IF ALGAE ARE THE PRIMARY OXYGEN PRODUCERS IN WATER,
HOW DO ALGAE BLOOMS CAUSE SEVERE OXYGEN DEPLETION IN WATER?

Both Congress and previous government administrations have recognized harmful algal blooms (HABs) and hypoxic events (severe oxygen depletion) as some of the most complex phenomena currently challenging management of aquatic and marine ecosystems. Virtually every coastal state has reported recurring blooms, and a recent national assessment revealed that over half of our Nation's estuaries experience hypoxic conditions.

Scientific understanding of harmful algal blooms (HABs) and hypoxic events (severe oxygen depletion) has progressed significantly since the early 1990's, but major impediments still remain for prediction, control and mitigation of these complex phenomena. Practical and innovative approaches to address eutrophication, hypoxia and HAB's in US waters are essential for management of aquatic ecosystems and to fulfill a stronger investment in the health of the coasts and oceans called for by the U. S. Ocean Action Plan and recent reports on ocean policy.

Harmful algal blooms (HABs) are one of the most scientifically complex and economically significant coastal issues facing the nation today. HABs have direct and indirect impacts on fisheries resources, local coastal economies, as well as public health and perception. HAB toxins can cause human illness and death, halt the harvesting and sale of fish and shellfish, alter marine habitats, and adversely impact fish, endangered species, and other marine organisms. In the past, only a few regions of the U.S. were affected by HABs, but now virtually every coastal state has reported major blooms. Economic losses associated with HABs are conservatively estimated to exceed $1 Billion over the next several decades. High biomass blooms can also profoundly affect marine and freshwater ecosystems.

Harmful algal blooms will continue to plague not just the coastal areas of the United States, but the rest of the world as well. Put simply, such blooms affect the water in three ways. A massive bloom of planktonic (floating) algae such as blue-green algae can contribute to oxygen depletion in three ways. A huge floating algae mass can also serve as a physical barrier to oxygen exchange between the atmosphere and water, and it can prevent light penetration to oxygen producing algae living below the water surface. Finally, aerobic bacteria can use up the remaining dissolved oxygen in the water while decomposing the dying mass of dead algae.

There are many gaps in current knowledge that need to be addressed concerning algal blooms. Development of methods for rapid, cost effective detection of HABs and their toxins is a critical first step. Predictive models and forecasts depend on an understanding of the basic biology of HAB species, the environmental processes that control HABs, and knowledge of how HAB toxins are transferred through the food web and impact the health of a variety of organisms, including humans. The role of human activities in stimulating HABs requires investigation. Effective methods for prevention, control, and mitigation need to be developed for successful management of algal blooms.