Abstract
Maritime Antarctic freshwater habitats are amongst the fastest changing environments on Earth. Temperatures have risen around 1°C and ice cover has dramatically decreased in 15 years. Few animal species inhabit these sites, but the fairy shrimp Branchinecta gaini typifies those that do. This species survives up to 25°C daily temperature fluctuations in summer and passes winter as eggs at temperatures down to -25°C. Its annual temperature envelope is, therefore around 50°C. This is typical of Antarctic terrestrial species, which exhibit great physiological flexibility in coping with temperature fluctuations. The rapidly changing conditions in the Maritime Antarctic are enhancing fitness in these species by increasing the time available for feeding, growth and reproduction, as well as increasing productivity in lakes. The future problem these animals face is via displacement by alien species from lower latitudes. Such invasions are now well documented from sub-Antarctic sites.In contrast the marine Antarctic environment has very stable temperatures. However, seasonality is intense with very short summers and long winter periods of low to no algal productivity. Marine animals grow slowly, have long generation times, low metabolic rates and low levels of activity. They also die at temperatures between +5°C and +10°C. Failure of oxygen supply mechanisms and loss of aerobic scope defines upper temperature limits. As temperature rises, their ability to perform work declines rapidly before lethal limits are reached, such that 50% of populations of clams and limpets cannot perform essential activities at 2–3°C, and all scallops are incapable of swimming at 2°C. Currently there is little evidence of temperature change in Antarctic marine sites. Models predict average global sea temperatures will rise by around 2°C by 2100. Such a rise would take many Antarctic marine animals beyond their survival limits. Animals have 3 mechanisms for coping with change: they can 1) use physiological flexibility, 2) evolve new adaptations, 3) migrate to better sites. Antarctic marine species have poor physiological scopes, long generation times and live on a continent whose coastline covers fewer degrees of latitude than all others. On all 3 counts Antarctic marine species have poorer prospects than most large faunal groups elsewhere.
Highlights
A current major focus for science is the prospect of global climate change
Oxygen consumption rates rise in an expected fashion with temperature, doubling for every 10°C rise in temperature in this species, with rates at 20°C four times higher than those at 1°C [11]. This indicates a metabolic scope for B. gaini of at least × 4
It is likely that species diversity, http://www.frontiersinzoology.com/content/2/1/9 community biomass and complexity will increase in coming years
Summary
A current major focus for science is the prospect of global climate change. It is internationally accepted that we are in a period of global change, that for some measures such as atmospheric carbon dioxide content, is faster than at any time in recent geological history [1,2]. In this review I evaluate the major characteristics of Antarctic species and contrast the threats and abilities to cope with change for aquatic organisms from terrestrial and marine environments. Pools that sustain significant populations of fairy shrimps, Branchinecta gaini, occur near Rothera station on the Antarctic peninsula (Fig. 1) In these pools summer temperatures are positive, but fluctuate between 0°C and 20°C, whereas in winter tempera-. Oxygen consumption rates rise in an expected fashion with temperature, doubling for every 10°C rise in temperature in this species, with rates at 20°C four times higher than those at 1°C [11] This indicates a metabolic scope for B. gaini of at least × 4 (where a metabolic, or physiological scope refers to the maximum ability to raise a function over the minimum required for long-term survival). Figure modified from [25, 31]
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