Point Sampling Data from Eelgrass (Zostera marina), Seaweeds and Selected Invertebrates at Six Embayments and Two Islands at the End of the Alaska Peninsula

Boat-based surveys were performed at embayments and islands known to contain eelgrass beds from 19 August through 6 September 2012 along the lower Alaska Peninsula. Survey points were distributed across each of the sites using a systematic random design and accessed by a global positioning system (GPS) unit. Points were sampled by snorkeling in dry suits primarily during high tide. Water temperature and depth, salinity, substrate type and depth, and water clarity as determined with a 20cm-diameter Secchi disk were measured at each point. We assessed percent cover of eelgrass and seaweeds within four, 0.25 m2 quadrats that were spaced approximately 5 m apart in cardinal directions around the point. To minimize among-observer differences in estimates of eelgrass and seaweed cover, a cover score was assigned between 0 and 5 based on the Braun-Blanquet (BB) visual estimation technique (Braun-Blanquet, 1972; BB score of 0 percent =0; 1–5 percent=1; 6–25 percent =2; 26–50 percent =3; 51–75 percent =4; 76–100 percent =5). We also evaluated the presence and absence of selected invertebrates: sea stars (Pisaster and Evasterias spp.), sponges, live bivalves, Telmessus sp. crabs and epiphytes on eelgrass leaves, such as the small bivalve Turtonia minuta, caprellid shrimp, amphipods, and isopods within these quadrats. Cover was defined as the part of the quadrat area obscured by eelgrass and seaweeds while viewed in water from above. When eelgrass was present, 5 represented shoots were collected from each quadrat for measurements of length of the sheath and total shoot. When seaweeds were present, an estimate of cover was made for all species combined and the dominant seaweed genus was identified within each of the four quadrats.