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Marine Ecology Progress Series

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MEPS 192:239-247 (2000)  -  doi:10.3354/meps192239

Temporal variation in body composition and lipid storage of the overwintering, subarctic copepod Neocalanus plumchrus in the Strait of Georgia, British Columbia (Canada)

Melissa Evanson1,*, Elizabeth A. Bornhold2, Robert H. Goldblatt3, Paul J. Harrison3, Alan G. Lewis3

1Department of Zoology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
2Ocean Science and Productivity, Institute of Ocean Sciences, 9860 West Saanich Rd, Sidney, British Columbia V8L 4B2, Canada
3Department of Earth and Ocean Sciences (Oceanography), University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada

ABSTRACT: Neocalanus plumchrus (Marukawa) was sampled between October 1996 and August 1997 in the upper 400 m of the water column in Strait of Georgia (49° 15' N, 123° 45' W), a large, partly enclosed basin in British Columbia, Canada. The overwintering vertical stage distribution of N. plumchrus is described together with the temporal variations in total body length, dry weight, lipid and body composition in copepodite stage V (CV) and adult females. Adult males and females were found at depths of less than 200 m from January to March. Regressions of total body length to total dry weight showed significant correlations for CVs and females. Carbon and nitrogen isotopic analysis (δ15N and δ13C) indicated no temporal increase, suggesting a lack of feeding in CVs (October to December) and females (January to March) at depth and a dependency on stored lipid reserves accumulated during times of high primary production in the euphotic zone. Total lipid content per individual copepod showed significant decreases from 0.5 to 0.2 mg during the time of adult female gonadal development between January and February. A decrease in total dry mass per copepod from 0.9 to 0.4 mg also occurred during this time period. Lipid composition showed preferential retention of long-chained fatty acids until the onset of egg release in March. Significant decreases in carbon and nitrogen from January to February and, to a lesser extent, between February and March were observed, corresponding to periods of gonad maturation and egg release, respectively. Significant increase in nitrogen content suggests the possibility of bacterial ingestion by late moulting CVs. The significant decrease in C:N ratio, from 8.7 to 4.1, suggests a depletion of lipid reserves and resultant reliance on proteins as an energy source for egg release. Variations in organic content verify that the CVs remain in a state of dormancy in which minimal lipid reserves are depleted, while the onset of maturation and reproduction is the major energy consumer.

KEY WORDS: Neocalanus plumchrus · Lipid · Body composition · Vertical distribution · Temporal variation

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