Mass Bleaching in Intertidal Canopy-Forming Seaweeds after Unusually Low Winter Air Temperatures in Atlantic Canada

Abstract

Contemporary climate change is increasing the occurrence of extreme weather events, heat waves being common examples. Here, we present visual evidence of mass bleaching in intertidal seaweeds following an unusually severe cold snap in Atlantic Canada. In February 2023, the air temperature on the Nova Scotia coast dropped below −20 °C for the first time in at least ten years. Such extreme temperatures lasted for several hours at low tide and were followed by extensive bleaching in whole thalli of the canopy-forming algae Chondrus crispus and Corallina officinalis. The loss of these foundation species might negatively impact intertidal biodiversity.