High-frequency coastal upwelling events influence octopus vulgaris larval dynamics on the NW Iberian shelf

Abstract

Planktonic larval dispersal affects the structure, management, and conservation of many fish and coastal invertebrate populations. The dynamics in coastal upwelling areas favour transport of larvae to the open ocean during upwelling episodes, and concentration of larvae in coastal waters under upwelling relaxation or downwelling conditions. Recent work provides evidence that pelagic larval stages in upwelling areas are influenced by specific larval behaviour, biogeography, and life history parameters among others. Nevertheless, very few of these studies have addressed these findings quantitatively. Here, we present a general approach for assessing the influence of high-frequency upwelling events on Octopus vulgaris planktonic larvae. Specifically, we analyse the rates of change in abundance and biomass of the O. vulgaris early larval phase in the NW Iberian coast, where upwelling events occur with a frequency of 10 to 20 d from April to September. Our analysis indicates that the increase in larval abundance and biomass is significantly correlated with the simultaneous decrease of water column integrated nitrate, ammonium and chlorophyll levels. These conditions occur during the early stage of the relaxation phase of coastal upwelling events, when nutrient salts are consumed to produce biogenic matter, which is retained in the system and transferred through the food web.