Relative contribution of bacterial and photosynthetic production to metazooplankton as carbon sources

Abstract

Percentages of label transfer (PLT) from bacteria and autotrophs to metazooplankton during 4 h were determined in parallel using dissolved organic and inorganic 13C tracers, respectively, in in situ batch incubations, to estimate the relative contribution of each production to the metazooplankton food requirement. The batch incubation for each pathway was done eight times, respectively, during 20 days in a mesocosm where continuous species succession of organisms was observed. The PLT in the two pathways, dependent on metazooplankton abundance and species composition rather than changes in the activities of producers (bacteria or autotrophs), showed a similar tendency of change and were of a similar magnitude: mean 1.0% (0.09- 2.7%) in the photosynthetic pathway and 0.5% (0.22-1.5%) in the bacterial pathway. This finding suggests that metazooplankton are supported by entire microbial food webs including both the bacterial and photosynthetic pathways.