Fewer fish seemed to come around, and the strong smell of rotting algae grew more common, especially where the causeways met land.

Studies dating back as far as 1980 showed no significant benefit from causeway removal, but scientists still weren’t sure.

Now, the second study in a little more than a year suggests the causeways ought to stay, putting to rest — for now — the idea that removing them would make for a healthier lagoon with more fish.

“There will be no more resources or money spent on this,” said Deborah Peterson, a planning technical leader with the U.S. Army Corps of Engineers. She said the Corps would only revive the idea if more compelling scientific evidence surfaced.

Instead, the Corps plans to focus on restoring wetlands and digging more storm-water ponds to improve the lagoon’s water quality.

Scientists are meeting this week in Cocoa Beach to discuss the alternatives.

The newest causeway research was part of a larger $7 million study of ways to restore as much of the lagoon’s sea grass, fish and other wildlife as possible. About 20 percent of the lagoon’s sea grass has disappeared since 1943, according to government studies.

The study said replacing causeways with raised pillar bridges would fail to grow back enough seagrass or sea trout in the lagoon to merit the huge cost of doing so.

“Our findings show that removal of causeways would not have any significant beneficial effects on the lagoon,” said Paul Stodola, who studied the concept for the U.S. Army Corps of Engineers planning division in Jacksonville.
The larger Corps study looks at how to improve the ecological health of the northern 128 miles of the lagoon, from Fort Pierce Inlet to Ponce De Leon Inlet. The Corps expects to finish the study by next year and approach Congress for funding in 2008. Work on lagoon restoration projects is expected to begin by 2012 and be complete by 2015.

Based on Stodola’s findings, removing part or all of the causeways won’t be part of the plan, because it would provide little benefit.

Runoff blamed

Soil erosion and stormwater runoff have a much greater influence on seagrass growth than the causeways do, Stodola says. Runoff sends silt into seagrass beds. Wind and boat wakes stir the silt, clouding up the lagoon and blocking sunlight from reaching the valuable bottom plants. Those problems would remain regardless of whether the causeways were removed, he said.

“The distribution problem for seagrass doesn’t appear to be causeways, it appears to be a turbidity problem,” Stodola said.

Last year, a study by the St. Johns River Water Management District found removing the causeways might even hurt water quality. It would allow wind to stir up more of the fine sediment that runs off onto the lagoon bottom.

Fish such as spotted sea trout, which rely on seagrass as nursery habitat, wouldn’t see much benefit from extracted causeways, either, Stodola said.

“Their distribution doesn’t seem to be limited by the existence of the causeways,” Stodola said. “They appear to be spawning on both sides of the causeways.”

Toxic gas

But if fish larvae for fragile species such as spotted sea trout settle out too close to causeways, excess algae and low oxygen in the water there can kill them.

“The real problem is, ‘Where do the larvae end up?’¤” said Grant Gilmore, a fish biologist who’s studied the lagoon for three decades.

The algae decay near the causeways also emits a rotten-egg hydrogen sulfide gas familiar to longtime residents and sometimes harmful to marine life.

“That sulfide is toxic to a lot of marine organisms,” Gilmore said. Cutting out culverts in areas closest to land may still be worthwhile, he said.

There are 17 causeways to the barrier islands, from the Haulover Canal to the St. Lucie Inlet. Most of Brevard’s 12 causeways on the Indian River and Banana River lagoons were built in the 1950s and 1960s.

While they provide public access for fishermen, the fishing’s usually not as good there as elsewhere in the lagoon. The algae that laps up and rots there is anything but a tourist attraction.

“I smell the sulfide there every time I go over the causeways. Typically, you didn’t have it in the lagoon,” Gilmore said.

“I don’t think they have a lot of information on what the causeways are doing.”

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