Using a box model to examine large-scale spatial and temporal patterns in harmful algal blooms for the Potomac River estuary

The EPA's Chesapeake Bay Program maintains over 200 water quality monitoring stations throughout the Chesapeake Bay and its tributaries. These fixed monitoring stations are sampled in the same place, twice a month, year-round, resulting in an extensive data set from 1985-present. One of the Chesapeake Bay Program's primary objectives is to monitor for high concentrations of chlorophyll a, an indication of detrimental or harmful "blooms" of algae. However, in today's financial climate, environmental managers are forced to cut back on the number of monitoring stations to save money, and offset the increasing cost of equipment and personnel. The issue facing managers today is which stations should be kept, and which stations should be dropped. This study uses the historic data from existing water quality monitoring stations to determine which monitoring stations best capture harmful algal blooms. We developed a mathematical box model that describes the general circulation patterns in one of the Bay's tributaries (the Potomac River Estuary). This box model uses the historic data to predict where algal blooms are likely to aggregate, and where algal growth is maximal. The results of the model and our recommendations to environmental managers will be discussed.