Journal of Geophysical Research: Biogeosciences

Cover image for Vol. 122 Issue 10

Impact Factor: 3.395

ISI Journal Citation Reports © Ranking: 2016: 34/188 (Geosciences Multidisciplinary); 57/229 (Environmental Sciences)

Online ISSN: 2169-8961

Associated Title(s): Journal of Geophysical Research

Changing Chilean coastal currents could drive aquatic evolution

For invertebrate and fish species that spend most of their lives in rich coastal waters rather than migrating freely throughout the open ocean, the formation of island populations and the associated risk of genetic diversity loss are threats to long-term population health. Many species cope through a spawning mechanism whereby larvae are released en masse into the near-shore ocean currents, like pollen adrift in the wind. The larvae are viable in open waters from days to months, but only those that find their way back to shore can settle and develop. To increase their chances, different species' larvae often use particular swimming behaviors, for example, varying their depth in the water column throughout the day. Off the coast of central Chile, the effects of climate change on oceangoing larvae are investigated by Aiken et al. (2011). Observations and climate simulations suggest that the southerly winds that blow along the Chilean coast will become stronger and more frequent by the end of the century, given a fragmented and economically motivated global response to climate change. Using an ocean circulation model, the authors found that this change will increase coastal upwelling and the strength of surface eddies. Applying a particle dispersion model to the forecast of future currents lets the authors identify the likely success rate of larvae making their way back to the coast. They found that the viability of passively drifting larvae was severely degraded, as the strong flows often carried them along or away from the shore. The vertical swimmers, on the other hand, could sink below the 20-m-thick Ekman transport layer, marginally increasing their chances of finding a viable habitat. The authors suggest that changing coastal currents could become a powerful evolutionary selection pressure, favoring species with vertically mobile larvae over those without.

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