OXYGEN-CONSUMPTION, NITROGENOUS EXCRETION, AND FILTRATION-RATES OF DREISSENA-POLYMORPHA AT ACCLIMATION TEMPERATURES BETWEEN 20 AND 32-DEGREES-C

Mussels were acclimated to each of four experimental temperatures (20, 24, 28, and 32 degrees C) for 30 days. Mussels averaged 10.29 mg tissue dry weight. Oxygen consumption rates at 32 degrees C were 3.65 times larger than consumption rates at 20 degrees C (p < 0.01). Ammonia excretion rates at 32 degrees C were 4.9 times greater than those at 20 degrees C (p < 0.01). O:N ratios were > 60 at 20 and 24 degrees C but declined (p < 0.01) at 28 and 32 degrees C to < 40. Filtration rates, an estimate of feeding rates, were not significantly different at 20 and 24 degrees C (p > 0.50) but declined at 28 and 32 degrees C (p < 0.01). Filtration rates at 32 degrees C were only 27% of the rates at 20 degrees C. These results indicate that (i) the metabolic expenditure of Dreissena polymorpha rose 265% as the temperature rose from 20 to 32 degrees C, (ii) metabolism relied more heavily on lipids and carbohydrates at 20 and 24 degrees C while protein catabolism increased at 28 and 32 degrees C, and (iii) the potential feeding rates of D. polymorpha declined by 73% as temperature rose from 20 to 32 degrees C. Above 28 degrees C D. polymorpha was unable to match energy expenditures with concurrent food intake and forced to rely on stored fuels.