THE SEASONAL AND GEOGRAPHIC DISTRIBUTION OF PRIMARY PRODUCTIVITY OFF THE WASIIINGTON AND OREGON COASTS

Abstract

The distribution of chlorophyll a and phytoplankton productivity off the Washington and Oregon coasts has been observed during 14 cruises of the RV Brown Bear from January 1961 to June 1962. Surface waters in the area covered by the Columbia River effluent generally contained more phytoplankton and had a higher rate of photosynthesis than ambient waters. The densest and most variable populations were found during summer in coastal upwelling areas and directly off the river mouth. Although there was little seasonal change in standing stock, production was quite variable, with minima in winter and summer, a large spring bloom, and a smaller autumn pulse. The major influence of Columbia River water on phytoplankton production appeared to be in the timing of events in the seasonal cycle. Phytoplankton development was noticeably affected by differences in the depth of the mixed layer and the sharp pycnocline during summer. However, total annual production both inside and outside the plume was similar (60 g C m −2 a yr −1 ) . The nutrients introduced by river water appeared to be spent in high‐production areas immediately off the mouth of the river. The seasonal variation of C 14 uptake‐chlorophyll a ratios was marked. Low values occurred during winter, and a maximum occurred during the spring bloom. “Dead” or inactive chlorophyll appeared to be negligible at all times, judging from regressions of these relationships.