Pitt shifted his eyes toward Giordino. “There might be certain crew members who can’t be trusted on a rum-producing island like Jamaica.”
Giordino shook his head. “Ye of little faith.”
“We got your email describing the dead zones,” Dirk said. “Have you learned anything more?”
Pitt led them to the wardroom, where poster-sized photos were taped to a corner bulkhead. “These are seafloor images of the three dead zones we surveyed. Photomosaics, actually, stitched from individual images recorded by the AUV. As you can see, there is a symmetrical depression at the center of each zone. We didn’t identify the source of the toxicity until Al and I took the Starfish down for a closer look at one of them and found a hydrothermal vent at its center.”
“The thermal vents we’ve explored in the Pacific are rich in minerals and highly acidic,” Dirk added, “but not broadly toxic.”
“These are. They are in relatively shallow water for a thermal vent, less than a thousand feet, which may contribute to the problem. We’re finding methyl mercury plumes over ten miles long.”
“Mercury?” Summer asked.
Pitt nodded. “Surprising, but it shouldn’t be. The largest source of mercury in the environment comes from the volcanic eruptions. Two hundred and fifty million years ago, give or take a few weeks, the seas were completely poisoned by mercury from volcanic activity, to the extent that virtually all marine life was killed off. Hydrothermal vents, we know, are nothing more than a vestige of underwater volcanic activity. For whatever reason, the mounts and ridges in this part of the ocean are rife with mercury.”
“Now that you mention it,” Dirk said, “I recall reading about an underwater volcano off the southern tip of Japan that’s spewing a high concentration of the stuff.”
“Same principle in effect here,” Pitt said.
Summer pointed at one of the photos. “It’s odd that there’s a similar depression around each of the thermal vents.”
“That’s no coincidence,”
Pitt said. “We’re quite sure the craters were formed by man-made explosions.”
“Why would someone blow up a thermal vent?” she asked.
“Someone,” Giordino said, “was plowing up the bottom in the name of subsea mining.”
“Of course.” Summer nodded. “Hydrothermal vents are often surrounded by rich sulfide ore deposits.”
“Looks like somebody tried panning for gold in a serious way,” said Dirk.
“That’s our guess,” Pitt said. “They blasted open the vent, then sent down mining equipment to vacuum it all up.”
“Walking away with the gold,” Summer said, “and leaving an environmental mess in their wake.”
“So who’s responsible?” Dirk asked.
“We don’t yet know,” Pitt said, shaking his head. “Hiram ran a check on all known subsea mining ventures, and associated ocean lease agreements, and found nobody operating in this area. Legally, at least.”
“Could it be the Cubans?” Summer asked.
“Possibly,” Pitt said, “but we don’t think they possess the technology. They’d have to contract for the equipment and that would find its way into the public record. But we do have one clue.”
“What’s that?” Summer asked.
“These tracks.” Pitt pointed to a mass of parallel lines that crisscrossed the depression. “Al and I saw similar tracks near the wellhead where the Alta sank.”
“And those tracks looked fresh,” Giordino said.
“Was it the company that’s drilling for oil?” Dirk asked.
“I contacted the captain of the drill ship and he said they had no equipment that could have created those tracks.”
“So you think whoever blew these three vents is working on the other side of Cuba?” Summer asked.
“It’s the best we have to go on,” Pitt said, “so we’re heading back to the Florida Straits. About twenty miles off of Havana.”