Monitoring Watershed Water Quality Impacts on Near-Shore Coral Reef Ecosystems in American Samoa using NASA Earth Observations
Monday, 15 December 2014
Land use changes can greatly increase erosion and sediment loads reaching watersheds and downstream coastal waters. In coastal environments with steep terrain and small drainage basins, sedimentation directly influences water quality in near-shore marine environments. Poor water quality indicators (i.e., dissolved nutrients and high particulates) affect coral calcification, photosynthesis, and coral cover. The abundance, recruitment, and biodiversity of American Samoa’s coral reefs have been heavily affected by population growth, land cover change, pollution, and sediment influx. Monitoring, managing, and protecting these fragile ecosystems remains difficult due to limited resource availability, steep terrain, and local land ownership. Despite extensive field hours, traditional field and lab-based water quality research produces temporally and spatially limited datasets. Using a ‘ridge to reef’ effort, this project built a management tool to assess coral reef vulnerability using land use, hydrology, water quality, and coral reef cover in American Samoa to provide local agencies and partners with spatial representation of water quality parameters and site-specific implications for coral reef vulnerability. This project used land cover classified from Landsat 7 and 8 images, precipitation data from NOAA, and physical ocean factors from Terra MODIS. Changes in land cover from 2000 to 2014 were also estimated using Landsat imagery. Final products were distributed to partners to enhance water quality management, community outreach, and coral reef conservation.