An active red tide event renders swimming generally unsafe due to the presence of toxins in the water and air. Red tide is the common term for a harmful algal bloom (HAB), which is a rapid overgrowth of microscopic algae. While not all algal blooms are harmful, the species that cause red tide produce potent neurotoxins that pose a risk to human health. Public health experts advise people to stay out of the water when a bloom is present to avoid potential illness.
What Causes Red Tide
Red tide events are caused by the dense proliferation of single-celled organisms known as dinoflagellates. Along the Gulf of Mexico, the organism Karenia brevis is common; it multiplies rapidly under specific environmental conditions. This rapid increase, or bloom, is often triggered by an abundance of nutrients like nitrogen and phosphorus, warm temperatures, and low salinity.
The danger lies in the potent neurotoxins they produce, specifically compounds called brevetoxins. These toxins affect the central nervous system of marine life and humans. Their concentration increases dramatically during a bloom, creating hazardous conditions in the water and surrounding atmosphere.
Health Effects of Water Contact
Direct contact with contaminated water can lead to symptoms affecting the skin and mucous membranes. Swimmers often report skin irritation, including rashes, especially where swimwear holds water close to the body. The toxins can also cause burning and soreness in the eyes.
Incidental ingestion of water while swimming poses a risk to the gastrointestinal system. Swallowing contaminated seawater can lead to symptoms like nausea, vomiting, and diarrhea. While severe illness is uncommon, the toxins irritate the digestive tract, resulting in temporary distress. Washing thoroughly with soap and fresh water immediately after leaving the affected water reduces exposure.
The Danger of Airborne Toxins
The inhalation of aerosolized toxins is a widespread danger, affecting individuals even if they never enter the water. As waves break and sea spray is generated, Karenia brevis cells rupture, releasing brevetoxins into the air. These microscopic particles carrying the neurotoxins can be carried inland by onshore winds.
Exposure primarily causes upper and lower respiratory symptoms, including a dry cough, throat irritation, nasal congestion, and sneezing. For healthy individuals, these effects are temporary, subsiding quickly once they move to a location with clean air. However, the effects are more pronounced for people with pre-existing respiratory conditions.
Individuals with asthma, emphysema, or Chronic Obstructive Pulmonary Disease (COPD) are especially susceptible to severe reactions. The toxins can trigger bronchoconstriction, leading to wheezing, chest tightness, and difficulty breathing. These sensitive populations should avoid red tide areas entirely, as exposure can exacerbate their chronic conditions.
Following Official Safety Warnings
The most reliable way to determine beach safety during a red tide event is to check local advisories issued by health departments. Many coastal areas utilize beach flag systems and post signage to alert the public to the presence and severity of a bloom. If a warning is in effect, stay away from the shoreline and out of the water.
Public health officials also advise against harvesting or eating molluscan shellfish, like oysters or clams, from an affected area, as these organisms accumulate toxins. If you experience persistent respiratory symptoms, seek medical attention. Closing windows and running the air conditioner with a well-maintained filter can help reduce indoor exposure for residents near affected beaches.