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Microhabitats: Thermal Refugia for Rocky Intertidal Invertebrates

Paper Reviewed
Lathlean, J.A., Ayre, D.J., Coleman, R.A. and Minchinton, T.E. 2014. Using biomimetic loggers to measure interspecific and microhabitat variation in body temperatures of rocky intertidal invertebrates. Marine and Freshwater Research:

Lathlean et al. (2014) introduce their unique study by writing that "until recently, marine scientists have relied heavily on satellite sea surface temperatures and terrestrial weather stations as indicators of the way in which the thermal environment, and hence the body temperatures of organisms, vary over spatial and temporal scales," but they go on to note that "rocky intertidal shores are characterized by high degrees of topographic complexity producing a variety of microhabitats, including those that may function as thermal refugia for organisms sheltering from extreme heat stress," citing Denny et al. (2011) and Lathlean et al. (2012). And they also note that technological advances over the past decade "have allowed marine ecologists to use biomimetic loggers to record the temperatures experienced by target organisms over extended periods of time," citing Pincebourde et al. (2008), Broitman et al. (2009), Lima and Wethey (2009) and Szathmary et al. (2009), which loggers, in their words, "are capable of estimating interspecific variation in body temperatures because they incorporate the unique morphological characteristics (i.e. size, color, shape and composition) of each species."

In light of these facts, the four Australian researchers designed and deployed biomimetic temperature loggers that mimic the habitat-forming barnacle Tesseropora rosea, the predatory whelk Dicathais orbita, and the intertidal limpet Cellana tramoserica, with the objective to test (1) "whether the unique morphological characteristics of each species influenced the body temperatures of individuals exposed to the same environmental conditions" and (2) "whether the body temperatures of invertebrates are lower when they occupy certain microhabitats thus allowing those habitats to function as thermal refugia."

In pursuing the first of these objectives, Lathlean et al.(2014) did indeed find that across the many microhabitats they studied, daily maximal temperatures of the limpet were on average 2.1 and 3.1°C higher than the body temperatures of the whelk and the barnacle, respectively. Likewise, with regard to the second objective -- and for all three species -- they report that "microhabitat temperatures were considerably higher than their body temperatures, with differences as great as 11.1°C on horizontal rocky substrata."

This being the case, the scientific team from 'down under' concludes -- and rightly so -- that these "unique thermal properties and microhabitat preferences may be important determinants of species' capacity to cope with climate change," and they therefore write that "microhabitats that act as thermal refugia are expected to play an increasingly important role in mitigating future impacts of climate change on these benthic communities."

Broitman, B.R., Szathmary, P.L., Mislan, K.A.S., Blanchette, C.A. and Helmuth, B. 2009. Predator-prey interactions under climate change: the importance of habitat vs body temperature. Oikos 118: 219-224.

Denny, M.W., Dowd, W.W., Bilir, L. and Mach, K.J. 2011. Spreading the risk: Small-scale body temperature variation among intertidal organisms and its implications for species persistence. Journal of Experimental Marine Biology and Ecology 400: 175-190.

Lathlean, J.A., Ayre, D.J. and Minchinton, T.E. 2012. Using infrared imagery to test for quadrat-level temperature variation and effects on the early life history of a rocky-shore barnacle. Limnology and Oceanography 57: 1279-1291.

Lima, F.P. and Wethey, D.S. 2009. Robolimpets: measuring intertidal body temperatures using biomimetic loggers. Limnology and Oceanography 7: 347-353.

Pincebourde, S., Sanford, E. and Helmuth, B. 2008. Body temperatures during low tide alters the feeding performance of a top intertidal predator. Limnology and Oceanography 53: 1562-1573.

Szathmary, P.L., Helmuth, B. and Wethey, D.S. 2009. Climate change in the rocky intertidal zone: predicting and measuring the body temperature of a keystone predator. Marine Ecology Progress Series 374: 43-56.

Posted 9 June 2015