Sea urchin size, density, and species from transects surveyed in Palau and Yap in 2017 and in the Federated States of Micronesia in 2018 (NCEI Accession 0277820)

Acquisition Description:
Palau and Yap:
Sea urchins were measured for test diameter and classified as either Diadema , Echinometra , and 'other' in transects. Survey depth was maintained between 2 to 5 meters, to examine the potential of shallow-water reef-carbonate production. Urchins were identified in 10 m long by 60 cm wide transects, 30 cm either side of the 10 m tape. Each urchin’s test diameter was measured in the field. Surveys in Palau were conducted in June 2 to June 24, 2017, and from June 25 to July 6, 2017 in Yap.

Federated States of Micronesia (FSM):
Twenty-four study sites were randomly selected in each of Pohnpei (6.2°N, 158.2°E) and Kosrae (5.3°N, 162.9°E) FSM using a randomly stratified sampling approach with the package sp in R. In Pohnpei, reefs were stratified as inner reefs, patch reefs, and outer reefs. In Kosrae, we only stratified the reefs as either inner reefs or outer reefs (because of the lack of patch reefs). Sample size of each strata was determined by calculating the geographic area of each reef type, using the area function from the R package raster, and allocating the number of sites in accordance with the area estimates. Reef surveys focused on the 2–5 meters depth contour to estimate shallow-water carbonate production.

Six, 10 m transects, using a modified line-intercept technique that followed the reef substrate, were used to measure the benthic composition for every centimeter, at each site of the 48 sites. A few meters gap was allocated between the ends of the transects to ensure no overlap of substrate between transects. The urchins were recorded as Echinometra , Diadema , and 'Other', and the diameter of each echinoid test was measured to the nearest 0.5 cm.