Infrared thermography in marine ecology: methods, previous applications and future challenges

Infrared thermography (IRT) is being increasingly utilised by animal physiologists and ecologists to investigate the role of thermal stress and small-scale thermal variability on the distribution and abundance of species. Due to the inability of infrared cameras to work under water, ecological studies that use IRT have largely been undertaken on terrestrial systems, while fundamentally limited to surfacing mammals in aquatic ecosystems. In recent years, however, IRT has been used to investigate the thermal ecology of intertidal organisms, which are intermittently exposed. The aim of this paper was to summarise the rapidly growing application of IRT in marine ecology, to discuss best practises for using IRT in the marine environment whilst outlining some common limitations, and to suggest future research directions. IRT has been successfully used to count and track the movements of a range of marine mammals as well as to quantify previously unobserved nocturnal feeding patterns. On rocky intertidal shores, IRT has largely been used to assess thermoregulatory processes in gastropods, mussels and sea stars and the effect of heat stress on barnacle recruitment. Ground-truthing and calibration procedures still remain the largest drawback for the use of IRT in ecological studies. However, once the appropriate calculations and working procedures have been implemented, thermal imaging is a reliable and rapid tool for measuring environmental and biological temperature variability. We believe such techniques will become increasingly popular as global temperatures, and hence thermal stress, continue to rise.