Using biomimetic loggers to measure interspecific and microhabitat variation in body temperatures of rocky intertidal invertebrates Justin A. Lathlean A,C , David J. Ayre A , Ross A. Coleman B and Todd E. Minchinton A A Institute for Conservation Biology and Environmental Management & School of Biological Sciences, University of Wollongong, NSW 2522, Australia. B Centre for Research on Ecological Impacts of Coastal Cities, School of Biological Sciences, The University of Sydney, NSW 2006, Australia. C Corresponding author. Email: jlathlean@gmail.com Abstract. 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. We designed biomimetic temperature loggers for three species of rocky intertidal invertebrates to determine whether mimic body temperatures differ from the external environment and among species and microhabitats. For all three species, microhabitat temperatures were considerably higher than the body temperatures, with differences as great as 11.18C on horizontal rocky substrata. Across microhabitats, daily maximal temperatures of the limpet Cellana tramoserica were on average 2.1 and 3.18C higher than body temperatures of the whelk Dicathais orbita and the barnacle Tesseropora rosea respectively. Among-microhabitat variation in each species’ temperature was equally as variable as differences among species within microhabitats. Daily maximal body temperatures of barnacles placed on southerly facing vertical rock surfaces were on average 2.48C cooler than those on horizontal rock. Likewise, daily maximal body temperatures of whelks were on average 3.18C cooler within shallow rock pools than on horizontal rock. Our results provide new evidence that unique thermal properties and microhabitat preferences may be important determinants of species’ capacity to cope with climate change. Additional keywords: Australia, barnacle, Cellana tramoserica, climate change, Dicathais orbita, habitat temperature, limpet, Tesseropora rosea, whelk. Received 1 November 2013, accepted 13 March 2014, published online 26 November 2014 Introduction In a warming world, interspecific differences in body tem- peratures and thermal tolerances will produce a variety of responses among key species within a community. Rocky intertidal shores and their associated biological communities have emerged as excellent study systems to investigate how climate change will affect marine organisms (Helmuth et al. 2006b). As for many other biological communities, the persis- tence of rocky intertidal organisms will be dependent on their ability to adapt to the changing conditions, either physiologi- cally or behaviourally (by seeking out more benign micro- habitats) (Helmuth et al. 2006a; Tomanek 2008; Somero 2010). Because many intertidal organisms live at or close to their thermal limits (Denny and Harley 2006; Somero 2010), such physiological responses may be limited. Rocky intertidal shores are characterised 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 (Denny et al. 2011; Lathlean et al. 2012). Our ability to assess how these microhabitats mitigate the neg- ative effects of global warming for rocky intertidal communities is primarily dependent on characterising interspecific variation in body temperatures within and outside thermal refugia. Due to the dynamic nature of the marine environment, measuring body temperatures of marine organisms has proven somewhat difficult, and ambient temperature measurements taken by simple waterproof sensors may not reflect the actual body temperatures of an organism (Fitzhenry et al. 2004). Technological advances within the past decade, however, have allowed marine ecologists to use biomimetic loggers to record the temperatures experienced by target organisms over extended periods of time (Pincebourde et al. 2008; Broitman et al. 2009; Lima and Wethey 2009; Szathmary et al. 2009). These biomi- metic loggers are capable of estimating interspecific variation in body temperatures because they incorporate the unique mor- phological characteristics (i.e. size, colour, shape and composi- tion) of each species. Biomimetic loggers have been used successfully to measure broad-scale body temperatures of single CSIRO PUBLISHING Marine and Freshwater Research http://dx.doi.org/10.1071/MF13287 Journal compilation Ó CSIRO 2014 www.publish.csiro.au/journals/mfr Short Communication