Hydrothermal vents, methane seeps play big role in marine life, global climate

The hydrothermal vents and methane seeps on the ocean floor are a major force in ocean ecosystems, marine life and global climate, said researchers in a new study.

Once thought to be geologic and biological oddities, the strange, isolated worlds on the ocean bottom were first discovered 40 years ago by researchers from Oregon State University (OSU) in the U.S. Pacific Northwest.

These habitats, now considered to be fountains of marine life, surprised the scientific world with reports of hot oozing gases, sulfide chimneys, bizarre tube worms and giant crabs and mussels, life forms that were later found to eat methane and toxic sulfide.

"It was immediately apparent that these hydrothermal vents were incredibly cool," said Andrew Thurber, an assistant professor in the OSU College of Earth, Ocean and Atmospheric Sciences, and co-author of a new report, published in Frontiers in Marine Science, involving 14 international universities and organizations.

"These vents and seeps are much more than just some weird fauna, unique biology and strange little ecosystems," said Thurber. "They are prevalent around the world, both in the deep ocean and shallower areas. They provide an estimated 13 percent of the energy entering the deep sea, make a wide range of marine life possible, and are major players in global climate."

The vents pour out gases and minerals, including sulfide, methane, hydrogen and iron, which is one of the limiting nutrients in the growth of plankton in large areas of the ocean. In an even more important role, the life forms in these vents and seeps consume 90 percent of the released methane and keep it from entering the atmosphere, where as a greenhouse gas it is 25 times more potent than carbon dioxide.

"We had no idea at first how important this ecological process was to global climate," Thurber said about findings as a result of reviewing the status of these marine geological structures and the life that lives around them. "Through methane consumption, these life forms are literally saving the planet. There is more methane on the ocean floor than there are other forms of fossil fuels left in the oceans, and if it were all released it would be a doomsday climatic event."

The vents and seeps and the marine life that lives there create rocks and habitat, which in some settings can last tens of thousands of years, according to the researchers. They release heat and energy, and form biological hot spots of diversity. They host extensive mussel and clam beds, mounds of shrimp and crab, create some prime fishing habitat and literally fertilize the ocean as zooplankton biomass and abundance increases. While the fluid flows from only a small section of the seafloor, the impact on the ocean is global.

As more about their role in sustaining a healthy Earth is being understood, however, these systems have already been damaged by human exploitation, and others are being targeted, the researchers noted. Efforts are beginning to mine them for copper, zinc, lead, gold and silver. Bottom trawling is a special concern, causing physical disturbance that could interfere with seeps, affect habitat and damage other biologic linkages.

Oil, gas or hydrate exploitation may damage seeps. Whaling and logging may interfere with organic matter falling to the ocean floor, which serves as habitat or stepping stones for species reliant on chemosynthetic energy sources. Waste disposal of munitions, sewage and debris may affect seeps. Endit