What's Next for Our Estuaries?

 

Unlike mangroves, Australian pines did little to protect shorelines.

When lives of coastal residents returned to normal, anglers began taking stock of the storms' effects on fishing grounds. Giant swells and flood tides clearly impacted vital marine nurseries below the waterline, but didn't make The Weather Channel's continuous coverage. The Indian River Lagoon, Charlotte Harbor and Pensacola Bay bore the brunt of the multi-pronged assault.

 

It is the lingering, long-term impacts to marine ecosystems that we're beginning to fully assess going into the spring of 2005.

Hurricane Frances and Jeanne, while individually not as powerful as Ivan or Charley, may have brought the biggest changes.

Although Hurricane Frances' Category 2, 105 mph winds were the lowest of the four hurricanes, the southern Indian River Lagoon's near-absence of shallow bottom vegetation can be blamed on her unwillingness to budge from the landfall point at Stuart. Frances parked herself over the area for a day, a 140-mile-wide washing machine that scrubbed the estuary floor from Stuart to Vero Beach. Then the remnants of Hurricane Ivan circled back with heavy wind and rain and Jeanne struck before the water even began clearing. Researchers with the St. Johns Water Management District recorded the highest turbidity levels ever noted in areas remote from inlets following the onslaught.

A month after Jeanne, slowly clearing water revealed a bottom scoured clean, largely devoid of seagrass or other vegetation. Wave action scraped oysters and barnacles from dock pilings more efficiently than any herd of sheepshead. Silt was flushed from channels, many of which were miraculously left several feet deeper.

Despite the lack of bottom cover, schools of glass minnows, juvenile pilchards, mullet and pinfish still swarmed the naked flats and shorelines. Lake Okeechobee water releases banished most lifeforms from the St. Lucie Estuary, but snook continued to make life miserable for bait schools in the IRL. Spotted seatrout threatened to reach nuisance levels on some outings, including numbers of big trout. And redfish, which are normally a hit-or-miss species south of Fort Pierce, maintained a welcome presence throughout the winter.

Jeff Beal, Florida Fish and Wildlife Conservation Commission IRL Marine Habitat Coordinator, said the consistent fishing and even the increase in redfish numbers shouldn't come as a surprise.

“Larger fish are largely unaffected by storms,” he explained. “They find holes in the rivers and inlets or just offshore and quickly return. And redfish, which are somewhat sensitive to temperature but very sensitive to salinity levels, would find preferable conditions in the southern end of the lagoon, since the southern lagoon is naturally saltier. Normal salinity would have returned to the area between Fort Pierce and Stuart sooner due to the proximity of the inlets versus areas farther north.”

It's the next three years that have Beal concerned.

“It's the plankton and juveniles—fish larvae, microscopic organisms, shrimp, crabs—the bottom of the food chain—that are really at the mercy of the storms. The small stuff that survived the storms became easy prey for predators, since they had nowhere to hide. Couple that to the loss of habitat, and we might see the real effect on fishing next year.

“Post-storm studies in Texas show a three- to five-year recovery period for seagrass. We're particularly concerned about Johnson's seagrass. Even under normal conditions it has such a narrow range—from Sebastian to southern Biscayne Bay—but the only places in the lagoon we've found it since the storms are right around the Fort Pierce and Jupiter inlets. It normally dies back somewhat in the winter, making it hard to find, so we're hoping it will re-emerge when warm weather arrives.”

To the storms' credit, many soft-bottom areas that previously made wade-fishing a sticky adventure now sport hard sand bottom. The first tiny tendrils of grass re-emerged in selective patches by mid November, and were up to three inches tall by early December.

Feeding frenzies marked hurricane-exposed Indian River Lagoon bait school.s

Other shorelines and spoil islands took a hard hit, but demonstrated the shoreline-stabilizing value of mangroves. While Australian pine roots gave way in the wet soil and now house snook instead of pelicans in their branches, mangroves lost leaves but stayed put. Forming a fringe around the islands, black mangrove breathing tubes trapped soil and cushioned crushing waves that inundated the islands for hours on end.

 

Beal is looking forward to a comprehensive aerial seagrass assessment of the entire lagoon that the St. Johns Water Management District will be conducting over the next nine months.

“In the 1940s, seagrass grew to a depth of two meters throughout the lagoon,” said Beal. “Even before the storms last summer, that depth had decreased to 1 to 1 1/3 meters due to lower water clarity. So it will be interesting to see if the hurricanes created further declines.”

The downside to the removal of silt from lagoon waters is that the silt now resides on offshore reefs, according to Beal.

Hurricane Andrew, which visited Biscayne Bay in 1992, served as a useful comparison. Despite over $15 billion of damage onshore, seagrass damage in most areas was minimal. Beds west of Totten Key, just south of Elliott Key on the eastern side of south Biscayne Bay, suffered the most damage. Localized grassbed losses of up to 80 percent were observed. The worst damage, according to the Miami-Dade Department of Environmental Resources Management (DERM), was to mangrove shorelines. Larger trees especially were hard hit. There were a lot of questions about the recovery of the mangroves, but shorelines today compare with pre-Andrew photos.

While sponge and coral in Biscayne Bay did not fare as well, seagrass beds in the storm track survived largely intact. Biscaynefish stocks remained remarkably unaffected.

Some attribute the light seagrass destruction to Andrew's rapid advance and short visit. That scenario appears consistent with hurricanes that showed similar characteristics last fall. Hurricanes Charley and Ivan struck hard, but didn't stick around long.

“We monitor 50 seagrass locations around Charlotte Harbor, and we didn't observe any significant changes to beds following Hurricane Charley,” said Florida Department of Environmental Protection (FDEP) Estuary Resource Manager Judy Ott. “We did detect temporary changes in our water chemistry—higher dissolved nutrient loads followed by depressed oxygen levels a week or two after Charley came through—as flood waters from the Peace River reached Charlotte Harbor. Most fish species simply moved, but species that couldn't react quickly, like flounder and crabs, suffered some losses.”

Consistent with post-Andrew assessments, mangroves took the hardest hit.

“The red mangroves were trashed, and most of them won't recover,” said Ott. “They have to regenerate from seed pods, so that will take some time. The good news is, their root systems will remain in place to protect shorelines for quite a while. Black mangroves, on the other hand, regenerate quickly from their stalks and root systems, so we could see them replace red mangroves in many areas.”

Although some species temporarily changed locations in response to oxygen levels, “fishing remained good, according to fishermen I talked to,” said Ott. That is consistent with reports from the Pensacola area.

“The redfish were here before Ivan struck, and they were still here when the water cleared up two weeks later,” declared Capt. Wes Rozier, as he described a December Pensacola Bay charter which produced 80 bull redfish releases in four hours. Hurricane Ivan didn't seem to affect them at all.”

Rozier describes the area's seagrass beds as fine.

“The only difference in the grassbeds is that they're now decorated with pine tree branches and furniture. Trout and flounder never stopped biting. Shore anglers face the biggest impediment right now. They're hurting due to the loss of so many piers and bridges, and access to beaches is limited. The beach at Fort Pickens was breached. The Pensacola Fishing Pier was the one bright spot in this whole mess. It was built with this kind of storm in mind, and lost a few railings and planks, many of which just popped up and were put right back on. And the bait shops all reopened by December.”

As anglers watch the recovery process in their respective fishing grounds, every Floridian maintains a wary eye on something else—the calendar. The 2005 hurricane season starts June 1. And while Colorado State's Dr. William Gray, the nation's leading prognosticator of hurricanes, foresees nothing close to the hurricane activity of 2004, his annual forecast again calls for slightly above-average hurricane activity in the Atlantic basin, with higher than usual probabilities for landfall in the U.S. U.S., as in us.

FS