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

Abstract

2004. Carbon cycling through the pelagic foodweb in the northern Humboldt Current off Chile (23(S). e ICES Journal of Marine Science, 61: 572e584.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 (1e8 gC m ÿ2 d ÿ1 ) were mostly due to the net-phytoplankton size fraction (O23 mm). 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 filterfeeding 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 mgC ind ÿ1 d ÿ1 , 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 6e11%). However, when the pico-C 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 ÿ1 d ÿ1 , respectively. In terms of biomass consumed, the potential impact of carnivorous gelatinous zooplankton on the small-size copepod community ( preferred prey) was important (2e12% 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.

Spatio-temporal structure of the jellyfish community in the transition zone of cold and warm currents in the northwest Pacific

“…Understanding of its fragile gelatinous inhabitants has been gradually progressed by using modern survey technologies such as multiple opening/closing nets, crewed submersibles, remotely-operated vehicles (ROVs) and visual/video plankton recorders (VPRs), and it is now obvious that many kinds of gelatinous plankton inhabit the midwater zone in large numbers (Mackie 1985, Larson et al 1991, Toyokawa et al 1998, Kitamura et al 2008, Raskoff et al 2010. This indicates that gelatinous organisms may play a significant role in marine food webs, material transfer and transformation (Bailey et al 1995, González et al 2004, Sweetman & Chapman 2011. Studies of the actual biomass, community structure and species diversity are crucial to the understanding of the dynamics of the global marine ecosystem.…”

Biochemical features of a <i>Protoceratium reticulatum</i> red tide in Chipana Bay (Northern Chile) in summer conditions

“…The upwelling area of northern Chile is one of the most productive systems around the world, supporting fisheries and aquaculture in both the pelagic and benthic zones González et al, 2004;Arntz et al, 2006). During the annual cycle, phytoplankton composition and productivity change in this area Herrera and Escribano, 2006).…”

Bacterial and Phytoplankton Production in Two Coastal Systems Influenced by Distinct Eutrophication Processes

“…GonzalezRodriguez et al 1992, Gonzalez-Rodriguez 1994 are under the fi nds from other upwelling systems (e.g. Gonzalez et al 2004, Montecino et al 2004. This is probably a consequence of reduced surface heating (Valentin 2001) and high grazing pressure over the phytoplankton (Guenther et al 2008a).…”