Indian River Lagoon is facing a new threat from blue-green algae, specifically a species known as dapis pleousa. This cyanobacteria, formerly called lyngbya, has become a growing concern for local ecosystems and public health in 2025.
Blue-Green Algae in Indian River Lagoon
The presence of blue-green algae in Indian River Lagoon has increased in recent years. Dapis pleousa, a brown, foul-smelling cyanobacteria, is now commonly seen in the lagoon, especially during the warm summer months.
This algae can be mistaken for raw sewage due to its dark color and strong hydrogen-sulfide odor. Residents and visitors have reported sightings of large mats of dapis pleousa, particularly in areas like north Indian River County and near the Stuart Sandbar in Martin County. In addition to algae, the lagoon faces other threats; for example, Port St. Lucie residents recently reported a massive fish kill in a local canal, highlighting the interconnected environmental challenges in the region.
Impacts on Seagrass and Marine Life
One of the main concerns about blue-green algae in Indian River Lagoon is its effect on seagrass beds. Seagrass serves as a critical food source for manatees and provides habitat for fish, crabs, and other marine life.
Dapis pleousa can harm seagrass in several ways:
- Overgrowing and smothering seagrass beds on the lagoon floor
- Ripping up seagrass when mats detach and float in the water
- Blocking sunlight needed for photosynthesis when mats reach the surface
These effects can reduce food options for wildlife and disrupt the lagoon’s ecosystem balance. As seagrass declines, concerns grow for vulnerable species, leading Port St. Lucie residents to advocate for a manatee protection zone in the C-24 Canal to help safeguard these gentle marine mammals.
Health Risks for Humans
Blue-green algae in Indian River Lagoon is not only an environmental issue but also a public health concern. The algae can cause skin rashes, such as “swimmer’s itch,” and may trigger respiratory problems in sensitive individuals.
Because dapis pleousa resembles sewage and emits a rotten-egg smell, it can also create confusion and worry among local residents. Reports of large algae mats have sometimes been mistaken for sewage spills, especially following incidents like the raw sewage spill in Brevard County in June 2025.
Why Dapis Pleousa Blooms in the Lagoon
Dapis pleousa thrives in the shallow, nutrient-rich waters of Indian River Lagoon. Warm temperatures from May through September create ideal conditions for cyanobacteria blooms.
The main sources of nutrients fueling these blooms include:
- Outdated septic systems leaking nitrogen and phosphorus
- Stormwater runoff carrying fertilizers and waste
- Discharges from Lake Okeechobee
- Nutrient-rich muck at the lagoon bottom
These factors contribute to the rapid growth and spread of blue-green algae, making management difficult. Compounding the problem, the overall health of Indian River Lagoon has declined amid parasite scarcity, further stressing the ecosystem and its ability to recover from repeated algal blooms.
Challenges in Tracking and Managing Algae
Unlike other harmful algal blooms, such as microcystin and red tide, dapis pleousa is not widely monitored by government or research agencies. According to H. Dail Laughinghouse of the University of Florida’s Institute of Food and Agricultural Sciences, little is known about the long-term impacts and behavior of this cyanobacteria.
This lack of data makes it harder for agencies to predict blooms or respond quickly to new outbreaks. The dynamic nature of Indian River Lagoon, with its mix of freshwater and saltwater, adds to the complexity of managing blue-green algae.
Innovative Tools for Algae Removal
To address the blue-green algae threat in Indian River Lagoon, new technology is being tested. Tetra Tech, an engineering consulting firm working with Martin County, has developed a tool to collect dapis pleousa from the lagoon floor before it damages seagrass meadows.
The device is simple in design, resembling a rake attached to a PVC pipe frame with small wheels. Early trials have shown that this tool can effectively gather algae mats for removal.
Tetra Tech is currently refining the technology to handle larger areas and is developing ways to store and dispose of the collected algae on land. Storing the algae safely remains a challenge, but ongoing research aims to find effective solutions.
Recent Fish Kills and Environmental Concerns
Blue-green algae blooms have coincided with other environmental issues in the region. In Port St. Lucie, the Florida Fish and Wildlife Conservation Commission and city officials are investigating a fish kill in the Sawgrass Lakes community. While the cause is under review, nutrient pollution and algal blooms are known to contribute to such events.
Efforts to reduce nutrient inputs, such as bans on sewage discharge into the lagoon, are ongoing. However, enforcement and long-term solutions remain key challenges for local and state agencies.
Frequently Asked Questions About Blue-Green Algae in Indian River Lagoon
What is blue-green algae in Indian River Lagoon?
Blue-green algae, also called cyanobacteria, are microorganisms that can form large blooms in Indian River Lagoon. The species dapis pleousa is a type of blue-green algae that looks brown and smells like rotten eggs.
How does blue-green algae affect seagrass and marine life?
Blue-green algae can smother seagrass beds, block sunlight, and reduce food for manatees and fish. It can also disrupt habitats for crabs and other marine species in the lagoon.
Are blue-green algae blooms dangerous to people in Port St. Lucie?
Yes, blue-green algae can cause skin rashes and breathing problems for some people. Its strong odor and sewage-like appearance can also cause concern among residents and visitors.
Can you see blue-green algae blooms in PSL during summer?
Yes, blue-green algae blooms are most common in Indian River Lagoon from May to September. Large mats may appear brown and float on the water or rest on the lagoon floor.
Where are blue-green algae problems most common in the Treasure Coast?
Blue-green algae issues are reported throughout Indian River Lagoon, especially in areas with warm, shallow water and high nutrient levels. Reports have come from Martin County, north Indian River County, and near Port St. Lucie.
Port St Lucie Talks
