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

Abstract

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 underwater, 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.

Mapping microhabitat thermal patterns in artificial breakwaters: Alteration of intertidal biodiversity by higher rock temperature

“…Ecological engineering solutions to enhance biodiversity and values for ecosystem functioning in artificial infrastructures, should consider the complex spatial‐temporal thermal structure of these novel habitats in their research and planning agendas. Therefore, future studies could consider complementary methodologies to deal with variation of thermal patterns at different spatial scales (e.g., see Judge et al, ; Lathlean & Seuront, for reviews), in a suite of integrated coastal artificial infrastructures. This could shed light on the potential large‐scale effect of coastal urban infrastructures in contributing to exacerbate the local effect on biota of frequent heat waves, and in the subsequent alteration of the coastal climate.…”

“…We used infrared thermal imaging as a noncontact and noninvasive technique for temperature measurement (Lathlean & Seuront, ; Lathlean, Seuront, & Ng, ; Seuront et al, ). This method is widely used in a range of fields, especially in intertidal rocky shore systems (Chapperon & Seuront, , ; Lathlean, Ayre, & Minchinton, ; Lathlean & Seuront, ; Rojas et al, ), and allows measurement of the complex thermal patterns of natural and/or artificial surfaces at micro‐scales (few cm's) (Seuront et al, ). We used this technique because we were focused on the spatial patterns of substrate temperature instead of organisms' tissue temperatures, for which data loggers or thermocouples would be more appropriated (see Judge, Choi, & Helmuth, ).…”

Biodiversity and thermal ecological function: The influence of freshwater algal diversity on local thermal environments

“…Thermography quantifies thermal infrared radiation, in particular, that is emitted by the focal organism(s) (e.g., mammals, mollusks (Lathlean & Seuront, 2014;Seuront, Ng, & Lathlean, 2018), or, here, phytoplankton); it is distinct from greenness, which concerns reflected light (most often from chlorophyll in relatively transparent freshwater algal species). Thermography quantifies thermal infrared radiation, in particular, that is emitted by the focal organism(s) (e.g., mammals, mollusks (Lathlean & Seuront, 2014;Seuront, Ng, & Lathlean, 2018), or, here, phytoplankton); it is distinct from greenness, which concerns reflected light (most often from chlorophyll in relatively transparent freshwater algal species).…”

“…We measured sensible heat using thermography. Thermography quantifies thermal infrared radiation, in particular, that is emitted by the focal organism(s) (e.g., mammals, mollusks (Lathlean & Seuront, 2014;Seuront, Ng, & Lathlean, 2018), or, here, phytoplankton); it is distinct from greenness, which concerns reflected light (most often from chlorophyll in relatively transparent freshwater algal species).…”

Comparing infrared imagery to traditional methods for estimating ringed seal density

“…Thermal imaging in biological research has been used extensively in the study of wildlife in terrestrial environments (Cilulko et al ). The use of infrared cameras in studies of marine mammals is increasing (Lathlean and Seuront ) and has included aerial surveys to detect ringed seal ( Pusa hispida ) lairs (Kingsley et al ) and polar bear ( Ursus maritimus ) dens (Amstrup et al ), and estimate abundances of walruses ( Odobenus rosmarus ; Udevitz et al , Speckman et al , Lydersen et al ), harbour seals ( Phoca vitulina ; Cronin et al ) and ice‐associated seals (Conn et al , Sigler et al ). Although the attempts by Kingsley et al () to detect ringed seal lairs conducted in the late 1980s had limited success, more recent surveys in Alaska, USA, have demonstrated the potential for infrared technology in surveys of ice‐associated seals (Sigler et al ).…”