VOLUSIA COUNTY, Fla. – The latest update from the St. Johns River Water Management District reveals a dramatic resurgence of seagrass in the Indian River Lagoon.
It’s a development researchers are calling exciting, but are careful not to overstate.
The 2025 aerial mapping study, which tracks seagrass extent across the 156-mile lagoon, from Volusia County down to Jupiter, shows a 72% increase in seagrass coverage since 2023 - equivalent to roughly 7,000 hectares, or about 13,000 football fields.
“We are excited to say that we saw a substantial increase of seagrasses in the IRL,” said Lorae Simpson, supervising environmental scientist at the St. Johns River Water Management District. “It points to improvements in water quality, but I also want to caution this, we are still 42% behind the seagrass coverage that we had in 2009 and 2007.”
The district has monitored seagrass in the Indian River Lagoon since the early 1990s using a two-tiered approach. Every two years, aircraft fly over the lagoon and photograph the waterway. Those images are then translated into high-resolution maps that allow scientists to calculate seagrass acreage across the entire lagoon.
“When you have the map, it’s essentially the whole extent of the Indian River Lagoon overlaid with green polygons - and that’s the seagrass,” Simpson said. “While the maps are very informative, it’s really the data we pull from that map and the actual numbers of hectares that matter.”
The aerial survey is paired with on-the-ground, in-water monitoring conducted twice a year - once in winter and once in summer to capture peak seagrass productivity. ,
Teams wade into the lagoon carrying one-meter-square PVC frames called quadrats, which they use to methodically measure seagrass coverage, species diversity, density, and blade height at fixed transect sites.
“We will even go as far as to count every single seagrass blade in some of these squares, which can get up into the hundreds,” Simpson said.
Simpson says water clarity is the single biggest driver of seagrass recovery. Seagrasses require sunlight to photosynthesize, and murky water - caused by algal blooms, nutrient runoff or freshwater pulses - can wipe out entire beds.
A multi-year drought has played a significant role in the recent gains. Less rainfall means less water flowing off the surrounding landscape and into the lagoon, reducing the nutrient loads that fuel harmful algal blooms.,
“When we have long periods of clear water quality - no algal blooms, no turbid events - this is when we see increases,” Simpson said. “Our management initiatives, coupled with our drought right now is probably why we’re seeing the seagrass.”
Water diversion projects are also contributing. Simpson said large volumes of water that had historically been redirected away from the St. Johns River and into the Indian River Lagoon are now being rerouted back to where they belong.
The recovery is not uniform across the lagoon’s six distinct sub- lagoons. According to Simpson, five of the six regions saw increases in seagrass coverage but the central Indian River Lagoon bucked the trend, recording a 2% decline.
“In the one region where seagrasses weren’t coming back, it has historically been an area with low seagrass coverage, and the water quality issues there are making it difficult for seagrasses to come back,” Simpson said. “It’s just a reminder that we need to continue with our management initiatives.”
Simpson noted that unlike areas in South Florida, which benefit from two tidal inlets that help flush and clean the water, the central lagoon lacks that natural water exchange, making recovery there more difficult.
Seagrass isn’t just a plant on the lagoon floor - it’s what scientists call a “foundation species,” one that connects and supports nearly every other habitat in the ecosystem.
“75% of our commercially and recreationally important fishery species spend some portion of their life cycle in the IRL,” Simpson said. “You think about the livelihoods it supports. You think about the recreation and the wonderful memories you have out on the IRL - those might actually have started within a seagrass bed if you’re out fishing.”
Beyond fishing, seagrass plays a critical role in shoreline protection, erosion control, carbon storage, and nutrient cycling. It also serves as a food source and habitat for manatees, sea turtles, and hundreds of fish species.
“It’s hard to care about something you might not always interact with,” Simpson said. “But the second you can enjoy it, you really want to protect it.”
Perhaps the most surprising finding in the new data is that the seagrass recovery appears to be entirely natural. A previously little-understood seed bank in the lagoon floor appears to be driving regrowth on its own.
“The seagrass recovery we’ve seen is actually 100% natural, which means there is a seed bank out there that we had not previously fully understood,” Simpson said.
Despite the encouraging numbers, Simpson said the district is not celebrating prematurely. The 2016 and 2010 algal blooms serve as stark reminders of how quickly progress can be reversed.
“When you head out to monitor the seagrass, and there’s nothing there to monitor, it’s very disheartening,” Simpson said. “I am just cautiously optimistic because I want people to remember that while we did see an increase, we are still so far behind where we used to be. We can’t take our foot off the gas right now.”
Simpson, who has worked in the Indian River Lagoon for roughly 15 to 20 years and monitored seagrass specifically for the last seven, says the new data is a powerful reminder of what’s possible.
“Recovery is possible with water clarity,” She said. “If we can just keep moving in that direction, we can see our seagrass hopefully reach historical levels.”