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Harmful Algal Blooms (HABs) and their effects on us

By Staff | May 13, 2009

Last week, I wrote about a new bill in the United States Senate which will authorize money for research and to help communities like ours manage the effects of Harmful Algal Blooms (HABs). This week, I would like to provide more information about HABs. This information comes from the National Oceanic and Atmospheric Administration (NOAA) and the Centers for Disease Control (CDC).

According to NOAA, “Harmful Algal Blooms are blooms of species of algae that have negative impacts on human, marine environments, and/or coastal economies. HABs include blooms of both microalgae (microscopic, single celled) and macroalgae (seaweeds).”

While there are many different forms of both, the most common for us are red tide and red drift algae.

Most algae are very important to salt and fresh water ecosystems and most species are not harmful. However, Harmful Algal Blooms have been reported in almost every U.S. coastal state and according to NOAA they are on the rise. So while we have seen HABs in our waters over the years, and in particular red drift algae, as seen in this photo from 2007, this is a national issue.

Another problem with HABs is oxygen depletion. They can block sunlight that other organisms need to live, and some HAB-causing algae release toxins that are dangerous to animals and humans. It is only a small percentage of algae that produce toxins that can kill fish, shellfish and other marine life. These can also cause illness in people. Again, these are rare but can be debilitating or even fatal.

According to the CDC, “Scientists do not yet understand fully how HABs affect human health. Authorities in the United States and abroad are monitoring HABs and developing guidelines for HAB-related public health action. The U.S. Environmental Protection Agency (EPA) has added certain algae associated with HABs to its Drinking Water Contaminant Candidate List. This list identifies organisms and toxins that EPA believes are priorities for investigation.”

The CDC works with public health agencies, universities and federal partners to investigate how the following algae – which can cause HABs – may affect public health:

Cyanobacteria, also known as blue-green algae, can produce toxins that may taint drinking water and recreational water. Humans who drink or swim in water that contains high concentrations of cyanobacteria or cyanobacterial toxins may experience gastroenteritis, skin irritation, allergic responses or liver damage.

Harmful marine algae, such as those associated with red tides, occur in the ocean and can produce toxins that may harm or kill fish and marine animals. Humans who eat shellfish containing toxins produced by these algae may experience neurologic symptoms (such as tingling fingers or toes) and gastrointestinal symptoms. Breathing air that contains toxins from algae associated with red tide may cause susceptible individuals to have asthma attacks.

Pfiesteria piscicida, a single-celled organism that lives in estuaries, has been found near large quantities of dead fish. Scientists do not yet know whether P. piscicida affects human health. However, reports about symptoms such as headache, confusion, skin rash, and eye irritation in humans exposed to water containing high concentrations of P. piscicida have prompted public concern.

There is a lot we don’t know about HABs and both CDC and NOAA are working hard to learn more.

According to NOAA, “The factors controlling HAB development and decline are not well understood for many harmful species. In general, algal growth is enhanced when environmental conditions (such as light, temperature, salinity, and nutrient availability) are optimal for growth.” Many believe the increased nutrients in our waters from pollution are a significant contributing factor to the growth of both red tide and red drift algae.

Also from NOAA, “Perhaps the best known HAB is the ‘red tide’ that occurs nearly every summer along Florida’s Gulf Coast and that Spanish explorers first observed in the 16th century! The organism that causes the Florida red tide (which may not always appear red), a microscopic alga called Karenia brevis, produces a toxin that makes shellfish dangerous to eat. It also kills fish, and in some instances, dolphins and manatees. It may also make the surrounding air difficult to breathe due to aerosolized toxins. Scientists have been monitoring and studying the phenomenon for a number of years to determine how to detect and forecast the location of the blooms. The goal is to give communities advance warnings so they can adequately plan and deal with the adverse environmental and health effects associated with these red tide events.”

HABs can also have an economic impact. It is estimated that they cause, on average, about $82 million in economic impacts to the seafood, restaurant and tourism industries each year. HABs reduce tourism, close beaches and shellfish beds, and decrease the catch from both recreational and commercial fisheries.

The new bill in the Senate is a reauthorization of the original Harmful Algal Bloom and Hypoxia Research and Control Act which was signed into law on November 13, 1998, and was reauthorized in December 2004. The Act recognized that many U.S. coastal areas suffer from HABs and hypoxia each year, threatening coastal ecosystems and endangering human health. This new bill will expand the program so that communities can better predict HAB events and manage the impact.