Algae blooms – both blue-green algae and red tide — occur naturally and are found around the world. However, human activities and nutrients from stormwater, agricultural and urban land use, and sewer and septic systems continue to contribute nutrients to local waters. Florida is no exception.
Given Florida’s explosive growth – more than 900 people move to the Sunshine State every day – the problem will continue to worsen without solutions that involve all stakeholders in Florida: residents, businesses, utilities, agricultural operations and others.
While fingers have been pointed at a number of sources, there is no one source. The fact is that everyone who lives in Florida contributes in some way to the problem of nutrients that pollute our water. We care for our lawns. We flush toilets. We use municipal water systems. We grow food for people to eat. In the same way, we all can and should be part of the solution.
Cyanobacteria, more commonly referred to as blue-green algae, is one of the oldest life forms on our planet and is found worldwide. In Florida, it is in almost every freshwater ecosystem. Algae blooms are most likely to occur in streams, rivers and lakes that have high concentrations of nutrients – in particular, nitrogen and phosphorus. Some lakes and rivers have naturally high nutrient concentrations. However, in Lake Okeechobee and the St. Lucie and Caloosahatchee estuaries, manmade nutrient pollution from their watersheds contributes to the blooms.
A year of extreme weather preceded the blue-green algae bloom that occurred in 2018. In 2017, prolonged drought was followed by heavy spring rainfall and Hurricane Irma in the fall. Nutrients that were stored in sediments and soils during the drought were released during Irma’s heavy rains, helping to fuel the bloom in Lake Okeechobee. Florida Department of Environmental Protection data show that more than twice the average amount of phosphorus flowed from the northern Kissimmee River region into Lake Okeechobee in 2018. Most of that — 70 percent — flowed into the lake immediately after Hurricane Irma.
The toxic, naturally occurring red tide is found almost exclusively within the Gulf of Mexico. The marine organism that causes it is completely unrelated to the bacteria that causes freshwater blue-green algae. Florida red tide blooms originate 10 to 40 miles offshore and are brought onshore by winds and water currents. Although there is no direct link between the initial development of a bloom and human-derived nutrients, once a bloom comes onshore, those nutrients may fuel its growth. Mote Marine Laboratory notes that red tides occurred in Florida long before human settlement, and severe red tides were observed in the mid-1900s before the state’s coastlines were heavily developed.
The most recent red tide along Florida’s Gulf coast began in the fall of 2017 and intensified in the summer of 2018. Prevailing winds and currents kept the bloom onshore where land-based nutrients caused it to explode. The results were devastation to marine life, human-health concerns and harm to local coastal businesses.
Science shows runoff from communities is a large contributing factor in the blue green algae issues plaguing the St. Lucie and Caloosahatchee estuaries. According to a report from the University of Florida’s 2015 Water Institute, “On average, 70 to 80 percent of the freshwater discharge and 65 to 80 percent of the nutrient load to the St. Lucie and Caloosahatchee estuaries originates in the local basins, with the remaining balance contributed from Lake Okeechobee.” When algae blooms occur, they are further fueled by the runoff coming from local lands and communities.
According to a 2018 Florida Atlantic University study on the impact of septic tanks in the 2016 algae blooms in Martin County, “Contrary to the widespread misconception that periodic discharges from Lake Okeechobee alone produced these harmful algal blooms, FAU Harbor Branch’s study provides multiple lines of evidence that nutrient sources in the local basins, including on-site sewage and septic systems, contaminated the St. Lucie Estuary, in particular its urbanized sections as well as its watershed.”
In addition to nitrogen and phosphorous flowing into water systems from communities, agricultural operations also produce runoff of these nutrients. During the wet season when it rains in Fort Myers, Stuart, West Palm Beach or Orlando, it usually rains in the farming areas around Lake Okeechobee, too. Just like coastal and urban communities, farm fields flood during the rainy season.
South Florida Water Management District data shows, however, that in the past 5 years, only 5 percent of the total phosphorous and 8 percent of the total nitrogen going into Lake Okeechobee originated from the basin south of the lake where the Everglades Agricultural Area and the towns of Clewiston, South Bay, Belle Glade and Pahokee are located. The district’s data shows that during this same period, on average 95 percent of nutrient-laden water flowing into Lake Okeechobee came from north of the lake.
There are a variety of strategies to help reduce runoff of nitrogen and phosphorous flowing into Florida’s water bodies:
• Collaboration by the University of Florida’s Institute of Food and Agricultural Sciences with other educational institutions and agencies to find workable solutions to reduce blue-green algae and red tide, including research on recommended rates for fertilizing and advanced fertilizer technology
• Support for researchers to work on understanding the dynamic nutrient processes in urban stormwater systems
• Funding to help residents on septic systems convert to municipal systems or replace existing septic systems with those that use newer, more efficient technology
• Requirements for proper maintenance of existing sewer systems
• Adequate funding for the state’s Office of Agricultural Water Policy to continue successful programs that address nutrient runoff
• Community education programs that give incentives to homeowners who use urban best management practices to conserve water and improve water quality
Florida’s farmers take seriously their responsibility to clean the water flowing from their lands. Farmers throughout the state that operate within an area that is covered by a Basin Management Action Plan, which is a blueprint to restore impaired waters, must use Agricultural Best Management Practices (BMPs). Additionally, all farmers in the Everglades Agricultural Area around Lake Okeechobee are required to use BMPs.
BMPs are practical, cost-effective measures developed by the state that farmers use to conserve water and reduce the amount of pesticides, fertilizers, animal waste and other pollutants entering water resources. BMPs are designed to benefit water quality and conservation while maintaining or enhancing agricultural production.
Typical practices include:
• Determining the need for fertilizers and managing their application to minimize impacts to water resources.
• Managing irrigation practices – both the method and the schedule — to reduce water use.
• Using buffers, setbacks and swales to reduce or prevent sediments and nutrients from washing into bodies of water.
Farmers in the Everglades using BMPs have reduced phosphorus in the water flowing south by an annual average of 55 percent since 1996, with a 66 percent reduction in 2018. Growers use a variety of advanced farming techniques that include using GPS to level fields, vegetation control, canal cleaning and reduced soil erosion.
During the past 20 years, farmers have provided more than 120,000 acres of once-productive
farmland to the state for the purpose of Everglades restoration, including the land now being used to develop the EAA reservoir, making it the most land any private entity has given up for restoration.
Combined, Florida’s farmers have also invested more than $450 million into research, restoration, and on-farm water and soil-cleaning efforts – more than any private entity has spent to date. Farmers also support efforts to fix the Herbert Hoover Dike. A fortified dike will help reduce the need for the U.S. Army Corps of Engineers to discharge water from Lake Okeechobee during the rainy season.
When the water in Lake Okeechobee rises above a certain level, it puts pressure on the aging Herbert Hoover Dike that surrounds the lake for flood control. The U.S. Army Corps of Engineers (the Corps) is charged with protecting communities surrounding the lake from flooding. During some periods of extreme rain, the Corps is required by the Lake Okeechobee Regulation Schedule to discharge water from the lake out to the St. Lucie and Caloosahatchee estuaries.
Lake Okeechobee water levels are heavily managed and the outflow capacity of the east and west structures far exceed that of the south. Every year during the rainy season, the Corps sends up to 23 percent of the water in Lake Okeechobee south. It can’t send more because the state’s Water Conservation Areas, Stormwater Treatment Areas and Everglades National Park south of the lake often are already full.
Other limiting factors include:
• Downstream capacity: The Kissimmee River watershed north of the lake is a 5,000-square- mile basin that drains into 730-square-mile Lake Okeechobee. When this area fills up with rain, the area south of the lake usually fills up as well.
• Wildlife: Threatened wading birds south of the lake are protected by low water levels during mating seasons. The federal government prohibits additional water when these rules are in effect.
Water storage north and south of Lake Okeechobee is key in reducing the need for discharges from the lake during times of heavy rainfall. To that end, there is a need for science-based solutions in every part of the system that will address the problem.
Some solutions include:
• Precision irrigation technologies to minimize the use of irrigation water
• Use of advanced soil moisture sensors to avoid unnecessary irrigation
• Use of mobile irrigation labs to ensure irrigation systems do not waste water
• Partnerships between land owners and the government to store water on private lands
• Storage projects such as the EAA reservoir, C-43 and C-44 canal expansion, and the Lake Okeechobee Watershed Project north of Lake Okeechobee that will allow the South Florida Water Management District to capture, store and treat water before it enters the lake
• Innovative technology such as deep injection wells, aquifer storage and recovery wells, and above-ground storage north of the lake to reduce the need for discharges
Scientists are still looking at what role – if any – the Lake Okeechobee discharges play in contributing to Florida offshore red tide. Mote Marine Laboratory officials say there are many sources of land-based nutrients besides Lake Okeechobee, including runoff from rainfall and runoff from creeks and rivers into coastal ecosystems. More research is needed, the laboratory says.
The scientific data available so far suggests that it is possible for nutrients flowing from land to sea — including natural and human-contributed nutrients carried by stormwater runoff and the input of rivers — to serve as additional “food” for growth of red tide blooms that have moved to shore. This occurrence is more likely in years when high freshwater discharge flows out of the Caloosahatchee estuary, however, the sources of these nutrients that feed the red tide have not been identified. Furthermore, Mote Marine Laboratory notes that there is no direct link between nutrient pollution and the frequency or severity of red tide.
The South Florida Water Management District uses back-pumping as a flood-control measure to protect neighborhoods, businesses, schools, hospitals and farms around the lake. Compared to all of the water entering into Lake Okeechobee from the north, water pumped in from the communities south of the lake represents less than 3 percent of all the water in Lake Okeechobee. Farmers do not back-pump into Lake Okeechobee.
Sources: Mote Marine Laboratory, University of Florida Institute of Food and Agricultural Sciences, South Florida Water Management District, Florida Atlantic University