Red Tide… a look at this problem
Most of us have now have heard about the red tide occurring in southwest Florida and the terrible impact it is having on the economy, and quality of life, for our friends down there. Now we are hearing about it in the Florida panhandle and some are concerned about the possible impacts here. At the time of this writing, red tide has been reported at background levels offshore in almost every one of the panhandle counties. The levels have reached low to medium in Bay County and fish kills have occurred. There has been a lot written about this situation, but what I would like to do here is give a few bullet points about it and links to other Sea Grant articles with more information. I hope that by the time you read this things have settled a little in the panhandle, but it could still be an issue.
- Red tide is a naturally occurring event. There are records that the Spanish experienced red tides during the colonial period – so they are not events that originate with human produced pollution.
- Red tides typically originate offshore. They occur across the Gulf coast but are more common in southwest Florida. Red tides are certainly nothing new to our friends down there.
- Red tide is actually a bloom of a type of marine algae. The group of algae that cause this are known as dinoflagellates. They are single celled plant-like creatures that possess an exterior shell with two grooves within. One groove runs from top to bottom, the other across the “waist” and both house a flagella – hence the name “dinoflagellate”. The flagella are used to orient themselves in the water and move up and down within the current.
- Not all dinoflagellates produce red tide, of the ones that do – Karenia brevis is the species that dominates the Gulf of Mexico communities.
- Being plant-like creatures, blooms of these algae occur in warm waters with high nutrients. K. brevis prefers high salinity and so blooms tend to form offshore. They tend to occur in the summer when the shallow waters off southwest Florida are warmer. The source of increased nutrients in this part of the Gulf is not quite understood and more research here is needed.
- K. brevis occurs naturally in the water column of the Gulf, and that includes the panhandle. Concentrations are typically less than 1000 cells / liter of seawater. When stressed, K. brevis will release a toxin. At these “non-detectable” concentrations, there are no impacts.
- As the summer months warm the Gulf, and nutrient levels increase, K. brevis will begin to multiple reaching levels of 1000 cells / liter or higher. As they increase in number, the water darkens with their presence giving the ocean a “red” color and the name for the phenomena.
- A red tide can dissipate within the few days, or a front can disperse them across the Gulf, lowering their concentration and negative impacts. However, the weather can actually fuel increased growth and red tides have been known to last for up to 18 months.
- At times, fronts will push red tides towards the coast. Monitoring by volunteers with FWC, will begin to detect and report them. Many times, they are at background, or low, concentrations and little impact is noticed. Other times the concentrations are at low to medium levels and fish kills will occur. Human issues involve the respiratory system – coughing, sneezing, burning eyes and throat are common responses. Those with pre-existing respiratory issues have a particularly tough time when red tides come close to shore.
- When concentrations reach 5000 cells / liter – shellfish harvesting will close. Bivalves are filter feeders and feed on K. brevis and other forms of phytoplankton. It does not affect the bivalve, but the brevotoxins the red tide produces can increase in concentration and the risk of shellfish poisoning from consuming them can increase.
- Marine mammals and sea turtles have a low tolerance for these brevotoxins and many will die during a red tide.
- Many times, when the red tide approaches shore, the nutrient rich estuarine water flowing into the Gulf of Mexico will fuel it. This can enhance the red tide to high concentrations and the negative effects heightened. At the time of this writing, concentration between Pinellas and Collier counties is over 1,000,000 cells / liter. Much of the increased nutrients in the bay waters is human produced. Massive fish, reptile, and mammal kills are occurring along southwest Florida now. The red tide there has been lingering for months and has caused problems for the locals.
- Many of the red tide events in the Florida panhandle are actually blooms that originated in southwest Florida and fronts (or storms) push them into our area. The situation is the same – much stays offshore but weather and currents can drive them inshore and, depending on the concentration, can cause problems for us.
- In recent years, we have had red tides that have closed scalloping in St. Joe Bay, and in 2015, we had one that lasted until December killing fish all along our shores. Currently, red tide has been reported at background-low levels from Gulf to Santa Rosa counties. Over the last few weeks, only one sample from Escambia County had background concentrations. Fish kills have been reported in Bay and Walton counties, and respiratory problems in Bay and Gulf counties.
- We have no idea how high the concentrations will get, or when the event will end. Hopefully, by the time this goes to print, it will be over for us.
- The green algae bloom you see on commercials is not the red tide but a bloom of toxic blue-green algae known as cyanobacteria. These are freshwater species and have negatively affected the east coast of Florida. It is believed this bloom was generated from excessive nutrients running off into local waterways and flowing into Lake Okeechobee. The Army Corp of Engineers discharges water from the lake during hurricane season to reduce the risk of overflowing the dike system during a storm. The water they are discharging is heavy with nutrients and does flow to both the east and west coasts.
I hope this answers some of your questions about the red tide event. Below are more articles with much more information about both blooms.
- Who is This Creature That Causes Red Tide: Information on Karenia brevis. Rick O’Connor, Florida Sea Grant – http://nwdistrict.ifas.ufl.edu/nat/2018/09/21/who-is-the-creature-that-causes-red-tide-information-on-karenia-brevis/.
- Frequently Asked Questions About the 2018 Red Tide Bloom – Betty Staugler, Florida Sea Grant – http://blogs.ifas.ufl.edu/charlotteco/2018/08/14/frequently-asked-questions-about-the-2018-red-tide-bloom/.
- Understanding Florida’s Red Tide – Betty Staugler, Florida Sea Grant – https://www.flseagrant.org/news/2018/08/understanding-the-florida-red-tide/.
- Watching and Waiting: Uncertainty About When the Algal Blooms Will End – Dr. Karl Haven, Florida Sea Grant – https://www.flseagrant.org/news/2018/07/watching-and-waiting-uncertainty-about-when-algae-blooms-will-end/.