Uptake of phytodetritus by three ostracod species from the Baltic Sea: effects of amphipod disturbance and ostracod density

Abstract

Three species of ostracods (Candona neglecta, Paracyprideis fennica and Hetero-cyprideis sorbyana) are common in the Baltic proper and often contribute more to the total meiobenthic biomass than any other taxon. An earlier experiment has shown that C. neglecta assimilates more labelled diatoms (Skeletonema costatum) than any other meiobenthic species, and 10 and 100 times more than the other 2 ostracod species, respectively. The uptake of phytodetritus by the 3 ostracod species was investigated in 2 separate experiments with special reference to (1) effects of the presence of amphipods and (2) variable density of ostracods. The amphipods had negative effects on the uptake rate of phytodetritus by ostracods. Mechanical disturbance, which may have caused burial of the phytodetritus, is one plausible explanation. There was no evidence of competition for phytodetritus among the ostracod species, i.e. the absence/presence of C. neglecta did not affect the uptake of phytodetritus by P. fennica and H. sorbyana. A density-dependent uptake of phytodetritus was, however, observed in C. neglecta, where the uptake of phytodetritus was stimulated at an intermediate density [KEYWORDS: C-14 radio-labelled phytodetritus, ostracoda, amphipoda, meiofauna, disturbance, competition]