In Dixie County, cornstalks sway like dancers in a warm fall breeze. Twenty miles down the Suwannee where the river meets the Gulf of Mexico, seagrass mirrors the corn’s gentle wave, pushed by northwestern currents.
Despite their distance, the two plants are tied together in a complex waltz.
Fertilizer regulates their tempo. Too much and corn thrives at the expense of seagrass, nitrogen- polluted waters causing algae blooms downstream. Too little and crop yields plummet, keeping waters clear but farm profits unlivable.
At the same time, climate change throttles both the agricultural and ecological wealth. In 2023, Florida’s agricultural economy lost approximately $1.2 billion to hurricanes, floods, drought and extreme heat, all worsened by climate change. In 2018, a red tide bloom caused $2.7 billion in losses to the state’s recreational fisheries and other coastal tourism sectors.
These tensions among agriculture, water quality and fishing play out from the Suwannee River Valley in Florida to to northern states, like Ohio, around Lake Erie. Amid ongoing discussions of the waterways’ inherent ecological value, new research zeros in on water quality and economic impacts of future land use changes.
The nitrogen problem
Where tannic waters of the Suwannee River bloom like black ink in the Gulf of Mexico, seagrass is dying.
The darkness itself is harmless: a natural consequence of cypress branches and tupelo leaves steeping in 246 miles of free-flowing water. Nitrogen is the seagrass’ killer.
The chemical element flows into the river in fertilizer-rich streams of runoff from the more than 800,000 acres of farmland in the Suwannee River Basin. At the river’s mouth, local currents usher nitrogen northwest into the shallow waters of the Big Bend, which is home to some of the nation’s largest seagrass meadows.
Fertilizer in water acts as it does on land, giving the bottom of the food chain a boost. Marine algae, called phytoplankton, suck it up hungrily and cause a population explosion. Smelly, green algal blooms cover the coastline, blocking sunlight and depleting oxygen.
Humans and fish can search for clearer waters, but seagrass, tethered to the seafloor, wilts and dies. Warming waters, boat propellers and extreme weather contribute to seagrass death, too.
Between 2015 and 2022, the 12-mile coastal region spanning from the mouth of the river to Horseshoe Beach lost 92% of its seagrass beds.
That’s a problem for Brent Woodard, captain of Reel Native Fishing Charters, whose catches –redfish, snook, black drum and more– depend on seagrass to survive.
“Go look at how much turtle grass we used to have,” Woodard said, “go to those spots now and it's just mud.”
“We've gotten to the point now where we can see, in a five-year span, a major change [in fish numbers] and that's pretty scary.” Woodard attributes the loss to more anglers on the water, rising water temperatures and especially seagrass losses.
“I mean, anybody that's anybody realizes that's probably one of the biggest things out there,” he said.
A recent cross-discipline study by the University of Florida Water Institute evaluated how a variety of land use changes in the Suwannee River Basin could affect water quality, food webs and fishery profits in the region up to the year 2045.
The mixed fate for fish
As of 2020, agriculture covered 25% of land in the Suwannee River Basin while forests and wetlands filled 35%. Researchers modeled 30 future land use scenarios, the most extreme of which simulated converting all available land to agriculture or conservation forestry.
Although unrealistic, these extreme models allowed researchers to understand the relationship between ecology and economy in the river’s ecosystem.
Researchers found some species of fish, including snook and spotted seatrout, would actually increase under agricultural expansion scenarios while numbers of sand seatrout, clam and mullet would fall.
Fertilizer runoff from agriculture boosts phytoplankton, giving smaller fish plenty to snack on. Fattened up with nowhere to hide, the prey become a filling meal for snook and spotted seatrout.
The runoff also causes much more damaging effects, though, even for the fish at the top of the food web. Agricultural expansion would decrease seagrass cover and increase periodic losses to shellfish aquaculture. It would increase the frequency and intensity of harmful algal blooms, multi-million dollar coastal catastrophes already worsening due to climate change.
Researchers found economic gains from agricultural expansion would outweigh monetary losses from commercial fishing and aquaculture. Importantly, they cautioned any extreme change in land use could be detrimental, especially as rising temperatures and changes in salinity exacerbate ecosystem damages.
Further, industrial impacts don’t capture the full value of the Suwannee River ecosystem.
The ecosystem helps mitigate flooding, lessening damage to riverfront homes and businesses as extreme rain events become more frequent in Florida. Its banks are home to native plants and pollinators, preserving a wealth of biodiversity. The river is a place for afternoon picnics, springs hopping and recreational paddling and fishing trips, the economic impacts of which the study didn’t quantify.
“The problem is these things are a balancing act,” said UF fisheries professor Mike Allen, the study’s lead author and director of the Nature Coast Biological Station.
“You could have one part of the system be very productive from a jobs and economic standpoint, but downstream those effects could be devastating ecologically and also economically to the coastal regions.”
A struggling waterway
According to Dr. Robert L. Knight, founder of the Florida Springs Institute, the Suwannee River is already feeling devastating effects.
While the Florida Department of Environmental Protection updated measures in 2018 to reduce nitrogen levels in the Suwannee River Basin, levels in most of the river and its springs increased since the rule’s implementation.
In 2008, FDEP set a monthly nitrate target of 0.35 mg/L. As of October 2024, total nitrogen levels at nearshore areas at the mouth of the Suwannee, where Woodard fishes, were nearly triple that: 1.02 mg/L.
“You're not supposed to ever go over that standard and they've been over the standard since the time they developed it,” Knight said. “There is no more room for additional nitrogen loads or additional groundwater consumption.”
Nitrogen – in its oxygenated form, nitrate – can promote algal blooms, decrease biodiversity and even harm human health. While all of the Suwannee River is impacted by nitrate, concentrations in the groundwater and springs that feed the river are much higher.
According to a 2017 DEP report, more than half of groundwater wells in the Fanning Springshed had nitrate concentrations above 1 mg/L. About 5% of the wells sampled had nitrate levels above the federal drinking water standard of 10 mg/L.
The Florida Springs Institute monitored four springs feeding the Suwannee from January 2021 through March 2022. In Fanning Spring, the most contaminated by nitrogen, maximum nitrate levels surpassed the federal drinking water standard of 10 mg/L. Researchers reported the spring’s ecosystem was unhealthy for at least two thirds of 2021.
Economic analyses may not capture these impacts, but river basin residents and recreationists feel them.
A parallel situation across the country
Similar negotiations among agriculture, fisheries and conservation happen 800 miles north in Lake Erie.
On this “problem child of the Great Lakes”, another fertilizer ingredient, phosphorus, threatens water quality, explained Euan Reavie of the Natural Resources Research Institute at the University of Minnesota Duluth.
Phytoplankton gorge on phosphorus, forming algal blooms that turn the lake’s summer waters a murky green. As algae dies off, it sinks to the lake’s bottom where bacteria feast, zapping the water’s oxygen in the process.
While some fish appreciate the boost in energy from nutrients in the food chain and can safely avoid low oxygen zones, bottom-dwellers struggle.
A study published by University of Michigan and Ohio State researchers on Oct. 28 found three key species for the lake’s commercial fish industry each react differently to phosphorus-induced low oxygen.
The phosphorus harms lake whitefish that sulk in the lake’s low, cool, oxygen-depleted waters but helps yellow perch that feed on fertilizer-hungry zooplankton. Its effect on walleye, however, is somewhere in between.
“Not all species respond similarly,” said Stuart Ludsin, aquatic ecology professor at the Ohio State University and one of the study’s authors.
“It doesn't appear based on our study that there's one perfect amount of nutrients that can come into the system that can support all everything,” he said, especially when considering fisheries, farmers, boaters and environmentalists are all shareholders.
“Each of these different sectors manages a different set of services or things society cares about. It doesn't mean that it's right or ethical or fair to manage just one sector over the other.”
The Great Lakes Water Quality Agreement is a joint effort of the United States and Canada aimed at balancing each sector’s needs on the countries’ shared water resources.
Launched in 1972, the agreement includes everything from wastewater management to invasive species control. It puts special emphasis on reducing phosphorus levels in Lake Erie: an area historically walloped by algal blooms due to industrial and agricultural runoff.
In 2016, both countries set a goal to reduce total phosphorus entering Lake Erie by 40% by 2025.
Ludsin and his coauthors reported the goal may be too strict to support maximum fishery output right now, but it will be necessary —and perhaps not strict enough— to offset worsening water quality likely to be caused by climate change in the next decade.
Progress and what stalls it
By analyzing phytoplankton in Lake Erie’s fossil record, Reavie and his team found the lake's health improved once the agreement was implemented. Then it got worse.
Lake Erie didn’t meet its 2020 phosphorus benchmark and is unlikely to reach its 40% goal by 2025.
Nitrogen concentrations in north Florida’s groundwater average about one part per million, three times higher than the state standard and 20 times higher than natural levels.
“We are currently in many cases around the state, not meeting the nutrient criteria that we would like to see,” Allen said. “There's lots of research and better best management practices that are underway to try to get us there, but we're not there yet.”
“I live on a farm, so I get you gotta grow the grass for the cows. You gotta do this, you gotta do that,” Woodard said. “But there's got to be a little better way of managing it.”
Kelly Aue, outreach coordinator for the Suwannee River Partnership, says the barrier to farmers implementing those better ways is funding. The program brings together farmers, policymakers and researchers to transfer water management practices from theory to the field, though it’s easier said than done.
As the DEP drafts updated nitrate targets for July 2025, Aue said the goals “seem more daunting”.
“It feels like you almost have to get rid of all our culture to be able to get close to that number,” she said. “It's hard because farmers are doing so much to try to reduce fertilizer.”
As of 2020, about half of agricultural acres in the Suwannee River valley are enrolled in best management practices: a voluntary program for farmers to commit to climate-friendly measures.
Measures include soil moisture sensors and irrigation center pivots controllable by a phone app, among many others. They let farmers monitor fertilizer’s movement in soil through its electrical conductivity and time their waterings accordingly.
In 2018, the Suwannee River Water Management District reported soil moisture sensors saved an average of six million gallons of water per day, decreasing groundwater withdrawals and runoff.
Sensor installation, maintenance and data storage can cost thousands of dollars per field. While the water district and various state agencies have cost-sharing programs to reduce the strain on farmers, Aue says they’re not enough.
“We do have our early adopters where they have the money to be able to make these changes pretty quickly,” she said, “but then you have these smaller guys – it just doesn't make economic sense to purchase this up front.”
It can take years to see a return on their investment, a risk some growers —battered by hurricanes and facing rising input costs— aren’t willing to take.
Still, Aue and Allen are both optimistic.
“This is the first time I felt very hopeful for the future and what we're able to accomplish. I think people are a little bit more dialed in on exactly what needs to be done,” Aue said.
“I've been most impressed in this study of seeing people that are willing to talk and work together to look for solutions,” Allen said. “There's a lot of good from people realizing that they're interconnected and that what they do affects each other and that they need to consider that in their actions.”
Recreational anglers, too, were willing to contribute to the solution. The Water Institute’s study surveyed 1,000 recreational anglers to determine what species they’d be willing to pay to protect. To Allen’s surprise, respondents were more willing to pay to increase seagrass abundance than to increase some fish numbers.
“The anglers we surveyed really cared about the habitat quality in the region,” he said. “I think people have a very good recognition that if you have good habitat, you're going to have good fish populations.”
For Woodard, protecting aquatic environments is a given. He feels an obligation to protect the ecosystem because, just as his farmer neighbors, “that is my livelihood.”