Abstract
BackgroundPredicting the spatial and temporal patterns of marine larval dispersal and supply is a challenging task due to the small size of the larvae and the variability of oceanographic processes. Addressing this problem requires the use of novel approaches capable of capturing the inherent variability in the mechanisms involved.Methodology/Principal FindingsIn this study we test whether dispersal and connectivity patterns generated from a bio-physical model of larval dispersal of the crab Carcinus maenas, along the west coast of the Iberian Peninsula, can predict the highly variable daily pattern of wind-driven larval supply to an estuary observed during the peak reproductive season (March–June) in 2006 and 2007. Cross-correlations between observed and predicted supply were significant (p<0.05) and strong, ranging from 0.34 to 0.81 at time lags of −6 to +5 d. Importantly, the model correctly predicted observed cross-shelf distributions (Pearson r = 0.82, p<0.001, and r = 0.79, p<0.01, in 2006 and 2007) and indicated that all supply events were comprised of larvae that had been retained within the inner shelf; larvae transported to the outer shelf and beyond never recruited. Estimated average dispersal distances ranged from 57 to 198 km and were only marginally affected by mortality.Conclusions/SignificanceThe high degree of predicted demographic connectivity over relatively large geographic scales is consistent with the lack of genetic structuring in C. maenas along the Iberian Peninsula. These findings indicate that the dynamic nature of larval dispersal can be captured by mechanistic biophysical models, which can be used to provide meaningful predictions of the patterns and causes of fine-scale variability in larval supply to marine populations.
Highlights
Most marine populations are demographically open, as individuals are regularly exchanged among sets of local populations, either through the transport of planktonic propagules by currents or by the movement of adults [1], [2]
Observed time series of megalopal supply Observed supply of Carcinus maenas megalopae to the Ria de Aveiro in 2006 and 2007 (Figures 2A and 3A) showed periods of several weeks with zero or very low supply punctuated with supply events driven by along-shore winds, as well as several instances when supply events occurred with semilunar periodicity during spring tides in spring and summer, in 2006
The Base experiments without diel vertical migration (DVM) resulted in very high levels of larval wastage from the shelf, compared with those with DVM, with a decrease of one order of magnitude in supply and only a few tens of particles successfully recruiting to the Ria de Aveiro
Summary
Most marine populations are demographically open, as individuals are regularly exchanged among sets of local populations, either through the transport of planktonic propagules by currents or by the movement of adults [1], [2]. Instantaneous mortality rates for marine larval stages are on the order of 0.0161 to 1.0100 [12] Combined, these processes further decrease the likelihood of detecting larvae by conventional sampling methods, ones that are dispersed large distances away from their population of origin [13]. Predicting the spatial and temporal patterns of marine larval dispersal and supply is a challenging task due to the small size of the larvae and the variability of oceanographic processes. Addressing this problem requires the use of novel approaches capable of capturing the inherent variability in the mechanisms involved
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