A red tide, the common name for a harmful algal bloom, has developed off Southwest Florida over the past few weeks. Its effects have become noticeable on Longboat Key in the past two days as dead fish have appeared on the beach and cough-inducing air has blown ashore.
Caused by an excessive bloom of Karenia brevis, a dinoflagellate, red tide plagues areas of the Gulf Coast every year, especially during the summer months. While nutrient rich effluent has been blamed in the past, the Florida Fish and Wildlife Commission reports that the blooms usually develop 10-40 miles offshore and may be fueled by a combination of environmental factors, including intense sunshine, calm surface waters, warm sea temperatures and upwelling currents. Until such conditions abate, the bloom can worsen and toxins released by the algae kill many species of marine fish, shellfish and even manatees. Carried by onshore winds, algal debris often irritates the eyes and respiratory tract of humans, aggravating asthma and emphysema in persons with those conditions.
Since warm sea temperatures may play a significant role in the development of harmful algal blooms, it seems likely that such events will increase in frequency and severity as our climate warms. In our personal history on Longboat Key, spanning13 years, this is the first time that we have encountered a red tide during the winter months.