standing stocks

Abstract

Although an extensive biological time series data set of phytoplankton and zooplankton standing stocks has been collected over a 30 yr period in the NE subarctic Pacific at Ocean Station Papa (OSP), the majority of these data were obtained before recent advances in our understanding of the structure and functioning of the manne microbial food web. In addition, recent studies did not obtain data during the winter penod. This paper provides the first contemporary biological description of the NE subarctic Pacific dunng winter Data from 2 winter cruises in the vicinity of OSP indicate that the abundance and composition of the autotrophic and heterotroph~c assemblage at these times are similar to those observed during late spring and summer by others. In contrast, winter mesozooplankton standing stocks are considerably less than observed In summer. These findings confirm the hypothesis that the relatively shallow winter mixed layer permits relatively high standing stocks of phytoplankton (20 mg C m-3) and consequently of microheterotrophs (7.1 to 13.1 mg C m-7 to subsist over the winter period. An assessment of autotrophic and heterotrophic biomass suggests that the requirements of the mesozooplankton (Stages IV to VI), microzooplankton and heterotrophic nanoflagellates may potentially be balanced by the standlng stocks of microplankton, nanoplankton/picophytoplankton, and picoplankton, respectively. However, the carbon requirements of heterotrophic bacteria cannot be balanced without invoking slower turnover times for thls pool relative to the turnover times for the dissolved organic carbon (DOC) pool.