II-C-14 



Anderson, G.C. 1964. The seasonal and geographic distribution of primary 



productivity off the Washington and Oregon coasts. Limnology and 



Oceanography 9:284-302. 



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 small autumn pulse. 



The major influence of Columbia River water on phytoplankton production 

 appeared to be in the timing of events in the seasonal cycle. Phyto- 

 plankton 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"^ yr~^). The nutrients introduced by river water 

 appeared to be spent in high-production areas immediately off the mouth 

 of the river. 



14 

 The seasonal variation of C 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. 



There is little information on the effects on plankton of large 

 freshwater discharges into oceanic areas. However, it may be expected 

 that the effect of the Columbia River discharge on the distribution 

 and activity of plankton organisms will be marked and will vary seasonally 

 with the amount and quality of discharge and its subsequent distribution. 



The primary objective of this paper is to relate the standing crop 

 and production of plankton to seasonal variations in the distribution 

 of Columbia River effluent. (A. A. -modified) 



Keywords: primary productivity, chlorophyll a^, phytoplankton, Washington, 

 Oregon 



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