Intra-seasonal variation of upwelling and its effects on copepod community structure off central/southern Chile (2002–2009)
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Copepods are major components of zooplankton in the Humboldt Current system. Here, intra-seasonal (monthly) variation of upwelling and its influence on the copepod community were assessed. Species abundances, species richness, diversity (Shannon–Wiener index) and dominance, were studied during four upwelling periods (2002–2009) at the Station 18 time series off of Concepción (36°S). Although 77 species were identified, most variability of the community structure was explained by few (<10) species. A negative trend in copepod abundance over the years was associated with lower oxygenation of the mixed layer. A generalized linear model test for relationships among community descriptors and environmental parameters (temperature, dissolved oxygen, chlorophyll, and water column stratification) revealed that diversity was positively correlated with stratification. Upwelling variation, reflected in alternate periods (active and relaxed), characterized two distinct communities during the spring–summer. The study concludes that upwelling interacts with copepod populations by changing stratification, and temperature and oxygenation gradients. The study also suggests that greatly increased upwelling may negatively impact copepods by reducing oxygenation, cooling down the mixed layer and causing more advection. The same mechanisms may be operating in other systems, and thus this study provides clues on how zooplankton communities can respond to climate-induced variation of upwelling.
KeywordsCopepods Chile Upwelling Intra-seasonal variation Community structure
This work has been supported by The Chilean Funding for Science and Technology, Grant FONDECYT 113-0511, and the Instituto Milenio de Oceanografía (IMO-Chile) funded by Iniciativa Científica Milenio (ICM) of Chile. Zooplankton sampling was carried out during the COPAS Time Series Study funded by Funding for Priority Areas (FONDAP) of the Chilean Commission for Science and Technology (CONICYT). We are indebted to P. v. Dassow, who carefully reviewed the work and provided us with valuable comments. Two anonymous reviewers greatly helped improve earlier versions of the work. This work is a contribution to IAI ANTARES CRN3094 and LIA MORFUN project.
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