Journal Article

Carbon cycling through the pelagic foodweb in the northern Humboldt Current off Chile (23°S)

H.E. González, R. Giesecke, C.A. Vargas, M. Pavez, J. Iriarte, P. Santibáñez, L. Castro, R. Escribano and F. Pagès

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 61, issue 4, pages 572-584
Published in print January 2004 | ISSN: 1054-3139
Published online January 2004 | e-ISSN: 1095-9289 | DOI:
Carbon cycling through the pelagic foodweb in the northern Humboldt Current off Chile (23°S)

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  • Environmental Science
  • Marine and Estuarine Biology


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The structure of the zooplankton foodweb and their dominant carbon fluxes were studied in the upwelling system off northern Chile (Mejillones Bay; 23°S) between October 2000 and December 2002. High primary production (PP) rates (1–8 gC m−2 d−1) were mostly due to the net-phytoplankton size fraction (>23 μm). High PP has been traditionally associated with the wind-driven upwelling fertilizing effect of equatorial subsurface waters, which favour development of a short food chain dominated by a few small clupeiform fish species. The objective of the present work was to study the trophic carbon flow through the first step of this “classical chain” (from phytoplankton to primary consumers such as copepods and euphausiids) and the carbon flow towards the gelatinous web composed of both filter-feeding and carnivorous zooplankton. To accomplish this objective, feeding experiments with copepods, appendicularians, ctenophores, and chaetognaths were conducted using naturally occurring plankton prey assemblages. Throughout the study, the total carbon ingestion rates showed that the dominant appendicularian species and small copepods consumed an average of 7 and 5 μgC ind−1 d−1, respectively. In addition, copepods ingested particles mainly in the size range of nano- and microplankton, whereas appendicularians ingested in the range of pico- and nanoplankton. Small copepods and appendicularians removed a small fraction of total daily PP (range 6–11%). However, when the pico- + nanoplankton fractions were the major contributors to total PP (oligotrophic conditions), grazing by small copepods increased markedly to 86% of total PP. Under these more oligotrophic conditions, the euphausiids grazing increased as well, but only reached values lower than 5% of total PP. During this study, chaetognaths and ctenophores ingested an average of 1 and 14 copepods ind−1 d−1, respectively. In terms of biomass consumed, the potential impact of carnivorous gelatinous zooplankton on the small-size copepod community (preferred prey) was important (2–12% of biomass removed daily). However, their impact produced more significant results on copepod abundance (up to 33%), which suggests that carnivorous gelatinous zooplankton may even modulate (control) the abundance of some species as well as the size structure of the copepod community.

Keywords: coastal foodweb; gelatinous zooplankton; Humboldt Current system; trophic carbon flow

Journal Article.  7059 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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