Tuesday, September 16, 2008

Sights from Shallow Hydrothermal Vents

This entry is contributed by expedition member Larry Madin.

Larry Madin and Alan Dynner on board the expedition vessel

When we awoke Sunday morning, the ARGO was arriving off Puerto Escondido, the "hidden port" south of the colonial town of Loreto, nestled in calm blue water in the shelter of Danzante and Carmen islands. Below us was the dive site with the recently discovered hot water vents, and over on the nearby shore was the site where my wife and I did our first field work, camping on the beach nearly 40 years before. A long way from those days of homemade boats and subsistence fishing to the luxurious and high tech ship we're operating from now!

Hydrothermal systems are one of the most intriguing ecosystems in the ocean. Discovered only 30 years ago, they have revealed a biological world almost totally alien from our own, fueled by the heat and chemistry of the earth instead of the light of the sun and air of the atmosphere. Further north in the Gulf, there are extensive vents thousands of meters down in the Guaymas Basin, but here we were sitting only 450 feet above the newly discovered vents.

Orange fish crowd around a shallow hydrothermal vent

It didn't take long to find the vents in the sub. After taking some time to get portraits of an unfamiliar sting ray with bull's eye spots on its wings, we moved up to a rock face where the shimmering distortion revealed openings where hot water was rising out of the earth. These shallower vents do not give rise to the tubeworms and giant clams of deep-sea hydrothermal communities, but the growth of white bacterial mats around the vents suggests that the fluid is contributing nutrients as well as warmth. Dozens of orange fish clustered in cracks nearby, unfazed by the looming submersible just inches away.

With battery voltage getting low, it was time to leave, but we had seen another example of the intimate connection between earth and ocean, a reminder of the volcanic history of the Sea of Cortez.

-Larry Madin

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