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IH313 Are animals living in extreme environments best equipped to deal with climate change? Prof Wayne Bennett and Theresa Dabruzzi, University of West Florida The global climate is changing and researchers are predicting that the western Indo-Pacific will experience an increase of 2°C in sea surface temperatures over the next 50 years. Studies into the potential implications of climate change are focusing heavily on coral reefs as well as on reef organisms that inhabit these unique habitats. Whereas animals inhabiting open reef zones will likely experience rather gradual changes in water temperatures, the effects of warming will be more acutely felt in shallow reef margins, seagrass meadows, mudflats, and mangal habitats. Animals living in these areas will see not only higher average temperatures, but also more dramatic temperature extremes. It might be argued that these species are already exposed to markedly higher environment temperatures than their reef counterparts and therefore should possess well-developed physiological adaptations for dealing with thermal stress, hypoxia, and higher metabolic demands that typically accompany warming environmental conditions. It is unclear, however, if this is in fact the case. Indeed, a good argument can be made that fishes, arthropods and mollusks in shallow tropical waters are already living very near their upper thermal maximum, and any further increases in water temperature would exceed the ability of these animals to mitigate the negative impacts associated with exposure to harsh environmental extremes. Global climate change is one of the leading contemporary problems facing biologists and ecologists in the 21st century. For more than 80 years a fundamental tenet of physiological ecology has been that temperature is the “Abiotic Master Factor”. The underlying truth of this statement can be seen in the fact that temperature is either the experimental treatment factor, controlled for, or at the very least recorded in all biological studies. Temperature (or more precisely heat) influences biochemical reactions, sets the rate or pace of biological functions, masks effects of other biological entities, limits animal distribution, directs animal movement, and in extreme cases, sets the biokinetic limits for life. Temperature’s profound influence on living systems suggests a multitude of possible investigations into how warming temperatures may affect thermal ecology of shallow water species including: capacity acclimation limits, thermal niche determinations, metabolic compensation, and regulatory (masking) effects on other environmental conditions. Many of these physiological processes are poorly understood, and for some groups completely unknown, yet they are critical to conservation, restoration or mitigation efforts. The tropical marine waters of Indonesia fall within a zone known as the Golden Triangle, a region recognized as the center of marine biodiversity on planet Earth, and a global priority for conservation. Hoga Island in southeast Sulawesi is located within the Golden Triangle and boasts an extraordinary range of habitats and environmental conditions that play a major role in supporting the island’s staggering biodiversity. Nearly 3000 fish species as well as a countless number of invertebrates can be found in the immediate area, hundreds of these frequent the coral reefs, seagrass meadows, mudflats and mangrove habitats on Hoga’s margins. The term “marginal habitat” describes not only the relative location of these areas, but also alludes to the austere conditions that animals living in these habitats must endure. During low tide, for example, temperatures in Hoga’s marginal habitats may increase by up to 14°C in just a few hours. Over the same period, salinity can rise by as much as 10‰ while elevated biological oxygen demand dramatically reduces dissolved oxygen levels. In spite of their stark abiotic conditions, marginal habitats are critically important to the health and biodiversity of nearby reef and pelagic zones. The same conditions that challenge resident animal populations also exclude predators and competitors, making marginal zones attractive nursery areas. Preliminary studies suggest that these habitats are essential nursery areas for as many 20% of reef fish species as well as hundreds of invertebrate species – many of which are culturally or commercially valuable to local villages. In addition a wide array species spend their entire lives in marginal zones and many others move freely between habitat types depending on tide and season. Quantifying animal responses to temperature, especially those from extreme environments, will help us to better understand the likely consequences of environmental change on ecosystem organization, biodiversity, and ecology. Reading List: Beitinger, T. L., W. A. Bennett and R. W. McCauley. 2000. Temperature Tolerances of North American Freshwater Fishes Exposed to Dynamic Changes in Temperature. Environmental Biology of Fishes, 58:237-275. Bennett, W.A. 2010. Extreme Physiology of Intertidal Fishes of the Wakatobi. in J. Clifton, R. K..F. Unsworth and D. J. Smith, editors. Marine Research and Conservation in the Coral Triangle: The Wakatobi National Park. Nova Science Publishers, Hauppauge, New York. Eme J and W.A. Bennett. 2009. Acute temperature quotient responses of fishes reflect their divergent thermal habitats in the Banda Sea, Sulawesi, Indonesia. Australian Journal of Zoology. 57:357362. Eme J. and W. A. Bennett. 2009. Critical Thermal Tolerance Polygons of Tropical Marine Fishes from Sulawesi, Indonesia. Journal of Thermal Biology. 34, 220-225. Eme, J., T. F. Dabruzzi, and W. A. Bennett. 2011. Thermal responses of juvenile squaretail mullet (Liza vaigiensis) and crescent terapon (Terapon jarbua) acclimated at near-lethal temperatures, and the implications for climate change. Journal of Experimental Marine Biology and Ecology. 399:35–38. Fangue, N. A., and W. A. Bennett. 2003. Thermal Tolerance Responses of Laboratory-acclimated and Seasonally-acclimatized Atlantic Stingray, Dasyatis sabina. Copeia, 2003(2):315-325. Taylor, J. R., M. M. Cook, A. L. Kirkpatrick, S. N. Galleher, J. Eme and W. A. Bennett. 2005. Thermal Tactics of Air-breathing and Non Air-breathing Gobiids Inhabiting Mangrove Tidepools on Pulau Hoga, Sulawesi, Indonesia. Copeia. 2005 (4):886-893.