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Ship activities – Page 2 – Polar Night Cruise 2017
Who said that the polar night is nap time? According to recent research, the polar night has a relatively high biological activity, disproving the common belief that everything goes to sleep during the full-night cycle in polar regions. If you ask my small critter, life goes on like usual even if the lights are off! You can think of them as teenagers at New Year’s Eve instead of grandparents getting ready for bed…
And I think that this is very interesting! So here I am, studying small copepods (small crustaceans at the base of the food web) during this Polar Night cruise. My aim is to gain an insight of their reproductive output during winter and relate it to the distribution of their different life stages.
The big picture is to understand how small copepods’ ecology differs from the bigger copepod species. It is believed that small copepods will adapt more easily than the bigger species to a warming Arctic. This is due to their different ways of living. Most big copepods hibernate for winter and possess a long life cycle adapted to the strong seasonality of the Arctic. It is predicted that in the future, the Arctic algal bloom (the food source of copepods) will arrive earlier in the spring and there will be a second autumnal bloom. Therefore, it could prove challenging to adapt to an earlier food supply when their life cycle is timed to a later productive season.
On the other hand, small copepods like Oithona similis and Microcalanus sp. have a more flexible biology, meaning they can live in a wide range of temperatures (they are found throughout all of the world’s ocean). They have shorter life cycles, but reproduce year round which means that their offspring can take advantage of any productive food event.
To help me I have Peter Glad, the Filtration Guru, whom I want to thank for his invaluable help during the cruise. Peter helped me filter the water at our different sampling stations. Water filtration gives an indication of the amount of food available to small copepods, both algae and detritus. The amount of food available can then be linked to their metabolism and their reproductive output.
The fish team has been using a MIK net to sample the pelagic (open water) zone during our cruise. A MIK net (shown in video below) has a large opening and can be towed at certain depths and is eventually brought to the surface.
Things were not so calm the day the fish team brought up this net! Around this time it was -14C with winds up to 17 km/hour. Brrr. Thanks to Malin Daase for this excellent video!
We are now in at 81N, 14E. It took us some time getting up here, but we are finally north of Svalbard!
One of the reasons to travel this far north is to look for ice-associated amphipods. Amphipods are members of the crustacean family, and can be found in many different marine and freshwater habitats. In the Arctic, amphipods can be found in the benthos (sea floor), in the pelagic (open water) zone, as well as under and within sea ice.
Arctic sea ice has been drastically changing—it has become thinner and the overall extent of sea ice has been shrinking. While disappearing sea ice has immediate consequences for larger marine mammals that rely on sea ice for a hard surface to give birth (many species of seals) and to travel and hunt (polar bears), the smaller animals that use sea ice as habitat will also be affected.
In 2012, researchers found one ice-associated amphipod species, Apherusa glacialis, as deep as 2000 meters, far away from their sea ice home. They suggested that Apherusa might be using deep-water layers to overwinter, then migrating back up to the sea ice in the spring. This hypothesis (which you can read more about here) is compelling, as many scientists wonder how ice-associated organisms (from amphipods to polar bears) will survive without sea ice. Therefore, we are on the hunt for amphipods. We are casting deep-water multinet samples (as deep as 1800m!) to see if we can find any of these ice-associated amphipods in deep water. So far, we have found two Apherusa glacialis at 800-400m depth (one juvenile and one pregnant female).
While the sun never rises above the horizon up here during polar night, it does get a little brighter in the southern sky at midday, around the hours of 10am and 2pm. Add to that some light from the moon which is getting fuller every day, a little light from the stars, and a dash of aurora (northern lights), and there are quite a few photons here. In all, this makes for an interesting mix of skylight that still appears pretty dim to the human eye, but can be measured with instruments we have brought along. So each day at noon, Kim Last and I dress up in our warmest clothing and measure these photons in the sky. We have made a great set of measurements so far, starting as we left the dock in Tromsø, and continuing through today here in Krossfjorden. A big theme of the Arctic ABC project is light, and these measurements will be useful for interpreting the data generated by ice-tethered POPEs to be deployed in the near future.
But there is another bit to all of this. Many zooplankton swimming around in the waters up here produce their own light – they are bioluminescent. We have also brought along instruments to measure bioluminescence in the ocean. After Kim and I measure light from the sky, I run down to the CTD garage and lower these instruments, which we call the “light cage”. It takes about 30 minutes for the cage to descend to around 100 meters, stopping at intervals along the way to slurp up luminescent animals and record the light that they emit. Once the cage is back on the ship, I recover the data and after the cruise will examine how much bioluminescence exits at our stations, and determine the identity of the organisms doing it, which can be done by looking at the speed that the flashes of light occur.
In all, measuring light in both the sky and underwater is providing us with information on quantities of light that are not obvious to the human eye, but are important parts of marine ecology in the polar night.
It’s very rare indeed that you can immerse yourself in science, 24 hours a day, for days on end. But that’s exactly what’s going on aboard the HH (R/V Helmer Hanssen). We sleep (a little), eat (really great food) and work, (“crunch” data) and discuss science (when not sleeping, eating or crunching data). It’s terrific, and a privilege to be part of this cruise!
I’m interested in zooplankton behaviour and how they respond to light, or more specifically lack of it. You see, most of the planet experiences very regular light/days cycles with virtually all biological processes “entrained” to this cycle. Underpinning this is the circadian clock, a molecular machine which allows animals and plants to anticipate future cyclic events, much like you or I when we wake in the morning just before the alarm clock goes off – it’s our circadian clock, not the alarm telling us when to rise! In order to study this process we need a special device that measures cyclic behaviour, no mean feat when you are looking at a zooplankton only a few millimetres long. We use arrays of “activity monitors”, more usually found in labs working on fruit flies, which enable us to house hundreds of animals all individually swimming about in test tubes about the length of your index finger. If we see a rhythm of activity we know that this is the expression of the circadian clock and may aid survival when light is limiting. However, the activity monitors also provide data on frequency of swimming, telling us if they are hibernating or still actively looking for food. We can also tell differences between male and female swimming, useful for example, in understanding mating behaviour. Ultimately, since zooplankton are at the base of the food chain, supporting fish stocks and sea mammals, deciphering how they function and survive during the Polar Night is central to what we aim to achieve. However such science requires a lot of teamwork and without the researchers aboard the HH to help, and for inspirational discussions leading to new experiments, none of this would be possible.
Now it’s time to sign off and check on the animals, download the latest activity data. It’s a bit like being a detective I imagine, the data will hold clues and lead to the next experiment. I suspect it might be a long night.
Now that we have safely transferred the Arctic ABC technology team to the Marine Laboratory in Ny Ålesund with all their equipment, our plan was to first to head west towards the shelf break for one deep station in the core Atlantic water inflow; then we wanted to head north towards Rijpfjorden and the shelf-break north of Svalbard. Well, again weather changed our plans and, again, we have to adapt our sampling program. The wind had picked up after we had last checked the weather forecast in the marine lab in Ny Ålesund and a storm warning was now, again, on the horizon. Besides the difficulty of operating our gear in strong winds (and people’s stomachs feeling unhappy) the team on the bridge is very concerned about icing of the vessel. With the winds coming from the northwest and high waves hitting the boat and coming over the bow, the vessel would be covered in a solid and heavy ice layer, adding a lot of undesired weight. The only option at the moment is to stay in the fjord.
While this is rather (very) frustrating, all 14 of the science crew still onboard quickly agreed that no valuable ship time should be wasted by just sitting and waiting for better conditions. The observant cook must have noticed our disappointment and handed out a round of ice cream as we sit around the couch table in the lounge next to the mess and discuss our options. With that treat and the sense of an unexpected opportunity it takes no longer than some minutes before the group comes up with all kinds of new plans! Coralie sets up a new 3-station transect stretching across Krossfjorden (just north of Kongsfjorden where Ny Ålesund is located), Kim and Jon design an additional experiment to study individual copepod behaviour of a different species than before, Martí moves his planned experiment to this fjord, the trawl team hopes for more polar cod that are in good enough shape for sampling and so on. Soon we are underway to the innermost part of the fjord in the vicinity of the glacier front. And actually the moon is lighting up just enough of the winter wonderland fjord scenery to get a sense of place. In the protected fjord waters, sampling progresses according to Plan B (well, perhaps Plan M by now). We do keep up our hopes for better weather to allow offshore sampling!
Yesterday, we stopped in Van Mijen fjord to deploy CTD’s, collect grab samples of the benthos (the bottom of the sea floor), and zooplankton data using a multinet.
Associate Professor Tove Gabrielsen (University Centre in Svalbard, UNIS) is part of the FAABulous project, another research project under the Mare Incognitum project umbrella. The FAABulous project, or Future Arctic Algae Blooms and their role in the context of climate change, studies the ongoing changes in Arctic primary production due to decrease in sea ice over and the resultant changes in light conditions. Eva Leu, another member of Mare Incognitum, is the project leader.
Tove studies microbial protists (organisms made up of a single cell), and she identifies small protist species and further investigates drivers in protist community composition in Svalbard fjords. As seen in the photo below, Tove is taking the top centimeter of the grab sample from the benthos to analyze later at UNIS.
Associate Professor Janne Søreide (University Centre in Svalbard, UNIS), also took samples from this fjord. In addition to teaching a sea ice course in Van Mijen fjord, she is interested in the zooplankton community structure in this fjord system. What is the ecological role of ice in Van Mijen fjord? It is documented that small creatures use the tiny cracks and crevices in sea ice as a nursing area. If ice disappears in this fjord system, can these small organisms survive without the ice? To answer these questions, Janne and her master’s students will study what organisms are living in this fjord and who is using the ice habitat. Janne looked at the rest of the grab sample to look for any ice-associated meiofauna (small benthic invertebrates) and any adult organisms that produce meroplankton (larval stages of larger organisms like sea stars, urchins, and mussels).
In previous posts we discussed taking biological samples with a multinet. A multinet is a multiple plankton sampler that is pulled up vertically through the water column. It can carry up to 5 different nets, and each net can be programmed to open at particular depths within the water column (for example, 500-200 meters).
Here, the R/V Helmer Hanssen is pulling up the multinet:
After the multinet is on the trawl deck, each net is rinsed with a hose to ensure that all the zooplankton make it into the red containers below.
The red containers are brought into the laboratory, where organisms are sifted into small bottles and analyzed at a later time (usually when the boat is in calmer seas, because it isn’t quite fun looking through a microscope in rough seas!).