Vertical distribution and feeding ecology of a copepod Gaetanus variabilis in the southern Japan Sea during winter

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Vertical distribution, gut fullness and gut contents were investigated on an aetideid copepod Gaetanus variabilis during winter at a station in the southern Japan Sea. Most individuals of C3-C6 (adult) G. variabilis were distributed between 500 and 1000 m depth. While early copepodid stages resided deeper than older ones, no diel vertical migration was detected throughout the copepodid stages. Feeding activity of G. variabilis as judged by gut fullness scores varied with developmental stage/sex, but no diel feeding rhythm was observed. Adult males cease feeding as a reflection of degeneration of their feeding appendages. The gut content analysis showed that G. variabilis is a particle feeder consuming mainly upon silicoflagellates, followed by diatoms, tintinnids and fragments of metazooplankton. An estimated daily ration of G. variabilis population based on calculated metabolic rates was 5.03 mg C m-2 day-1, which accounts for 4.5% of the local primary production or 54% of particulate organic carbon flux down to the 500 m depths at southern Japan Sea.
2007-02-28