Natal site and offshore swimming influence fitness and long-distance ocean transport in young sea turtles
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Although long-distance transport of marine organisms is constrained by numerous oceanic and biological factors, some species have evolved life-histories reliant on such movements. We examine the factors that promote long-distance transport in a transoceanic migrant, young loggerhead sea turtles (Caretta caretta), from the southeastern U.S. Empirical data from near-surface buoys and simulations in two ocean circulation models indicated that passive drifters are often retained for long periods shoreward of oceanic fronts that delineate coastal and offshore waters. Further simulations revealed that offshore swimming aided newly hatched turtles in moving past fronts and increased turtles’ probability of survival, reaching distant foraging grounds, and encountering favorable temperatures. Swimming was most beneficial in regions that were more favorable under scenarios assuming passive drift. These results have broad implications for understanding the movement processes of many marine species, highlighting likely retention of more planktonic species and potential for dispersal in more nektonic species.
NFP, GCH, and RS conceived the project. PV developed ICHTHYOP software, NFP ran the HYCOM simulations, and RS and RM calculated the NEMO trajectories. NFP and RS analyzed the data, NFP wrote the manuscript with contributions from all authors. NFP was supported by NCSU’s Initiative for Biological Complexity and a Journal of Experimental Biology travel fellowship. RS was funded through a PhD studentship awarded to GCH from the Natural Environment Research Council. GCH was supported by grants from the Natural Environmental Research Council, The Esmée Fairbairn Foundation and the Climate Change Consortium for Wales (C3W).
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