Distribution and abundance of zooplankton in the north Pacific Subarctic Frontal Zone and adjacent water masses

Abstract

Zooplankton were collected from two depth strata (0 - 75 m, and 75 - 150 m) with oblique Tucker trawls at 40 stations across the Subarctic Frontal Zone of the North Pacific Ocean and adjacent water masses. Thirteen zooplankton taxanomic groups were identified and their vertical and spatial distributions are 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 deeper stratum, primarily due to the overlapping distributions of the two predominant chaetognath species, Sagitta elegans and Eukrohina hamata, and the abundant deeper dwelling mysid, Euchaetomeropsis merolepis, found in our 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 the most abundant in TZ. Mysids were found only in the SAFZ. Overall, the most significant change in the zooplankton community occurred between the SD and the SAFZ.


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