Deep midwater respirometry system (MRS) deployment

November 9, 2013

Overnight we transited to the deep MRS site (see yesterday’s post and the cruise background for an introduction to the MRS). This site has a mooring in much deeper water than yesterday’s site, about 3,000 meters. This mooring has hangers where we can deploy the MRS at multiple depths. The goal today was to collect deep-living animals (between 2,550 and 2,800 meters), hang the MRS on the 2,800-meter hanger, and measure the animals’ respiration for two days.

The ROV quickly descended to 2,500 meters where we starting looking for animals large enough to measure their respiration in the MRS. Very small animals will not make any detectable changes in the oxygen content of the water in the sampler. There are eight chambers in the MRS and we collected four mysids (deep-sea shrimp-like animals) and two jellies called Poralia rufescens. The last two chambers were left without animals as controls for the experiment. Measuring the oxygen in the control will let Kim Reisenbichler know if anything went wrong with the experiment. Large changes in the control indicate a malfunction.

Left, a small Poralia rufescens and right, a mysid that were put in two of the MRS chambers.

Left, a small Poralia rufescens and right, a mysid that were put in two of the MRS chambers.

People often think that nothing lives that deep in the ocean, but I can assure you there are plenty of interesting animals down there. After we deployed the MRS, we had the rest of the day to search for target species. We have a long list of animals that are of interest to the science team and their collaborators. Here are a few of the fascinating and rare animals we came across today:

Upper left: This cydippid comb jelly is about the size of a cantaloupe. Upper right: This beautiful jelly, Crossota millsae is somewhat rare—in 25 years we've only seen it approximately 70 times with our ROVs. It is named after one of our favorite jelly researchers, Dr. Claudia Mills. Lower left: Stygiomedusa gigantea is one of the largest jellies we see in the deep sea. The bell (in the center of the photo) was about 60 centimeters (nearly two feet) in diameter and the oral arms (trailing up and to the right in the photo) are many meters long. MBARI's ROVs have only seen this jelly eight times. Lower right: Atolla gigantea is a rare jelly only that we collected for our colleague at home George Matsumoto.

Upper left: This cydippid comb jelly is about the size of a cantaloupe. Upper right: This beautiful jelly, Crossota millsae is somewhat rare—in 25 years we’ve only seen it approximately 70 times with our ROVs. It is named after one of our favorite jelly researchers, Dr. Claudia Mills. Lower left: Stygiomedusa gigantea is one of the largest jellies we see in the deep sea. The bell (in the center of the photo) was about 60 centimeters (nearly two feet) in diameter and the oral arms (trailing up and to the right in the photo) are many meters long. MBARI’s ROVs have only seen this jelly eight times. Lower right: Atolla gigantea is a rare jelly only that we collected for our colleague at home George Matsumoto.

—Susan von Thun