Hardness does not affect the physiological responses of wild and domestic strains of diploid and triploid rainbow trout Oncorhynchus mykiss to short-term exposure to pH 9.5.
This study examined the effects of water hardness on the physiological responses associated with high pH exposure in multiple strains of diploid and triploid rainbow trout Oncorhynchus mykiss. To accomplish this, three wild strains and one domesticated strain of diploid and triploid O. mykiss were abruptly transferred from control soft water (City of Vancouver dechlorinated tap water; pH 6·7; [CaCO3 ] < 17·9 mg l(-1) ) to control soft water (handling control), high pH soft water (pH 9·5; [CaCO3 ] < 17·9 mg l(-1) ), or high pH hard water (pH 9·5; [CaCO3 ] = 320 mg l(-1) ) followed by sampling at 24 h for physiological measurements. There was a significant effect of ploidy on loss of equilibrium (LOE) over the 24 h exposure, with only triploid O. mykiss losing equilibrium at high pH in both soft and hard water. Furthermore, exposure to pH 9·5 resulted in significant decreases in plasma sodium and chloride, and increases in plasma and brain ammonia with no differences between soft and hard water. There was no significant effect of strain on LOE, but there were significant differences between strains in brain ammonia and plasma cortisol. Overall, there were no clear protective effects of hardness on high pH exposure in these strains of O. mykiss.
The University of Calgary, 507 Campus Drive NW, Calgary, AB, T2N 4V8, Canada.
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WA
Thompson
Department of Zoology, The University of British Columbia, 6270 University Blvd, Vancouver, B.C., V6T 1Z4, Canada.
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TM
Rodela
Department of Zoology, The University of British Columbia, 6270 University Blvd, Vancouver, B.C., V6T 1Z4, Canada.
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Richards
D000641:Ammonia / Q000097:blood; D000818:Animals; D000829:Animals, Domestic; D001923:Brain Chemistry; D002119:Calcium Carbonate; D002712:Chlorides / Q000097:blood; D004171:Diploidy; D006854:Hydrocortisone / Q000097:blood; D006863:Hydrogen-Ion Concentration; D017686:Oncorhynchus mykiss / Q000502:physiology*; D011003:Ploidies; D013312:Stress, Physiological; D057885:Triploidy; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical
D002712:Chlorides; D014874:Water Pollutants, Chemical; D014867:Water; D000641:Ammonia; D002119:Calcium Carbonate; D006854:Hydrocortisone
ammonia; brain swelling; hard water; high pH; ion regulation; loss of equilibrium