08/22/2021
Great info on Red Tide
Unfortunately, we are having to again cancel our upcoming wading trips (the nighttime wading trip on 8/21 and morning trip on 8/24) due to Red Tide concentrations being elevated in our area and dead fish washing up near our park. While this is bad news, we'd like to use this opportunity to teach about this phenomenon.
Red Tide in our area primarily comes from Karenia brevis. This is a species of dinoflagellate, a type of phytoplankton present in our waters. They are present year-round, typically in lower numbers and further offshore. However, they do have a cyclical nature where they will periodically bloom in higher concentrations in inshore waters, causing what we know (and are currently experiencing) as Red Tide. Red tides occur all over the world with different types of phytoplankton that have various effects, and there are even many different species of Karenia present in the Gulf of Mexico. Karenia brevis is just the main species that affects our local waters.
The problem with K. brevis primarily lies in the toxins, called brevetoxins, that exist within the the K. brevis cells. No one is really sure what purpose these toxins serve; it could be an incidental byproduct created by something within their metabolism, it could be a deterrent to grazers that would be trying to eat them, etc. These toxins are what kill so many fish, birds, and other marine life, and cause respiratory distress in people. K. brevis can also cause issues because when they bloom in high numbers, they will eventually die and fall to the bottom. There, aerobic bacteria will begin to proliferate to break down them down, and can use up much of the available oxygen in the water column. These areas of water with very low oxygen concentrations are called "Dead Zones" and can also result in fish kills.
So what causes Red Tide blooms? That's a million dollar question. What we do know is that Red Tide blooms are natural occurrences. They typically bloom in the warmer, wetter months like right now. Warmer water temperatures help fuel rapid growth for blooms, and the summer rains carry nutrients in runoff that flow into our coastal waters and serve as fertilizer for the phytoplankton blooms. These factors influence all nearshore phytoplankton, but what SPECIFICALLY leads to a Red Tide bloom? Again, there is still so much research that needs to be done to understand this, but it seems like there is a strong connection with K. brevis blooming after blooms of a type of cyanobacteria called Trichodesmium, aka Sea Sawdust. This bacteria blooms in offshore waters and actually can fix atmospheric nitrogen gas from the atmosphere, providing much higher levels of nitrogen in the waters near them. This is important because nitrogen and phosphorous are considered limiting factors for algal growth. Basically, phytoplankton rely on both phosphorous and nitrogen to grow, but there are finite amounts of them readily available in the ecosystem for the phytoplankton to use. So having an abundance of nitrogen present near the Trichodesmium, coupled with Florida's natural abundance of phosphorous, can certainly present the "ingredients" that could lead harmful algal blooms like Red Tide to occur.
There is also a lot of information out there that human activities on land are resulting in pollution and excess nutrient levels (known as eutrophication) that are causing Red Tide. We can see that these activities do not CAUSE Red Tide blooms to occur; however, they absolutely do exacerbate the blooms when they do happen. Excess nutrients from overuse of fertilizers, destruction of Florida's natural hydrology through draining of wetlands and canal construction, and the already occurring threat of the Climate Crisis all absolutely can lead to Red Tide blooms that are more frequent and more severe.
For more information on Red Tide blooms and current conditions in our area, please visit https://myfwc.com/research/redtide/statewide/. Thank you for your patience and understanding as we navigate these events when trying to plan these programs for you.
