On 5/29/2003, a second species of potentially toxic algae, Karlodinium micrum, was found in greater than background concentrations of 4,638 cells/ml at the Chesapeake Bay water quality monitoring station on the Lower Patuxent River (Station LE1.1 - Jack Bay). Karlodinium has been found to produce sufficient toxin to kill fish with concentrations of at least 10,000 to 30,000 cells/ml. While this species has been associated with fish kills in Chesapeake Bay in the past, no evidence of toxic activity or fish kills was present at the site. The water sample collected at Station LE1.1 showed a major bloom of Prorocentrum minimum (243,800 cells/ml) was still in progress during late May (see HAB News from June 5, 2003: "Mahogany Tide continues on the Lower Patuxent River and tributaries at the end of May.").