PULSE 53: Pelagic-Benthic Coupling and the Carbon Cycle
September 17 - September 23 , 2007

September 19, 2007

Mike Vardaro writes:
Long Term Sediment TrapWhen it's a clear, bright sunny day at Station M it's easy to forget that you're on a tiny ship in the middle of the Eastern Pacific Ocean. Which makes it that much more surprising when a 20 foot swell rolls up and tries to knock you off your feet. The weather's been unpredictable like that, with gusting winds that die away and leave it muggy and hot, followed by a brief rain shower, and then the sun comes back along with winds that whip the ocean into whitecaps and blow the equipment around as we try to arrange it on deck. Today we pulled up the long-term mooring that is the centerpiece of our ecological research here. It's made up of a time-lapse camera and several sediment traps attached to about 700 meters of heavy line. The mooring has been in place at this site almost continuously since 1989, collecting data on animal activity and particulate flux, which is then analyzed and correlated to try to connect surface weather and seasonal changes with activity in the deep sea. The sediment traps capture samples of the material that falls out of the surface waters (dead phytoplankton, zooplankton, fecal pellets, gelatinous material, etc.) in cups that rotate into place on a motorized track every 10 days according to a computer program. The material recovered from the cups is then looked at under a microscope to count and identify the organisms that have been trapped, and test the chemical composition, volume and weight.

The camera used to use 35mm film (and we still have that camera on the frame, to compare and keep the record consistent and continuous), but on our last cruise to Station M in June we also added a digital camera, so we were able to download the pictures and immediately see that the camera worked and captured about 2500 frames, one per hour since June 5th. Now comes the hard part - looking at each one of those frames, identifying animals of interest (fish, sea urchins, sea cucumbers, etc.) and large patches of detritus and counting and tracking them over time. Each time we collect data like this it adds to the value of the long-term time series, our knowledge about life in the deep sea and the surprising connections between the surface and the seafloor thousands of feet below.

After the mooring was recovered, the ROV Tiburon was launched and piloted to the elevator to pick up and deploy the enrichment chambers. As each one was placed on the sediment surface next to the elevator, the ROV hit a plunger that injected algae into the chamber. Control cores of sediment without algae were collected and brought back to the surface to compare the animals and microbes in normal sediment with the ones that will hopefully be stimulated to grow by the addition of algae. These cores are being sliced into sections, sieved and put into bottles to be shipped back to Aberdeen and analyzed later with specialized equipment.

If the weather cooperates, we'll put the long-term mooring back in the water tomorrow (we spent most of the day today re-attaching the lines and getting it ready to deploy) and get enough time for another ROV dive. We also want to test another type of robot: The Rover!

So long from Station M, Mike

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