Rocky Intertidal Data from Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park

Sampling sites and transects: Transects for rocky intertidal sampling were marked with stainless steel eye-bolts and a site ID marker plate to ensure consistency in sampling location. Additionally, several eye-bolts were placed along the transects' horizontal length to ensure similar placement of the line. Tide prediction software and GPS clocks were used to estimate MLLW for the swath lower boundary, but coordinates were not recorded. Rather, each year when re-sampling the site, the same tools were used to conduct the star swath count.

Sea star counts: Observers used transect tapes and visual estimations of 4 m wide swaths. Sea stars were counted along 50 to 100 m long x 4 m wide swaths at each of several randomly selected sites within sheltered rocky shorelines. The lower edge of the transect was placed at MLLW. Note that all animals were observed without moving rocks and animals under rocks were not counted. This likely resulted in an underestimate of the number of individuals on a transect. Leptasterias epichlora (small sea stars often found under rocks) were not counted.

Snail and chiton counts: Observers used transect tapes and quadrat frames. Nucella spp. and Katharina tunicata were counted in 12 systematically placed quadrats at the mid and low tidal elevations (0.5 and 1.5 m above MLLW) along 50 to 100 m transects at randomly selected sites within sheltered rocky shorelines. In 2006, 100 m transects were sampled. Thereafter, sampling was conducted along 50 m transects. Quadrat sizes were 1 square meter at all sites in 2006 and 2007 and 2 square meters at all other times and sites with the exceptions noted in this metadata record.

Random point contact data: Observers used transect tapes, quadrat frames with cross-strings, and pointers to identify invertebrates and algae. Percent cover of intertidal algae and sessile invertebrates was measured within 12 systematically placed 1/4 square meter quadrats at the low and mid tidal elevations (0.5 and 1.5 m above MLLW) along 50 to 100 meter long transects at randomly selected sites within sheltered rocky shorelines. In 2006, 100 meter transects were sampled. Thereafter, sampling was conducted along 50 meter transects. Each algal or sessile invertebrate species that occurred under each of 49 (in 2006 and 2007) or 25 (2008 and thereafter) systematically placed points in each quadrat was recorded. Species that were observed in each quadrat but did not fall under a systematically placed point were entered as layer 0. The zero data were used to generate species lists and number of species present, but not percent cover.

Limpet counts and measurements: The density of Lottia persona was measured along 50 meter transects at randomly selected sites within sheltered rocky shorelines. The transects were placed within the approximate center of the vertical distribution of L. persona along the shoreline, generally 3 to 4 m above MLLW. The radius of a circle within which the first 20 L. persona that were encountered occurred was measured to the nearest 1.0 cm at each of 6 points along the transect. The first limpet circle start point was determined by placement of the random-point contact quadrat. Every other quadrat placement location along the horizontal tape was selected yielding 6 limpet circles per rocky site. Each individual limpet was measured with dial calipers to the nearest millimeter. The distance in centimeters from the start of the circle to the farthest limpet was recorded as the search radius. Limpet densities may be calculated as the number per area of the circle. In some cases where limpets were rare, fewer than 20 limpets were encountered.