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Title: Primary Production in the Columbia River Estuary. II. Grazing Losses, Transport, and a Phytoplankton Carbon Budget 
Author: Lara-Lara, J Ruben; Frey, Bruce E.; Small, F. Lawrence
Date: 1990-01
Publisher: University of Hawaii Press
Citation: Lara-Lara JR, Frey BE, Small LF. 1990. Primary production in the Columbia river estuary. II. grazing losses, transport, and a phytoplankton carbon budget. Pac Sci 44(1): 38-50.
Abstract: Mean loss of phytoplankton carbon as a result of microcrustacean
grazing ranged from 0.03 to 8.94 mg C m- 3 day-1", depending upon time of year
and location in the estuary. On an annual basis, median grazing rate was 1893 mt
C yr-1, which represented 6.3% of the annual primary production in the estuary.
Daily transport of phytoplankton carbon decreased from the fluvial
regions to the ocean, with the largest decrease occurring at the freshwater-brackish
water interface. Annual import to the study area from upriver (excluding the
May 1980 data, which were affected by the eruption of Mt. Saint Helens) was
61,440 mt C yr-1", while annual export to the ocean was 40,560 mt C yr–1. Total
phytoplankton carbon input to the estuary was 91,316 mt C yr-1, a summation
of import from upriver and in situ primary production (29,876 mt C yr-1", from
a previous report). Export to the ocean plus median in situ grazing loss equalled
42,453 mt C yr-1", so that there was an unaccounted balance of 48,863 mt C yr-1.
Some of this was night-time respiratory loss from the phytoplankton, estimated
at 12,209 mt C yr-1. If the standing stock of phytoplankton carbon in the estuary
was reasonably in steady state on an annual basis, the remaining balance must
have been satisfied by conversion of phytoplankton carbon to non -chlorophyllous
detrital particulate carbon (mostly at the freshwater-brackish water interface)
and/or by conversion to dissolved organic carbon during transit through the
estuary. Some indirect evidence suggests that phytoplankton carbon was mainly
converted to detrital particulate carbon during the short transit time through the
estuary, but verification requires further data.
ISSN: 0030-8870

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