Feeding ecology of phaeodarian radiolarians at the VERTEX North Pacific time series site

Feeding ecology of five species of phaeodarians was analyzedusing samples collected in a timeseries of sediment trap deploymentsfrom October 1986-May 1988 from 100–2000 m at an oligotrophicnorth Pacific site. Quantitative analysis using transmissionelectron microscopy of contents of feeding vacuoles showed thatheterotrophic flagellates and eukaryotic algae followed by bacteria,and then prokaryotic algae, constituted the largest volumesof recognizable organisms consumed throughout the depth rangesampled. Phaeodarians were predominantly generalists, appearedto feed on sinking organic aggregates, and may select eukaryotesover higher biomass bacteria. Other than a decrease in totalrecognizable cells with increasing depth, few seasonal or depthpatterns in consumed food occurred in this oligotrophic environment.Vacuole contents of co-occurring species showed no evidenceof food resource partitioning. The trophic role of phaeodariansis that of consumers of small eukaryotes and prokaryotes andrepackages of detritus throughout the water column. ³Present address: Electron Microscope Laboratory, 26 GianniniHall, University of California, Berkeley, CA 94720, USA