Marine and Estuarine Harmful Algal Blooms: Impacts on Human and Animal Health

In the last quarter century, harmful algal blooms (HABs) have been increasing on a global scale in frequency, distribution, and in the ramifications of their effects on public health, living resources, and local economies (Burkholder, 1998; Hallegraeff, 1993, 1995; Hoagland et al., 2002; Landsberg, 2002; Sellner et al., 2003; Shumway, 1990; Steidinger, 1993; Van Dolah, 2000;Van Dolah et al., 2001). The marine and estuarine HABs with which we are most familiar tend to be planktonic, often visibly obvious because of their pigment levels at high biomass and because of their involvement in acute shellfish or fish poisonings of humans or mass mortalities of aquatic organisms. Although not strictly pathogenic, approximately 3.5% of the known species of marine microalgae are considered to be harmful or toxic with an increasing number being reported almost annually (Hallegraeff, 1993, 1995; Landsberg, 2002; Smayda, 1990; Sournia, 1995). Some of this apparent increase can be attributed to the recent inclusion of benthic microalgae and nonphotosynthetic harmful species that do not typically “bloom,” to the inclusion of species described previously as benign but determined recently to be harmful, to technological improvements in our ability to accurately identify HAB species and their toxins, and to enhancements in global monitoring and surveillance (Hallegraeff, 1993; James et al., 2003; Landsberg, 2002). Anthropogenic influences interacting with natural processes have also helped to increase the frequency of blooms, and the frequency with which toxic species are transferred globally (Hallegraeff, 1995).