1. “Red Tides,” or Harmful Algal Blooms
Seth Winkenwerder
Phycology, Spring 2009
Topic Presentation, May 21, 2009
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2. “Red Tides” are actually Harmful Algal Blooms, or simply Algal Blooms.
Algal blooms are not always red, can also be green, brown, orange, or even not pigmented at all.
“Red Tides” have little to no relation to actual ocean tides.
Many different species and organisms can cause the phenomenon, and there is no single cause.
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3. Algal Blooms
Abnormally large concentrations of algae in an aquatic environment
Can be caused by a variety of different species
May occur naturally, but mostly the result of human activity (such as chemical waste released into the ocean)
“Harmful” variety produce toxins.
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4. Species involved Too many to find a single definitive list.
Predominantly Phytoplankton
Bright green blooms caused by cyanobacteria (can appear to be thick green goo)
Less common, but Macroalgae
can also cause bloomevents
to take place.
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5. What causes them? Natural causes???
Compounded by upwelling or unusually calm weather in some cases.
Human waste
Nitrogen-fertilizer runoff
Untreated waste
Other industrial bi-products

6. How are they detected?
When in coastal regions and colorful, obviously easy to spot.
In most cases, amounts of certain pigments are a reasonably accurate way to check the concentration
Satellite imagery is used to look at blooms that are very large or are harder to study from the surface (such as large blooms in the Baltic Sea.)
It is possible that monitoring systems may be able to be implemented in the future using the knowledge we are currently building and new technologies. (Schofield 1999)

7. Impact on Human Health
Around 2000 cases of human poisoning are reported each year (Zingone p.729)
National Institute of Health study on Karenia brevis blooms in Florida (Backer 2003)
Known to kill millions of fish and other marine animals, but human affects were unknown
Humans who came in contact with aerosolized toxins studied during harmful algal blooms off the Florida coast

8. NIH Study Results (Backer 2003)
High exposure days resulted in more (in both quality and quantity) severe symptoms.
Only a couple people that were not already showing ‘symptoms’ before exposure were afterwards, but those that were got slightly worse.
The bloom did not come onto the beach, and measured levels of brevetoxin on the beach and in the air over the beach were very low.
Could be less of a big deal, or the conditions of the study
Study did confirm that such exposure can cause upper and lower respiratory and even skin irritation, but more studies and more intense experiments would have to be undertaken to learn more than that.

9. Affect on other marine animals
Some studies have recently shown that brevetoxins produced can remain in food webs for long periods of time, as they accumulate in fish and seagrass. (Flewelling2005)
Studies were done to try to explain increased mantate, dolphin, and fish death in some recent algal blooms compared to what would have been expected
Toxins can build up in shellfish, which harm other organisms, not just humans.

11. Negative Economic Effects (Hoagland 2002)
Congress estimated in 1998 that HAGs had caused 1 billion dollars in damage in the last decade
September 1980 closure of the Maine coastline- estimated $15 million lost.
Loss of value of coastal property in areas strongly affected by algal blooms
Estimated loss of $68 million by tourism industry in Florida due to HAGs for the summer of 1971.

12. Works Cited:
Backer, Lorraine et. al. “Recreational exposure to aerosolized brevetoxins during Florida red tide events. Harmful Algae. 2(1) p March 2003.
Flewelling, Leanne et. al. “Red Tides and Marine Mammal mortalities.” Nature. Vol. 435 p June 2005.
Hoagland, P. et. al. “The economic affects of harmful algal blooms in the United States.” Estuaries. Vol 25, no 4B, p August 2002
Zigone, Adriana and Henrik Oksfeldt Enevoldsen. “The Diversity of Harmful Algal Blooms: a challenge for science and management.” Ocean and Coastal Management. 43 p
Schofield, Oscar et. al. [including Mark Moline ] “Optical monitoring and forecasting systems for harmful algal blooms: possibility or pipe dream?” Journal of Phycology 35, p