# posted by Maren Wellenreuther
Hanna and I are in northern Norway to sample populations of seaweed flies (Coelopa frigida). As the name indicates, these flies live on seaweed that has been washed up on the shore and form wracks. The temperature in these wrackbeds can easily be 30 degrees above the ambient temperature and it is therefore no surprise that you can find these flies thriving year round, even in these northern latitudes. We are interested in how the flies manage to survive in different habitats (e.g. gradients in salinity, exposure, extremes of temperatures), and are planning to compare populations in southern Sweden with populations in northern Norway. Comparisons will entail genomic and transcriptomics analyses of adult and larval life stages, and experiments testing fitness in different habitats.
We arrived on Tuesday and have been studying the maps of the coastline to find stretches that are exposed to ocean swell, which is needed for the accumulation of wrack. The expansive fjords that characterize the landscape in this part of Scandinavia make is hard to get to the outer coast, and the journey from one side to the fjord to the other typically leads over numerous tunnels and bridges that seem to disappear in the sky. Snow covered mountains are framing the view wherever we go and the temperatures that we have experienced during the days have ranged from -15 to +7. All in all, this part of the world is full of extremes and stunning beauty.
Yesterday we found our first population. We traveled all day to an exposed stretch of coastline north of the town Bodo, which is only accessible with a short ferry journey. At the very end of the fjord we found an 80 cm deep wrack, and surely enough, seaweed flies were abundant at that site too. It had just been raining heavily with gale force winds, so all adults were hiding among the wrack.
The flies were cold and did not move at all, which made sampling easy, because we could literally pick the flies up by hand and drop them into the Eppendorf’s. At the end of the sampling the rain and wind stopped, and within minutes all the flies came out and ‘basked’ in the light.
All the best to Lund and happy greetings from the Lofoten!