If you consult the websites of the Florida Fish and Wildlife Conservation Commission or the Mote Marine Laboratory, both considered authorities on marine environmental issues in the state of Florida, red tide outbreaks associated with Karenia brevis are "natural phenomena," 'beyond our ability to control,' and explicitly not fed by nutrient pollution or causally linked to land-based, human activities. And yet, longtime residents of the Florida Gulf coast (the author included) can tell you from first-hand experience that the blooms have been getting progressively worse, closer to shore, and persisting for a greater length of time, indicating that if it is an entirely natural cycle, it has undergone concerning changes of late.
The reality is that authorities who deny the involvement of land-based activities and algae blooms are conveniently ignoring the science, which is peer reviewed and published, that instructs us on what is feeding red tide near shore.
Florida has only so many industries that sustain its fragile economy, many of which would have to enact substantial and costly reforms in order to improve the environmental situation. The tourism and real estate industries also have a vested interest in minimizing and/or denying the extent of the problem, at least in the short term. The long-term outlook, however, is dismal for these industries, who, failing to act, would see the primary attractor for tourists or potential buyers of real estate -- the Gulf of Mexico -- transformed into a Petri dish. It is for this reason that the truth about red tide must gain a wider audience, and we hope, widespread acceptance.
How Red Tide Is Measured and Misleadingly Contextualized For the Public
Since late September last year, the Southwest Florida Gulf Coast has been under siege by laboratory-verified blooms [see Status Maps], growing to its present state of significant outbreaks of a million cells per liter or higher, and stretching all the way from Manatee County to the Florida Keys. This is one of the worst red tide outbreaks in recorded history.[i]
Karenia brevis levels are measured by state environmental authorities using the cells/liter scale as follows:
- Not Present – Background (0-1000)
- Very Low (more than 1,000 to 10,000)
- Low (more than 10,000 to 100,000)
- Medium (more than 100,000 – 1,000,000)
- High (more than 1,000,000)
So-called "Low" levels, or 10,000 to 100,000 cells per liter, can cause fish kills. Once you get to "Medium" and "High" red tide represents a serious health threat to exposed populations, keeping in mind that one does not have to be "at the beach" to be affected, as red tide brevetoxins are aerosolized (made airborne) via wave action, and can be carried on the wind many miles inshore. In fact, at so-called "Low" levels (more than) 50,000 cells/liter the saturation of Karenia brevis is already significant enough that it can be detected by satellite.
At present, levels along the affected Southwest Florida Gulf Coast have reached "High" in several areas, including off the coast of Lee County where I am presently reporting from. I can speak directly from experience that this is a particularly noxious outbreak.
For instance, I had a bronchial asthma attack for the first time in 20 years and have found myself, my family, and the local community I serve to be at greatly increased susceptibility to prolonged cold and flu bouts, over the past five months.
Another important consideration is that red tide sampling occurs primarily in surface water (80% surface sampling; 20% bottom sampling). The problem is that Karenia brevis blooms have been found to penetrate coastal waters along the bottom without surface expression until nearshore. This means that "negative" surface findings do not necessarily indicate the absence of a problem.
So, What Is The Real Cause of Prolonged, Near-To-Shore Red Tide Outbreaks?
So, back to the question: Are these outbreaks entirely natural phenomena, as many health authorities, and certainly folks within the mainstream media, tourist and real estate industry, often maintain?
The answer is a resolute and resounding NO. In April, 2009, the journal Aquatic Microbial Ecology published a groundbreaking study titled, "Grazing by Karenia brevis on Synechococcus enhances its growth rate and may help to sustain blooms," which provided the missing link in how red tide is directly fed by human, land-based activities. Here is the study abstract:
ABSTRACT: Grazing rates of Karenia brevis Clones CCMP2228 and CCMP2229 were determined in laboratory experiments using Synechococcus sp. Clone CCMP1768 as food. Grazing by K. brevis thus enhances the range of nutritional substrates available to meet its growth requirements, and may play a substantial role in sustaining natural populations in inorganic N-poor waters. With evidence that blooms of Synechococcus can be enhanced due to anthropogenic nutrients, the potential importance of this particulate nutrient source for sustaining red tide blooms in situ is large and may help to resolve the current uncertainty as to how K. brevis blooms are maintained. It can now be hypothesized that as cyanobacterial blooms increase, so too does the potential for Karenia brevis growth to be enhanced and for blooms to be sustained through grazing, especially under the low light conditions associated with bloom self-shading. Recognition of this pathway is at least one step toward reconciling the long-term reported increase in K. brevis blooms (e.g. Brand & Compton 2007) and the tendency for blooms of this species to develop offshore in seemingly oligotrophic waters (e.g. Vargo et al. 2004, 2008)What this research essentially proves is that the runoff from land-based applications of urea nitrogen fertilizers such as commonly used in lawn care, as well as additional sources of nitrogen urea from septic tanks, sewage spills and close-to-water sewage treatment effluent, result in Synachoccus blooms, which is a harmless, green slime algae (have you noticed the green slime at your beach?). Karenia brevis (red tide) uses the green slime as an energy source. The more Synachoccus the more red tide; simple cause and effect.
At the root of the problem are nitrogen urea fertilizers, which are overused in Florida lawn care practices, as well as in Florida agriculture (more on this later). According to a Sierra Club report linking fertilizers to red tide blooms, residential fertilizer use in the state of Florida increased by 153,533.95 tons or 45% from 2003 to 2006 alone.[ii] One might ask the question to Floridians: is the "health" of your lawns (read: aesthetic appearance) more important than the health of the Gulf of Mexico (and by implication, your own health)?
Ironically, plants need primarily magnesium (for chlorophyll) and potassium, and not nearly as much nitrogen, which is presently being used at up to 5 times higher levels than required. In fact, excess nitrogen leads to plasmolysis in plants, causing excess water to leave the plant entering the soil, resulting in wilting. The excess nitrogen, of course, leaches into the soil and eventually a portion of its causes water pollution.
The obvious solution to the accelerating red tide problem is to reduce land-based applications of urea nitrogen, especially in the summer months. As the green slime is reduced, the red tide will have no additional energy source and will die out.
How Red Tide Adversely Affects Human Health
In order to understand how red tide affects human health, one must first understand brevetoxins, the primary "poisons" produced by this organism.
There are at least 9, and as many as 14, brevetoxins divided into two classes: Brevetoxin A and Brevetoxin B, with 3 subtypes characterized among Brevetoxin A and 4 subtypes among Brevetoxin B.
Brevetoxins are extremely toxic. The brevetoxin B subtype, PB-TX2, for instance, has an oral LD50 (the acutely lethal dose that kills 50% of the test group) equivalent to cyanide (6 mg/kg) at 6.6 mg/kg in the 24 mouse model of acute exposure. No one truly knows the extent of the synergistic toxicity associated with exposure to all 9-14 brevetoxins simultaneously, which is what may occur in real-world exposure, because it has not (to my knowledge) been researched.
Brevetoxins are known primarily as a neurotoxic. They bind to voltage-gated sodium channels in nerve cells, leading to disruption of nerve transmission and in some cases nerve cell death. Animal research indicates that as little as 2 days of subacute exposure to the Brevetoxin B, PbTx-3, is sufficient to induce neuronal degeneration in a discrete reason of the mouse cerebral cortex.[iii]
In humans, a condition known as Neurotoxic Shellfish Poisoning (NSP) caused by the consumption of shellfish contaminated by brevetoxins has been identified. Symptoms include vomiting and nausea and a variety of neurological symptoms such as slurred speech.[iv] Of course, lower concentrations, especially in more susceptible populations already suffering from neurological issues, likely contribute to these symptoms, as well as headache, myalgias (muscle soreness), and related aches and pains that would be hard to attribute to such an invisible toxin, whose health threat is generally downplayed by the media and medical establishment.
Neurotoxicity, however, is only the tip of the iceberg. A 2004 study, published in the Journal of Toxicology and Environmental Health, found that the immune system, and not the nervous system, is the primary target of brevetoxins.[v] Animals exposed to brevetoxin saw a more than 70% suppression of humoral immunity. A 2005 study confirmed this finding.[vi]
Then, in 2011, it was found that brevetoxin A inhalation worsens the pulmonary response to influenza A in the male rat. [vii] The study authors concluded: "These results suggest that repeated inhalation exposure to brevetoxin may delay virus particle clearance and recovery from influenza A infection in the rat lung."
This finding indicates that red tide blooms may therefore worsen the seasonal flu epidemics that commonly afflict the Southwest Florida, especially when the bloom persists into the fall and winter months, as is the present case.
It is already well known that hospital verified cases of respiratory issues can increase by over 50% during sustained red tide outbreaks.[viii]
Considering that much of the mortality associated with influenza infection is associated with pneumonia complications, reducing red tide outbreaks via fertilizer use reductions should be considered a top priority by health authorities.
But the adverse health effects do not end with neurotoxicity and immunotoxicity, as serious gastrointestinal complaints may also follow from red tide exposure. A 2010 study examined whether the presence of a Florida red tide bloom affected the rates of admission for a gastrointestinal diagnosis to a hospital emergency room in Sarasota, FL.[ix] According to the study:
The rates of gastrointestinal diagnoses admissions were compared for a 3-month time period in 2001 when Florida red tide bloom was present onshore to the same 3-month period in 2002 when no Florida red tide bloom occurred. A significant 40% increase in the total number of gastrointestinal emergency room admissions for the Florida red tide bloom period was found compared to the non red tide period.We can therefore add gastrointestinal issues to the growing list of red tide associated health issues. Other potential health effects that have been noted in the biomedical literature include:
- Bilateral Mastoiditis (infection of the mastoid bone behind the ear)
- Hemolytic Anemia
- Neuromuscular Diseases
1) REDUCE EXPOSURE: First, if you live in South Florida, remember to monitor your area's levels by visiting the Status Maps. Please keep in mind that proximity is not the only factor in exposure, due to the well-known aerosolization of these toxins and the inability of surface water testing to fully reveal its presence.
Next, visit the site WindMaps.com, to see if the winds are moving inshore, or going offshore. This simple step may enable you to reduce exposure, by reducing time outside, and certainly keeping off the beach, on days that aerosolized red tide brevetoxins may be moving inshore. Also, consider that if you are driving, keep the air circulating within the cabin. Unfortunately, there is nothing you can do if your AC unit is continually pulling air from outside inside your home, but you could reduce your AC usage on these days. Eating cooling foods, and wear lighter clothing, for instance.
2) REDUCE TOXIC EFFECTS: The primary mechanism through which brevetoxins cause respiratory harm is through IgE-independent mast cell activation.[x] Mast cells are immune cells which if over-activated can produce a wide range of potentially harmful substances, such as:
- Histamine (inflammatory)
- Thromboxane (vasoconstrictive)
- Prostaglandin D2 (brochoconstrive)
- Leukotriene C4 (bronchoconstrictive)
3) CONTRIBUTE TO THE LONG-TERM SOLUTION: The long-term solution is to reduce the use of nitrogen urea fertilizers in both lawn and agricultural applications. There is no question that nitrogen urea rich agricultural runoff, primarily from the sugarcane and citrus industries, are sizable contributors to the overall nitrogen burden in the Gulf of Mexico. Much of Big Sugar's agricultural runoff ends up in Lake Okeechobee, which eventually empties into the Gulf of Mexico.
A 2006 study published in the journal Biogeochemistry titled, "Escalating worldwide use of urea – a global change contributing to coastal eutrophication," indicates worldwide use of urea as a nitrogen fertilizer and feed additive has increased more than 100-fold in the past 4 decades. The study pointed out:
Long thought to be retained in soils, new data are suggestive of signiﬁcant overland transport of urea to sensitive coastal waters. Urea concentrations in coastal and estuarine waters can be substantially elevated and can represent a large fraction of the total dissolved organic nitrogen pool. Urea is used as a nitrogen substrate by many coastal phytoplankton and is increasingly found to be important in the nitrogenous nutrition of some harmful algal bloom (HAB) species.They also noted that "the global increase from 1970 to 2000 in documented incidences of paralytic shellﬁsh poisoning, caused by several HAB species, is similar to the global increase in urea use over the same 3 decades."
The reality is that these agricultural practices have been a long time in the making, and will take considerable time, energy and political clout to change. The good news is that you can make changes at the local level, from the bottom up, as it were, by starting with your own lawn. You can also organize at a county level to enact ordinances that restrict fertilizer use, as Ed Rosenthal, founder of the non-profit organization Advocate the Precautionary Principle, has done with great success in Sarasota county. These results are encouraging, and indicate that we can build a grassroots movement with an end goal to enact stricter regulations at the state level.
[i] Herald Tribune, Oct. 9th, 2012, Worst Red Tide Outbreak Since 2007
[ii] Sierra Club, Fertilizer Use and its Impact on Harmful Red Algae Blooms (Red Tide)
[iii] Xiuzhen Yan, Janet M Benson, Andrea P Gomez, Daniel G Baden, Thomas F Murray. Brevetoxin-induced neural insult in the retrosplenial cortex of mouse brain. Inhal Toxicol. 2006 Dec ;18(14):1109-16.
[iv] Sharon M Watkins, Andrew Reich, Lora E Fleming, Roberta Hammond. Neurotoxic shellfish poisoning. Mar Drugs. 2008 ;6(3):431-55. Epub 2008 Jul 12.
[v] Janet Benson, Fletcher Hahn, Thomas March, Jacob McDonald, Mohan Sopori, JeanClare Seagrave, Andrea Gomez, Andrea Bourdelais, Jerome Naar, Julia Zaias, Gregory Bossart, Daniel Baden . Inhalation toxicity of brevetoxin 3 in rats exposed for 5 days. J Toxicol Environ Health A. 2004 Sep 24 ;67(18):1443-56.
[vi] Janet M Benson, Fletcher F Hahn, Thomas H March, Jacob D McDonald, Andrea P Gomez, Mohan J Sopori, Andrea J Bourdelais, Jerome Naar, Julia Zaias, Gregory D Bossart, Daniel G Baden. Inhalation toxicity of brevetoxin 3 in rats exposed for twenty-two days. Environ Health Perspect. 2005 May ;113(5):626-31.
[vii] Janet M Benson, Molly L Wolf, Adriana Kajon, Brad M Tibbetts, Andrea J Bourdelais, Daniel G Baden, Thomas H March . Brevetoxin inhalation alters the pulmonary response to influenza A in the male F344 rat. J Toxicol Environ Health A. 2011 ;74(5):313-24.
[viii] Barbara Kirkpatrick, Lora E Fleming, Lorraine C Backer, Judy A Bean, Robert Tamer, Gary Kirkpatrick, Terrance Kane, Adam Wanner, Dana Dalpra, Andrew Reich, Daniel G Baden. Environmental exposures to Florida red tides: Effects on emergency room respiratory diagnoses admissions. Harmful Algae. 2006 Oct 1 ;5(5):526-533.
[ix] Barbara Kirkpatrick, Judy A Bean, Lora E Fleming, Gary Kirkpatrick, Lynne Grief, Kate Nierenberg, Andrew Reich, Sharon Watkins, Jerome Naar. A significant 40% increase in the total number of gastrointestinal emergency room admissions for the Florida red tide bloom period was found compared to the non red tide period. Harmful Algae. 2010 Jan 1 ;9(1):82-86.
[x] Susana C Hilderbrand, Rachel N Murrell, James E Gibson, Jared M Brown. Marine brevetoxin induces IgE-independent mast cell activation. Arch Toxicol. 2011 Feb ;85(2):135-41. Epub 2010 Jun 13.
This article first appeared at GreenMedInfo. Please visit to access their vast database of articles and the latest information in natural health.
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