Florida’s coastal nightmare

*This is a guest post by Katherine Datuin- student in my 'Causes & Consequences of Biodiversity' course. 

Imagine going on vacation to beautiful, warm Florida just to find entire beaches strewn with the rotting remains of hundreds of fish, sea turtles and manatees. This is unfortunately not a nightmare, but a current reality for the residents of southwestern Florida, and it has been this way for almost a year now. What causing all this? This little guy. 

Figure 1. Kareina brevis living cell. Photo modified from Florida Fish & Wildlife Conservation Commission.

These events were brought to my attention through a recent article published by Vox news highlighting the consequences of such large and long-lasting harmful algal blooms, specifically the “Red Tide” in southwestern Florida (Resnick B. 2018). Kareina brevis, the algal species responsible, has been in bloom since November of last year. According to the article, this event constitutes the longest “Red Tide” algal bloom in history. Regularly, blooms occur seasonally, lasting only from a few weeks to a couple months. The length of bloom in combination with the species responsible is catastrophic for the surrounding environment. This species of algae produces a suite of neurotoxins known as brevetoxins (Gebhard et al. 2015). Exposure to these toxins within marine environments has resulted in massive fish kills and increased mortality in loggerhead turtle, and marine mammal populations (Walsh C. et al. 2010).

 

Figure 2. Kemp's ridley sea turtle on Sanibel Island. Photo modified from Andrew West/The News-Press via USA TODAY

Then why is all this so scary? It is because such Red Tide of this nature have never been recorded. This situation is novel, and therefore its overall effect on the underlying ecosystem is unknown. What is known is that mortality rates are increasing. More and more animals are dying as a result of this bloom, but the significance of the losses is still unknown. Will the affected species recover following this event? Will species be lost? Is the length of this bloom unique or will future blooms also be so long? What factors contributed to or enabled such a long-lasting bloom?   

It is equally important to consider the impacts such events will have on us humans. Human health can be directly or indirectly effected by these toxins through toxic aerosols and consumption of contaminated shellfish respectively. Studies have shown that an increased incidence of both respiratory and digestive illnesses can be found in relation to Red Tide presence, especially in those aged 55 or older (Hoagland P. et al. 2014). According to the United States Census Bureau, from estimates in 2017, about 20% of Florida’s population is 65 years of age or older. This means a high percentage of the population is at risk of suffering either respiratory or digestive illnesses due to this bloom. As well as its effects on human health, the Red Tide greatly impacts Florida’s fishing and tourism industries.

Figure 3. Red Tide devastation in Florida. Photo modified from Ben Depp Via National Geographic.

What can we do to prevent these blooms?
Although the specific conditions which enabled this bloom are unknown, many studies have hypothesized which factors likely contributed to this increase in length and frequency. The article states that human activity and climate change are likely the two factors with greatest influence. This is probably because like all other algal species, K. brevis requires sufficient macro-nutrient to enable blooms (Hoagland P. et al. 2014). Increased agricultural practices, water runoff and changes to atmospheric depositions could all contribute to a surplus of nutrients entering the water system and thus becoming available for these algae (Hoagland P. et al. 2014).  To mitigate the impacts of Red Tides, it is important to educate the local communities about how their actions effect their environment. For example, improving the public understanding of how fertilizer use can lead to greater blooms and how blooms effect charismatic species like turtles and dolphins. The public should also be informed of the ways in which Red Tides directly affect their communities from damage to fisheries and tourism to public health concerns.

The effects of the Florida Red Tide can be felt among all trophic levels in the surrounding marine and terrestrial environments. The causes and consequences of this specific event are still unknown and will likely be the subject of rigorous future studies. We should look to determine how we can prevent or minimize the length and severity of these blooms in order to protect the marine environment, the fisheries and tourism industries, and finally our own health.


References
Gebhard, E., Levin M., Bogomolni A., Guise S.D., “Immunomodulatory effects of brevetoxin (PbTx-3) upon in vitro exposure in bottlenose dolphins (Tursiops truncates)” Harmful Algae. 44(2015): 52-62.

Hoagland P., Jin D., Beet A., Kirkpatrick B., Reich A., Ullmann S., Fleming L.E., Kirkpatrick G. “The human health effects of Florida Red Tide (FRT) blooms: expanded analysis”. Environment International. 68 (2014) 144-153.

Resnick, B. Why Florida’s red tide is killing fish, manatees, and turtles. Vox news. October 8th, 2018. https://www.vox.com/energy-and-environment/2018/8/30/17795892/red-tide-2018-florida-gulf-sarasota-sanibel-okeechobee

Walsh C.J., Leggett S.R., Carter B.J., Colle C. “Effects of brevetoxin exposure on the immune system of loggerhead sea turtles”. Aquatic toxicology. 97(2010): 293-303.