Great Lakes Water Quality Products and Assessments using Tuned “Lake” Color Algorithms
Robert A Shuchman1, Michael Sayers2, Karl Bosse2, Gary Fahnenstiel1, George Leshkevich3, Philip Chu4 and Steven A Ruberg5, (1)Michigan Tech Research Inst, Ann Arbor, MI, United States, (2)Michigan Tech Research Institute, Ann Arbor, MI, United States, (3)NOAA, MI, United States, (4)NOAA, United States, (5)NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, United States
Abstract:
A robust suite of water quality monitoring algorithms have been developed for the Laurentian Great Lakes utilizing SeaWiFS, MERIS, MODIS, VIIRS, Sentinel-2 and 3, and Landsat satellite data. Great Lakes specific algorithms are necessary due to the complex nature of these waters. Standard ocean color algorithms assume a single optically active constituent (OAC) (i.e. phytoplankton) while Great Lakes waters contain multiple OACs in variable assemblages which differ significantly from coastal marine environments. To support the generation of these specific algorithms, extensive optical property measurements have been made throughout the Great Lakes. These algorithms generate daily, weekly, monthly, and annual products that include chlorophyll, CDOM, non-algal particles, Kd and euphotic depth, inherent optical properties, phytoplankton production, harmful algal blooms (HABs), as well as mapping submerged aquatic vegetation. Daily products are generated using novel assimilation techniques. These validated products are available to stakeholders which include researchers, water resource managers, and the general public through a number of websites that include the NOAA CoastWatch Great Lakes Node.
The Great Lakes-specific algorithms have been used to assess decadal water quality in the Great Lakes. The observed changes in these products over time are a direct result of the introduction of invasive species such as the Dreissena mussels as well as anthropogenic forcing and climate change. For example these time series show the effect mussels have had on the Great Lakes: increased water clarity due to declining algal populations, decreased primary productivity and chlorophyll concentrations, and an increase in submerged aquatic vegetation. Comparing water quality metrics in Lake Superior to the lower lakes is insightful because it is the largest and most northern lake and to date has not been affected by the invasive mussels and can thus be considered a control. In contrast, Lake Erie, the most southern and shallow of the lakes, is heavily influenced by agricultural practices (i.e., nutrient runoff) and climate change, which directly influence the increasing annual extent of HABs.
