Florida shores are heating up to record breaking temperatures, and while the scorching surface waters are deterring some beachgoers searching for a reprieve, below the surface the heat is deadly. In July 2023 Florida coastal waters breached 100 degrees Fahrenheit, a significantly hotter temperature than the 85-degree average normally experienced in July. The hot weather is a consequence of abnormal atmospheric conditions caused by climate change that have weakened the seasonal trade winds that cool Florida in the summer. As a result, Florida is left to fry. Much of that heat gets absorbed by the ocean, and as the water warms ocean life pays the price.  
 
Corals are particularly susceptible to hot temperatures. As the water warms corals become stressed. In a last-ditch effort to save themselves they expel symbiotic algae called zooxanthellae. These single-celled algae normally photosynthesize and pass some of the food they make from the sun’s energy to their coral hosts, and in exchange the coral animal gives nutrients to the algae. Losing the algae causes the coral to bleach, and often means the corals die.  
 
In the Florida Keys where temperatures are around ten degrees higher than the normal July average, corals of every species are bleaching. Scientists from the Smithsonian Marine Station in Fort Pierce witnessed several species of bleaching coral off the coast of Long Key and Grassy Key. Of note, was the coral bleaching at a dive site called Coral Gardens—all the corals were bleached. The same goes for many places close to shore where the water temperatures get the hottest. Often, the hottest temperatures occur in September, meaning the present bleaching event is months earlier than normal and there are still several weeks left for the water to continue to heat up. 

 
Another concern for all ocean life is suffocation. Despite living underwater, marine life still relies on oxygen. Ocean water is filled with dissolved oxygen, which fish, corals, and other animals then filter with special adaptations, like gills. But when water gets warmer the amount of dissolved oxygen it can hold steadily decreases. Swimming in bath water temperatures is like hiking at extreme altitudes. With every breath there is less oxygen to absorb, and eventually the oxygen is so scarce it can lead to death. In the ocean this is called hypoxia. When large areas of ocean become depleted of oxygen and the event occurs over an extended period of time it is called an anoxic event, also known as a dead zone. Often animals like coral, sponges, and shellfish, are the hardest hit by a dead zone because they can’t move away from the deadly conditions. But sometimes the dead zone is large enough that even mobile fish find it hard to survive. Off the coast of Texas tens of thousands of menhaden fish washed ashore in July because they suffocated in low oxygen waters. 
 
Large blooms of algae, called harmful algal blooms, can also cause dead zones, and hot water can trigger a large algae bloom. The growth of algae then exacerbates oxygen depletion. As the algae die, they provide a feast for microbes, who multiply and consume oxygen as they help decompose the dead algae. But algae blooms can be deadly in other ways too. In the Florida Keys the hot water has triggered a bloom of cyanobacteria. The algae now covers much of the seafloor and corals, inhibiting other seafloor dwelling species from going about their normal activities. Coral larvae, which float in the water before settling on the seafloor, must now compete with the algae for space, and Smithsonian scientists worry it will negatively affect this year’s larvae from successfully settling on the seafloor. 
 
Scientists continue to race for answers about how marine life will fare in the face of climate change, hoping that with knowledge we can help them overcome the new challenges. At the Smithsonian's marine station in Fort Pierce, Florida, Jennifer Sneed is studying how bacteria symbionts can help buffer the blow of hot water, potentially protecting the corals from bleaching. She is hoping to find bacteria that can help corals survive the increased temperatures.  
 
Ariel Pezner, also with the Smithsonian, studies corals and their response to low oxygen. Her research shows that 84 percent of the reefs she surveyed experience weak to moderate hypoxia and 13 percent experience severe hypoxia. Her goal is to understand the impacts of multiple stressors, like hypoxia, on coral health and survival so that corals can one day be better protected from the effects of continued climate change. 
 
This most recent heat wave is a reminder that climate change isn’t a far-off idea anymore. We are living through the consequences today. Corals and other marine life will continue to face increasingly hot temperatures and the challenges that accompany the heat. Ocean life may be hidden underwater, but that doesn’t mean they are shielded from harm. Bleaching, hypoxia, and algal blooms are regularly occurring phenomenon, and as the Earth heats up, these challenges are likely to become more frequent and more intense. One day soon 100-degree oceans may just be another common reality.