Mahogany Tide
Conditions of low dissolved oxygen have been associated with a mahogany tide of the dinoflagellate Gyrodinium estuariale (Figure 1) primarily in the area of Herring Bay and the Patapsco River on the western shore of Chesapeake Bay (up to 39,750 cells/milliliter on July 3 in the Mill Creek area). The bloom and subsequent die-off of the algae consumed significant amounts of oxygen in the water.  Fish kills associated with these low dissolved oxygen effects were documented in the region and fishermen in the Herring Bay area experienced fish kills in their nets beginning the week of June 29.

Elevated concentrations of Gyrodinium estuariale (9,275 cells/milliliter) were most recently reported in the Patapsco River in the area of Key Bridge as fish kill events continue to be investigated in the area. 

Figure 1.  Concentration of Gyrodinium estuariale in 
Chesapeake Bay and tributary monitoring, 2001