Seasonal and interannual coupling between sea surface temperature, phytoplankton and meroplankton in the subtropical south-western Atlantic Ocean

Meroplankton abundance (Bivalve larvae, Cirripede larvae and other non-identified larvae), phytoplankton biomass and sea surface temperature (SST) from a 15-year time series (19952009) in the Cabo Frio region, south-western Atlantic Ocean, were analysed to assess temporal patterns of co-variation. Weekly zooplankton sampling included vertical hauls (approximate to 20m) with a 100 m net, taken in triplicate. All data were standardized to monthly within-year anomalies (n 180), monthly between-year anomalies (n 12) and annual anomalies (n 15). Monthly and annual anomalies were compared by means of cross-correlation analyses, and trends were estimated by linear regression in time series after removing serial dependence. The degree of coupling between phytoplankton and meroplankton was estimated from the analysis of their interannual changes during the seasonal maxima of these variables. The three variables displayed a strong seasonality, and there is evidence of coupling between phytoplankton biomass and meroplankton abundance, dominated by bivalves and cirripedes, during the austral spring (mostly September to November). Meroplankton abundance was positively correlated to SST and negatively to phytoplankton; the latter correlation suggested that a sudden supply of meroplankton larvae can contribute to controlling phytoplankton biomass during the upwelling season. In contrast, annual changes in SST and phytoplankton biomass fail to account for the interannual variation in larval supply.