The Molloy Deep
The deepest point in the Arctic Ocean is at 5500 m in the Fram Strait. It's a depression called the Molloy Deep, and it's also a HAUSGARTEN station. We steamed over here from the east Greenland continental margin and are collecting samples from the water column and the seafloor.
The Molloy Deep is a really unique place. It's basically a giant bowl at the bottom of the ocean, so it tends to collect organic matter that rolls down the steep sloping sides. The sediment is extremely fluffy on top but changes to thick, gray clay about 10 cm down. Very few species live here – there are sea pigs that crawl along the top of the sediment and digest whatever organic matter they can find, but that's about it. Most deep-sea sediments are chock-full of worms, but the Molloy Deep is almost barren.
The sampling program near the Molloy Deep is all about the benthos. A number of HAUSGARTEN stations fall very close together here to capture changes in the seafloor community across a depth gradient. Because the stations are so close together, the water column people don't really need samples from all of them and the sampling program turns into a seafloor marathon. Multi-core, box core, next station. Multi-core, box core, next station – five in a row most years. I helped sieve one of the box core samples this morning and enjoyed the chance to play in the mud.
I'm not getting any deep larval samples from this station, but I did take a surface sample with a small hand net. We found a couple bivalve veligers (little baby clams) that seem pretty similar to specimens I've seen at other stations. I wonder if they belong to a common species.
Finding any larvae near the Molloy Deep is actually pretty exciting, because it means one of two things: either this is the larva of a shallow-water species that's wandered way offshore, or this is the larva of a deep-sea species that swam all the way up to the surface. There are examples of deep-sea species that swim to the surface as larvae to feed (the hydrothermal vent crab Bythograea thermydon comes to mind), but I've never heard of any in the Arctic. I'll know more when I identify the bivalve species at home.
We have only a few more days of sampling left!
The Molloy Deep is a really unique place. It's basically a giant bowl at the bottom of the ocean, so it tends to collect organic matter that rolls down the steep sloping sides. The sediment is extremely fluffy on top but changes to thick, gray clay about 10 cm down. Very few species live here – there are sea pigs that crawl along the top of the sediment and digest whatever organic matter they can find, but that's about it. Most deep-sea sediments are chock-full of worms, but the Molloy Deep is almost barren.
The sampling program near the Molloy Deep is all about the benthos. A number of HAUSGARTEN stations fall very close together here to capture changes in the seafloor community across a depth gradient. Because the stations are so close together, the water column people don't really need samples from all of them and the sampling program turns into a seafloor marathon. Multi-core, box core, next station. Multi-core, box core, next station – five in a row most years. I helped sieve one of the box core samples this morning and enjoyed the chance to play in the mud.
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| A bivalve larva from near the Molloy Deep |
I'm not getting any deep larval samples from this station, but I did take a surface sample with a small hand net. We found a couple bivalve veligers (little baby clams) that seem pretty similar to specimens I've seen at other stations. I wonder if they belong to a common species.
Finding any larvae near the Molloy Deep is actually pretty exciting, because it means one of two things: either this is the larva of a shallow-water species that's wandered way offshore, or this is the larva of a deep-sea species that swam all the way up to the surface. There are examples of deep-sea species that swim to the surface as larvae to feed (the hydrothermal vent crab Bythograea thermydon comes to mind), but I've never heard of any in the Arctic. I'll know more when I identify the bivalve species at home.
We have only a few more days of sampling left!
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