The nature of the HAB problem has changed considerably over the last two decades in the United States (Figure 2). Where formerly a few regions were affected in scattered locations, now virtually every coastal state is threatened, in many cases over large geographic areas and by more than one harmful or toxic algal species. Few would argue that the number of toxic blooms, the economic losses from them, the types of resources affected, and the number of toxins and toxic species have all increased dramatically in recent years in the United States and around the world [ Anderson, 1989; Smayda, 1990; Hallegraeff, 1993]. Disagreement only arises with respect to the reasons for this expansion. Possible explanations include: a) species dispersal through currents, storms, or other natural mechanisms (e.g. Anderson et al., [1982]); b) nutrient enrichment of coastal waters by human activities, leading to a selection for, and proliferation of, harmful algae [ Smayda, 1990]; c) increased aquaculture operations which can enrich surrounding waters and stimulate algal growth [ Gowen and Bradbury, 1987]; d) introduction of fisheries resources (through aquaculture development) which then reveal the presence of indigenous harmful algae in waters formerly ``free'' from HAB problems [ Anderson, 1989]; e) dispersal of HAB species via ship ballast water or shellfish seeding activities [ Hallegraeff and Bolch, 1992]; f) long-term climatic trends in temperature, wind speed, or insolation [ Reid et al., 1990]; and g) increased scientific and regulatory scrutiny of coastal waters and fisheries products and improved chemical analytical capabilities that lead to the discovery of new toxins and toxic events [ Work et al., 1993].
If we accept that the expansion is real, and that it has many causes, both natural and human-assisted, what can be done about it in a practical sense? What information is needed to efficiently manage the affected fisheries resources, protect the public health, encourage and support aquaculture development, and contribute to policy discussions about coastal zone issues such as pollution or dredging? If human activities are making the HAB problem worse, how can that be demonstrated, and what steps should be taken to minimize further impacts? These are important practical issues, and the apparent trends in HAB incidence make them even more pressing. The need for focused research is clear, and fortunately, far from being mundane, the issues requiring investigation are of fundamental importance to many oceanographic disciplines. A few of these are highlighted below.