Intertidal Seastars' Responses to Ocean Warming and Acidification
McElroy, D.J., Nguyen, H.D. and Byrne, M. 2012. Respiratory response of the intertidal seastar Parvulastra exigua to contemporary and near-future pulses of warming and hypercapnia. Journal of Experimental Marine Biology and Ecology 416-417: 1-7.
Against this backdrop and working with adult P. exigua specimens collected from Little Bay, Sydney (Australia), McElroy et al. measured the metabolic rates of the seastars at conditions characteristic of high tide (ca. 18°C and pH 8.2), as well as at 3 and 6°C warmer conditions and at additional pH values of 7.8 and 7.6 "in all combinations," as they put it. And what did those rates reveal?
The three Australian researchers report that "the metabolic response of P. exigua to increased temperature (+3°C and +6°C) at control pH [8.2] indicates that this species is resilient to periods of warming as probably often currently experienced by this species in the field." And they also report that they "did not observe a negative effect of acidification on rate of oxygen consumption at control temperature, a combination of stressors that this species currently experiences at night time low tide."
Although the metabolic response of P. exigua is resilient to current levels of extreme temperature and pH stress - which are equivalent to mean conditions predicted for the end of the 21st century - it is possible that the extreme seawater temperatures and pH levels at that future time (if IPCC predictions prove true) will be greater than the extreme levels of today, which could prove to be a real challenge for the seastars. However, McElroy et al. write, in the concluding paragraph of their research report, that "species such as P. exigua with a broad distribution from warm to cold temperate latitudes may possess scope for adaptation (evolutionary change) and/or acclimation via phenotypic plasticity (Visser, 2008), as suggested for sympatric echinoid and ophiuroid species (Byrne et al., 2011; Christensen et al., 2011)." And based on the information archived under the heading of Aquatic Life Evolution in our Topical Archive, that possibility is beginning to look like a real likelihood.
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Stevenson, J.P. 1992. A possible modification of the distribution of the intertidal seastar Patiriella exigua (Lamarck) (Echinodoermata: Asteroidea) by Patiriella calcar (Lamarck). Journal of Experimental Marine Biology and Ecology 155: 41-54.
Visser, M.E. 2008. Keeping up with a warming world; assessing the rate of adaptation to climate change. Proceedings of the Royal Society B 275: 649-659.