Scientists and researchers have gotten to the bottom of the ‘Green Banana' blue hole off Florida’s coast

Blue holes are thought to be ecological hot spots whose nutrients help supply the food chain around the world
Green Banana
Green Banana
Published: Oct. 15, 2020 at 8:47 PM EDT
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Blue holes are underwater sinkholes, similar to sinkholes on land. Underwater sinkholes, springs, and caverns are karst (calcium carbonate rock) features that are scattered across Florida’s Gulf continental shelf. They vary in size, shape and depth, but most are ecological hot spots with a high diversity of plants and animals.

In May and September 2019, a team of scientists from Mote Marine Laboratory, Florida Atlantic University/Harbor Branch, Georgia Institute of Technology and the U.S. Geological Society, with support from the NOAA Office of Ocean Exploration and Research, explored one blue hole, dubbed “Amberjack Hole,” approximately 30 miles offshore west of Sarasota.

In the mid-1970s, a boat captain sailing spotted a blue hole roughly 50 miles west of Sarasota where an unripe banana peel was floating above it. It then became known as the Green Banana. Scientists and researches visited this underwater cavern off the coast of Florida that humans had never fully explored—until August.

“There are coral, seagrass, algae, sponges, crab, clams, schools of fish and there have even been reports of whale sharks around the blue hole,” says Dr. Emily Hall, Ocean Acidification Program Manager with Mote Marine Laboratory & Aquarium.

Scientists believe it may have formed more than 10,000 years ago when a sinkhole opened to form a cavern 265 feet deep and 425 feet below the surface of the Gulf, farther than typical scuba divers are capable of reaching. The team used technical divers and a benthic lander, a 600-pound submersible that houses multiple scientific instruments, to explore Green Banana’s lower ring.

“Chemically speaking these holes are so unique and they are so different from the rest of the Gulf of Mexico. We continue to find more and more of these holes. We have so many questions that we are trying to answer. For example, are these holes connected to our groundwater system here on the mainland?” says Dr. Emily Hall.

Scientists want to know if there’s something special about the sediment at the rim of Green Banana, and one thing they want to know is whether the organisms that feed on the sulfide release nutrients that fertilize red tide or other algae. Analysis of Green Banana’s water and sediment samples won’t be complete for weeks.

“There’s a big difference in carbonate chemistry in these holes and one of the reasons why that is so important is because a lot of the work that I do for example is what we think our oceans are going to look like in the future with climate change and ocean acidification. Some of the stuff we are seeing in these holes, chemically speaking, is what we are predicting to see in our oceans in the future,” states Dr. Hall.

The next planned expedition to visit the Green Banana is in May of 2021. It’s part of a big project funded by the National Oceanic and Atmospheric Administration (NOAA) exploration and research. Once the research is complete scientists will compile the data and findings collected over time into research papers.

* The video that was shared with us was from Kristin Paterakis (@kikidives), who is a scuba instructor and an underwater photographer.

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