Blue-green algae in Florida waters Effects on water quality

Blue-green algae, or “cyanobacteria,” are Equally important, persistent blooms FAST FACTS structurally similar to bacteria but, like block sunlight that feeds plants growing plants, use sunlight to grow. Blue-green on the bottom of lakes, resulting in the Blue-green algae algae occur naturally in both freshwater loss of rooted aquatic vegetation, which and marine (salt) water bodies. Most live is valuable habitat. When blooms end, occur naturally in with other types of algae and microscopic the decay of the blue-green algae bodies of animals in floating “plankton.” consumes much of the oxygen in the freshwater. water, causing fish to die. The dead Blue-green algae multiply quickly in lakes algal cells settle to the bottom of water High nutrient levels with high nutrient levels, particularly when bodies, creating layers of soft sediments. can cause algal the water is warm and the weather is calm. blooms. This proliferation causes “blooms” of Blooms of blue-green algae were blue-green algae that turn the water recorded as early as 1188. A small green, often with floating layers of number of blue-green algal species are green scum. responsible for most freshwater algal blooms worldwide. Many are from the Some species of blue-green algae do algal groups, or “genera,” Anabaena, not need much of the nutrient nitrogen Aphanizomenon, Cylindrospermopsis, present in the water because they take Microcystis, and Planktothrix (or Oscillatoria). in nitrogen from the air to grow. These Several species from these genera occur “nitrogen-fixing” algae actually increase in freshwater lakes in Florida. nitrogen levels in the water. Lower levels of the nutrient phosphorus in the water A species common in Australia, usually limit growth of these blue-green Cylindrospermopsis raciborskii was first algae. Therefore, reducing phosphorus identified in the United States in the levels in water bodies is the most effective 1950s and in Florida in the mid-1990s. means of preventing blooms of nitrogen- Recently, it has been found in several fixing blue-green algae. lakes throughout north and central Florida. C. raciborskii, a nitrogen-fixing Blooms of blue-green algae that last blue-green alga, is different from some more than a few months are often harmful other bloom-forming blue-green algae to lake ecosystems. Plankton is the base that occur in Florida because it rarely of the food chain in open water bodies; forms surface scums and it appears to algae (phytoplankton) use sunlight to require less phosphorus to grow. make food and are eaten by microscopic animals (zooplankton). Small fish eat A bloom of this new species has persisted the zooplankton, and larger fish and for at least two years in Lake Griffin, a other large animals eat the small fish. high-nutrient lake in Lake County. The However, blue-green algae are often St. Johns River Water Management difficult to eat or are of poor nutritional District is working to restore this value for zooplankton. Consequently, degraded lake through a multifaceted zooplankton, particularly types that are restoration program which emphasizes the best fish food, often decline during reduction of nutrient levels, particularly blooms. This decline is followed by phosphorus, in the lake water. declines in numbers of small fish and then of larger fish. Continued on back

St. Johns River Water Management District • P.O. Box 1429 • Palatka, FL 32178-1429 Phone: (386) 329-4500 (Palatka headquarters switchboard) • On the Internet: http://sjr.state.fl.us 8/99 Toxic blue-green algae in Florida Compiled by the Blue-Green Algae Project of the Florida Harmful Algal Bloom Task Force

Blue-green algae and their associated more recently, Cylindrospermopsis raci- FAST FACT toxins are believed to have existed in borskii. However, no instances of human Florida lakes for thousands of years. poisoning from toxins from blue-green A special legislative However, information regarding toxins algae have been documented in Florida. task force is from blue-green algae and risks to humans, fish and wildlife is very In 1997, the Florida Harmful Algal investigating limited. Also, little is known about the Bloom Task Force (HAB) was formed harmful algal environmental conditions that cause due to concerns about harmful algae blooms and their toxin production. in freshwater and marine habitats. potential effects on This multiagency task force includes water resources Although toxins from blue-green algae members from the water management and public health. have an aquatic origin, they appear districts, Florida Marine Research to be more hazardous to terrestrial Institute, Florida Department of Health, mammals. Primary problems associated Florida Department of Environmental with toxins from blue-green algae Protection, and University of Florida. include damage to the nervous system or liver of animals that ingest the toxin. A special Florida legislative appropriation provided funding for a statewide survey Algal toxins are released when the cell to detect the presence of blue-green dies or is ingested. Most toxic events algae and their toxins in Florida’s surface attributed to blue-green algae involve waters. Samples are being collected and livestock, when animals are forced to analyzed this year from 125 surface drink lake water in which large amounts water bodies throughout Florida that of algae have been concentrated along have blue-green algae blooms. Results the shoreline due to prevailing winds. from this preliminary survey will be Previous toxic events where human available in 2000. Additional funding health has been at risk from toxins from has been provided by the Florida blue-green algae have evolved from the Legislature this year to investigate application of copper sulfate to control harmful algal blooms and to assess blooms in public water supplies. The their potential effects on water mass death of algae caused by the resources and public health. copper sulfate released toxins into the water.

The few reported cases of toxins from blue-green algae in Florida lakes involved Microcystis and Anabaena, and

St. Johns River Water Management District • P.O. Box 1429 • Palatka, FL 32178-1429 Phone: 386-329-4500 (Palatka headquarters switchboard) • On the Internet: http://sjr.state.fl.us 8/99