Mitigation and Control of Harmful Algal Blooms

Abstract

Harmful algal blooms (HABs) have traditionally been a natural phenomenon. However, human activities have promoted the occurrence and global spread of HABs to such an extent that they have now become a serious environmental problem in most coastal waters around the world. Presently, accurate prediction of HAB occurrence remains a highly challenging task. Because HABs affect areas with important social and economic values, such as cooling water sites of nuclear power plants, aquaculture sites, and tourism beaches, therefore urgent mitigating measures are needed to reduce risks and damage. This chapter briefly reviews those methods that are now available to control and mitigate the impacts of HABs, with a focus on the approaches using clay or modified clay. Controlling HABs using natural clay is a method used in many parts of the world and has been studied most intensively in Japan, South Korea, China, and the USA. However, the efficiency of natural clay in removing HAB organisms is generally low. On the other hand, the use of modified clay has proven to be superior in removal efficiency, the theory of which is summarized in this chapter. Our studies have shown that modified clays have increased the removal efficiency by several hundred times and have had no detectable negative impacts on aquatic organisms and environment.