Final lab tests were completed by Dr. Wayne Carmichael's Wright State laboratory on blue-green algal bloom samples collected by Maryland DNR from the Potomac River in September. Samples collected in the vicinity of Smith Point during the peak of the Potomac River bloom during the first week of September (see HAB News from August 29, 2003: "Blue-green algal bloom hotspots: Sassafras River, Upper Bush River and middle Potomac River and tributaries.") contained the greatest toxin concentration of blue-green algal bloom samples collected in the Bay this year (187 µg/L). This is also the first evidence of toxin associated with blue-green algal blooms in the Potomac River. Toxin levels overall for the year remained below those measured in September 2000 on the Sassafras River (591-1041 µg/g dry weight).