Model-derived connectivity patterns along the western Iberian Peninsula: asymmetrical larval flow and source-sink cell

Abstract

Predicting the spatial and temporal patterns of marine larval dispersal and supply is a challenging task, requiring the use of novel approaches capable of capturing the inherent variability in the mechanisms involved. Biophysical models are emerging as important tools used to understand dispersal and recruitment of marine larvae on several scales, and are used here to investigate these problems in the Northeast Atlantic Iberian Upwelling system. We used a Regional Ocean Modelling System configuration coupled with an individual-based model in order to simulate diel vertical migration and estuary-reinvasion behaviours, growth and mortality of larvae of the common shore crab Carcinus maenas. With this simulation we aimed to hindcast coast-wide connectivity patterns under the atmospheric and river flow forcings of the years 2001 to 2009. In a previous study, this model had been shown to produce time series of larval supply to a single population, at daily frequencies, that were strongly correlated with observed time series. In the current application, the model predicts that along-shore advection of larvae is variable from year to year; is correlated with the annual North Atlantic Oscillation index, which reflects the strength and persistence of equatorward winds; and is usually asymmetric, with a predominant equatorward transport. The model also predicts a source-sink cell located between the Muros- Noia and Mondego estuaries, where populations in the north consistently act as net sources of larvae supplying net sink populations to the south. This source-sink cell appears to be related to the existence of habitat gaps, coast geo metry and an oceanographic retention effect associated with upwelling dynamics.