© 2004 by ICES/CIEM International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer
Metabolism and chemical composition of mesopelagic ostracods in the western North Pacific Ocean
Marine Biodiversity Laboratory, Graduate School of Fisheries Sciences, Hokkaido University 3-1-1, Minato-cho, Hakodate, Hokkaido 041-0821, Japan
*Correspondence to H. Kaeriyama: present address: Nakaminato Laboratory for Marine Radioecology, National Institute of Radiological Sciences, 3609 Isozaki-cho, Hitachiraka-shi, 311-1202 Japan; tel: +81 29 265 9659; fax: +81 29 265 9659. e-mail: hideki_k{at}nirs.go.jp.
Oxygen consumption rates and bodily elemental composition (carbon (C) and nitrogen (N)) were determined on three dominant ostracods (Discoconchoecia pseudodiscophora, Orthoconchoecia haddoni, and Metaconchoecia skogsbergi) from the mesopelagic zone of the Oyashio region. Specific oxygen consumption rates of the three species at near in situ temperature (3°C) were similar (0.39 µl O2 mg DW–1 h–1), but bodily C composition and C:N ratios of D. pseudodiscophora were significantly higher than those of the other two species. Metabolic comparison in terms of "daily body C loss" or "adjusted metabolic rate" revealed that metabolic rates of the ostracods are 0.3–0.4 times those of other zooplankton at comparable temperature conditions. The present results were combined with standing stock data of each ostracod in the Oyashio region to estimate their POC ingestion. Our calculation indicates annual ingestion by the ostracods to be 875 mgC m–2 yr–1, which equates to 3.7% of annual POC flux reaching 200–600-m depth (mid-point: 400-m depth) in this region.
Keywords: C:N ratio, mesopelagic, ostracods, oxygen consumption, Oyashio region