Coastal-oceanic distribution gradient of coccolithophores and their role in the carbonate flux of the upwelling system off Concepción, Chile (36°S)

The role of coccolithophores in the biogenic carbonate cycle was studied in the coastal upwelling zone off Concepción, Chile (36°S), and in adjacent oceanic waters during spring 2004. Coccolithophore abundance and diversity increased steadily from coastal to oceanic regions. The presence of an active coastal upwelling center clearly partitioned the study area into coastal, transition and two oceanic zones. Coccolithophores and diatoms showed an inverse relationship: coccolithophores with higher abundances in oceanic zones and diatoms more abundant in coastal zones. The suspended coccolithophore carbonate reached maximum values in the oceanic zones. Emiliania huxleyi was the only coccolithophore species observed in the coastal, upwelling-influenced region. The vertical export of coccolithophore carbonate offshore from Concepción (traps deployed between December 2005 and October 2006) was highly variable, with greatest flux during summer, dominated by coccoliths and coccospheres of large species: Calcidiscus leptoporus and Helicosphaera carteri. The contribution of coccoliths and coccospheres carried downward in appendicularian fecal pellets to total carbonate flux was low (1%); however, they contributed a major fraction to the coccolithophore carbonate export (mean of 27%). Our results highlight the relevance of large and less abundant coccolithophores and their coccoliths to the vertical flux of coccolithophore carbonate to the deep sea.