I have written a lot about extreme heat events, and in the past two years the summer temperatures generated plenty of discussion, both locally and around the world. However, south Florida started off 2025 with a delightful cold front, waking up to temperatures in the 50’s and 60’s, with the days reaching perhaps 70 degrees. Milder winters are why the majority of us south Floridians put up with the unbearable summers, but in the case of a prolonged cold event, there is the possibility of real damage being done.
As agriculture is a major industry for Florida, UF/IFAS Extension agents throughout the state assist local crop producers in responding to cold events, which you can read more about here. Cold events can wipe out entire vegetable fields and kill fruit trees that are not cold protected. Generally speaking, sub-tropical and tropical species evolved in areas with limited ranges in temperature, making them particularly sensitive to extreme temperature changes (Hardy et al. 2019). What do cold events mean for the marine environment?
Effects to corals
Reef-building stony corals don’t have a well-documented tolerance range for cold, but we know that their optimal conditions include a temperature range of: 73.4°F – 84.2°F (23°C – 29°C) (NOAA 2024).
In January of 2010, south Florida experienced a notable period of prolonged cold temperatures. For six days, water temperatures were recorded below 16°C, or 61°F. As a result, large scale coral death on Florida’s Coral Reef was documented (Lirman et al. 2011). Certain stony coral species exhibit greater tolerance to cold, but as a result of this cold event, major reef-building corals like Orbicella faveolata bleached and died, indicating their susceptibility to this type of thermal stress.
While the winter normally serves as corals’ time to recover from summertime warm water bleaching events, the 2010 cold event further cemented that these organisms’ need to have conditions that are not too hot, not too cold, but just right.
Effects to mammals/reptiles
Our state marine mammal, the manatee, is another creature that has very bougie temperature preferences. Like me, they prefer warm water! This is why, as we shift into the winter or dry season, manatees tend to congregate in north and central Florida at the springs where the water remains at a constant temperature all year round. If manatees encounter prolonged cold periods (when temperatures drop below 20°C, or 68°F), they have a difficult time regulating their body temperature in cold water (Hardy et al. 2019).
Reptiles, including sea turtles and iguanas (while not a marine creature, worth mention simply due to their notoriety), are ectothermic (cold-blooded), meaning that they cannot regulate their body temperatures the way that mammals do. This makes the temperature of their surrounding environment critical to their health. While prolonged cold (temperatures less than 50°F) is unusual in Florida, cold snaps like the aforementioned January 2010 event can be detrimental to sea turtles, causing their metabolisms to slow down. For turtles, they are less able to successfully swim and eat, often ending up floating on the surface of the water, potentially further exposed to cold air, boat traffic and predators.
Cold events force iguanas into this dormant state, or torpor. We often hear about this on the news or social media prior to a cold event, to be on the lookout for “falling iguanas.” While this does produce a funny visual, it has happened and if you have iguanas that visit your home, you should be prepared for this possibility.
As we move forward into the 21st century and continue to experience the effects of global climate change, it’s important to keep in mind that one of those includes extreme temperature changes-both hot and cold.
What you can do:
If you observe a manatee or sea turtle injured or in distress, please do not attempt to move it. Contact the Florida Fish and Wildlife Conservation Commission at 1-888-404-FWCC (1-888-404-3922). If you are underwater and you observe signs of coral bleaching, please file a report at www.SEAFAN.net.
Lastly, if an iguana drops out of a tree, do not attempt to move it—they can snap out of their dormant state in an instant, and could potentially react in a violent way. They have sharp teeth and can also use their long tails to lash, causing injury. Contact a professional iguana remover to assist.
References
Hardy, S., Deutsch, C., Cross, T., de Wit, M., Hosteteler, J. 2019. Cold-related Florida manatee mortality in relation to air and water temperatures. Plos One, Vol. 14, Issue 11, 22pp.
Lirman, D., Schopmeyer, S., Manzella, D., Gramer, L., Precht, W., Muller-Karger, F., Banks, K., Barnes, B., Bartels, E., Bourque, A., Byrne, J., Donahue, S., Duquesnel, J., Fisher, L., Gilliam, D., Hendee, J., Johnson, M., Maxwell, K., McDevitt, E., Monty, J., Rueda, D., Ruzicka, R., Thanner, S. 2011. Severe 2010 Cold-Water Event Caused Unprecedented Mortality to Corals of the Florida Reef Tract and Reversed Previous Survivorship Patterns. Plos One, Vol. 6, Issue 8, 10 pp.
National Oceanic & Atmospheric Administration. 2024. Marine Heatwave and Coral Bleaching Response FAQs. Florida Keys National Marine Sanctuary and Mission: Iconic Reefs. https://floridakeys.noaa.gov/coral-bleaching-faqs.html#:~:text=73.4%C2%B0F%20-%2084.2%C2%B0,with%20its%20color%20and%20nutrients.