Understanding Algal Bloom Dynamics in Lake Okeechobee
The U.S. Geological Survey (USGS) is conducting studies to better understand algal bloom dynamics to enhance lake management. Recent research, in Lake Okeechobee, Florida, focused on phytoplankton community and abundance. Phytoplankton can be a potential driver of harmful algal blooms (HABs).
Lake Okeechobee covers approximately 730 square miles (1,900 square kilometers), making it the second-largest freshwater lake in the contiguous United States. The lake is part of the Greater Everglades Watershed in Florida and serves as a crucial natural resource for the surrounding ecosystem. Phytoplankton are essential to healthy lake ecosystems, but alterations e.g., watershed development, irrigation, drought mitigation, water treatment) to the Lake Okeechobee system and surrounding watershed have made it susceptible to excessive growth of phytoplankton leading to harmful algal blooms (HABs). These HABs are made of up many different types of phytoplankton some of which can produce toxins leading to negative health outcomes and can also impact recreational use of the lake. Lake Okeechobee plays a vital role in the ecology and economy of Florida, and understanding its complex dynamics is essential for effective management and conservation efforts.
To support effective lake management, USGS and its partners have been conducting studies to gain insights into phytoplankton and HAB dynamics in the Lake Okeechobee system, which includes the Caloosahatchee and St. Lucie rivers that flow from the lake into the west and east coasts of Florida, respectively. A major part of this research involves counting and identifying the different types of phytoplankton found in the lake and understanding how various environmental factors—like water quality and seasonal changes—affect them over time and across different areas of the lake. From their studies, researchers have discovered that Lake Okeechobee can be divided into seven distinct zones, each with its own unique phytoplankton communities. While the types of phytoplankton didn’t show clear seasonal changes, the total number of these organisms was highest at the end of the wet season. The dominant group of phytoplankton was cyanobacteria which has potential to produce toxins.
Nutrients are essential for phytoplankton growth. Like other eutrophic lakes, there is an inverse relationship between phytoplankton abundance and nutrients (nitrate and orthophosphate), likely due to the “boom-bust” cycles of algal blooms. During the “boom” phase, algae numbers spike, depleting nutrients, light availability, and altering water chemistry. Eventually, the lake cannot support such high algae levels and the bloom begins to die off. This decay consumes more oxygen than is produced, resulting in the “bust” phase, where algae numbers decline, nutrients become available again, and light availability improves setting the stage for new phytoplankton growth shifting back to "boom". Different types of phytoplankton are associated with different stages of this cycle.
The distinct phytoplankton communities being identified are helping to pinpoint areas in the lake where harmful algal toxin producers are likely to be found. Understanding these zones is crucial because if toxin production occurs in specific areas, even if those toxins are later transported by water or wind, this information can improve prediction and monitoring efforts to reduce human exposure.
Current studies emphasize the complexity of phytoplankton and HAB dynamics. Ongoing research is essential to enhance our understanding and develop predictive models that resource managers can use for effective HAB mitigation and prevention strategies. Implementing high-frequency, high-resolution monitoring systems could improve management decisions significantly. Achieving these goals will take time due to the lingering impacts of nutrient loading, necessitating a continuous adaptive management approach as new information emerges. In the meantime, understanding the drivers of HABs in Lake Okeechobee could help reduce future in-lake treatment costs.
This study was supported by the USGS Ecosystems Mission Area, through the Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology) and U.S. Army Corps of Engineers Aquatic Nuisance Species Research Program.
The U.S. Geological Survey (USGS) is conducting studies to better understand algal bloom dynamics to enhance lake management. Recent research, in Lake Okeechobee, Florida, focused on phytoplankton community and abundance. Phytoplankton can be a potential driver of harmful algal blooms (HABs).
Lake Okeechobee covers approximately 730 square miles (1,900 square kilometers), making it the second-largest freshwater lake in the contiguous United States. The lake is part of the Greater Everglades Watershed in Florida and serves as a crucial natural resource for the surrounding ecosystem. Phytoplankton are essential to healthy lake ecosystems, but alterations e.g., watershed development, irrigation, drought mitigation, water treatment) to the Lake Okeechobee system and surrounding watershed have made it susceptible to excessive growth of phytoplankton leading to harmful algal blooms (HABs). These HABs are made of up many different types of phytoplankton some of which can produce toxins leading to negative health outcomes and can also impact recreational use of the lake. Lake Okeechobee plays a vital role in the ecology and economy of Florida, and understanding its complex dynamics is essential for effective management and conservation efforts.
To support effective lake management, USGS and its partners have been conducting studies to gain insights into phytoplankton and HAB dynamics in the Lake Okeechobee system, which includes the Caloosahatchee and St. Lucie rivers that flow from the lake into the west and east coasts of Florida, respectively. A major part of this research involves counting and identifying the different types of phytoplankton found in the lake and understanding how various environmental factors—like water quality and seasonal changes—affect them over time and across different areas of the lake. From their studies, researchers have discovered that Lake Okeechobee can be divided into seven distinct zones, each with its own unique phytoplankton communities. While the types of phytoplankton didn’t show clear seasonal changes, the total number of these organisms was highest at the end of the wet season. The dominant group of phytoplankton was cyanobacteria which has potential to produce toxins.
Nutrients are essential for phytoplankton growth. Like other eutrophic lakes, there is an inverse relationship between phytoplankton abundance and nutrients (nitrate and orthophosphate), likely due to the “boom-bust” cycles of algal blooms. During the “boom” phase, algae numbers spike, depleting nutrients, light availability, and altering water chemistry. Eventually, the lake cannot support such high algae levels and the bloom begins to die off. This decay consumes more oxygen than is produced, resulting in the “bust” phase, where algae numbers decline, nutrients become available again, and light availability improves setting the stage for new phytoplankton growth shifting back to "boom". Different types of phytoplankton are associated with different stages of this cycle.
The distinct phytoplankton communities being identified are helping to pinpoint areas in the lake where harmful algal toxin producers are likely to be found. Understanding these zones is crucial because if toxin production occurs in specific areas, even if those toxins are later transported by water or wind, this information can improve prediction and monitoring efforts to reduce human exposure.
Current studies emphasize the complexity of phytoplankton and HAB dynamics. Ongoing research is essential to enhance our understanding and develop predictive models that resource managers can use for effective HAB mitigation and prevention strategies. Implementing high-frequency, high-resolution monitoring systems could improve management decisions significantly. Achieving these goals will take time due to the lingering impacts of nutrient loading, necessitating a continuous adaptive management approach as new information emerges. In the meantime, understanding the drivers of HABs in Lake Okeechobee could help reduce future in-lake treatment costs.
This study was supported by the USGS Ecosystems Mission Area, through the Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology) and U.S. Army Corps of Engineers Aquatic Nuisance Species Research Program.