Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4535202 | Deep Sea Research Part I: Oceanographic Research Papers | 2009 | 15 Pages |
Abstract
Seasonal change in the downward carbon transport due to respiration and mortality through diel vertical migration (DVM) of the calanoid copepods Metridia pacifica and Metridia okhotensis was estimated in the Oyashio region, western subarctic Pacific during six cruises from June 2001 to June 2002. M. pacifica (C4, C5 and adult females) was an active migratory species throughout the year though its DVM amplitude varied among seasons and stages. The mean distribution depths of adult females during the daytime were positively related with the illumination level in the water column, being shallowest in April and deepest in January. M. okhotensis generally showed less-extensive migrations than M. pacifica. Therefore, together with their lower abundance, this species is considered to be a less-important mechanism of downward transport of carbon except for April when their DVM was more active and descended deeper than M. pacifica, which remained in the upper 150 m even during the daytime. The mean migrating biomass of the two Metridia species was 558 mg C mâ2 dâ1 and was high during summer to winter (263-1676 mg C mâ2 dâ1) and low during spring (59-63 mg C mâ2 dâ1). Total downward flux through DVM fluctuated between 1.0 and 20.0 mg C mâ2 dâ1 with an annual mean of 8.0 mg C mâ2 dâ1. Contribution of the respiratory flux was greater than the mortality flux and accounted for 64-98% of total migratory flux throughout the year except for January when contribution of both fluxes was equal. Overall the annual carbon transport by DVM of Metridia spp. was estimated as 3.0 g C mâ2 yearâ1, corresponding to 15% of the annual total POC flux at 150 m at the study site, suggesting that DVM is a significant process for carbon export in the subarctic region as well as that in tropical and subtropical oceanic regions. Since DVM in M. pacifica is more active during the non-bloom season when the gravitational flux of particulate matter is low, this species plays an important role in driving the biological pump in the subarctic Pacific during summer to winter.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geology
Authors
Kazutaka Takahashi, Akira Kuwata, Hiroya Sugisaki, Kazuhisa Uchikawa, Hiroaki Saito,