Ground-truthing

I am sitting in the winch control room, a long room full of white tables covered in computer monitors and cables galore. The outer wall is lined with windows overlooking the working deck. Outside, the Arctic sun tilts towards the horizon.

A purple anemone (now closed up) collected for identification
during the ROV dive.

Today was our first day on station, and my team has spent the vast majority of it collecting samples. During an ROV dive, my colleague, Melanie, and I sat in the control van and showed the pilots which animals we wanted to collect. The AWI Deep-Sea Ecology Group has been monitoring the epibenthic megafauna in the Fram Strait since the early 2000s, and believe it or not, some of the species identifications are still unknown. Of course the easily-collected species were identified a long time ago, but there are still a few stubborn species holding out, refusing to be collected, keeping their names a well-guarded secret.

Particularly shady groups are the anemones and the sponges. Anemones that burrow into the sediment can close up and disappear into the mud whenever a collector approaches, so they are not very often found in benthic trawls. Today, we had the advantage of an ROV and the possibility of precise sampling with its manipulator arm, but many of the anemones still proved elusive. We eventually started launching stealth attacks, approaching the anemones quietly from the side, positioning the ROV’s slurp gun right above the specimen, and then turning on the vacuum. It only worked a few times, but that’s enough to identify another species.

A large sponge attached to a rock collected for
identification during the ROV dive.

Sponges are extremely difficult to collect for one reason: they live attached to rocks. You have your choice of collecting whole rocks (heavy and extremely difficult), or using an ROV to scrape the sponge off the rock. As you might imagine, getting a robot to scrape a small, delicate sponge off of a rock underwater from 2.5 km away is not easy. We did succeed, though! Four species of sponge made it to the surface.

Just to give you some perspective, there are over 20 putative species of sponge in the eastern Fram Strait, and two of the species we collected today were already known. It’s slow, steady progress, but friends, if Arctic deep-sea research were easy, somebody would have done this already.