Tolerance of the deposit-feeding Baltic amphipods Monoporeia affinis and Pontoporeia femorata to oxygen deficiency

Abstract

Tolerances of the 2 most common species of amphipods in the Baltic Sea to low oxygen concentrations were determined over a range of ambient salinities in the Baltic. For both species more than half of the tested individuals had died by the end of 24 h of exposure to nearly anoxic water (0.2 mg O2 l-1). Despite its higher respiration rate and level of activity, Monoporeia affinis was significantly more tolerant than Pontoporeia femorata both to short (1 to 5 d) and long (24 d) periods of exposure to low oxygen levels. As long as the amphipods survived the tested salinity, there were only minor effects of salinity on their tolerance to oxygen deficiency. Among the common macrobenthic soft-bottom species in the study area, M. affinis and P. femorata seem to be the most sensitive to oxygen deficiency.