Green Tide

Greenwell didn't bother to unstrap his rusting fishing rod from the side of his kayak. There was nothing to see in the water, and no fish worth having would bother to stick around here. The sunlight-hogging algae had strangled the sea grass. There was little left for fish to feed on, and nowhere for them to hide.

As Greenwell set out for the south side of the bay, a few hundred yards off, each paddle stroke cut through the olive surface like a straw sinking into a lime ricky. Laminated satellite photos and navigational maps were strapped to the deck. A global positioning unit and an emergency radio were in the hatch. But Greenwell was going by feel. He didn't hesitate on his way to a narrow channel connecting Little Blackwater with its bigger sibling, Blackwater Sound.

The channel, carved out when Henry Flagler built his railroad to Key West a century ago, is dotted with rotting wood posts that once supported the weight of freight trains. The thud of the rails has long since been replaced by the droning hum of the nearby highway. As paved arteries spread south from Miami's sprawl, the once-lonely Keys became an easy trip. While the islands have lost hurricane-weary residents in recent years, their draw remains strong, even as their once-bohemian culture shifts upscale. "Resort communities" such as the Colony in Islamorada offer condos starting at $2 million.

Coming out of the channel and into Blackwater Sound, Greenwell twisted his torso with each motion and kept the paddle close to horizontal, minimizing his exertion as he tried to outrun the bloom. Sunlight bounced off the opaque, still water and rippled along the underside of the red mangroves that line the aquatic hallway. Like tiny stars in a green galaxy, yellow "sacrificial leaves" soak up lethal doses of salt from the water to ensure the trees' survival.

Greenwell's route hugged the shoreline as he made his way to the sound's western edge. A kind of wilderness Mister Rogers, Greenwell is tall and somewhat lanky, with a fast smile and mischievous eyes. He tends to repeat hoary old jokes and, with a patient voice, points out cormorants beating the water with their wings and ospreys circling their nests.

Around a bend, deep-throated singing rose into the sky from a flock of gangly wood storks who cruised in formation low overhead. As the storks approached a landing spot out of sight behind the shoreline's tall grass and Australian pines, a flush of white — a group of ibis and great egrets — erupted into the air with a cacophony of trumpeting. A rookery was nearby, Greenwell surmised, making a mental note of the spot for future trips.

Not far from here is the only place in the world where both alligators and crocodiles find refuge. It's a favorite stop on many of the trips Greenwell has led for the Paradise Paddlers, a club with members from across the country and as far away as Europe. People always seem stunned by the area's exoticism, its overwhelming wildness. "They can't believe that there's some place like this," Greenwell said, "that there's a place so primitive, so beautiful." On the horizon behind him, the faint outlines of metal cranes framed the hulking mass of the Jewfish Creek Bridge, currently under construction.

As far back as anyone can remember, the waters of Florida Bay were almost always crystal-clear. Then, in the early Eighties, fishermen began to notice algae blooms in the western and northern-central stretches of the bay. The blooms appeared consistently, usually growing and subsiding within a matter of days or weeks. In the mid-Nineties, one particularly massive bloom — close to 200 square miles in diameter — wiped out acres of sea grass and killed off sponges, lobsters, shrimp and other bottom-dwellers too slow to escape its gloomy onset. Scientists were caught off-guard.

A 1995 report by the Florida Bay Science Review Panel, comprising independent scientists as well as federal and state researchers, noted an "appalling lack of information" about the bloom, describing most of the explanations as, "at best, hypotheses based on inferences rather than evidence."