SEDIMENT COMMUNITY RESPONSE TO A TEMPORALLY VARYING FOOD-SUPPLY AT ANABYSSAL STATION IN THE NE PACIFIC

Long time-series measurements were made to examine the effect of episo dic inputs of organic matter to the benthic boundary layer on the sedi ment community at a site in the eastern North Pacific (Sta. M). Chloro phyll a and pheopigments were used to assess sediment enrichment, and the response of the sediment community was examined with seasonal meas urements of sediment community oxygen consumption (SCOC) and sediment ATP from February 1992 to July 1996. In addition, macrofaunal density and biomass were examined in 26 sediment grab samples taken over a 2-y ear period. In order to determine whether the presence or absence of d etrital aggregates correlated with macrofaunal density and biomass, 54 tube core samples were collected with the submersible Alvin at times when detrital aggregates were present on (August/September of 1994) an d absent (April 1995) from the sea floor. Large, seasonal inputs of pa rticulate organic carbon (POC) generally resulted in sediment enrichme nt and significantly correlated with increases in SCOC. Summer maxima in SCOC occurred consistently over our study period, indicating that t his trend is a regular seasonal occurrence at Sta. M. Protozoans, prim arily agglutinating foraminiferans, and five of the six dominant metaz oan taxa exhibited seasonal increases in density during winter months after detrital aggregates had disappeared from the sea floor and appro ximately eight months after peak SCOC and POC measurements, over a 2-y ear period. Alvin tube core samples showed that relative protozoan den sity and biomass increased significantly over a 4-week period followin g an input of phytodetritus, indicating that these organisms may respo nd to organic matter inputs on time scales as short as weeks. (C) 1998 Elsevier Science Ltd. All rights reserved.