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Algae chokes Pine Island Sound
Usually clean area suffers second bloom in 16 months

By Kevin Lollar
klollar@news-press.com
Originally posted on May 03, 2007

A 60-foot-wide carpet of greenish-brown goo lines a beach at Pineland.

Nearby, the goo, called gopher guts by old-time fishermen, hangs from red mangrove prop roots like dried mucus, and thick mats float on the estuary’s surface.

For the second time in 16 months, thick, macroalgae are fouling the usually alga-free northern Pine Island Sound.

“It’s all over the place, on the bay side of Cayo Costa, Demere Key, just about everywhere,” fishing guide Capt. Rogan White said. “There are tons of it. It’s nasty. I hate it because my engine likes to drink up all that stuff, and it clogs the intake, so I’m always on the lookout for it.”

While macroalgal blooms have coated southern Pine Island Sound and the beaches of Sanibel and Estero islands almost continuously for more than a year and sporadically for several years, massive macroalgal blooms are rare for northern Pine Island Sound. Macroalgae, sometimes called seaweed, are algae that can be seen with the naked eye; microalgae can be seen only through a microscope.

A macroalgal bloom hit northern Pine Island in early 2006 and disappeared a few months later, and several weeks ago, massive quantities of macroalgae reappeared.

On barrier islands, a major concern about macroalgal blooms is the effect on tourism; for commercial fisherman and fishing guide Capt. Shane Dooley of Bokeelia, the bloom in northern Pine Island Sound is affecting his livelihood.

“You can’t throw a cast net: You’ll come up with 200 pounds of algae, so we’re having a hell of a time catching mullet,” said Dooley, who has seen thick patches of algae from Blind Pass to Boca Grande and from Demere Key to Bokeelia. “Even with rod and reel, the stuff gets on your line, and there’s no fish in the woods, no redfish, snook, nothing.”

Two requirements

Macroalgal blooms have two requirements, nutrients and clear water, which lets light reach the plants.

People have blamed southern Pine Island Sound’s macroalgal blooms on nutrient-rich releases from Lake Okeechobee down the Caloosahatchee River after the extremely wet summers of 2004 and 2005.

Others have pointed out large amounts of nutrients also flow into the river downstream from the lake.

But northern Pine Island Sound is far from the influence of the Caloosahatchee, and scientists speculated Hurricane Charley, which hit the estuary Aug. 13, 2004, was partly to blame for the 2006 algal bloom.

Charley’s 145-mph winds blew tons of leaves and tree branches into the sound; over time, the debris rotted and released nutrients into the water.

Those nutrients mixed with nutrients from human sources such as fertilizers and septic systems until the combined nutrient load created a critical mass and triggered the algal bloom.

The present algal bloom might be a recurrence of the Charley influence, said Aaron Adams, head of Mote Marine Laboratory’s Charlotte Harbor Field Station.

“Any time you get a big slug of nutrients in a system, it doesn’t cycle through in a short time, especially in a place like Charlotte Harbor, where you get water exchange but not like you get in the Gulf Stream,” he said.

System maxed out

Add to that the human-related nutrients, he said, and “The system is maxed out.”
But why, more than a year after the 2006 bloom in northern Pine Island Sound, have the algae returned?

It might have drifted in from elsewhere, said Jason Hale, senior scientist at the Charlotte Harbor Environmental Center.

Another possibility is recent weather.

“It’s easy to say last year it was nutrients from Charley,” Hale said. “Well, this year, it still could be. You have a front with winds blowing hard — I wouldn’t be surprised if it turned the water in the estuary and released nutrients from the sediment.”

According to macroalga expert Brian Lapointe of Harbor Branch Oceanographic Institution, the Pine Island Sound algal bloom is a combination of factors.

“You have nutrients building up in the sediments and clear water,” he said. “Temperatures are warming, so bacterial activity is increasing, breaking down organic matter and releasing more nutrients.”

But the recurring algal blooms in the usually bloom-free northern Pine Island Sound, Lapointe said, are a sign of the times.

“We’re seeing increasing development in Lee County — the population has increased more than 25 percent since 2000 — which puts more nutrients into the system,” Lapointe said. “And when you add that to the extremely wet summers recently, clearly we’re reaching a tipping point with nutrients coming into coastal waters.

“Nutrients in coastal waters are reaching an all-time record high. These algal blooms are the ecological indicators of the level of nutrients you’re having in Lee County.”

THE TROUBLE WITH MACROALGAE IN ESTUARIES
• Macroalgae can smother seagrass, destroying habitat for fish and invertebrates.

• They can cover oyster bars. Because oysters are filter feeders, they help clean estuaries by removing pollutants from the water.

• Excess algae use oxygen in a water body. And when algae die, the rotting mass sucks even more oxygen from the water, thus creating dead zones, sometimes killing fish and animals.

• Algae can cover shallow creek bottoms, reducing habitat for juvenile snook and other fish.

• Nutrients from rotting macroalgae are stored in sediments on the bottom and can be recycled to fuel future algal blooms.