A swath across the great divide: Kelp forests across the Samalga Pass biogeographic break

Continental Shelf Research
By: , and 



Biogeographic breaks are often described as locations where a large number of species reach their geographic range limits. Samalga Pass, in the eastern Aleutian Archipelago, is a known biogeographic break for the spatial distribution of several species of offshore-pelagic communities, including numerous species of cold-water corals, zooplankton, fish, marine mammals, and seabirds. However, it remains unclear whether Samalga Pass also serves as a biogeographic break for nearshore benthic communities. The occurrence of biogeographic breaks across multiple habitats has not often been described. In this study, we examined if the biogeographic break for offshore-pelagic communities applies to nearshore kelp forests. To examine whether Samalga Pass serves as a biogeographic break for kelp forest communities, this study compared abundance, biomass and percent bottom cover of species associated with kelp forests on either side of the pass. We observed marked differences in kelp forest community structure, with some species reaching their geographic range limits on the opposing sides of the pass. In particular, the habitat-forming kelp Nereocystis luetkeana, and the predatory sea stars Pycnopodia helianthoides and Orthasterias koehleri all occurred on the eastern side of Samalga Pass but were not observed west of the pass. In contrast, the sea star Leptasterias camtschatica dispar was observed only on the western side of the pass. We also observed differences in overall abundance and biomass of numerous associated fish, invertebrate and macroalgal species on opposing sides of the pass. We conclude that Samalga Pass is important biogeographic break for kelp forest communities in the Aleutian Archipelago and may demark the geographic range limits of several ecologically important species.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title A swath across the great divide: Kelp forests across the Samalga Pass biogeographic break
Series title Continental Shelf Research
DOI 10.1016/j.csr.2017.06.007
Volume 143
Year Published 2017
Language English
Publisher Elsevier
Contributing office(s) Alaska Science Center Biology MFEB
Description 11 p.
First page 78
Last page 88
Country United States
State Alaska
Other Geospatial Aleutian Archipelago, Samalga Pass
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