and 4.8 plus Al,
increased greatly and expired water pH (pHex) decreased with time. There was a small increase in
over 44 h at pH 4.4 plus Al, and no changes in pHex. In contrast, during 44-h exposures to pH 5.2, 4.8, and 4.4 in the absence of Al, such changes were much smaller or absent. During both short- and longerterm exposures, measured Al accumulation on the gills was only 5–18% of that calculated from cumulative Al extraction from the water, suggesting considerable sloughing of Al. In free-swimming trout, gill Al accumulation was greatest during exposure (2h) to Al at pH 5.2, lower at pH 4.8, and least at pH 4.4 and 4.0. Our results suggest that Al deposition occurs at the gills, causing respiratory and ionoregulatory toxicity, because the pH in the branchial micro-environment is raised above that in the acidic inspired soft water. Higher pH at fish gills may result in Al precipitation due to loss of solubility, or Al accumulation because of shifts in Al species to Al-hydroxide forms which more readily adsorb to the gills.Abbreviations
pH
ex
expired pH
-
pH
in
inspired pH |
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Keywords: | Aluminum pH Gills Trout Water chemistry |
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