The northern stations
After stopping in the east near Svalbard, we headed north. Long-term research stations in the HAUSGARTEN stretch up to nearly 80° N, which is usually where we find the ice edge. Not this year. We were headed deep into the ice.
One of our biggest tasks at the northern stations was to exchange two long-term oceanographic moorings. These large installations include an array of physical and biological sensors deployed on a line that stretches vertically through the water column. The instruments collect temperature, salinity, oxygen, and other data year-round, but they also collect something else: biofouling.
For the past 4 years, I've treated moorings in the Arctic as experimental substrata and collected whatever settles on them. I started out by deploying my own samplers on the mooring lines but then later realized there was more biodiversity in the organisms fouling up the oceanographic instruments than those landing in my samplers. Now every time a mooring comes up, I stand out on deck with forceps in hand (to the amusement of the mooring team) and pull specimens off the floats before they get power-washed.
The moorings being recovered this year are actually 2 years old – they were put out in 2019, the last time I was on board – and they've got some really fascinating growth on them. The most common species I found were all hydroids. They kind of look like hair when hanging from an instrument out of the water, but if I put them in a dish under the microscope, they spread out and are really beautiful. Most hydroids have a two-phase life-cycle with an attached seafloor stage and a swimming pelagic stage. In the swimming stage, they look like little jellies.
I had long suspected that the hydroids we found on the moorings had a swimming medusa (jelly-like stage) that enabled them to disperse far and wide through the Arctic and that this broad dispersal is what allowed them to reach our moorings. This year, I was finally able to confirm my suspicions for two of the most common species. I was used to seeing their beautiful little polyps (we call the regular ones "autozooids") under the microscope, but this year, my specimens also had what are called gonozooids – polyps that are specialized for reproduction. I could see new structures developing inside the gonozooids, too - orange streaks leading to masses of tissue that did not resemble the autozooids
at all.
But here's the key: elsewhere in my dish were medusae. Swimming jellies with the same orange streaks, the same general size and shape as what I saw developing in the gonozooids. The jellies must have been budding off of the hydroid right there in my dish!
It's really awesome that I can now directly link hydroid colonies that live attached to a hard surface with the medusae they bud off and send into the water column. I can also conclude that the species I observed reproduce in June – which is important information in itself. I'm not sure if anyone has studied these species before or figured out how they reproduce, so I'll have to check the literature when I get home.
Toward the beginning of the cruise, I made a list of all the common species in the HAUSGARTEN and what is known about their reproduction and larval biology. Obviously, there are a lot of blanks, and it occurred to me that the only way to fill those blanks would be to study them one at a time. Today, I'm able to fill in a blank for two common hydroid species: they reproduce via a medusa stage. Having a swimming stage in their life-cycle helps them disperse broadly across the Fram Strait, and they're also not picky about where they settle (plastic oceanographic instruments seem good enough).
It's a good feeling to figure that out.
One of our biggest tasks at the northern stations was to exchange two long-term oceanographic moorings. These large installations include an array of physical and biological sensors deployed on a line that stretches vertically through the water column. The instruments collect temperature, salinity, oxygen, and other data year-round, but they also collect something else: biofouling.
For the past 4 years, I've treated moorings in the Arctic as experimental substrata and collected whatever settles on them. I started out by deploying my own samplers on the mooring lines but then later realized there was more biodiversity in the organisms fouling up the oceanographic instruments than those landing in my samplers. Now every time a mooring comes up, I stand out on deck with forceps in hand (to the amusement of the mooring team) and pull specimens off the floats before they get power-washed.
 |
| Autozooids and gonozooids of the hydroid Stegopoma plicatile |
I had long suspected that the hydroids we found on the moorings had a swimming medusa (jelly-like stage) that enabled them to disperse far and wide through the Arctic and that this broad dispersal is what allowed them to reach our moorings. This year, I was finally able to confirm my suspicions for two of the most common species. I was used to seeing their beautiful little polyps (we call the regular ones "autozooids") under the microscope, but this year, my specimens also had what are called gonozooids – polyps that are specialized for reproduction. I could see new structures developing inside the gonozooids, too - orange streaks leading to masses of tissue that did not resemble the autozooids
at all.
 |
| Stegopoma plicatile hydromedusa |
It's really awesome that I can now directly link hydroid colonies that live attached to a hard surface with the medusae they bud off and send into the water column. I can also conclude that the species I observed reproduce in June – which is important information in itself. I'm not sure if anyone has studied these species before or figured out how they reproduce, so I'll have to check the literature when I get home.
Toward the beginning of the cruise, I made a list of all the common species in the HAUSGARTEN and what is known about their reproduction and larval biology. Obviously, there are a lot of blanks, and it occurred to me that the only way to fill those blanks would be to study them one at a time. Today, I'm able to fill in a blank for two common hydroid species: they reproduce via a medusa stage. Having a swimming stage in their life-cycle helps them disperse broadly across the Fram Strait, and they're also not picky about where they settle (plastic oceanographic instruments seem good enough).
It's a good feeling to figure that out.
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