Feeding preferences of abyssal macrofauna inferred from in situ pulse chase experiments

Climatic fluctuations may significantly alter the taxonomic and biochemical composition of phytoplankton blooms and subsequently phytodetritus, the food source for the majority of deep-sea communities. To examine the response of abyssal benthic communities to different food resources we simulated a food sedimentation event containing diatoms and coccolithophorids at Station M in the NE Pacific. In one set of experiments we measured incorporation of C-diatom and N-cocco into the macrofauna using isotopically enriched C-13-diatoms and N-15-coccolithophores. In a second experiment we measured incorporation of C and N from dual-labelled (C-13 and N-15) diatoms. The second experiment was repeated 2 months later to assess the effect of seasonality. The simulated food pulses represented additions of 650 - 800 mg C m(-2) and 120 mg N m(-2) to the seafloor. In all cases rapid incorporation of tracer was observed within 4 days, with between 20% and 52% of the macrofauna displaying evidence of enrichment. However, incorporation levels of both C-diatom and N-cocco were low (