NCCOS Mapping: Characterizing Benthic Habitats West of Saipan, Commonwealth of the Northern Mariana Islands (CNMI), 2018-11-05 to 2022-04-29 (NCEI Accession 0291792)

This data package contains information and maps showing the geology and biology of select submerged lands (0 to 40 meters deep) offshore of western Saipan, Commonwealth of the Northern Mariana Islands (CNMI). This information and maps were developed using benthic information from underwater photographs, environmental predictor variables derived from satellite imagery and bathymetry, and machine learning modeling approaches. From this process, two types of map products were created. The first type describes the spatial distribution of 5 substrate and 14 biological cover types, where each grid cell denotes the probability (0 to 100%) that a given habitat is present. The second product was a classified map depicting the 7 most common combinations of substrate and cover types (plus artificial structures). The performance and accuracy of these products were evaluated using an independent of underwater photographs. The overall accuracy of the classified map was 91.5% with user’s accuracy of individual habitat classes between 84% and 100% correct. The substrate and cover predictions had little bias (𝑥̅ error = 0.01 ±0.01 SE), good to excellent ability to discriminate between presences and absences (𝑥̅ area under the curve = 0.82 ±0.02 SE) and they explained almost a quarter of the variation in the data (𝑥̅ percent deviance explained = 23.8% ±2.9 SE).

Over 95 square kilometers (km2) of seafloor was characterized west of Saipan, CNMI. Overall, ‘Live and Upright Dead Coral Reef, Mixed Algae’ was the most abundant habitat type mapped inside and outside the Lagoon, comprising 32% (31 km2) of the area. The largest, continuous patches were located outside the Lagoon north Susupe Point, as well as inside the lagoon on the reef crest and back reef north of the harbor channel. Most live coral (all species) observations were documented outside the Lagoon from the harbor channel to Agingan Point, as well as inside the Lagoon north of Garapan. Enhalus acoroides and Halodule uninervis seagrass were both located exclusively inside the Lagoon, from Tanapag Beach south to Oleai as well as north of Tanapag to Pau Beach and south of Garapan to Agingan Point, respectively.

Endangered Species Act (ESA) protected corals (i.e., Acropora globiceps) were documented at 4 sites outside the Lagoon, located seaward of the reef crest between Susupe and Agingan Points. No nuisance species (i.e., C. vieillardi) or crown of thorns sea star (COTS) were photographed outside the Lagoon. The prevalence of coral bleaching and marine debris were also very low outside the Lagoon (<0.7% and <0.9%, respectively). Theses maps mark the first time that the seafloor area outside the Lagoon has been mapped since 2005, providing an updated inventory of marine resources and new baseline for future monitoring and management decisions in the region.