Irma battered South Florida. Now at least one part of the state might be grateful

JENNY STALETOVICH Miami Herald 28 Sep 17;

Sixteen days after Hurricane Irma bulldozed a path across the Florida Keys, leaving a trail of steamy misery, roadside trash piles growing by the day, and a foot of water on his first floor, Capt. Steven Friedman stood on the bow of his boat in Florida Bay marveling at what he saw before him.

Happy, oblivious, rolling tarpon gorging on a shrimp hatch in a browning mat of dead seagrass.

Friedman grabbed a rod, made a few casts and hooked a tarpon. Then, after a few jumps and a valiant struggle, the fish delivered what seemed like solid evidence of nature’s capacity to fight back: It leaped into his boat.

Just moments before, Friedman, commodore of the Florida Keys Fishing Guide Association, had reasoned that Florida Bay would rebound if efforts to fix the Everglades stayed on track. That’s after a half hour ride from an Islamorada marina down a channel stinking like rotten eggs, across soupy brown water that’s normally gin clear and through a raft of dead turtle grass.

“I’m a fisherman, so my default makes me an eternal optimist,” he said.

In the days since Irma, scientists have worried about the storm’s toll on a bay battered by a triple whammy of damaging events in the past two years. More than 60 square miles of seagrass died in 2015, spreading a sulfuric yellow cloud. Algae blooms followed, although they never reached the magnitude of a stinky green bloom that erupted in the 1990s, crashing the bay and crippling fishing for years. But the bay is especially vulnerable now, following decades of flood control that cut off parts of it from an Everglades supply of freshwater. Restoration work remains many years from completion.

If South Florida undergoes another hot winter — 2016 stands as the hottest year on record — they worry that too much dead seagrass from Irma could overload the bay.

“My concern is as this continues to decay, this material is going to continue releasing nutrients that could cause another algae bloom,” said Everglades Foundation wetland ecologist Steve Davis, who organized the outing to examine Irma’s damage. “We just need to be vigilant.”

Just after the storm, Davis flew over Cape Sable and photographed vast mats of floating dead seagrass. But from the air, it was hard to tell exactly what kind, and where the grass might have come from. On the water this week, Davis found seagrass beds looking healthy, suggesting that they might have survived the storm’s powerful Category 4 winds, and the bay teeming with life.

In fact, there’s reason to believe both grasses and fish that evolved over eons of hurricane seasons could actually benefit from the storm.

Florida International University marine ecologist Jim Fourqurean said some scientists believe the bay suffers from too little circulation, allowing dead material to pile up. Cut off from historic overland flows, the shallow bay also tends to get too salty because water evaporates faster than rainfall or run-off can replenish it.

“So a big hurricane that causes a big displacement of water could also be good because it will freshen up the bay,” he said.

Hours before the storm, parts of Florida Bay emptied out. Fourqurean said a colleague reported seeing grass exposed just north of Key Largo, near Pelican Key, where water is normally four to five feet deep. As the storm passed, all that water came rushing back in, bringing fresher ocean water.

Hurricanes can also have a pruning effect on the grass by pulling out dead grass or loose blades, freeing up space and speeding up new growth.

After the 2015 die-off, heavy rain the following year helped stop the event from becoming as bad as scientists worried, Fourqurean said. Since then, faster-growing shoal and manatee grasses have started growing in the beds, a good sign of recovery. What’s not clear now is what will happen to those. Shoal and manatee grass have shorter roots than turtle grass, so a hurricane can uproot them more easily.

And where the dead grass ends up matters.

“If it’s scraped from hundreds of square miles and dumped in one place, that very well could cause problems in that place that received all that grass, so we’ll need to keep an eye on that,” he said.

In the coming days, he and other scientists will be taking a closer look at seagrass beds that since Hurricane Andrew have been more closely monitored.

Fish, including the young tarpon Friedman hooked and a nearby pod of bottlenose dolphins feasting around the grass, also have reason to thank Irma. When the storm churns up so much material, it releases nutrients that provide food for the smaller inhabitants of the food chain, like spawning shrimp. So that rotten egg smell? That’s a good sign too, if it doesn’t stick around for too long, drawing shrimp, crab and pinfish that lure bonefish, permit and tarpon — the backbone of a Keys sportfishing industry valued at about $722 million a year.

Mature tarpon, which spawn offshore this time of year, will “stay on the high side of a storm,” said Jerry Ault, a fisheries biologist at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. When a storm hits, young tarpon larvae can get washed over mud banks and into out-of-reach basins.

“It provides habitat they wouldn’t normally have access to and food,” he said. “They’re the kingpin feeding on it.”

And while it’s not good news for guides, a storm also dampens recreational fishing, easing the pressure on fish. Fish patterns can also change, making it harder to find them, said Audubon Florida research manager Pete Frezza, who’s also a fishing guide.

“That’s going to benefit people who spend a lot of time on the water — guides — rather than regular anglers,” he said.

So far, it also looks like nesting islands for wading birds, including Sandy, Tern and Frank keys, which had been stripped by Hurricane Wilma in 2005, did fine during Irma, Frezza said.

“The birds are very well adapted to hunker down in the mangroves,” he said.

There’s another potential boon. Near Rabbit Key, Friedman and Davis found a “rogue tree:” a clump of red mangrove ripped free by the storm and floating on a boat-sized ball of buoyant peat. The week before, Frezza also encountered two other rogues. If they’re lucky, the trees will wash onto a flat, take root and survive to become new homes to birds and fish.

“We got hit with a sucker punch, but we’re at the ready,” Friedman said. “We know we can find fish. We just have to find beds.”

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