Carbon 13 carbon 12 and nitrogen 15 nitrogen 14 isotope ratios in the southern benguela ecosystem indicators of food web relationship among different size classes of plankton and pelagic fish differences between fish muscle and bone collagen tissues

Sholto Douglas, A.D.; Field, J.G.; James, A.G.; Van Der Merwe, N.J.

Marine Ecology Progress Series 78(1): 23-31

1991


ISSN/ISBN: 0171-8630
Accession: 007078878

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Abstract
Measurements of the stable isotope ratios of carbon and nitrogen were obtained for 3 size-fractions of plankton and 2 species of pelagic fish, Engraulis capensis Gilchrist and Etrumeus whiteheadi Wongratana, from the Benguela current system on the southwest coast of Africa. There was a trend towards enrichment in 13C and 15N with increasing plankton size. The data are consistent with the hypothesis that larger plankton feed further up the food web than smaller plankton. Fish muscle and bone collagen tissues tended to be more enriched than the plankton. There was depletion of the heavier isotopes with increasing fish length, in contrast to the opposite tendency with increasing plankton size and towards the trophic position of fish. The fractionation of 13C/12C and 15N/14N ratios during the formation of muscle tissue was different from that for bone collagen. Bone collagen was richer in 13C than muscle tissue, whereas muscle was richer than bone collagen in 15N. For both 13C and 15N, the less enriched tissue displayed the stronger negative correlation with fish length.