Red Tide Phenomenon

This topic submitted by Stephanie Doupnik ( at 10:20 PM on 6/8/05.

This stingray seems to be flying at Molasses Reef, Key Largo, Florida.

Tropical Field Courses -Western Program-Miami University

Red Tide Phenomenon

The ocean is filled with unsolved mysteries and has continued to stump scientists with new discoveries everyday. One of the most puzzling issues is the phenomenon known as “Red Tide”. With records dating back to the mid 1800’s, Red Tide has continued to frustrate researchers with the cause of this unusual event (About Red Tide 2005). Although Red Tide has occurred all over the world: Maine, Norway, Africa, Japan and even Oregon, I will be mainly concentrating on the Florida region in order to learn more about this catastrophic act of nature (Hunting Dangerous Algae 2002). First I will discuss some background information on Red Tide and give a brief description on how they can occur and which species are responsible for this disturbing phenomenon. Next I will concentrate on how Red Tide affects not only marine life, but our lives as well. With the wealth of information published about Red Tide, I will only be able to brush upon key aspects of it. With further research and education, someday we may be able to prevent some of the devastation caused by the Red Tide.

Red Tide is caused by a rapid population growth of microscopic plankton. These microscopic plankton release toxins that have severe affects on marine life and humans (Red Tide 2001). The toxins are “environmental chemicals” that can interfere with metabolism, nerve conduction, and the central nervous system (From Monsoons to Microbes 1999). The blooms mainly take place in coastal, warm waters. Factors that promote red tide occurrences are 1. Warm temperatures 2. High nutrient content 3. Low salinity 4. Calm seas and 5. Rain followed by sunny weather. As the plankton multiply and grow, they cause a discoloration in the water near the shoreline (Red Tide 2001). Often it turns a reddish-brown color, hence the name red tide. There have been occurrences where the water has turned a yellow, brown, or even a purple shade (Fish and Wildlife Research Institute 2005)

Scientist has summarized the development of Red Tide into four stages. The first stage is where the plankton is introduced into the area. Next is the growth stage where the population begins to multiply rapidly over a few weeks time span. As they reach the peak of growth they enter into stage three, maintenance. Here is where the bloom can either continue to live offshore or can be moved inshore by tides or strong winds. If the bloom moves closer to shore, nutrients are in greater abundance, which can cause the bloom to grow even larger. Finally, the bloom will eventually dissipate, ending the cycle (Red Tide 2001).

Red Tide occurs most often in the Florida region, particularly on the gulf side. Although there are thousands of microscopic species of plankton, one in particular resides only in Florida. The Karenia brevis is a dinoflagellate that was first identified in 1947 (Red Tide 2001). The Karenia brevis has caused most of the red tide occurrences within Florida’s gulf waters. The organism is extremely fragile and can break easily when going through rough waves along beaches. They can be broken apart from the tides allowing the toxins to be released into the water (Literature review of Florida red tide 2003).

One of the newest developments in Florida’s Red Tide research has been the connection between red tide and the dust storms from Africa. Scientists believe that the dust clouds that travel from the Saharan desert could be triggering these algae blooms. The iron is deposited into the water and then is used by the bacteria called Trichodesmium to fixate nitrogen. Since there is an abundance of nitrogen in the ocean, the water is more susceptible to creating toxic blooms (Dust from Africa 2005).

Organisms involved in Red Tide are not always harmful to the marine life, but unfortunately there is a great number that are. These harmful algal blooms (HABs) have caused death among fish, birds, manatees, and several other vertebrate species. Eating the toxic plankton, eating other organisms already infected with the toxins, or simply by exposure through the water can contaminate organisms (Effects of Florida Red Tide 2005). The toxins do not affect filter-feeding shellfish even though the toxins are concentrated in their organs. Other fish, however, are not so lucky and end up being victims to the powerful red tide (Literature review of Florida red tide 2003).

The death rate of fish during Red Tides has reached extreme numbers. Estimates are that over 100 tons of fish can be killed during a Red Tide in a single day (Literature review of Florida Red tide 2003). Once the fish is infected, they begin to twist and swim in a corkscrew fashion. They begin to defecate and regurgitate as well as experience convulsions. Their body slowly begins to paralyze and prior to death they begin to experience respiratory failure. This process unfortunately can take from a couple of days to a full week before the organism eventually dies (Effects of Florida Red Tide 2005).

Manatee and dolphin mortality numbers are on the rise due to red tide toxins. In 1996 150 manatees along the Florida region were reported dead over a two-year period from a red tide occurrence (Hunting Dangerous Algae from Space 2002). This single red tide wiped out 10% of the Florida manatee population as well as 162 dolphins within Mexico’s waters (START 2004). Along the shoreline of Siesta Key and Lido beaches, there have been at least 44 manatees that have died from coming into contact with red tide (Red Tide Toxins Hit Florida Beachgoers 2005). Although these numbers seem extreme it is the reality of Red Tide. In June 1987 to May 1988 one of the largest dolphin kills was reported along the Atlantic coastline. 740 bottlenose dolphins died from red tide during this period (Effects of Florida Red Tide 2005).

Red Tide has affected humans as well. The impact is both medical and economical. The diagnosis of Red Tides physical affects has been narrowed down into five different types of poisoning. 1. Amnesic Shellfish Poisoning (ASP). Symptoms are vomiting, headache, diarrhea, memory loss, seizure, or even coma. You can get this type of poisoning from eating a contaminated clam or mussel 2. Ciguatera Fish Poisoning (CFP). Symptoms for CFP are skin irritation, temperature reversal, hallucinations, and muscular and joint pain. 3. Diarrheic Shellfish Poisoning (DSP). Symptoms are chills, vomiting, nausea, and diarrhea. Scallops, mussels and short-necked clams cause DSP. 4. Neurotoxin Shellfish Poisoning (NSP). Symptoms for NSP are tingling of limbs, muscle aches, and dizziness. Clams, scallops, mussels, and oysters are all associated with NSP. 5. Paralytic Shellfish Poisoning (PSP). Symptoms are rash, fever, numbness of mouth, drowsiness, and vomiting (Shellfish Poisoning 2005). The earliest record of PSP was in the year of 1793 when a man died and four others were left ill (Saving the Oceans 1992)

From 1978 to 1987, half of the reported seafood poisonings were the result of Red Tide toxins (From Monsoons to Microbes 1999). Becoming contaminated with these toxins can be deadly unless you take necessary precautions. To treat most of the cases, you should go to your local hospital to get your stomach pumped or induce vomiting in order to get the toxins out of your system. If you cannot get to a hospital your best choice is to call the poison control center for further instructions. Eating contaminated shellfish tastes no different than if they were not contaminated. The only way to avoid a Red Tide poison is to be aware and cautious of when and where you eat shellfish (Red Tide 2001).

The economy has also been left to survive the blows of red tide. “The West Florida shelf is a hot spot for fishing, aquaculture and tourism, all of which can be drastically affected by a surprise visit from a red tide” (Dust from Africa Leads to Large Toxic Algae Blooms 2005). Tourism is one of Florida’s most profitable businesses. Families don’t want to attend a beach where they will suffer an irritating cough and itchy eyes. Restaurants suffer from the lack of tourism and locals refusing to eat out in order to avoid eating something that could be contaminated (Businesses pursue Red Tide solution 2004). Oyster harvesting is another huge business in Florida that is getting hit by HAB’s lately. On numerous occasions, Florida has had to shut down the oyster industry in Apalachicola Bay because of the threat of red tide contamination (Red tide threatens oyster harvest 2003).

Red Tide has created a large impact on our oceans and our lives. It’s increasingly affecting our marine life and our own health and economic prosperity. Programs have been established to try and reduce the harmful effects of the Red Tide and keep people educated about this phenomenon. The next step in coming closer to solving the mystery is more research. Whatever is causing red tide, and the answer behind stopping it is out there. We just have to keep diving deeper for the truth…


About Red Tide. Mote Marine Laboratory. 6 May 2005 .

Daley, Beth. Red Tide Toxins Hit Florida Beachgoers In Lungs. Rense. 6
May 2005 .

Dust from Africa Leads to Large Toxic Algae Blooms in Gulf of Mexico, Study Finds.
NASA Goddard Space Flight Center. NASA. 24 May 2005 .

Effects of Florida Red Tide on Marine Animals. Fish and Wildlife Research Institute. 6
May 2005 .

Fish and Wildlife Research Institute. DataGlyphics, Inc. DataGlyphics. 27 Mar. 2005

From Monsoons to Microbes: Understanding the Ocean’s Role in Human Health.
National Academy Press. Washington, D.C. 1999.

Kirkpatrick, Barbara; Fleming, Lora E.; Squicciarini, Dominick; Backer, Lorrie C.;
Clark, Richard; Abraham, William; Benson, Janet; Cheng, Yung Sung; Johnson, David; Pierce, Richard; Zaias, Julia; Bossart, Gregory D.; and Baden, Daniel G. Literature review of Florida red tide: implications for human health effects. ELSEVIER. 27 Aug. 2003. pg. 99-115.

Macinnis, Joseph. Saving the Oceans. Firefly Books Inc. Buffalo, NY 1992.

Red Tide. Charles H. Bronson. No. 1. 2 Nov. 2001.

Rogers, Ibram. Red tide threatens oyster harvest Dead Fish washing ashore since Friday.
GAIN Inc. 24 Sept. 2003. GAIN. 6 May 2005 .

Sanchez, Dana. Businesses pursue Red Tide Solution. Bradenton Herald. 16 Sept. 2004.
The Herald. 6 May 2005 .
Shellfish Poisoning. Fish and Wildlife Research Institute. 6 May 2005

START: Soultions To Avoid Red Tide on Florida’s Gulf Coast. 2004.
START. 23 Mar. 2005 .

Yohe, Evelyne. Hunting Dangerous Algae from Space. NASA Earth Science4
Enterprise Data and Services. 9 July 2002. NASA. 29 Mar. 2005 .

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