||Benthic Surveys in Vatia, American Samoa since 2015: benthic images collected during belt transect surveys in 2015
||Jurisdictional managers have expressed concerns that nutrients from the village of Vatia, Tutuila, American Samoa, are having an adverse effect on the coral reef ecosystem in Vatia Bay. Excess nutrient loads promote increases in algal growth that can have deleterious effects on corals, such as benthic algae outcompeting and overgrowing corals. Nitrogen and phosphorus can also directly impact corals by lowering fertilization success, and reducing both photosynthesis and calcification rates. Land-based contributions of nutrients come from a variety of sources; in Vatia the most likely sources are poor wastewater management from piggeries and septic systems.
NOAA scientists conducted benthic surveys to establish a baseline against which to compare changes in the algal and coral assemblages in response to nutrient fluxes.
The data described here were collected via belt transect surveys of coral demography (adult and juvenile corals) by the NOAA Coral Reef Ecosystem Program (CREP) according to protocols established by the NOAA National Coral Reef Monitoring Program (NCRMP). In 2015 data were collected at 18 stratified randomly selected sites in Vatia Bay. These data include photoquadrat benthic images. These photos have been analyzed for benthic cover (documented separately).
Data from coral demographic surveys, including 1) an assessment of coral colony density and size-class distribution, 2) an assessment of coral recruitment, and 3) an evaluation of coral colony mortality, disease, and evidence of sediment stress, were also collected for the selected monitoring sites and are documented separately by CREP.
Also, in 2016, American Samoa Department of Marine and Wildlife Resources (DMWR) is collecting benthic images approximately every 2 months at three shallow sites where permanent transects were established. DMWR will then forward the photos to CREP to be analyzed and checked for seasonal changes in algae. Three to four sets of images are expected. The first set, as of the publication of this record, have not yet been received.
Monthly water quality sampling for nitrate/nitrite, ammonium, urea, total nitrogen, orthophosphorus, and total phosphorus data are also collected as part of this project to quantify the nutrient dynamics of the Bay. These additional data are described separately by the NOAA National Centers for Coastal Ocean Science (NCCOS).