Click on the Picture and check out the nice article on Svalbard and climate research published on Forskning.no
By Morgan Bender
With over 240 polar cod sampled, 30 weeks gone by, and 2.310 bags of precisely prepared, weighed, chopped and labeled portions of calanus fish food, the long term chronic dietary exposure experiment has come a great distance! Here is a small glimpse into what the sampling and experimental design has been like so far.
Periodic measurements on all fish in the experiment has allowed us to monitor growth throughout the reproductive development without removing the fish from the experiment. It also gave us a chance to check up on our favorite individual fish progress over the span of many months.
This cold room at Kårvika havbrukstasjon outside of Tromsø has been the experimental grounds for the duration of the project. The temperature of the water is now 3 degrees and the air isn’t much warmer, following the temperature variations of Kongsfjorden on Svalbard, where most of the fish are from.
Inside the cold room its polar night and has been since November following a 79 degree North light regime. That means that work for us is also done in the dark. A total of ten tanks in this room are used for the dietary exposure experiments and are monitored continuously by technicians at the research station.
Calanus copepods are one of the main food items for polar cod and we feed them a lot of it! The different doses of crude oil are mixed with this bright orange zooplankton and fed to fish twice weekly, the remaining food for the week is untainted calanus. Feeding is done by tank and biomass of the tank is used to calculate how much food that tank receives. This amount is adjusted based on growth and sampling every 6 weeks.
Work has already been done in the lab looking at sex steroid hormones extracted from blood plasma. This will give us indications of hormone signalling involved in reproductive development and possible endocrine disruption with chronic exposure to petroleum compounds.
Over the course of the experiment, smaller sampling points using unexposed fish have allowed us to narrow in on specific events in the reproductive process with regard to planning full sampling events at critical time points.
Samples of gonads have undergone histological analysis in pace with sampling to closely follow development. This methods require deep concentration as exemplified by Master student Libe Aranguren as she cuts 5 μm slices of tissue on a microtome using a very shape knife.
Our first results! Histological analysis of female gonad samples from early December reveal that fish are nearing spawning. Yolk gobules are forming the cytoplasm of the eggs as female fish invest more nutrients and energy into the gonadal development. Timing is most critical for females thus we are following their development more closely.
Text: Ingrid Wiedmann
Pictures: Camilla Svensen
High quality fish tanks are essential for live samples of polar cod to keep the caging effect as low as possible for subsequent ecotoxicological experiments. To ensure proper handling conditions, 17 volunteers of the CarbonBridge project (https://site.uit.no/carbonbridge/) examined the quality of the fish tank (water temperature, tank size and depth) on 80.5°N, 15°E under the harsh conditions in the Arctic Ocean. The fish tanks were found good in all aspect.
By Morgan Bender
Chose fish carefully, anesthetize efficiently, tag tactfully, measure and weigh accurately, place promptly in tank, repeat 700 times!!
This was the latest progress on the long-term exposure experiment. Despite the 25 degree sunshine blessing Kårvika, the biological station on Ringvassøya, Jasmine and I have toiled inside in the cooled 6 degree seawater lab. Over the course of 2.5 days, we have placed small rice grain sized PIT tags intraperitoneally in 716 polar cod, which will be exposed to three different doses of crude oil mixed with a diet of Calanus over the course of 6 months starting in the beginning of July. Initial measurements of length and weight were taken using a fancy fish measuring board that communicates with an antenna reading the tag inside the fish. The polar cod were admittedly quiet hardy and accepted the tags without much of a flinch in their sleepy state. These fish will be followed for changes in sexual hormone levels, growth, reproductive development, and energy, enzyme activities, and PAH concentrations in select tissues. Most fish are in a post spawning or immature stage with many larger fish in a thin state. We selected fish for the experiment from the many hundred collected during Polar night cruise this January based on size and condition, only “average” sized fish with some “meat on their bones”. With 1000+ choices, we hope that our quick decisions during netting will bring us closer to an even sex ratio. Our final experimental design includes a few extra tanks than previously planned; an addition control tank was added to be followed more attentively with narrower intervals between sampling events, allowing us to time sampling of the treatment tanks utilizing baseline knowledge from our “population” in the lab. We have also included two tanks that will provide information on significance of timing and recovery in the response to dietary crude oil exposure. One tank will not be exposed until after vitellogenesis, a central stage in the development of eggs and the other tank will be switched from a high dose to clean food at this same point, thus giving us information about recovery of fish. Currently all tanks are under a midnight sun light climate with 3 degree seawater, these conditions will change with the season to ensure that fish receive the necessary environmental queues to signal reproductive development. With fish happily settled in their new homes for the next six months, I start my next task- making 150 kilos of Calanus J‑ello shots laced with crude oil! Mathilde and Morgan tagging the last 250 polar cod on the last day!!
Experiment Completed: Three days ago, we completed our experiment. It was not without a lot of work and some troubles on the way.
After a mass mortality that seemed pretty much out of control in all our incubators and not at all dose related we were left with too few samples. After barely a week of exposure (start of gastrulation), we decided over a week-end (it always happens then) to start from scratch again!!!
Not without a lot of doubts and questions: Since our rock oiled system had been running for a week already, concentration is the water were already very diluted for this new start. Would we see any effects at all? Were we in such low levels that even sub-lethal effects would be tricky to see?
We needed to through away (well fix…) all the remaining eggs of experiment 1, to prepare the incubators for the new batches. But the fish left in our tanks seemed almost all done with spawning…would we find enough of then for a new start? Were we going to throw all away and not get enough eggs and sperm?
We took our courage “under our arms” and just did it!
New strategy: Obviously the egg quality was very different from female to female…basically spoiling all the incubators if you mixed all the eggs of all available females together. We thus separated the eggs from incubator to incubator, hoping that at least some of the eggs would be of good quality and not just die as soon as the development would reach a little more complicated stage than division…
And it worked, not without the (almost) loss of 2 out of 5 egg batches. But so far the data is really nice…not mortality from the treatment, but clear sub-lethal effects (see fig). The picture shows bachelor student Antoine and colleague Marianne stripping polar cod on sunday evening!
The Figure shows the larva from one batch of eggs (out of 5) at the end of the experiment (larva left after all previous samplings, etc). The blue bars are the percentage larva free swimming in the incubators, the red are those (still alive) malformed and laying on the bottom of the incubator. The numbers on the bars are the total count of larva per incubator.
Click on this link and you will see the heart beat of our eggs: embryotox
What is the scientific community doing these days in the Arctic? What are the challenges and risks for Arctic ecosystems? What are the effects of petroleum related compounds on eggs, larva, juveniles and adults? Is the Arctic more sensitive than other regions. We are certainly not (yet) finding answers to these questions… but by looking at a special Arctic fish — the polar cod- from all possible angles, we hope to come a bit closer to the answers.
A fantastic opportunity to share knowledge and develop new research ideas around this tiny but so important fish and the challenges of man-made activities in the Arctic. Click on the picture to download the preliminary programme. Pass this on, every one is welcome. If you would like to join, send an email to firstname.lastname@example.org
Yesterday, we started one of the years most exciting experiment..the oiled polar cod embryo experiment!! I am right now starting my 15th hour at work for today (only an hour more than yesterday) and the night is not over yet.… my sleeping bag is next to me just in case, but I do hope that I actually can drive the 40km home to Tromsø in about 2 or 3 hours.
After the wonderful job Ekaterina and Morgan did, fishing polar cod in the Barents Sea, the last few days have been punctuated by sleepless nights wondering whether our catch would spawn unexpectedly and thereby just throw away all our efforts to run an embryotoxicity exposure in the beginning of February.
The last few months, there has been a lot of people hard working on the design of the study and the set up. The engineers at our biological station have been doing a great job putting together incubators and oiled-rock columns. The picture above shows Morgan filling the columns will oiled rocks, that Luca prepared.
Finally the ripe fish were just too ripe for us to dare postpone the big day one week more: stripping and in vitro fertilization was on the timetable. The small group of Flemming, Luca, Morgan and myself spent much of yesterday finding out what we may have forgotten for a successful start. We were both nervous and impatient. I spent quite some time drawing a scheme on how the fertilization would look like. How many eggs in that beaker, so much sperm into this vial … I drew the plan at least 4 times, just to make sure I new it by heart and it made sense.
Finally we started and it went just perfect.
Today, for the first time of my life, I saw fertilized polar cod eggs, reaching the 2 cell cleavage stage, and the four and now they are at 32 cells. They are so beautiful.…I feel like a mother.…sleepless nights taking care of the newborn.