Abstract
The Antarctic Peninsula has experienced a rapid increase in atmospheric temperature over the last 50 years. Whether or not marine organisms thriving in this cold stenothermal environment are able to cope with warming is of concern. Here, we present changes to the growth and shell characteristics of the ecologically important, small and short lived brooding bivalve Lissarca miliaris from Signy Island, Antarctica. Using material collected from the 1970's to the present day, we show an increase in growth rate and adult shell deterioration accompanied by a decrease in offspring size, associated with an increase in annual average temperatures. Critical changes to the bivalve's ecology seen today evidence the problem of a shift in baseline since the onset of warming recorded in Antarctica. These small bivalves are demonstrating ecophysiological responses to subtle warming that, provided warming continues, could soon surpass a physiological tipping point, adding to warming associated threats such as increased predatory pressure and ocean acidification.
Highlights
The rate of atmospheric warming at the Antarctic Peninsula has been around 0.56uC decade21 since 1950 [1], higher than the global average and most extreme in winter with an increase of 5– 6uC over the past 50 years [2]
Using monthly temperature date from the Argentinean Orcadas research station, an increase in air temperature is observed since the collections of L. miliaris began
Temperatures recorded fit closely to the monthly air temperature data collected at the British Signy research station from 1945 until 1995 when data collection halted (Figure S1) and have shown an average increase of 0.20uC decade21 over 100 years [1], much of this changes appears to be in the last 50 years
Summary
The rate of atmospheric warming at the Antarctic Peninsula has been around 0.56uC decade since 1950 [1], higher than the global average and most extreme in winter with an increase of 5– 6uC over the past 50 years [2]. The term ‘shifting baselines’ was first used to describe fishery scientists who failed to use historic data to evaluate the status of the ecosystem, instead using the ecosystem status at the start of their career as the baseline for change [10,11]. This concept has since been discussed to include a wide range of ecosystems that are only studied whilst in decline; in rare cases no historic data being available to develop a suitable baseline [12]. This is certainly the situation for many coral reefs [13,14], benthic environments [15] and in rocky shore ecology [16], where often no adequate baselines are currently attainable
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