How does offshore biodiversity differ across the Aleutian archipelago?

We sampled the epibenthic communities (bottom dwellers such as sea stars, sea urchins, and crabs) living on the continental shelf at various islands in the Aleutian archipelago using a plumb-staff beam trawl.  In order to compare epibenthic community composition among these islands and across the oceanographic break, Samalga Pass, we sorted, counted, and weighed organisms that were caught in the trawl net before they were returned to the ocean. 

Results

Preliminary data prepared by Aaron Bland , University of Alaska Fairbanks

 We used the abundance of species in our trawl surveys to test if communities differed among islands and across the oceanographic break, the Samalga Pass. Preliminary data indicates that different islands host distinctly different epibenthic communities (PERMANOVA Pseudo-F = 2.04, P(perm) = 0.001). Interestingly, we did not find  evidence of epibenthic communities differing across the Samalga Pass (PERMANOVA ,  Pseudo-F= 1.32, P(perm) = 0.26);  however, this may be a consequence of the low number of islands sampled.

Figure 1.  Non-metric MDS plot showing relative differences in epibenthic community abundances across the Aleutian archipelago. Solid shapes are West of Samalga Pass and shape outlines are East of Samalga Pass. Each point in this figure represents a sample, and points drawn closer together represent samples with more similar communities.

The trawl coming out of the water. Photo: B. Konar

At the end of the trawl we pull the the trawl net out of the water to see what we caught! Photo: B. Konar