Green Tide

Monitoring by local and state agencies revealed chlorophyll levels had quadrupled, and phosphorous concentrations had increased sixteen-fold in the affected waters. But why? Driving down U.S. 1 to his lab in Big Pine Key, Brian Lapointe came upon a likely answer. As he passed Blackwater Sound, the area where the bloom originated, Lapointe, an algae expert at Harbor Branch Oceanographic Institute, rolled down his windows. "You couldn't help smelling it," he said. "It's the classic rotten egg smell."

Lapointe's scientific mind put two and two together. Ongoing work on the highway had involved the decimation of about 30 acres of mangroves. When the dead trees' root systems began to decompose, they gave off oxygen-depleting phosphorous, Lapointe reasoned. In the absence of oxygen, sulfur in the surrounding seawater would bind with hydrogen and, voila: nasty, gassy hydrogen sulfide smells, a precursor to algae blooms. "That's telling you that you have a real water quality problem," he said.

It shouldn't be surprising that a major road project would have such an effect on an ecosystem as delicate and unique as Florida Bay, said Jerry Lorenz, head of the Keys chapter of the Audubon Society. Lorenz noted that the Florida Department of Transportation says their construction methods are used all over the world without a detrimental impact. "But they haven't been used in this environment," he said.

A July 2006 study by the South Florida Water Management District didn't exactly disagree with the hypothesis Lapointe and others shared, but it didn't entirely support it either. While the bloom's location near U.S. 1 would seem to implicate road construction as a cause, the study said, the bloom's timing also hints at a connection to the 2005 hurricane season, which stirred nutrient-rich sediment, and increased nutrient-rich agricultural runoff from the Everglades. The study estimated that a bloom that size would need three metric tons of phosphorous — significantly more than the construction work had produced — to sustain itself.

Some activists and scientists smelled a cop-out, accusing the district of trying to smooth over the disastrous environmental impact of the $270 million road project. "From a scientific point of view, the answers are easy," said Larry Brand, a professor of marine biology at the University of Miami. "From a political point of view, it's another issue."

Several marine biologists with the state Department of Environmental Resources Management have studied the bloom almost since its inception. But officials with the agency declined to comment, deferring questions to the water management district. Initially, scientists at the district did not return phone calls. After consulting with district director Chip Merriam, the lead author of the 2006 report, Dave Rudnick, agreed to answer written questions.

Mindful of the political controversy involved, Rudnick was terse. "I refrain from saying there is one cause or that one cause is overwhelming," he said. "There may be other things we don't know about."

Ed Phlips, a University of Florida marine biologist who carried out an extensive Florida Bay water sampling study in the Nineties, sees the plausibility of both sides. On one hand, he's aware of the political pressure at play. Shortly after the bloom was discovered spreading out from roadside construction sites, DOT officials came to Phlips for assistance in studying the phenomenon. "I asked them if they wanted a research project. They really wanted a consultant," he said. On the other hand, Phlips deemed the management district's study "reasonable," saying, "There really was not enough evidence to point blame at anyone."

So, fifteen months after it settled in, the algae bloom has yet to reveal its cryptic origin. "I don't think anybody really knows what's going on in terms of cause and effect and what's going to cause it to dissipate," said Joe Boyer, head of the Southeast Environmental Research Center at Florida International University. "It's like why did the Berlin Wall come down when it came down?"