100 years ago, water from Lake Okeechobee flowed across the vast grass prairies of the Everglades, southward into the bay to nourish all of the lands from the lake to the estuarine sites. With the construction of dams, highways, farmlands and ranches those waters have been diverted to tributaries, such as the St. Lucie River and the Caloosahatchee.Now the bay gets most of its fresh water from rainfall. When sufficient amounts of rain do not fall some pockets of saltwater do not receive the proper flush that can help the water quality when salinity rises and temperatures increase. As a result, the seagrass does not survive. It has experienced a balance that allowed it to survive for hundreds of years, and that no longer exists.
In 1987 a die-off occurred in Florida Bay, affecting nearly 15 square miles of grass beds. Over the next two years the area received little rain and that helped to propel an algae bloom that produced a malodorous slime and sent a $700 million a year sport fishing industry into collapse.
Because of weather patterns in recent years and, again, the lack of fresh water flow, the seagrass demise spread from about 25 square miles to more than 62 square miles over one season. This blanketed the central portion of the bay with a wide strand of yellow sulfide.
Some scientists fear that the summer temperatures will basically cook the uprooted seagrass and these rotting plants will take in the oxygen and produce even more of the sulfide gasses. Compared to 1987 the salinity levels are a bit more normal but parts of the bay are still weak and that has many environmentalists on the edge of their seats.
In normal conditions, oxygen in the water increases during the day to help plants breathe over a 24-hour cycle. With no fresh water, the salt trapped in some areas, combined with extreme heat, caused oxygen levels to fall sharply and this suffocated the grass at night. A prime example of this happened in 2015. The water temperature topped 93 degrees for 77 days!
Stated more simply the algae blocks out sunlight that grasses need to survive. Decaying seagrass consumes oxygen in the bay waters and this causes more die-off. The combination of heat, wind and lack of fresh water conjure the perfect mix of ingredients that will allow this problem to continue.
Florida Bay took nearly 20 years to recover from the 1987 event. 10 years later the same issue is again prevalent. If this is a recurring problem does it mean that the bay is going to have impaired fishing and water quality two-thirds of its life?
Seagrasses provide a necessary habitat for game fishes as well as many species of fish larvae. Those larvae eventually move on to populate the reef system of the Keys. Also, algae blooms can destroy sponge populations which filter the water and are used by young lobsters. Manatees also thrive on grass beds for their food source.
Florida Bay encompasses nearly onethird of Everglades National Park. Like the park’s sawgrass prairies and mangroves, this area also relies on fresh water to flow through it. The second major seagrass dieoff in 30 years is not a fluke. Something has definitely changed in the system. As one National Park director stated, “It’s basically a permanent, manmade drought, created by development to the north and a change in drainage patterns.”
Let’s pray that it is not too late to resolve this issue and that the Everglades Restoration Plan moves quickly enough to deter any long lasting negative results to this necessary part of the Everglades, Florida Bay.
Bob is the owner of Stepping Stone Ecotours as well as a Naturalist for a dolphin survey team on board the Dolphin Explorer. He has authored the pictorial book, “Beyond The Mangrove Trees,” with more than 160 photos about Florida wildlife. Bob loves his wife very much!