Thermal insulation of the intertidal zone by the ice foot

Few studies have looked at the ecological significance of the ice foot in intertidal habitats. During the 2007 winter, we quantified the hourly variation of temperature at the intertidal zone and at the upper, dry coast on the southern Gulf of St. Lawrence (Nova Scotia, Canada) using submersible data loggers. While air temperature dropped to − 20 °C at the peak of the winter, intertidal temperature was never below − 7 °C during the winter. In fact, for almost two months when the ice foot was stable, temperature ranged only between − 2.4 °C and − 1.1 °C at the intertidal zone. The intertidal values are higher than published values of lethal temperature for cold-water intertidal invertebrates and seaweeds. Thus, the ice foot may prevent these organisms from experiencing lethal levels of thermal stress, contributing to their long-term persistence in these environmentally stressful habitats.