Thermal limits of burrowing capacity are linked to oxygen availability and size in the Antarctic clam Laternula elliptica

Animal responses to changing environments are most commonly studied in relation to temperature change. The current paradigm for marine ectotherms is that temperature limits are set through oxygen limitation. Oxygen limitation leads to progressive reductions in capacity to perform work or activity, and these are more important and proximate measures of a population's ability to survive. Here we measured the ability of a large Antarctic clam to rebury when removed from sediment at temperatures between -1.5 and 7.5 degrees C and at three oxygen concentrations, 10.2, 20.5 and 27.7%. The proportion of the population capable of reburying declined rapidly and linearly with temperature from around 65% at 0 degrees C to 0% at 6 degrees C in normoxia (20.5% O2). Decreasing oxygen to 10.2% reduced temperature limits for successful burial by around 2 degrees C, and increasing oxygen to 27.7% raised the limits by 1-1.5 degrees C. There was an interactive effect of body size and temperature on burying: the temperature limits of larger individuals were lower than smaller animals. Similarly, these size limits were increased by increasing oxygen availability. Considering data for all temperatures and oxygen levels, the fastest burying rates occurred at 3 degrees C, which is 2 degrees C above the maximum summer temperature at this site.