Seagrass meadows of Pohnpei and And Atoll, Federated States of Micronesia, derived from field surveys conducted 26 October-03 November, 2005

Approximately 4,403.6 ±324.3 hectares (ha) of predominately intertidal and shallow subtidal seagrass meadows were mapped in the waters surrounding Pohnpei Island and And Atoll between 26 October and 3 November 2005. This was the first comprehensive survey of seagrass resources surrounding Pohnpei Island and And Atoll. The survey involved examination of 508 field validation points and identified 260 individual meadows. 3 species of seagrass (Cymodocea rotundata, Enhalus acoroides and Thalassia hemprichii) were identified in the shallow waters surrounding Pohnpei Island, and 2 species at And Atoll (Enhalus acoroides was absent). 21.3 ±11.8 hectares (ha) of seagrass was mapped in 8 meadows on the inner fringe of And Atoll. Mapping survey methodologies followed standardised global seagrass research methods (McKenzie et al. 2001, doi:10.1016/B978-044450891-1/50006-2) where observers walked or free-dived to assess survey points. Seagrass habitat characteristics including visual estimates of above-ground percentage cover (3 replicates of a 50cm x 50cm quadrat) and species composition were recorded at each point according to the Seagrass-Watch standard methodologies (McKenzie 2003, http://bit.ly/2r4hQHk). Water depth and visual/tactile description of sediment were also recorded at each survey site. A differential handheld global positioning system (GPS) was used to locate each survey point (accuracy ±5m). Seagrass meadow boundaries were determined based on the positions of survey points and the presence of seagrass, coupled with depth contours and remote sensing (e.g. aerial photography) where available. The meadow boundary accuracy varied from 5m to 15m. The resulting data of each seagrass meadow was saved as an ArcMap shapefile and projected to WGS84 UTM Zone 57N. Most seagrasses were found in water shallower than 3m and meadows were monospecific or consisted of multispecies communities, with up to 3 species present at a single location. 21 seagrass meadow community types were identified based on species presence and proportion of cover. Seagrass distribution appears to be primarily influenced by the degree of wave action (exposure), water clarity and nutrient availability. The dominant species encountered were Enhalus acoroides and Thalassia hemprichii. Pohnpei's seagrass habitats were categorised into six types: estuary, sheltered fringing reef, exposed fringing reef, patch reef, barrier reef and atoll