Vulnerability of Antarctic shelf biodiversity to predicted regional warming

Predictions of sensitivity to climate change of polar benthos vary markedly depending on whether physiological or ecological/biodiversity criteria are considered. A realistic consensus view must be achieved as soon as possible. Having been very cool and constant for several million years, polar hotspots such as the Antarctic Peninsula (AP) are now rapidly warming. The current rate of CO, increase and, with a lag phase, temperature, is unparalleled-maybe for 10s of millions of years. Experimental evidence suggests the shallow mega- and macrobenthos is very sensitive to temperature change (stenothermal). Being warmed to about 10 degrees C kills most species tested to date but even smaller experimental rises (just 2 or 3 degrees C above normal) drastically hinders their ability to perform critical functions, Such as predator avoidance behaviour. In contrast, new evidence of bathymetric and geographic distributions shows species ranges encompass localities with varying and warmer temperatures Such as the intertidal zone or the shelf of South Georgia. This suggests, at the species level, an unexpected ability to live in areas with significantly different and raised temperature regimes. Scientists have focused on potential responses of a few species in a few areas. However, these are often atypical of fauna on the whole. Distribution assessments suffer from not knowing the capacity differences between populations and how fast they, arise. To begin meaningful estimates of how shelf mega- and macrobenthos will respond to rapid warming, where and at what should we be looking? The AP continental shelf is probably amongst the most sensitive. A more widespread evaluation of the capabilities of different species and across life-history cycles is needed. We need to compare differences between communities in the more temperature-variable and -stable sites to predict ecological scale responses to future changes.

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