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Natural Awakenings Naples and Fort Myers

The Truth about Red Tide: Its Causes, Health Effects and Solutions

Mar 01, 2013 12:34PM ● By Sayer Ji

Several authorities on marine environmental issues in the state of Florida consider algal bloom outbreaks associated with karenia brevis, a single-cell algae, as natural events beyond our ability to control, rather than phenomena causally linked to land-based, human activities such as nutrient pollution from fertilizer runoff. The media and various stakeholder industries widely echo this perception. Yet, residents of the Gulf Coast can plainly see that the blooms—known as red tide—have progressively worsened, moving closer to shore and persisting for longer periods. If these outbreaks of red tide represent entirely natural cycles, they have recently undergone concerning changes.

Since late September 2012, the Southwest Florida Gulf Coast has been under siege by laboratory-verified blooms that now stretch all the way from Manatee County (Sarasota) to the Florida Keys and contain concentrations of karenia brevis at a million cells per liter or higher. According to the Herald-Tribune, in Sarasota, we are experiencing one of the worst red tide outbreaks since 2007.

Karenia brevis levels are measured by state environmental authorities using the cells-per-liter scale: Not Present – Background (0-1,000); Very Low (>1,000 to 10,000); Low (>10,000 to 100,000); Medium (>100,000 – 1,000,000); High (>1,000,000).

However, these figures are misleading, because very low levels (more than 1,000 up to 10,000 cells per liter) can lead to acute symptoms of respiratory irritation and shellfish harvesting closures. Medium and high levels of red tide represent a serious health threat to exposed human populations—people need not be at the beach to experience adverse effects, because red tide produces up to 14 brevetoxins (neurotoxins) that can be aerosolized, or made airborne, via wave action and carried many miles inland by the wind. Inhalation of the toxins can cause respiratory irritation, lung inflammation, a worsening of asthma symptoms and possible depression of the immune system, among other symptoms.

The real cause of prolonged, near-to-shore red tide outbreaks appears to be fertilizer pollution of the Gulf of Mexico. In April 2009, the journal Aquatic Microbial Ecology published a groundbreaking study that provided the missing link in how red tide is directly fed by human, land-based activities. The study’s research showed that runoff from applications of urea nitrogen fertilizers such as those commonly used in lawn care, and additional sources of nitrogen compounds from septic tanks, sewage spills and sewage treatment effluent results in blooms of synachoccus, a harmless, green slime algae (often noticeable at the beach). Karenia brevis uses the green slime as an energy source. The more synachoccus, the more red tide—simple cause and effect.

One obvious solution to the accelerating red tide problem is to reduce land-based applications of urea nitrogen, especially during the summer months. As the green slime is reduced, the red tide will have no additional energy source and will die out.

Sayer Ji is the founder and director of and co-author of the book, The Cancer Killers: The Cause is the Cure. His writings and research have been published in the Wellbeing Journal and the Journal of Gluten Sensitivity and have been featured on,,, and

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