Vertical segregation within four grazing copepods in the Oyashio region during early spring

• Published in: Journal of plankton research Vol. 33; no. 8; pp. 1230 - 1238
• Main Authors: Sato, Ken-Ichi, Yamaguchi, Atsushi, Ueno, Hiromichi, Ikeda, Tsutomu
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.08.2011
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Bacillariophyceae; Biological and medical sciences; Crustacea; Eucalanus bungii; Fundamental and applied biological sciences. Psychology; General aspects; Invertebrates; Metridia pacifica; Neocalanus cristatus; Neocalanus flemingeri; Synecology; INW, Pacific, Oyashio Current; diel vertical migration; gut content; habitat separation; ontogenetic vertical migration; Crustacea; Vertical; Plankton; Segregation; Arthropoda; Copepoda; Invertebrata
• ISSN: 0142-7873; 1464-3774
• DOI: 10.1093/plankt/fbr018

Fine-scale vertical distribution patterns of the calanoid copepods Neocalanus flemingeri, Neocalanus cristatus, Eucalanus bungii and Metridia pacifica were studied by stratified sampling (9 strata between 0 and 1000 m) with a vertical multiple plankton sampler (VMPS) every 3 h for 24 h during 21-22 March 2005 in the Oyashio region. Most C1-C5 stages of N. flemingeri and N. cristatus occurred in the 30-90 m and 70-200 m strata, respectively, both by day and night. Irrespective of day and night, C3-C6 E. bungii were distributed broadly in the 200-430 m stratum (C5 inhabiting the shallowest layer). Thus, these three copepods exhibited vertical partitioning of their habitats in the upper layers. The C1-C6 of M. pacifica were distributed broadly from 140 to 400 m during daytime and migrated up to the 100-180 m layer at night (except for non-migrant C1 and C6 males). The within-species zonation of copepodid stages was less marked, but older stages tended to occupy deeper zones (N. flemingeri, N. cristatus and M. pacifica) or shallower zones (E. bungii). Gut content analyses of N. flemingeri and N. cristatus revealed the predominance of diatoms in the guts of both species, but the proportion of broken cells was greater in the deep-dwelling N. cristatus than in the shallow-dwelling N. flemingeri, suggesting the importance of sinking phytoplankton aggregates as a food source for the former species.