MEPS 443:111-127 (2011)  -  DOI: https://doi.org/10.3354/meps09433

ABSTRACT: Coastal upwelling systems can directly or indirectly affect the population dynamics of marine invertebrates due to their influence on residual circulation patterns and biological production cycles. In the present study we evaluated the influence of shelf winds and continental runoff on settlement patterns of Mytilus galloprovincialis at 2 contrasting locations in an embayment (Ría de Ares-Betanzos) located at the northern boundary of the Iberian−Canary current upwelling system. We quantified settlement at 2 depths (1 and 6 m) every 15 d for a period of 2 yr at an outer location (Miranda) with direct oceanic influence and at an estuarine dominated site in the inner ría (Arnela). We explored the instantaneous and delayed (15 and 30 d) effects of the forcing variables to infer their influence at different times in larval development. The results showed a coupling between mussel settlement and the upwelling favourable season. Wind stress and Ekman transport along the main axis of the ría affected mussel settlement patterns significantly. Instantaneous and delayed responses showed the relevance of shelf winds at different larval developmental stages. Inverse patterns were observed between the inner and outer location in response to instantaneous winds. Onshore transport caused a decrease in settlement at Miranda, while only intense offshore transport showed a detrimental effect on settlement at Arnela. With regard to the 15 d delayed effect, maximum settlement abundances matched at both locations with transport values around zero. The 30 d delayed effect on settlement abundance showed a positive linear relationship with wind stress and Ekman transport at both locations. These relationships might be directly related to physical transport processes or indirectly associated with food availability and larval survival.

KEY WORDS: Coastal upwelling · Mussel · Settlement · Galician rías · NW Spain