Many fish and coastal invertebrates have complex life cycles with variations in the supply of settling larvae affecting the structure of their communities. The dynamics of coastal upwelling areas can favour larval “washout” by means of cross-shelf transport that may move larvae away from the settlement sites. Earlier studies provided evidences of sweeping offshore during upwelling and shoreward movement during downwelling. However, this picture has revealed more complex. Galicia constitutes the northern boundary of the Iberian-Canary current upwelling system where seasonal winds promote upwelling from April to September and downwelling the rest of the year. The upwelling season appears as a succession of wind stress/relaxation cycles of period 10-20 days. Here, we study the shorttimescale variability of upwelling episodes and their influence on the abundance of Octopus vulgaris paralarvae. We sampled a cross-shore transect in the Ría de Vigo and the adjacent shelf during three years under contrasting oceanographic periods. Paralarvae abundance and biomass increased when nitrate, ammonium and chlorophyll decreased. These conditions occur during the relaxation of upwelling events when nutrient salts are consumed to produce biogenic matter, which is retained in the system and transferred through the food web. A multiple linear relationship with these hydrographic variables explains up to 85%VAR of paralarvae abundance. Therefore, octopus paralarvae are affected by the high frequency variability of the upwelling characteristics increasing its abundance/biomass during the relaxation phase of upwelling events

Symposium GLOBEC–IMBER España, Valencia, 28-30 marzo 2007

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