| Summary: | On marine shores that freeze in winter, the intertidal zone becomes covered by an ice foot. Stable ice foots insulate intertidal organisms against highly negative air temperatures. On subpolar intertidal habitats that do not freeze, the periodic inundation with seawater at temperatures near its freezing point also prevents benthic organisms from experiencing highly negative temperatures. However, low tides do expose ice-free intertidal habitats to aerial conditions, but information on how negative temperature gets there during the winter is lacking. Using data loggers, this study measured the daily lowest temperature in rocky intertidal habitats on the Atlantic coast of Nova Scotia, Canada (which does not freeze), during the winter. As a control, temperature was also monitored above the intertidal zone (on tree branches). Intertidal temperature was almost as low as supratidal temperature, as the seasonal averages of daily minimum temperature were -4.2 °C and -6.4 °C (with absolute minima of -14.1 °C and -19.1 °C), respectively. The study site on the Atlantic coast is climatically similar to a site surveyed on the Gulf of St. Lawrence coast of Nova Scotia. However, the Gulf of St. Lawrence coast, which freezes in winter, showed milder intertidal temperatures, with a winter average of daily minimum temperature of -1.9 °C and an absolute minimum of only -6.8 °C. Therefore, despite tidal influences, the absence of an ice foot exposes subpolar intertidal habitats to highly negative air temperatures.
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