SEAWEEDS AS ECOSYSTEM ENGINEERS

Abstract

Canopy-forming seaweeds are often considered as important foundation species or ecosystem engineers. In wave-sheltered rocky intertidal habitats in Atlantic Canada, macroalgal canopies are composed primarily of Ascophyllum nodosum and secondarily of Fucus spp. Field experiments revealed that the effects of these canopies on benthic communities (considering primary producers and consumers) depend on the level of environmental stress that is determined by tides. Positive canopy effects occur at high and middle elevations, where canopies ameliorate the otherwise harsh conditions during low tides, but no significant effects occur at low elevations, where conditions remain mild during low tides regardless of canopy presence. Canopies of fucoid algae covering the intertidal zone during a low tide on a wave-sheltered rocky shore in Nova Scotia, Canada. Photograph by R. A. Scrosati. This photograph illustrates the data paper “Experimental and mensurative data on the abundance of primary producers and consumers from intertidal habitats in Canada” by Cortney A. Watt and Ricardo A. Scrosati, which appeared in Ecology 95(5):1429. http://dx.doi.org/10.1890/14-0071.1