Distribution and Abundance of Zooplankton in the North Pacific Subarctic FrontalZone and Adjacent Water Masses

摘要

Zooplankton was collected from two depth strata (0-75 m 75-150 m) with obliquetows of a Tucker trawl at 40 stations across the Subarctic Frontal Zone of the North Pacific Ocean and adjacent water masses in October and November 1989. Thirteen taxonomic groups were identified, and their vertical and spatial distributions were compared and summarized by three water-mass types: (1) Subarctic Domain (SD), (2) Subarctic Frontal Zone (SAFZ), and (3) Transition Zone (TZ). Chaetognaths and mysids were the only taxa that were more abundant in the deepter stratum, primarily due to the overlapping distributions of the two predominant chaetognath species, Sagitta elegans and Eurkohnia hamata, and the abundant deeper-dwelling mysid Euchaetomeropsis merolepis in the authors' samples. Abundances of the predominant taxa (gastropods, polychaetes, ostracods, copepods amphipods, euphausiids, and chaetognaths) were highest in the SD. Cirripede larvae, decapod shrimp larvae, fish eggs, and squid larvae were most abundant in the SAFZ. Fish larvae and mysids were most abundant in the TZ. Mysids were found only in the SAFZ and the TZ. Overall, the most significant change in the zooplankton community occurred between the SD and the SAFZ.