Increased salinity in oceans and coastal areas — the result of climate change and poor land use — has potentially devastating effects on coastal and nearby ecosystems, a new study concludes.

Climate change and man-made intrusions can lead to extreme flooding and drought. As sea levels rise, they push saltwater into coastal and low-lying areas, damaging seagrass beds, harming the shrimping and fishing industries and changing recreational environments, according to the study from the University of North Florida.

“These habitats are subject to change,” said Cliff Ross, one of the researchers on the study. “So as the salinity levels change, that’s going to have an impact on the ecosystem and may cause certain habitats like seagrass beds or other type of ecological environments, it may cause them to shift into something else or perhaps even die off.”

The St. Johns River is not immune to increases in salinity, or salt content. According to the 2019 State of the River report, salinity levels were increasing in the St. Johns River and its tributaries due to sea level rise and river dredging, causing concerns that continue today.

Lisa Rinaman, the St. Johns Riverkeeper, says more and more saltwater is getting further upstream, leading to threats further inland.

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“We’re seeing saltwater increases all the way south of the Buckman Bridge,” Rinaman said. “And we’re seeing barnacles in areas we haven’t seen it before. We’re seeing jellyfish in areas we haven’t seen before.”

Rinaman said extreme weather events, like droughts and too much water usage, harm the St. Johns River’s salinity levels the most. With the increase in salinity, the most concerning effect for the river is the loss of freshwater grasses, which have several different functions.

“These submerged grasses are the kidneys of the St. Johns and are also important fish habitat,” Rinaman said. “And so if you like to fish, or if you’d like to play in the St. Johns River, unfortunately, when we lose these grasses, you see more pollution issues like blue-green algae outbreaks that can be highly toxic and you see there’s less fish habitat.”

To help offset rising salinity levels in the river, both Ross and Rinaman suggest steps we can take.

Ross said the course is difficult to change. If you can reduce your carbon emissions, continue to do so, he advised, but we are going to have to deal with whatever changes happen to ecosystems and coastal areas, he said.

Rinaman suggests reducing your carbon footprint, reducing your water usage and advocating for policies that protect wetlands.

“One of the most important things we can advocate for to offset the saltwater intrusion is to advocate for reuniting Silver Springs, the Ocklawaha and the St. Johns River, which will restore 150 million gallons of freshwater flow to the river every single day” Rinaman said.

Environmentalists have long sought to remove Rodman Dam and restore the natural flow of the Ocklawaha River, which scientists say would help offset some of the harmful effects of dredging and sea level rise. Many state leaders and local officials have opposed the move, pointing to fishing that draws visitors to the reservoir and Northeast Florida.

Meanwhile, the next chance to measure salinity in the river will be the next State of the River report. It’s scheduled to be released in October.