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Harmful Algal Blooms
Harmful Algal Bloom (HAB) is a descriptive term that refers to the bloom phenomenon of a few microscopic algae that produce potent toxins which negatively affect public health, commercial fishing, recreation and tourism. Blooms of these algae are commonly called red tides, since they color the water where they become dominant, but this term can be misleading because they are not associated with tides, harmful species may never reach the densities required to color the water, and not all species of toxic algae give this red tint to the water. Algal toxins can be transferred through the food web where they affect and even kill higher forms of life such as zooplankton, shellfish, fish, birds, marine mammals, and even humans that feed either directly or indirectly on them. The toxins are filtered from the water by shellfish such as clams, mussels, oysters or scallops, which then accumulate the algal toxins to levels that are potentially lethal to humans or other consumers. These poisoning syndromes are named paralytic, diarrhetic, neurotoxic, and amnesic shellfish poisoning (PSP, DSP, NSP and ASP) and are specifically caused by biotoxins synthesized by a group of marine algae called dinoflagellates, except ASP which is caused by diatoms.
Until recently, harmful algal blooms were viewed as a natural event that made certain seafood toxic for consumption. HAB gained more attention in the Gulf of Mexico when it was discovered that the marine dinoflagellate, Karenia brevis, was responsible for the extensive blooms that occur in the region, especially in Texas and Florida. These dinoflagellates produce potent toxins, called brevetoxins, which have been responsible for killing millions of fish and causing shellfish poisoning in humans in the region. A combined estimate of the economic costs of HAB phenomena in the region is currently not available, but it is reported that a single red tide event in the Gulf Coast of Florida costs about $20 million, including losses to the tourism industry, hotel/motel suppliers, commercial fisheries, and local governments for the expense of beach cleanup.
Concerns about the problem have united workers in the field to conduct and collaborate on HAB research and formulate policies for the management of the regions coastal waters. Organizations leading the effort in HAB research include the Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) program. Their goal is to develop an understanding of the population dynamics and trophic impacts of harmful algal species, which can be used as a basis for minimizing adverse effects on the economy, public health, and marine ecosystems. NOAA’s coastal oceans Monitoring and Event Response for Harmful Algal Blooms (MERHAB) and Harmful Algal Program sponsored by the Center for Sponsored Coastal Research is also actively involved in building sustainable regional partnerships that provide managers with crucial information in time for critical decisions needed to mitigate HAB impacts. As a response to the need to inject science into management decision-making, an HAB Event Response Program was designed by CSCOR to support coastal managers faced with responding to unusual or unexpected HABs.
Ecology and Oceanography of Harmful Algal Blooms (ECOHAB). Viewed on the web on February 23, 2004 at: http://www.redtide.whoi.edu/hab/nationplan/ECOHAB/ECOHABhtml.html
National Oceanic and Atmospheric Administration Center for Sponsored Coastal Ocean Research Coastal Ocean Program (NOAA/CSCOR/COP)- The Harmful Algae Page. Viewed on the web on February 23, 2004 at: http://www.whoi.edu/redtide/whathabs/whathabs.html
Centers for Disease Control - Harmful Algal Blooms
North West Fisheries Center - Harmful Algal Blooms Program
Texas Parks and Wildlife - Harmful Algal Blooms in Texas
Keywords: Harmful Algal Bloom, Biotoxin, Dinoflagellate, Diatom, Red tide, Shellfish poisoning
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