After Irma, dead seagrass ‘as far as the eye can see’ in Florida Bay

Hurricane Irma blasted the Flamingo Visitor Center and offices at Everglades National Park. Park officials spent the week assessing the damage and can’t yet say when the park will reopen to visitors.
Hurricane Irma blasted the Flamingo Visitor Center and offices at Everglades National Park. Park officials spent the week assessing the damage and can’t yet say when the park will reopen to visitors. Everglades National Park

Hurricane Irma left a massive footprint across the Florida Everglades.

From Florida Bay to Shark River, signs of the Category 4 hurricane could be seen in vast mats of floating dead seagrass, mangroves stripped of their leaves, and rafts of seaweed pushed far ashore. Along the northwest side of Cape Sable, where the powerful hurricane’s storm surge hit hardest, a newly widened beach stretches toward the wetlands.

In the Dry Tortugas, the storm knocked down a 60-foot stretch of the moat wall at Fort Jefferson. The visitor center at Flamingo, hammered by Hurricane Wilma in 2005 and in the midst of restoration, got pounded again.

irma seagrass mats
After Hurricane Irma, floating mats of dead seagrass appeared near Cape Sable and Flamingo area of Everglades National Park. The mats raise concern because two years ago, a seagrass die-off that covered more than 60-square miles threatened Florida Bay. Stephen Davis Everglades Foundation

It will be a while before Irma’s full toll on the Everglades becomes clear, but a flyover this week by Everglades Foundation wetland ecologist Stephen Davis and early surveys by park staff provided a glimpse of the storm’s vast reach.

“As far as the eye could see to the south were floating mats of uprooted seagrass,” Davis said of the bay. “For me that was the most dramatic, and I don’t want to say most concerning because of the human impacts around this storm. But we’ve been keeping an eye on Florida Bay for a couple of years since that [seagrass] die-off.”

irma cape sable seagrass onshore
Hurricane Irma washed dead seagrass far inland on the northwest side of Cape Sable in Wracksin Everglades National Park. Stephen Davis Everglades Foundation

In 2015, a massive die-off triggered by a drought killed more than 60 square miles of seagrass in the bay that turned water a sulfuric yellow and threatened to trigger a massive algae bloom. So far, the blooms have not been widespread, but more dead plants could fuel a bigger bloom.

At Everglades and Dry Tortugas National Parks, superintendent Pedro Ramos said park workers spent the week checking buildings and facilities, including Everglades City and Fort Jefferson, where Irma likely hit hardest. A 60-foot stretch of the outer moat wall collapsed at the fort, he said, and the first floor of the visitor center in Everglades City was destroyed. The Flamingo Visitor Center, which got pummeled by Wilma 12 years ago, was damaged, along with staff housing.

Once buildings are cleared and power restored, staff will return, possibly next week, to begin assessing ecological damage, Ramos said.

“Clearly [there was] a lot of vegetation down throughout the park, in the front country and the back country,” he said. “A survey of Florida Bay has not been complete.”

It’s not clear when the park will reopen to visitors, although Florida Bay remains open to boaters and commercial fishing guides. Ramos said airboat operators along the Tamiami Trail have been given the all-clear to resume business once they’re ready. Damaged structures, including the moat wall, will be rebuilt, he said.

“That entire scarp has been there from the time the fort was constructed. Both it and the fort clearly have gone through worse,” he said.

Biscayne National Park suffered minor damage to the visitor headquarters and park offices, but with 95 percent of the park located in the bay, damage was minimal, said Park Service spokesman Mike Litterst.

cape sable pre irma
A satellite image of the northwest shore of Cape Sable before Hurricane Irma shows the narrow stretch of beach. Google Maps

irma cape sable widened beach
Hurricane Irma’s storm surge appears to have widened the beach along the northwest side of Cape Sable, where new deposits of sand and seaweed. Stephen Davis Everglades Foundation

Davis started his aerial tour at the Tamiami Executive Airport Wednesday about two hours before sunset. Flying due south, he passed over the Ernest F. Coe Visitor Center at Everglades National Park toward Florida Bay, crossed around Rankin Bite and Whipray Basin, where the seagrass die-off hit hardest, then headed up the northwest side of Cape Sable.

“The further west and up the coast we got, the more rain we saw. It’s incredibly wet out there. That’s no big surprise,” he said.

At the southwest tip of the peninsula, Davis said he saw what appeared to be evidence of a three- to five-foot storm surge pushing into freshwater marshes.

“We certainly saw areas where it looked like vegetation was sort of distributed in racks or mats,” he said.

irma shark river mangroves
Irma stripped leaves off mangroves along the lower Shark River, but does not appear to have knocked down many healthy trees. Shorter trees near the water’s edge appeared intact. Stephen Davis Evergladees Foundation

At the mouth of the Shark River, where towering stands of mangroves hug the riverbanks, trees were stripped of their leaves, but few were toppled. Those that were down looked like they have been felled earlier, or were diseased trees, he said.

“You could see all the way down to the soil surface in a lot of those forests that are usually under a closed canopy,” he said.

For now, the chief concern appears to be Florida Bay, Davis said.

“Knowing this area has been hit pretty hard for the past two years, that’s something we’re going to have to keep an eye on,” he said. “That’s the epicenter of Florida Keys fishing, and knowing it’s a cornerstone of the economy, making those connections is important.”

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