Mapping Cladophora and other submerged aquatic vegetation in the Great Lakes using satellite imagery.

We have developed a remote sensing algorithm to map the extent of Cladophora and related submerged aquatic vegetation (SAV) extent and biomass in the near-shore waters (0-15 meters depth) in the Great Lakes. The algorithm utilizes the visible bands of electro-optical satellites such as MODIS, MERIS, Landsat TM and commercial high-resolution satellite imagery from sources such as GeoEye and DigitalGlobe. The algorithm maps SAV using a depth-invariant bottom reflectance index and has been successfully tested on satellite data sets of varying resolutions in Lake Michigan where there is extensive lake truth on Cladophora extent and biomass. In Lake Michigan, the SAV is predominantly Cladophora, with localized areas of macrophytes, Chara, and diatoms. A time series analysis, both annually and seasonally, of Cladophora extent at Sleeping Bear Dunes National Lakeshore was also done using historical Landsat data. The area-weighted SAV biomass, calculated based on colonized substrate only, is 36 g Dry Weight/m2. This corresponds to a standing crop of 375,000 metric tonnes wet weight lakewide. The utility of mapping Cladophora using 1km MODIS or 330 meter MERIS data with its daily acquisitions is also compared to the results from the Landsat and commercial imagery