Algal biomass and diversity in the upper subtidal at a pack-ice disturbed site in eastern Newfoundland

Abstract

Over a 5 yr period, the effect of physical disturbance by ice-scour on biomass, diversity and community composition in the shallow macro-algae zone of eastern Newfoundland was examined. In the absence of ice-scour, Alaria exculenta formed a canopy which shaded the substratum; few species CO-existed and diversity was low. Winter and spring ice-scour, which was temporally and spatially patchy, removed the A. esculenta and made well-lighted rocky substratum available for colonization. Scoured patches were colonized by annual algae, resulting in an increase in species diversity. Diversity was greater when patchy scouring occurred throughout the winter-spring period, than when scouring was more restricted. Several species of annual algae persisted in patches among the unscoured A. esculenta, so diversity remained high during the summer following scouring.