Ice Binding Protein Activity Is Common Among Temperate Pacific Intertidal Invertebrates

Intertidal invertebrates often adopt freeze tolerance as a strategy to survive winter low tides, but the physiological mechanisms by which intertidal species survive freezing are not well understood. Ice binding proteins (IBPs) may play an important role, but their occurrence throughout the intertidal zone worldwide is not well-catalogued. Here we survey species in the intertidal zone of Vancouver, BC to assess IBP activities and the possible role they play in freeze tolerance. We conducted targeted assays in multiple intertidal species to measure three distinct activities of IBPs: ice nucleation, ice recrystallization inhibition, and thermal hysteresis. We also exposed intertidal species to a cold exposure mimicking a freezing event in the intertidal and measured survival post-exposure. We found that IBP activity was widespread across intertidal species, and that species with the highest degree of freeze tolerance also display ice nucleating activity attributable to proteins. We also found that species that live in the high intertidal appear to show more IBP activity than species that live lower in the intertidal. This work significantly increases the number of known species containing IBPs and provides a framework for sampling new species for IBP activity in the intertidal and elsewhere.