About the IRL Health Report

The current version of the Health Report is designed as a living document. It is reissued every year with current data, but also reflects feedback regarding methods and metrics from the community. In 2025, we added salinity as a sixth habitat health metric after discussions with scientists. This year we made three additional changes:

(1) We listened to your feedback about our word choices for describing Lagoon health and water quality. While the values of each assessment did not change, the words we use to describe the results did. “Okay” has been changed to “fair” when describing water quality and overall basin health. “Good” has been changed to “Large improvement”, “Poor” has been changed to “Slight decline” and “Very Poor” has been changed to “Large decline” when describing overall habitat health. “Good” and “Poor” remain descriptions of water quality parameters because this is the language used by the federal Environmental Protection Agency (EPA).

(2) Chlorophyll-a thresholds were changed to align with the most up-to-date EPA estuary guidelines, assessments by the water management districts, and Indian River Lagoon total maximum daily load (TMDL) thresholds published by the State of Florida. TMDLs are the maximum amount of a specific pollutant a water body can receive daily and still safely meet water quality standards. We encourage you to visit our methods document to learn more about this change. Past Report results have also been updated so 2024–2026 results are directly comparable.

(3) The points you see overlaying the basin averages are the sites are where MRC LagoonWatch citizen scientists collect biweekly water quality data. Because of equipment upgrades we have made to the program, comprehensive LagoonWatch water quality data are able to be included in the Report for the first time! LagoonWatch monitors were just equipped with dissolved oxygen probes and we plan to include point-data for our LagoonWatch sites in the 2027 Report (after a full year’s of data with the updated equipment). This will allow us to track both large- and small-scale changes across basins.

How You Can Help

Everyone has a role to play in restoring and protecting the Indian River Lagoon. In Spring 2025, Marine Resources Council launched Low Impact Living to approach Lagoon education, advocacy, and action on all scales: individual, family, community, and government. Check out our Low Impact Living website for tips, resources, or to request a presentation.

We also want to note that the annual IRL Health Report is prepared and released by MRC independent of any state, county, or municipal funding. Rather, it is supported entirely by community members like you. You can support next year’s Report with a donation or sponsorship. As always, please feel welcome to reach out with any questions, comments, or suggestions.

Important Considerations

It’s important to understand that an “improving” health assessment doesn’t mean that problems are solved or further improvement isn’t possible. We will need multiple years of improving (or even stability) strung together to see measurable and long-lasting ecosystem rebound. Likewise, a “declining” assessment doesn’t mean that efforts and money were wasted. We need to continue the projects and changes that we’ve started, like septic to sewer conversion, wastewater upgrades, stormwater improvements, living shorelines, native gardens, responsible land development, and others. And we’ll need new innovations and projects to continue restoring the Lagoon to a sustainable balance. Lagoons are variable systems by nature that change year-to-year, season-to-season, day-to-day, and region-to-region. We avoided catastrophic algae blooms and fish kill events at least in part due to previous progress in Lagoon health. 2026 did not have any Lake Okeechobee discharges into the St. Lucie River and Indian River Lagoon, which is notable in the southern Lagoon water quality improvements. The summer was hot and dry with the rainy season starting late and no hurricanes. It was a steady year for Lagoon health with mostly improvements, but we can’t predict next year and the work is far from done.

More About the Health Indicators

Harmful Algal Blooms (HABs)

In 2011, the Indian River Lagoon experienced the first catastrophic “super bloom” event. This event was caused by an increase of nutrients in the Lagoon resulting in a “bloom” of harmful algae. These algae physically blocked sunlight from reaching the bottom of the Lagoon, killing beneficial seagrass beds. As the algae decayed, decomposition used up oxygen in the water and caused fish deaths. Additional IRL “super bloom” events occurred in 2016, 2019, and 2020 leading to further loss of seagrass, fish, and manatees. In this Report, harmful algae concentrations were measured based on chlorophyll-a content in water quality data from Florida Department of Environmental Protection Watershed Information Network. Chlorophyll-a is used in photosynthesis (how algae get their energy) and is a common measure of how much algae is in the water.

The Mosquito Lagoon was the only basin that saw an increase in chlorophyll-a and HABs in 2026, leading to a downgrade from good to fair for algae concentrations. On the other hand, the North IRL improved due to lower algae concentrations. The other three basins remained stable with “good” chlorophyll-a concentrations based on EPA standards. Though a few small fish kills were reported in canals and mosquito impoundments after the February 2026 freeze, there were no significant fish kills related to HABs through August 1, 2026.

Salinity

Because the Indian River Lagoon is a delicate mix of salt and fresh water (brackish), widespread and long-lasting changes in salinity can severely affect the plants and animals that live there—especially those that cannot swim away to more habitable areas. Because salinity can change so quickly across small areas, scientists have struggled with how to meaningfully report salinity data. At the suggestion of colleagues after releasing the 2024 Report, we are reporting median salinity with respect to key species in the Lagoon (click here if you need a refresher on median vs. mean).

Seagrass, oysters, clams, and mangroves are organisms that are essential for a healthy Lagoon. They are the focus of restoration efforts and cannot relocate quickly if local conditions become unhealthy. Each one grows best in different levels of saltiness (salinity). How long water stays in one area, how close the area is to ocean or freshwater rivers, and the amount of stormwater runoff from land all affect salinity and how well these species can survive.

Seagrass Coverage

Seagrass is essential to lagoon and estuary health because it (1) reduces erosion, (2) removes excess nutrients (that cause HABs) from water, (3) provides habitat for fish and shellfish, (4) provides food for manatees, sea turtles, and other animals, and (5) stores carbon. Water and sediment quality can affect seagrass growth, and because seagrass is easier to see, it’s commonly used as a habitat health indicator.

Seagrass data came from St. Johns River Water Management District (SJRWMD), who performs an extensive seagrass survey every two years. While these data could be outdated by the time we report them, this is the most comprehensive and consistently-collected dataset available. The seagrass assessments presented in this Report were assessed by comparing 2023 seagrass acreage to 2025 sea acreage.

You’ll notice that seagrass coverage increased in every basin, but not to the same degree. It increased by over 4000% in the Banana River Lagoon and over 1000% in the North IRL—big wins for these regions. The Central and South IRL basins had more modest 21% increases in seagrass coverage. Mosquito Lagoon led the region in seagrass recovery during 2023, jumping by over 54% to reach 15,099 acres; it has held steady with an additional 1.5% coverage. While this Report emphasizes changes in acreage, we also note total coverage in each basin. Even though Mosquito Lagoon has the smallest percent increase, it has the largest overall seagrass coverage with 15,429 acres. Likewise, the South IRL had only a “slight increase” in coverage but has the second largest coverage with 9132 acres. Scientists are still trying to figure out all the factors that contribute to why seagrass has recovered in some areas more than others, emphasizing how complex the Indian River Lagoon ecosystem is.

Sediment Health

Sediment is the sand and soil that make up the bottom of the Lagoon. When scientists assess sediment health, they look at the grain sizes (sand, silt, mud), organic matter (carbon, nitrogen, phosphorus), and the animals that live in the sediments. Due to limited data availability, this Report only considers organic content. When there’s too much organic matter in the sediment from pollution like wastewater, fertilizers, or dead plant matter, the overall sediment health decreases and can’t support seagrass. This information is especially important for environmental efforts, like replanting seagrass or building living shorelines, to help restore the Lagoon’s ecosystem.

The sediment health data presented here came from research datasets collected by Marine Resources Council, Florida Institute of Technology, and Smithsonian Fort Pierce Marine Station scientists. However, because sediment health data are still so limited, they can not be used in the total basin assessment in a meaningful way. To really understand the health of the IRL, we need to gather more sediment data from all parts of the Lagoon and consider more than just organic content.

Wastewater Spills

Wastewater is untreated, partially treated, or treated sewage that comes from residential and commercial sources. The wastewater data presented here represent spills or discharges into the IRL watershed during tropical storms and hurricanes from wastewater treatment facilities, or from accidental cuts or breaks in sewer lines. There are other sources of wastewater like discharges from live-aboard boats, but those are more difficult to track. Wastewater spills presented in this Report were provided by the Florida Department of Environmental Protection and are limited to spills that directly affect the IRL watershed.

From August 1, 2025 to August 1, 2026 there were 152 wastewater spills into the Lagoon or in areas leading to the Indian River Lagoon—down from 182 reported last year. 23 of these spills were directly into the Lagoon and vary from 1-gallon to almost 1.5 million gallons. Small spills are often easily contained and cleaned up quickly. Larger spills can lead to significant amounts of nutrients and bacteria entering the IRL. Nutrients that end up in the water and the sediment can cause harmful algae blooms, seagrass death, and fish kills. High concentrations of harmful bacteria like E. Coli can also be found in the Lagoon after large wastewater skills. Luckily, the largest spills this year were treated wastewater (not raw sewage), but it’s important to remember that treated wastewater still has high nutrient concentrations even if harmful bacteria have been largely removed. This emphasizes the importance of investing in wastewater infrastructure improvements to prevent spills, especially as residents switch from septic to sewer systems.

Water Quality

When scientists and environmental professionals use the term “water quality,” they are referring to how clean or healthy the water is. This is determined by what’s in the water. Good water quality means the water is safe for people, other animals, and plants. Poor water quality can kill the plants and animals that live in or use the water, including making water unsafe for humans to swim in or drink.

Scientists check water quality by looking at things like:

• Temperature: Water that is too hot or too cold can hurt plants and animals.
• pH level: This measures whether the water is too acidic or too basic. Most living things need a balanced pH (between 6.0 and 8.0) to survive.
• Dissolved oxygen levels: Fish and other creatures need oxygen in the water to live. Low oxygen can harm them.
• Pollutants: Things like dangerous chemicals, excess nutrients (nitrogen and phosphate), trash, and bacteria can lead to poor water quality.

Here, we assessed values of pH, turbidity (which relates to water clarity), total nitrogen (high nitrogen can lead to HABs), total phosphorus (too much phosphorus can cause a reduction in dissolved oxygen levels), dissolved oxygen, and chlorophyll-a (how much algae is in the water). Data was gathered from the Florida Department of Environmental Protection Watershed Information Network, South Florida Water Management District’s DBHYDRO, and St. Johns River Water Management District Environmental Data. Assessments are based on U.S. Environmental Protection Agency (EPA) water quality standards.

Good water quality is important for maintaining healthy ecosystems and for human use, like drinking, swimming, and fishing. Poor water quality can lead to problems like algae blooms, fish kills, and the spread of diseases. Overall water quality stayed the same across all basins in 2025, but we saw a lot more variability in 2026. The Central IRL and South IRL had water quality improve due to fewer nutrients (nitrogen and phosphorus). This is the first year since the 2024 Report re-launch that the Central IRL hasn’t been rated “poor” for water quality! The Banana River Lagoon and North IRL overall water quality didn’t change (assessed “fair” according to EPA standards) with small changes in some measurements between years. Unfortunately, the Mosquito Lagoon water quality declined from “fair” to “poor” in 2026 due to increased turbidity and chlorophyll-a concentrations. In fact, all three northern basins (Mosquito, North IRL, and Banana River) had increased turbidity (meaning decreased water clarity), which can negatively impact seagrass.

Bacteria testing is not consistent across the Lagoon, but Marine Resources Council partners with Surfrider Foundation Space Coast to collect bacteria data from Lagoon and tributary waters. Check out Space Coast Blue Water Task Force for bi-weekly bacteria level reports.

Interested In Learning More?

Click on each basin on the map above to find out more about the five health indicators for each Indian River Lagoon basin. If you want to learn more about how health indicators were assessed, check out our methods.

Thank you to partner organizations, government agencies, collaborators, and many others who provided data and guidance for the Report. We couldn’t have done it without you! Please see our full list of acknowledgements included with our methods.