Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8776
Title: Temporal variation in the biochemical ecology of lower trophic levels in the Northern California Current
Author: Jessica A. Miller, W. T. Peterson, Louise A. Copeman, Xiuning Du, C. A. Morgan, Marisa N.C. Litz
Publication Year: 2017
Journal: Progress in Oceanography
Volume: 155
Pages: 1-12
Keywords: biochemical ecology,lower trophic levels,lipids and fatty acids,Northern California Current,"Oregon, USA"

There is strong correlative evidence that variation in the growth and survival of secondary consumers is
related to the copepod species composition within the Northern California Current. Potential mechanisms
driving these correlations include: (1) enhanced growth and survival of secondary consumers when lipidrich,
boreal copepod species are abundant, with cascading effects on higher trophic levels; (2) the regulation
of growth and condition of primary and secondary consumers by the relative proportion of certain
essential fatty acids (FAs) in primary producers; or (3) a combination of these factors. Disentangling the
relative importance of taxonomic composition, lipid quantity, and FA composition on the nutritional
quality of copepods requires detailed information on both the consumer and primary producers.
Therefore, we collected phytoplankton and copepods at an oceanographic station for 19 months and completed
species community analyses and generated detailed lipid profiles, including lipid classes and FAs,
for both groups. There was strong covariation between species and biochemistry within and across
trophic levels and distinct seasonal differences. The amount of total lipid within both the phytoplankton
and copepod communities was twice as high in spring and summer than in fall and winter, and certain
FAs, such as diatom indicators 20:5x3 and 16:1x7, comprised a greater proportion of the FA pool in
spring and summer. Indicators of bacterial production within the copepod community were proportionally
twice as high during fall and winter than spring and summer. Seasonal transitions in copepod FA
composition were consistently offset from transitions in copepod species composition by approximately
two weeks. The timing of the seasonal transition in copepod FAs reflected seasonal shifts in the species
composition and/or biochemistry of primary producers more than seasonal shifts in the copepod species
composition. These results emphasize the importance of interactions between the copepod community
and their available phytoplankton prey in regulating the nutritional quality of primary consumers.

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