Environment: Mother Superior's Secrets

David Long sounded as excited as a passenger aboard a space shuttle. "It was spectacular," he burbled. "It was like sitting in a big bubble and looking at a movie playing in front of you. We found sheer cliffs, we found pockmarked holes like dimples on a golf ball. And we found these little red marks all over the rocks." Long's exhilaration came not from leaving the earth's surface but from going beneath it, on the first submarine exploration to the bottom of one of the world's biggest bodies of fresh water, Lake Superior.

Long, a geochemist at Michigan State University, is one of a team of scientists who spent eight days last month exploring Lake Superior in the submersible Johnson-Sea-Link II. Their voyage was the first leg of a four-week, $550,000 expedition sponsored by the National Oceanic and Atmospheric Administration that will continue until Aug. 20. Until now researchers have seldom viewed Superior at depths below 200 ft., generally the limit to which scuba divers descend. But using the Sea-Link, they have been able to plunge right to the bottom. The deepest point: 1,330 ft.

The red blotches discovered on rocks as deep as 1,300 ft. provided an early, startling dividend of the expedition, the scientists disclosed last week in Marquette, Mich. Using a pair of tweezers, a biologist plucked a red spot from a stone that had been taken to the surface and placed it in a vial of water. Immediately the spot sprouted tentacles and unfolded into a hydra, a primitive invertebrate. "We were expecting that at these depths Lake Superior would be a biological desert," said Team Member John Krezoski, a biologist at the University of Wisconsin, Milwaukee. "We're coming away dazed and astounded."

Indeed, the bottom of the lake, a gray moonscape punctuated by boulders, rock-slides and l00-ft.-high sandstone walls, was teeming with life. Clouds of minute zooplankton drifted across the sub's windows like snowflakes. Burrowing burbot fish dug deep trenches in the silt, while sculpin fish created dimple-like holes as they nestled into the lake floor.

Two scientists and two crew members from the parent research vessel Seward Johnson took turns making the twice-daily three-hour dives in the Sea-Link. Originally built for ocean submersion, the craft had to be packed with a special foam embedded with air-filled glass bubbles to provide the greater buoyancy needed in less dense fresh water. The Sea-Link looks more like an underwater helicopter than a submarine. It has a bubble-like cockpit that seats the pilot and a scientist, and its nine reversible thrusters allow it to move in any direction or hover in place. Cameras and lights are mounted on the outside, as are racks to hold buckets for samples grasped by the robotic arm or sucked up by a vacuum tube.