The Boulder Patch (North Alaska, Beaufort Sea) and its Benthic Algal Flora

Abstract

We describe the benthic algal flora within the Boulder Patch, a unique and relatively isolated assemblage of cobbles and boulders in the Alaskan Beaufort Sea, on the basis of a compilation of opportunistic in situ collections made from 1977 to 2006. The Boulder Patch is a shallow (4–7 m) High Arctic kelp community containing 78 benthic algal species, all of which represent approximately one-half of the pan-Arctic benthic flora (140 species) including one recognized cyanophyte (Calothrix scopulorum), one dinophyte (Rufusiella foslieana), 26 green algae, 25 brown algae, and 25 red algal species. Two brown algae are Arctic endemics, and 41 of the 78 Boulder Patch species also occur in the North Pacific Ocean and southeast Alaska. Both endemic species occur widely in the Arctic Ocean and extend into the northern North Atlantic Ocean. All 78 Boulder Patch species occur widely in the northeast Atlantic Ocean. No recognizable endemic species from the boreal/subarctic Pacific and Atlantic Oceans are present in the Boulder Patch. Only four species, two of which are closely related and host-specific, show a poleward shift from the boreal to the High Arctic environment. The algal composition of the Boulder Patch and characterization of these algal communities represent an invaluable baseline in which to assess future change in an Arctic system that is undergoing rapid warming. Our baseline analysis of the benthic flora of the Boulder Patch reveals a habitat characterized by an unexpected high diversity and unique phytogeography for a relatively isolated benthic algal assemblage of the north polar ocean.