DONALD M. ANDERSON (Biology Dept., Woods Hole Oceanographic Inst., Woods Hole MA 02543 USA; 508 289 2351; danderson@whoi.edu)

Throughout the United States and the world, red tides and harmful algal blooms (HABs) pose a serious and recurrent threat to marine ecosystems, fisheries, human health, and coastal aesthetics. The significant public health, economic, and ecosystem impacts of HABs suggest that these phenomena would be legitimate targets for direct control or mitigation efforts, but little research on such strategies has been undertaken worldwide, even though human efforts to control insects, diseases, and weed species are common agricultural practices on land. The reasons for this lack of effort are many, but in general, the lack of research progress is not due to an absence of strategies worth exploring, but rather to a preference on the part of the HAB community to pursue fundamental research to better understand bloom phenomena. This talk will review the direct and indirect efforts that have been made to mitigate the impacts of HABs. Mitigation methodologies can be categorized as either "direct" or "indirect" depending upon whether the effort targets the bloom organisms specifically (e.g., bloom control), or strives to reduce impacts such as through bloom prediction, toxin monitoring, or through alteration of pollution inputs that be might stimulate blooms. General approaches to direct control include: 1) chemicals that kill or disrupt HAB cells during blooms; 2) clays or other materials that flocculate (precipitate) and scavenge cells and other particles from the water column, transporting them to the ocean floor; and 3) biological agents such as viruses, bacteria, or parasites which are lethal pathogens to HAB species. Examples of these diverse approaches will be presented and their potential assessed with respect to present status, feasibility, and environmental impacts. The objective is to present a balanced perspective on the challenges and risks associated with different means of bloom intervention and impact mitigation.