On June 12th, a field crew from the Maryland Department of Natural Resources (MD DNR), and subsequently on June 13th a crew from the Academy of Natural Sciences Estuarine Research Center (ANSERC), found bloom concentrations of the dinoflagellate Karlodinium micrum at station LE1.1 on the Lower Patuxent River. A surface water sample collected by MD DNR contained 18,762 cells/ml. ANSERC sampled the water at a depth of 2 meters where an elevated concentration of chlorophyll was detected and found 93,751 cells/ml of K. micrum. Researchers Dr. Allen Place and Jon Deeds at the Center of Marine Biotechnology in Baltimore, MD, have found fish kills associated with blooms of 10,000-30,000 cells/ml or more of K. micrum and the presence of karlotoxin. No fish kills have been evident in this area so far this year.

Earlier this spring the region of the lower Patuxent River harbored a Mahogany Tide bloom of Prorocentrum minimum, another potentially toxic dinoflagellate (see HAB News from June 5, 2003: "Mahogany Tide continues on the Lower Patuxent River and tributaries at the end of May."). The concentrations of P. minimum have largely declined in distribution and abundance over much of the Chesapeake Bay and lower tributaries. Prorocentrum minimum tends to bloom earlier in the spring than K. micrum (late spring and early summer) although both species may occasionally be found blooming throughout the year on a local scale.