The Recovery of our Benthic Lander
It is always traumatic to deploy very expensive science gear into the marine environment. Like fishermen, the military, or anyone who uses the ocean, sometimes gear is lost. For us, this risk is even more troublesome because in addition to perhaps losing equipment worth many thousands of dollars, we also lose invaluable data and experiments. But, if we do not take these risks, we will learn nothing, and the quest for knowledge that will help us understand and manage our ecosystems is of vital importance.
—Steve W. Ross and Sandra Brooke
This morning we successfully recovered the first UNCW lander deployed last fall. Imagine a triangular bunk bed outfitted with a variety of instruments. There are probes for monitoring water chemistry, such as dissolved oxygen. A wide variety of settling plates of different materials hang on the structure. Some made of of steel, some of limestone, some of sandstone for examining microbial growth. There were other plates made from plastic foam and mesh for determining if texture plays a role in settling. A rotating sediment cup trap, which collects samples for 30 day periods before switching to a new cup, is on it, as well as a current meter called an ADCP (Acoustic Doppler Current Profiler). This data allows us to do some interesting things, such as matching the sediment by month with the current data for that month. That might allow us to say “this flow brings organic matter,” or “this flow has sandy sediment,” etc. We will be able to tell when the current reverses and can characterize water masses in the canyons by looking at things such as speed, direction, temperature and salinity. This long-term data will give us a more complete picture of what is happening over time, which will complement the “snapshot” we get with an ROV dive.
Soon after the lander hit the bottom last year, the ship triangulated its position. This gave us an approximate position of the lander to go by this morning. We hovered over its calculated position and Mike Rhode (UNCW) signaled its acoustic releases to drop the 600 pound weight that anchored the lander to the seafloor. By constantly pinging the lander for its range, he could tell it was rising off the bottom. Based on its rate of ascent, we estimated it would get to the surface at 7:10.
Everyone was scanning the horizon, and right on time, the lander surfaced just off the bow of the R/V Ronald H. Brown. We could see the red flag and yellow floats as well as the trailing float line. Several Common Dolphins were spotted nearby, we suspect attracted to the pinging of the lander. The ship steamed alongside the lander, grappling its recovery line, and used a crane to lift the lander on board. The sea swells this morning made the lander swing as we brought it on deck, which was challenging. However the ship’s crew and science team got it on board safely. After being tied down, the lander was surrounded by scientists taking pictures, examining their experiments, and getting it ready to redeploy later today.