Download IH313 Are animals living in extreme environments best equipped to

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.