Composition, spatial distribution, and trophic structure of the zooplankton community in San Jorge Gulf, southwestern Atlantic Ocean

GIMENEZ ELOISA; WINKLER, GESCHE; HOFFMEYER, MÓNICA; FERREYRA, GUSTAVO

OCEANOGRAPHY

OCEANOGRAPHY SOC

Año: 2018

1042-8275

The goal of this study was to understand the zooplankton community composition and food web structure in San Jorge Gulf (45°?47°S, 65°30´W), a highly productive marine ecosystem in southern Argentina. A spatial grid of 14 stations was sampledin 2014. The sampled zooplankton community was composed of 30 taxa, with copepods accounting for 83% of the total abundance. Community composition was stronglyrelated to surface temperature and water column stratification. Two distinct zooplankton assemblages were present. The zones designated North and Center were dominated by Ctenocalanus vanus; copepodite stages of C. vanus, Clausocalanus brevipes,and Paracalanus parvus; appendicularians; and Oithona helgolandica. The South zonewas dominated by P. parvus, copepodites, Acartia tonsa, and Drepanopus forcipatus. Theplankton food webs were increasingly enriched in carbon and nitrogen stable isotopesfrom the North to the South. Depleted δ13C signatures in the North may be explainedby terrigenous inputs derived from strong westerly winds. The zooplankton taxa displayed a wide feeding range in the North, whereas the narrow trophic space of the Southfood web suggested similar feeding strategies among the taxa. Appendicularians werepositioned at the base of the food webs, copepods were in the middle, and chaetognathsoccupied high trophic positions.