University of Georgia Southeast U.S. Ecological Forecasting Hunting for Hydrilla: Mapping an Aquatic Intruder [Music starts] >> PETER: Hydrilla verticillata, known commonly as hydrilla, is an invasive aquatic plant native to Asia, Australia and Africa. Hydrilla was brought to the United States in the 1950s as an ornamental plant for home aquariums. In the subsequent years hydrilla was released, and spread throughout the southeast. Today, hydrilla spans the southern United States, up the east coast into New England and west into California and Washington state. >> PETER: Hydrilla outcompetes native plants by growing rapidly and forming a surface canopy that blocks light passing through the water column. This intensifies lake stratification, creating areas with low concentrations of oxygen which cause fatal conditions for aquatic life. On top of that, Hydrilla is also a host to a species of cyanobacteria which lives on the undersides of the leaves. When this cyanobacteria covered hydrilla is consumed by waterfowl, the birds become infected with a condition called avian vacuolar myelinopathy (AVM). These weakened waterfowl become easy prey to Bald eagles who in turn become infected and die. >> KENNETH BOYD: The waterfowl love it. Um, they feed on it when it gets up to that point when they migrate in here usually the timing of their migration in and the plants surfacing and becoming available to them usually is pretty close, so they take advantage of it. A lot of coots love it and a lot of other waterfowl will feed on it. >> SHUVANKAR: In addition to ecological effects, hydrilla is also a concern for the recreation and utility industries. Hydrilla’s large extensive mats clog boat motors and can become hazardous to swimmers. It is economically costly, obstructing water withdrawal for drinking, irrigation and power generation in many industries. >> ELIZABETH: Partners currently use traditional monitoring practices involving visual analysis, rake collection and sonar mapping. >> KENNETH BOYD: About six or seven years ago, we have GIS layers of the lake. And we put a dot every quarter mile on the shoreline and we pull in and throw a rake at every spot on the map and we have 1200 miles of shoreline. >> ELIZABETH: Our project aimed to use NASA’s Earth observations to create a low cost and less labor intensive solution to mapping the distribution of hydrilla. >> ELIZABETH: This project utilized NASA’s Landsat 8 Operational Land Imager multispectral sensor. >> ELIZABETH: Our project focused on five lakes found in Georgia, Florida and Alabama: Lake Thurmond, Lake Seminole, Lake Oliver, Lake Harding and Goat Rock Reservoir. We collected Landsat 8 data for the years 2013 through 2015. Data was collected through the year to help us understand hydrilla’s distribution as the seasons changed. >> ELIZABETH: Our team visited one of the study lakes to collect field data. Using a rake we gathered hyrdilla biomass samples to aqcuire information like the density of the plant. We also collected spectral readings of submerged hydrilla using a spectroradiometer. These detailed reflectance measurements allowed us to understand how hydrilla can be measured using remote sensing techniques. >> SHUVANKAR: Once the Landsat images were downloaded they underwent an atmospheric correction after which we applied two vegetation indices, the Normalized Vegetation Index or NDVI and Visible Atmospherically Resistant Index or VARI. While NDVI was used to identify vegetation floating on the water’s surface and along the shoreline, submerged vegetation was mapped using VARI. VARI allowed us to locate and classify hydrilla density and distribution. The results of these two indices provided us a complete look at floating and submerged hydrilla for a particular lake. >> SHUVANKAR: The resulting detection tool for monitoring Hydrilla distribution can be used for water quality restoration decision-making by the project partners such as Georgia Power, Joseph W. Jones Ecological Research Center, and Henry County Water Authority. [Music ends]