Tuesday, September 22, 2015

Torskevannet

If you look at a map and find all the places I've named so far on the route for this cruise, you'll notice we're traveling north and east. We started in Lonyearbyen, then hit up Kongsfjorden, Magdalene- and Smeerenburgfjorden, and finally Rijpfjorden, which is our turn-around point. Rijpfjorden is the northermost and easternmost fjord in the Svalbard archipelago, on the island of Nordauslandet. It's pretty different from the rest of the Svalbard fjords because it's primarily influenced by Arctic water coming down from the central Arctic basin. Along the west coast of Svalbard, the West Spitsbergen Current flows northward and brings with it heat, nutrients, and Atlantic organisms, so western fjords are much warmer and Atlantic-influenced. Rijpfjorden, by contrast, is a true Arctic fjord.

Contents of our Rijpfjorden trawl. Photo by Adrian Pop.
When I did my Svalbard image analysis last year, I found that stations in Rijpfjorden had the highest diversity of all of my stations - higher even than some on the north Svalbard shelf. I think that's mostly because Rijpfjorden is not as heavily influenced by sedimentation from melting glaciers, which sets it apart from the warmer western fjords. During this cruise, I once again got to observe incredible diversity in Rijpfjorden when my group did a bottom trawl at 200 m. The contents of our trawl could have supplied an entire semester-long zoology course with study material. There were sponges, soft corals, sea stars, crustaceans - you name it, we caught it. Paul, the leader of my course, commented that this trawl reminded him of the "old Svalbard," when the archipelago was renouned for its biodiversity. Nowadays, particularly the western fjords host large populations of Atlantic cod and haddock, so many of the invertebrates end up as prey.

Torskevannet
While we were in Rijpfjorden, there was just enough time for us to make an excursion onto land. We went ashore at a place called Torskevannet, which translates to "Cod Lake." The lake doesn't actually host any cod anymore, but it's still limnologically interesting. The lake sits behind a glacial moraine, and it has saltwater at the bottom but freshwater at the surface. At one point in time, the valley where the lake sits was a fjord, and the glacial moraine was a sill in the fjord. Then sea level fell, leaving salwater behind the sill, and freshwater from rain and snowmelt filled in on top. The result is a meromictic lake, with two distinct layers that don't mix. If you take a few minutes to dig through the pebbles in the glacial moraine, you're bound to find fossilized blue mussels, and a member of our group actually found one. The fossilized mussels indicate that the glacial moraine used to be underwater, but they also tell another story: the youngest fossils of blue mussels on Svalbard are from the Viking era, about 1000 years ago, but in recent years, blue mussels have returned. The first viable population was found in 2004, and the current hypothesis is that they were brought north as larvae in the West Spitsbergen Current. Read more about blue mussels on Svalbard here.

Zooplankton from Torskevannet
Ok, so the name of the lake is Torskevannet, or Cod Lake in English, but there aren't actually any cod in the lake. It's mostly inhabited by small zooplankton that can tolerate a wide range of salinities. We found a krill and an amphipod, but what's interesting is that the amphipod, Gammarus wilkitzkii, is usually found living on the underside of sea ice. Yes, things live on the underside of sea ice, and the communities are actually very unique. Anyway, G. wilkitzkii can allegedly tolerate salinities from 0 (freshwater) to 50 without breaking a sweat (normal seawater is 35, by the way). It has to have this wide tolerance because it normally lives in a mixture of melting freshwater ice and dense, salty brine, but this incredible tolerance also means it was pre-adapted to thrive in Torskevannet. It's really an impressive organism.

Bonfire on the beach in Rijpfjorden
We hiked around the lake for a bit and then headed back to the beach. There was plenty of evening left, so we built a bonfire and roasted hot dogs on sharpened sticks and reindeer antlers. Yes, I said reindeer antlers. We found several sets of them between the beach and the lake, and incidentally, they make great hot dog sticks. We relaxed and chatted, warmings ourselves by the fire, grateful for a break from our microscopes and the ship. Looking out over Rijpfjorden, where the ship sat waiting, we were witness to one of the most spectacular sunsets I've ever seen. The sky was completely clear, and the color of the sky was this intense, pure yellow that my camera simply cannot capture. The sea was just as intensely blue, and it reminded me of thick, undiluted paint in a Van Gogh masterpiece. Anyway, the sun chose to lay its head down right behind the Helmer Hanssen, giving us a beautiful view of our backlit ship. It was really a lovely excursion, and I'm glad I got to see Torskevannet.
Sunset behind the Helmer Hanssen in Rijpfjorden

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