Hydrothermal-vent chimney. In the center of the photo, you can see the vent fluid which appears like dark smoke due to the high levels of minerals and sulfides contained in the fluid. Look closely, and you will also see the chimney is crawling with Chorocaris shrimp and Austinograea wiliamsi crabs.

Hydrothermal-vent chimney. In the center of the photo, you can see the vent fluid which appears like dark smoke due to the high levels of minerals and sulfides contained in the fluid. Look closely, and you will also see the chimney is crawling with Chorocaris shrimp and Austinograea wiliamsi crabs. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas. Download larger version (jpg, 1.8 MB).

Dive 11: Hydrothermal Vent
May 2, 2016
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Hydrothermal Vents

This incredible active hydrothermal vent was imaged for the first time during the Marianas expedition. It was 30 meters high and gushing high-temperature fluid full of metal particulates. This vent was home to many different species, including Chorocaris shrimp, Munidopsis squat lobsters, Austinograea crabs, limpets, mussels, and snails. Video courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas. Download (mp4, 75.6 MB)

Dive 11 was the first remotely operated vehicle (ROV) exploration on a site for which there was prior evidence of active hydrothermal venting. After descending to 3,293 meters, we were very excited to quickly encounter a 30-meter chimney emitting black hydrothermal fluid. The base of the chimney was extinct sulfide, but the top was active with several black smoker orifices, beehives structures, skinny little chimney spires, and both iron and anhydrite precipitate. We measured a temperature of 339 degrees C, one of the highest temperatures ever recorded at a hydrothermal vent in the Marianas region. This “black smoker” was colonized by numerous organisms that exhibited strong zonation over very small spatial scales - there was a high density of Chorocaris shrimp and Paralvinella tubeworms directly at the vent effluent sites, then inches to feet away were Austinograea wiliamsi crabs and limpets (maybe Shinkailepis). In the more peripheral areas, the dominant fauna were Marianactis bythios anemones. As we moved away from the chimney, we realized there was a second, smaller chimney structure attached to the first. It was hard to turn the ROV away from all of the activity, but we continued on onto our next waypoint. Our track took us through an area of small vents - a series of small, thin chimneys venting hydrothermal fluids - and across an area of sedimented pillow lavas, where we saw a pair of cusk eels, scattered squat lobsters (Munidopsis galatheids), and some tiny anemones. Halfway through our dive, we made our way to a small, unusual crater that had been previously mapped by the Sentry autonomous underwater vehicle. The edge of this crater was composed of extinct sulfides. As we ascended to the top of the crater, we could see that the opposite interior wall was covered in white spots. These turned out to be squat lobsters, and at the base of the wall was a pile of dead snails (Alvinoconcha hessleri). We also encountered live snails, crabs, and shrimp associated with a small patch of diffuse flow, where we collected a rock. As we moved away from the crater, we came across a field of jumbled, ropy pillow basalts, and fauna that are not typically associated with vents, such as bamboo (isidid) coral, which we collected; several types of anemones; and an urchin that none of us had seen before. We also saw many “pregnant” cusk eels, with bellies distended with young. Finally, we entered another area of actively venting hydrothermal chimneys, but did not have enough time left to really explore the area. Aside from the chimneys and the crater rim, we had little elevation change, and left the bottom at 3,288 meters, all extremely excited by this great find!