THE NE SUB-ARCTIC PACIFIC IN WINTER .1. BIOLOGICAL STANDING STOCKS

Although an extensive biological time series data set of phytoplankton and zooplankton standing stocks has been collected over a 30 yr perio d in the NE subarctic Pacific at Ocean Station Papa (OSP), the majorit y of these data were obtained before recent advances in our understand ing of the structure and functioning of the marine microbial food web. In addition, recent studies did not obtain data during the winter per iod. This paper provides the first contemporary biological description of the NE subarctic Pacific during winter. Data from 2 winter cruises in the vicinity of OSP indicate that the abundance and composition of the autotrophic and heterotrophic assemblage at these times are simil ar to those observed during late spring and summer by others. In contr ast, winter mesozooplankton standing stocks are considerably less than observed in summer. These findings confirm the hypothesis that the re latively shallow winter mixed layer permits relatively high standing s tocks of phytoplankton (20 mg C m(-3)) and consequently of microhetero trophs (7.1 to 13.1 mg C m(-3)) to subsist over the winter period. An assessment of autotrophic and heterotrophic biomass suggests that the requirements of the mesozooplankton (Stages IV to VI), microzooplankto n and heterotrophic nanoflagellates may potentially be balanced by the standing stocks of microplankton, nanoplankton/picophytoplankton, and picoplankton, respectively. However, the carbon requirements of heter otrophic bacteria cannot be balanced without invoking slower turnover times for this pool relative to the turnover times for the dissolved o rganic carbon (DOG) pool.