Eutrophication is the over-abundance of nutrients in a body of water that results in harmful algal blooms, fish kills, and in some cases ecosystem collapse. In coral reef ecosystems, excess nutrients can directly impact the coral, or allow other organisms to outcompete the coral. Vatia Bay on the island of Tutuila, American Samoa is experiencing issues with reduced live coral cover. This may be associated with benthic algal blooms, which may be outcompeting corals.
Why We Care
Coral reefs are diverse, productive, and economically valuable ecosystems, but are threatened by a variety of stressors in including land based sources of pollution. Nutrients (nitrogen and phosphorus) are required by both plants and animals for healthy growth, but excess nutrients can cause a variety of problems for corals, including decreased light penetration in the water column, increased competition from benthic algae and direct impacts to coral, such as reducing coral reproduction and recruitment.
What We Are Doing
NOAA scientists from NOS-NCCOS and NMFS-CRED are working with local partners (American Samoa Department of Marine and Wildlife Resources, American Samoa Community College and American Samoa Environmental Protection Agency) to conduct nutrient and biological monitoring to assess the relationship between potential nutrient pollution and benthic algal communities. Nutrients will be monitored monthly, both under baseflow and stormflow conditions, using a YSI nutrient probe, as well as grab samples for lab analysis. Benthic communities will be assessed with photo quadrats. Pending outyear funding, the monitoring will continue for multiple years in order to capture potential interannual variability. The monitoring program will characterize key water quality parameters to allow coastal managers to assess the potential impact of nutrients and other stressors on coral reef ecosystems, as well as to detect change over time.
Benefits of Our Work
These data will be valuable to coastal managers for assessing the relationship between nutrients and benthic algae in Vatia Bay. If data suggests that nutrients from land are driving the observed benthic algal dynamics, management activities designed to reduce nutrient pollution can be pursued.
Initial field work is scheduled for May, 2015. During this two week field mission, NCCOS scientists will collect data during different flow regimes, as well as train local partners to conduct ongoing sampling. Project data will be available online via the National Status and Trends database, and will be synthesize, including statistical and geospatial analysis, in a technical memorandum.