OpKROP field blog
Field campaign March 2025: Follow our field blog here.
In OpKROP, we synthesize 20 year of data from Kongsfjorden that are based on measurements taken with moored instruments. While moored instruments provide high temporal resolution data, they are limited to a single spatial point. This raises a central question:
How representative are point measurements from the mooring for the wider fjord system?
To address this question, we will conduct four dedicated seasonal surveys of Kongsfjorden in 2025 to capture the biological system’s seasonality and monitor spatial heterogeneity across the fjord. We will use UiT’s unmanned surface vehicle (USV), Apherusa for continuous sampling with multifrequency hydroacoustic echosounders (EK80, WBAT, Kongsberg) to resolve the vertical distribution of fish and zooplankton (38 and 200 kHz) in the water column. The survey area will extend from Kronebreen in the inner Kongsfjorden to the mooring site further out in the fjord, thus expanding the geographical coverage of biological and biogeochemical observations. The USV surveys are complemented by additional measurements from KingsBay’s small vessel, MS Teisten, including CTD profiles, in situ optical measurements, water sampling, and zooplankton sampling.
OpKROP Field Campaign 17-31 March 2025
26 March: Still processing samples
It’s been another busy day in the lab for Laura and Estelle as the processing of the zooplankton from the pump experiment continued. After two days in the lab we now have taken over 600 pictures of copepods. The pictures will be used to determine the size, lipid content and coloration of each copepod. We will then analyse if any of these parameters can be linked to the timing of the vertical migration.
Meanwhile, the rest of the team prepared Apherusa for the tomorrows campaign. Emily and Kunuk managed to fix the winch on Apherusa during the stormy days last week. Now we could try out if everything was working as it should. Apherusa was launched again and the winch was now equipped with a light sensor that was mounted on a frame together with a CTD. Cruising around the harbour, Apherusa took several light profiles of the water column.
In between all the zooplankton, we also had the chance to observed four Orcas in the fjord just outside the lab. It is quite uncommon to see Orcas in Ny-Ålesund, so it was very exciting to spot them as we returned to the lab after lunch.
Photos: E. Coguiec
We have some data!
Last week, our colleagues from UNIS on board Helmer Hanssen were kind enough to take a a number of CTDs (i.e. vertical profiles of temperature and salinity) along a transect from the inner part of Kongsfjorden to the outer part. Here is the transect, showing that the water masses in the fjord now in March are very homogeneous. Water temperatures are below 1 degree Celsius throughout the fjord, and slightly colder in the inner part. We still don’t measure any fluorescence in the water column, indicating low algae biomass in the water.
When compared with similar data from last September, we see how much the water has cooled down now in March (from +8 degrees in upper 50 m in September 2024 to 0-1 degrees in March), while the surface layer of freshwater that is prominent in September (due to glacier and river-run off) has disappeared in winter.
Temperature, salinity and fluorescence along a transect from KB1 to KB5 (inner Kongsfjorden) 20 March 2025
Temperature, salinity and fluorescence along a transect from KB0 to KB5 (inner Kongsfjorden) in September 2024.
25 March: Sample processing
A busy day sampling is always followed by a busy day processing samples. The zooplankton team spent the day processing all the samples collected yesterday: 10 pump samples and 12 wp3 net! Abundance is low in the pump sample (common for this time of the year), but preliminary observations indicate a nice peak in abundance e of small copepods just after light starts decreasing (i.e. we caught the upward migrating populations). With a little luck we’ll be able to get more of a scatterer story once all net sample and the acoustics and light data are analysed together. Oveeall, it ws a busy day in the lab, and the work it is not yet finished.
Meanwhile, the Apherusa team got Apherusa back on land to continue fixing the winch. And in the afternoon, Jon conducted some light measurement just under the surface water in the harbor.
The weather was very nice and we enjoyed a nicely colored sky in the evening.
Photos: E. Coguiec
24 March: Evening migration
One aspect we are studying in OpKROP using the time series data from the mooring is vertical migration behavior of zooplankton. Some zooplankton species conduct diel vertical migration: they migrate vertical through the water column over a daily cycle, going to deeper waters during daytime and migrating to upper water layers during night. This an adaptation to minimize predation: when the sun is illuminating the upper water layers, organisms can hide at depth in darkness. And when the sun has set it is save migrate up to the surface and utilize food sources in surface layers. Using the acoustic sensors on the mooring (ADCP), we have studied these vertical migration patterns and how they change with season and environmental conditions. However, we still have open questions about who is migrating and what is controlling this behaviour. This is not as easy to study as one would think. It requires repeated sampling over the entire day, sampling over the short vertical intervals, and there is always the risk of disturbing the community when sampling at night with lights on.
Therefore, Laura and her colleagues at SAMS have come up with a new approach to try to catch the migrators at the time of top migration (at dusk or dawn, and during the equinox). A pump is deployed at 30 m depth just before dusk, with a hose pumping the water and the zooplankton community up on deck of Teisten where the sample is caught in the zooplankton net. This is done over several hours until the sun has set, resulting in a number of samples of the zooplankton community from 30 m taken in 20 min intervals. Differences in community composition and abundance over time will then provide insight who is coming to the surface during dusk. This set-up was tried out in Loch Etive (Scotland) a few weeks ago.
On Monday we tried this approach for the first time in Kongsfjorden. The team went out with Teisten to the mooring site at 5 pm and arrived early enough to set up everything to sample during the dusk-migration. Everything was ready to go by 6 pm and while the pump was pumping, the team could take a CTD profile and stratified net samples with the WP3 net (a net designed to catch larger zooplankton species). Nets were taken every hour, while pump samples were taken in 20 min intervals until 9 pm. Apherusa joined Teisten at the sampling site and remained stationary next to Teisten and recorded acoustics. Sampling went smoothly and the team returned to the harbor at 10:30 pm, where they first had to remove an iceberg before anchoring the boat.
(Photos: E. Coguiec)
22 March: Apherusa is launched
Today the zooplankton team processed the samples collected the evening before, while the Apherusa team couldfinally launch Apherusa. After some piloting testing in the harbor, Apherusa head out for its first survey around KB3, piloted by Emily and Kunuk from the marine lab. She returned back to the harbor just in time before the wind picked up again.
By evening, the wind had turned into a blizzard and we needed to protect our self as much as possible when going outside. That’s the Arctic in March!
maximal protection against the wind (Photo: E. Coguiec)
21 March: More ice and some sampling
The night was stormy, but the weather calmed down in the morning. The team was reshuffled today: Malin left in the morning and was replaced by Jon Cohen, our colleague from the University in Delaware who currently spends his Fullbright fellowship with us at UiT.
The plan was to go out with Teisten in the late morning to sample further in the fjord, but the storm in the night had consolidated the ice in the harbour and the team was first able to leave in the later afternoon to enjoy a cold but successful sampling trip to KB4.
We ain’t going no-where… time to switch to sea ice sampling? (Photo: Laura Hobbs)
20 March: Sample processing
The wind had picked up again, but after yesterdays sampling-marathon we had more than enough to do in the lab. David spend the day downloading data and calibrating his instruments; Emily and Kunuk continued fixing the winch on Apherusa; and Laura, Estelle and Malin sorted through 13 zooplankton samples, measuring a few hundred krill and arrow worms, photographing 100 Calanus, and setting up experiments.
It's a mens world (at least in March)
The Calanus population in Kongsfjorden in March was dominated by male C. finmarchicus. Male Calanus are short-lived, they reproduce and die, and are usually not observed for most parts of the year.
A grey and cold day in Kongsfjorden. Our colleagues from UNIS were in the fjord with on board of Helmer Hanssen and took the samples at KB3 that we did not manage to take yesterday.
19 March: Sampling and sea sick
Despite the ice in the harbour, we managed to get out with Teisten on Wednesday, 19 March. The aim was to sample at the mooring site and at KB3, one of our standard station in the deepest basin of the fjord. Our sampling included a CTD profile to measure temperature and salinity in the water column, water sampling from distinct depth to estimate the concentration of Chlorophyll a and suspended matter, optical profiling to measure absorption and scattering in the water column, as well as a number of zooplankton nets to determine species composition, abundance and biomass.
The wind had calmed and the sun was shining as we headed out. But once we approach our first sampling site we realised that the swell had build up substantially, which made Teisten a rather unstable platform. That made sampling (i.e. trying to stand upright on Teisten while deploying heavy gear and fiddling with small screws and bottles) rather challenging. In addition, half of the team had to deal with sea sickness (not a pleasant experience) and at -20 degrees we lost the feeling in our toes pretty soon (steel-capped rubber boots may be save but not warm). Despite all that, we actually got almost everything done! Between stations we dropped one team member off in the Ny-Ålesund, and were supplied with freshly backed cinnamon buns by another team member, which restored our energy level enough to enable us to sample most parameters at the second station. After 6.5 h at sea we could finally defrost in the marine lab in the later afternoon, and after a well deserved dinner we spend the evening processing the water samples.
18 March: Northerly winds and too much ice
We spend the day unpacking, setting up the lab and getting our USV “Apherusa” ready for action. The lab set-up was largely stress free, but the computer to pilot Apherusa caused quite some stress. But things worked out in the end, and we’re ready to head out for sampling tomorrow… if weather allows… It is still quite cold in Ny-Ålesund and in addition the wind started blowing strongly from the north, pressing a field of drift ice into the harbor. Teisten (the research vessel from Kings Bay) tried to head out today but could not get through the ice. The forecast says more northerly winds tomorrow, so we’ll have to wait and see if we start sampling tomorrow or not.
17 March: Arrival Ny-Ålesund
Our March campaign in Ny-Ålesund has started! It’s our spring campaign, or rather “spring-equinox” campaign because with temperatures around -20 degrees spring is definitely not in the air. But the light is back and we finally can enjoy the amazing landscape in all its Arctic glory. The March-Team consists of Malin, Estelle, Emily, Kunuk (all UiT), Laura (SAMS) and David (U Stratheclyde). The flight from Longyearbyen to Ny-Ålesund Monday afternoon provided a stunning views of snow-covered glaciers and mountains. Tomorrow we’ll unpack and hopefully head out to sample soon.
OpKROP Field Campaign January 2025
The January 2025 campaign marked the first of the seasonal campaigns. Having conducted polar night campaigns almost annually each January since 2012 we were well aware of the challenges of conducting marine surveys in darkness and in a season prone for low temperatures, strong winds, and poor visibility due to snowfall. With this in mind, we approached the campaign pragmatically and with tempered expectations. However, the weather and technology worked largely in our favor, making the campaign an overall success.
A team of six OpKROP researcher went to Ny-Ålesund from 3-20 January 2025. This included Malin Daase (project leader), Emily Venables (USV pilot), Tomasz Kopec (USV co-pilot), David McKee (marine optics), Maxime Geoffroy (hydroacoustics) and master student Carina Krämer.
The sampling plan (using state of the art mapping technology…)
Field diary
Clear skies and northern lights greeted us in when we arrived in Ny-Ålesund 6 January.
Apherusa was launched the next day, and on Wednesday, 9 January, we could conduct the first Apherusa survey around the monitoring site KB3, while Malin went out with Teisten to take water and zooplankton samples at KB3. The weather was on our side, cold but clear skies and relatively calm seas.
On Thursday, 10 January, we conducted a USV survey around the mooring site. Apherusa was piloted from shore, and David and Malin took Teisten to the site. Strong winds and high waves made sampling on board Teisten challenging and there was strong interference in the acoustic data from Apherusa, so sampling was cut short. The weather turned into a blizzard by later afternoon.
On Friday, we had full blizzard, but by Saturday, 11 January, we could go out again, survey KB4 with Apherusa and Teisten.
On Sunday we had another blizzard, but were busy in the lab processing samples.
On Monday, 13 January, the weather had calmed down and the polar night was at its best: full moon and clear sky.
We went with Teisten all the way to the inner part of Kongsfjorden, close to the glacierfront of Kronebreen. Emily and Tomasz piloted Apherusa from Teisten, Malin and David did the sampling. It was cold, but the scenery was beautiful. The WBAT showed high backscattering in the water column, suggesting a higher abundance of organisms here compared to the mooring site.
Tuesday and Wednesday, the weather had turned unpleaseant again. We made some attempts at sampling but had to return early. Thursday, 16 January, was our last sampling day and survey KB5 and went back to the mooring site for some zooplankton nets.
We also spend some time calibrating the EK80 on Apherusa.
On Friday, it was time to pack the lab and equipment. In the morning, a few test runs were conducted around the harbour with Apherusa and the 70 khz transducer. It was a cold and rather windy day, but we could get Apherusa out of the water before Dinner.
The weekend was spend punching data, Apherusa maintenance, packing and report writing. Maxime gave a talk in the Zeppelin lounge after dinner about his kayak expedition through the north-west passage last summer.
Aperhusa is back inside, safe and sound. Happy scientists!
Monday, 20 January, was departure day and Ny-Ålesund said Good Bye with purple skies! The light is coming back, and we will be back in March.
OpKROP Field Campaign June 2024
In June 2024, we had the opportunity to conduct a first field campaign in Kongsfjorden to try out Apherusa and conduct sampling using UiT’s reserach vessel Helmer Hanssen.
The main objectives of the cruise were:
- Hydroacoustic surveys in Kongsfjorden using the EK60 on Helmer Hanssen and “Apherusa”
- Recovery and re-deployment of two moorings in Kongsfjorden: currently, there are 3 moorings deployed in Kongsfjorden. The standard KROP mooring will be serviced in September, but the two additional moorings (ExFOOB) that have been deployed last year in collaboration with AWI and NPI were recovered and redeployed during this cruise.
- Pelagic sampling at standard stations in Isfjorden and Konsgfjorden
- Pelagic trawling to ground truth acoustic observations: to assess the species composition and biomass in the sound scattering layers detected by the EK60 and/or Apherusa trawls were deployed at selected sites.
We were lucky with the weather and had a very successful campaign and are ready for the next campaign in the polar night.
Successful recovery of ExFOBB1 in brilliant summer weather
Acoustic survey of the glacier front with Apherusa
Photos: Malin Daase (if not credited otherwise)