Acute and chronic physiological effects of silver exposure in three marineteleosts

This study evaluated the physiological effects of waterborne silver (added as AgNO3) on seawater fish, using acute (48-72 h) high level exposures (250 -650 mug/l Ag) on tidepool sculpins (Oligocottus maculosus), and chronic (u p to 21 day) low level exposures (1.5-50 mug/l Ag) on tidepool sculpins, pl ainfin midshipmen (Porichthys notatus), and rainbow trout (Oncorhynchus myk iss). Sculpins were tested at different salinities. Acclimation to lower sa linity (18 vs 30 ppt) led to altered physiology, with higher ammonia excret ion (J(Amm)), lower oxygen consumption (M-O2), and lower branchial and inte stinal Na+/K+-ATPase activities, but no difference in drinking rate. Short- term exposure to high silver levels tended to stimulate M-O2, J(Amm), and d rinking rate. However, long-term exposure to low levels of silver depressed both J(Amm) and M-O2, and also led to decreased drinking rates. Both inhib ition and stimulation of Na+/K+-ATPase activity occurred, dependent upon le ngth and concentration of exposure, salinity (18 vs 30 ppt), tissue (gill v s intestine), and fish species (sculpin vs midshipmen vs rainbow trout). Wh ile the effects were variable, due to differing balances between inhibitory and compensatory responses, chronic silver exposure significantly altered Na+/K+-ATPase activity levels in almost all tests. In total, these findings reinforce the view that intestinal osmoregulatory function (drinking, Na+/ K+-ATPase activity) is an important site of toxic impact for waterbome silv er, that gill Na+/K+-ATPase activity is also a site of impact, and that chr onic exposures at silver concentrations (1.5, 14.5 mug/l Ag) close to curre nt or proposed water quality guidelines (albeit much higher than normal env ironmental levels), exert a variety of sublethal effects on marine teleosts . (C) 2001 Elsevier Science B.V. All rights reserved.