Does scope for growth change as a result of salinity stress in the amphipod Gammarus oceanicus?

Physiological performance (feeding, metabolism, growth and excretion) across a broad range of salinity (5–30 psu) were determined for the benthic amphipod Gammarus oceanicus, a species of marine origin inhabiting brackish waters of the southern Baltic Sea. Feeding rates decreased with increasing salinity, whereas the nutritive absorption efficiency increased. Faeces production and ammonia excretion rates decreased strongly from the lowest to the highest salinity by 60% and 58%, respectively. Increasing salinity was accompanied by a reduction in the metabolic rate from 438 J g− 1 dry wt d− 1 (5.1 mW g− 1) at 5 psu to 245 J g− 1 (2.8 mW g− 1) at 30 psu. Individuals were able to maintain a positive energy balance at all experimental salinities. The greatest values for scope for growth were recorded at the environmental salinity (7 psu) with a mean of 769 J g− 1 dry wt d− 1 (8.7 mW g− 1).