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 investigated along a latitudinal gradient of phytodetritus deposition from 0 to 23°N in the central, equatorial Pacific (140–158°W). Nematode abundance 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 (0–1 cm) sediment layer were significantly higher at phytodetritus stations than at non-phytodetritus stations. Abundance and biomass were within the range recorded from other sites of comparable depth that also receive an input of phytodetritus. Abundance was also strongly correlated with microbial biomass. An increase in body size was associated with an increase in food supply. The results demonstrate that the equatorial Pacific represents an immense zone of relatively high nematode standing stock.