Tuesday, May 17, 2011

Seafloor Photography: Imaging the Ocean’s Secrets

May 16th 2011

One of the major research goals on this cruise is to examine the biodiversity and biogeography of corals across the Drake Passage. We are doing this in two ways on this expedition – the first is through physical sampling, such as trawling, dredging and coring; and the second is by taking images of the seafloor using the two camera systems we have onboard. Though as a biologist, having your hands on actual samples is the ultimate goal, sometimes there are better ways to examine the diversity of what lives on the seafloor than by collections alone.

Though underwater camera systems have been used in the ocean for many years, the advent of digital photography has seen a boom in both the number of systems and the sheer volume of image data available to us. On the ARV NB Palmer right now we have a TowCam and a DropCam, both of which have already been deployed and brought us fantastic photos of Burdwood Bank – our first sample area which we left a few days ago. The TowCam is a towed camera system – pulled behind the boat for 3-4km distance, and “flown” just 5m off the seafloor – this system brings back around 2000 images from each tow, showing us both what the ocean floor looks like, and what animals live there.

This system is great for giving us an overall look at what is there, but for a closer peek, we deploy the DropCam. While the boat is holding still we drop this camera to just 2m off the seafloor where a trigger weight is tied off. When this weight hits the seafloor, it takes a photo, we then pull it up a few meters, let the boat move, then drop it back down again to take another. In this way we “bounce” across seafloor features. Though this system can’t cover the large distances the TowCam can, it does take high resolution close up pictures, allowing us to identify more of the animals and relate that to what we see in the TowCam images and also to what we collect in our trawls. These two systems compliment each other and allow us biologists to see not only how diverse and abundant our corals are, but also how these animals live in their natural habitat on the deep-sea floor.

By: Rhian

Weather: Temperature 37°F, Windchill 16°F, Windspeed 15-20 knots, cloudy with sunny intervals

The WHOI TowCam is deployed from the Starboard A-frame by our MPC, Skip (L. Robinson).

ET Sheldon works tirelessly to get the DropCam ready for its first deployment on Burdwood Bank (A. Margolin).

Stian, Ben and Marc deploy the DropCam early in the morning at Burdwood Bank (R. Waller).

Why we biologists love deep sea images – on the left is a Thouarella sp. bottlebrush coral collected by the trawl and on the right is an image taken by the TowCam showing lots of corals all living together around a boulder alongside other species of coral and coral (NBP11-03)

An image from the DropCam, showing lots of corals and anemones living at 800m depth on Burdwood Bank (NBP11

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