Human and Ecological Risk Assessment: Vol. 7, No.5, pp. 1329-1345(2001) Health and Ecological Impacts of Harmful Algal Blooms: Risk Assessment Needs Frances M. Van Dolah,l,. Daniel RoeIke,2 and Richard M. Greene5 IMarine Biotoxins Program, Center for Coastal Environmental Health and Biomolecular Research, NOAA National Ocean Service, Charleston, SC 29412; Tel(voice): 843-762-8529, Tel(fax): 843-762-8700; fran.vandolah@noaa.gov. 2Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843-2258. 5US Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Gulf Ecology Division, Gulf Breeze, FL 32561 ABSTRACT The symposium session, Indicators for Effectsand Predictions of Harmful Algal Blooms, explored the current state of indicators used to assess the human health and ecological risks caused by harmful algal blooms, and highlighted future needs and impediments that must be overcome in order to provide a complete risk assessment of their impacts. Six recognized human poisoning ~dromes resulting from algal toxins (paralytic, neurotoxic, amnesic, diarrhetic shellfish poisonings, ciguatera fish poisoning, and putative estuary associated syndrome) impact human health through consumption of contaminated seafood, direct contact with bloom water, or inhala- tion of aerosolized toxin. Thorough health risk assessment for the variety of algal toxins is hampered to varying degrees because either the toxin has not been identified or indicators for exposure and effects remain poorly defined. Predicting the occurrence and determining the impacts of harmful algal blooms in coastal ecosystems are the two major ecological risk assessment needs. In the former case, the hazard is the suite of conditions that trigger bloom initiation, magnify bloom intensity or support bloom longevity, whereas in the latter case, the hazard is the algal toxin. In both cases, indicators (of triggering mechanisms, exposure, and effects) are better defined for some HAB species and toxins than others, but are by no means complete. Key Words: algal toxins, harmful algal blooms, phytoplankton, PSP, NSP, ASP, DSP, PEAS, ciguatera, risk assessment . Corresponding author. , 1080-7039/01/$.50 @ 2001 by ASP