Benthic community responses to pulses in pelagic food supply: North Pacific Subtropical Gyre

Time-series measurements of particulate organic carbon (POC) and particulate nitrogen (PN) fluxes, sediment community composition, and sediment community oxygen consumption (SCOC) were made at the Hawaii Ocean Time-series station (Sta. ALOHA, 4730m depth) between December 1997 and January 1999. POC and PN fluxes, estimated from sediment trap collections made at 4000m depth (730m above bottom), peaked in late August and early September 1998. SCOC was measured in situ using a free vehicle grab respirometer that also recovered sediments for chemical and biological analyses on six cruises during the 1-year study. Surface sediment organic carbon, total nitrogen and phaeopigments significantly increased in September, corresponding to the pulses in particulate matter fluxes. Bacterial abundance in the surface sediment was highest in September with a subsurface high in November. Sediment macrofauna were numerically dominated by agglutinating Foraminifera fragments with highest density in September. Metazoan abundance, dominated by nematodes was also highest in September. SCOC significantly increased from a low in February to a high in September. POC and PN fluxes at 730m above bottom were significantly correlated with SCOC with a lag time of p14 days, linking pelagic food supply with benthic processes in the oligotrophic North Pacific gyre. The annual supply of POC into the abyss compared to the estimated annual demand by the sediment community (POC:SCOC) indicates that only 65% of the food demand is met by the supply of organic carbon. r 2002 Elsevier Science Ltd. All rights reserved.