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No Great Need to Worry about Earth's Kelp in a Warming World

Paper Reviewed
Mohring, M.B., Wernberg, T., Wright, J.T., Connell, S.D. and Russell, B.D. 2014. Biogeographic variation in temperature drives performance of kelp gametophytes during warming. Marine Ecology Progress Series 513: 85-96.

Mohring et al. (2014) introduce their study by writing that "species with broad geographical distributions, extending across multiple latitudes, commonly span large temperature gradients," and they say that "in order to survive and optimize performance across their ranges, these species must adjust their physiology to local conditions and temperature regimes," citing Sunday et al. (2012). And this is what they would also have to do along the full latitudinal extent of their ranges if the Earth were to begin to warm globally once again. So how well are the Ecklonia radiata kelp along the shores of Australia prepared to meet this potential challenge?

To answer this question, the five Australian researchers investigated the effects of temperature on the density and size of gametophytes of the kelp in question across its Australian latitudinal distribution, which runs approximately between latitudes 9 and 33°S. This work revealed that gametophytes from warm, intermediate and cool biogeographic regions spanning a temperature range of 12 to 26°C all exhibited optimum temperatures of about 18 to 23°C, which they note was "well above current maximum temperatures in parts of the range," as well as "a positive relationship between in situ temperature and thermal optima for performance."

In commenting on their findings, Mohring et al. write that their results "document that present-day populations of E. radiata have adjusted their gametophyte thermal sensitivity according to their local environment, and further indicate that these differences are adaptive rather than phenotypic." Collectively, therefore, they say their findings suggest "the scope for thermal adaptation and gametophyte performance of E. radiata across most of its Australian distribution is within projected levels of future warming."

References
Sunday, J.M., Bates, A.E. and Dulvy, N.K. 2012. Thermal tolerance and the global redistribution of animals. Nature Climate Change 2: 686-690.

Posted 8 June 2015