Pollution and extreme weather killed vast acres of seagrass along Florida's coastal waters

Jim Waymer
Florida Today

Many tens of thousands of acres of seagrass that nurture billions of dollars in game fishing and environmental tourism in Florida have been lost over the past decade.The exact acreage of what is gone is uncertain.

What is certain is that extreme weather and storm runoff boosted algae blooms in recent years that killed seagrass beds along the Panhandle, Big Bend, southwest Florida, and the stretch of the east coast from Biscayne Bay to the northern Indian River Lagoon.

No one is really sure how much seagrass is (or was) in Florida. The most recent statewide reports (in 2016 and 2018) documented 2.5 million acres of seagrass in the state's nearshore waters. 

Sea Grass Monitoring 8/31/11-- In late August of 2011, Lauren Hall, environmental scientist with the St. Johns River Water Management District and Jonathan Linder, a scientist with Atkins, a company sub-contracted by the district, monitored sea grass growth in the Indian River Lagoon just south of the Wabasso causeway. More than half of the lagoon's seagrass died that year as widespread algae blooms blocked sunlight from reaching the bottom. (FLORIDA TODAY file)

According to reports in 2016 and 2018 by the Florida Fish and Wildlife Conservation Commission, the seagrass picture is a mixed bag but mostly showing decline: 

  • Statewide: Since 2012, runoff fed algae blooms that harmed seagrass in the Panhandle, Big Bend, southwest Florida, and along the east coast from Biscayne Bay to the northern Indian River Lagoon.
  • East coast: Seagrasses expanded to 58,300 acres since 2013, but these increases followed huge losses in 2010, as the result of widespread algae blooms, especially in the northern lagoon. 
  • West coast: In recent years, seagrass increased from Pinellas County – Tampa Bay to the Charlotte Harbor – and is estimated to be 143,000 acres. 
  • South Florida: Grass remained stable until the summer of 2015 when as many as 10,000 acres died in western Florida Bay, due to hot, very salty conditions.
  • Big Bend and Springs Coast: Big Bend lost seagrasses due to a prolonged period of poor water clarity from 2012 through 2014; Springs Coast grasses generally stable.
  • Western Panhandle: 40,500 acres. Some estuaries have increased acreage while in others declined.

The Indian River Lagoon, North America's most diverse estuary and a critical nursery and spawning ground for different species of fish and shellfish, suffered some of the biggest losses. According to the report, poor conditions from 2009 to early 2017 led to the loss of 39,634 acres of seagrass, or 56% of the acreage mapped in 2009 in the northern end of the lagoon.

A manatee munches on seagrass in the Indian River Lagoon. In 2009, seagrass had grown back to 1940s levels, but years of cold spells and algae blooms choked out the seagrass. This year, manatees are starving statewide.

The southern end lost 26% of its seagrass in just two years, from 2015 to 2017. A drought, then extreme cold set the stage for severe algae blooms that killed off the lagoon's seagrass, scientists concluded in 2015.

Stress from cold accounts for about 18% of manatee deaths in the past five years.

What exactly is killing the seagrass and why it's seems to be not growing back are big questions statewide. The answers are far from clear, officials say, because the Florida's coastal waters have withstood nutrients and cold snaps for decades, without showing such significant signs of stress. Whatever it is, this time the losses are severe, biologists say, and many estuaries may have reached ecological tipping points that could take decades to revers.

Indian River Lagoon economics

  • $1.39 billion — Estimated cost over 15 years to meet pending nutrient criteria for the Indian River Lagoon from Fort Pierce Inlet to northern Volusia County border
  • $3.7 billion — Annual economic benefit to Florida from the Indian River Lagoon
  • 15,000 — Jobs supported by the Indian River Lagoon

Sources: Brevard County Natural Resources Management Office, St. Johns River Water Management District

Jim Waymer is environment reporter at FLORIDA TODAY.

Contact Waymer at 321-242-3663                                         

or jwaymer@floridatoday.com.

Twitter: @JWayEnviro

Facebook: www.facebook.com/jim.waymer

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