Phytodetritus and the abundance and biomass of abyssal nematodes in the central, equatorial Pacific

The abundance and biomass of abyssal (4300-5000 m) nematodes were investiga ted along a latitudinal gradient of phytodetritus deposition from 0 to 23 d egreesN in the central, equatorial Pacific (140-158 degreesW). Nematode abu ndance in the oligotrophic, central, North Pacific gyre was 50% lower than at the equator while macrofauna abundance increased 6.5 times over the same transect, Nematode abundance and biomass in the surface (0-1cm) sediment l ayer were significantly higher at phytodetritus stations than at non-phytod etritus stations. Abundance and biomass were within the range recorded from other sites of comparable depth that also receive an input of phytodetritu s. Abundance was also strongly correlated with microbial biomass. An increa se in body size was associated with an increase in food supply. The results demonstrate that the equatorial Pacific represents an immense zone of rela tively high nematode standing stock. (C) 2000 Elsevier Science Ltd. All rig hts reserved.