Gut content analyses of three dominant Antarctic copepod species during an induced phytoplankton bloom EIFEX (European iron fertilization experiment)

The diet of three Antarctic copepods, Calanus simillimus, Rhincalanus gigas and Pleuromamma robusta, was studied from samples collected during the European iron fertilization experiment (EIFEX) in austral fall 2004. The diet was investigated using microscopical gut content analysis. The food spectra of the three copepod species showed a clear overlap. The pennate diatom Fragilariopsis kerguelensis was commonly found in all guts. Large numbers of cells were fractured, but some were found complete when arranged as chains. The same was true for the genus Chaetoceros, a centric diatom, of which even their long and complete setae could be observed. In general the ingested food particles extended over a wide size range up to a few 100 mu m. The copepod C. simillimus, for example, fed on large foraminifera and swallowed them whole. Compared to C. simillimus and R. gigas, P. robusta guts contained a higher percentage and larger diversity of hard-shelled protozoa including tintinnids, Radiolaria and Acantharia.