A slow start & sunny days in Husö, Finland.

We are Carmen (DE) and Sofia (FI), and together, we make up Team Finland 2022. Team Finland is working on the Åland islands at the Husö Biological Station, which belongs to Finland’s only Swedish-speaking University, Åbo Akademi University. The GAME topic of 2022 is the effect of artificial light at night (ALAN) on mussels, and in Finland, we will work with the blue mussel, Mytilus edulis, since it is the most abundant mussel species in the Baltic Sea. The blue mussel is a filter feeder and due to its capacity to effectively filter water it is an important component of coastal ecosystems in many temperate regions worldwide. Adult blue mussels filter up to 3 liters of water per hour(!) thereby improving the water quality immensely.

Location of the Åland archipelago and the Biological Station Husö.

To see how ALAN will affect our test organisms, we first need to acquire information about the mussels’ natural biorhythm. For this, we want to run a pilot study in which we do time-lapse photographing of the mussels over a 24h period. Although, the presence of a biorhythm has already been established for some populations of Mytilus sp. (Gnyubkin, 2011), no information about mussels from the central/northern Baltic Sea is available. As soon as we have determined the time when our blue mussels are active and inactive, we can schedule the daily feeding of the mussels in a way that it matches with their period of maximum activity. This is important as we do not want to superimpose a change in the natural rhythmicity of the mussels by the timing of the feeding events.

In the main experiment, during which we will expose the mussels either to the natural day/night cycle that currently prevails here in Finland or to artificial light at night, we will look at the following response variables: siphon area, clearance rate, byssus number, and byssus strength. The siphon is the opening in the mantle through which mussels filter feed, and its area is representative of the feeding behavior of the mussels. The clearance rate, in turn, quantifies how quickly food particles vanish from the water in the experimental tanks and, hence, is an indirect measure of the filtration rate of a mussel. Byssus is the strands that mussels produce for attaching themselves to surfaces and its production is energetically costly but necessary for the survival of mussels. Therefore, it could be detrimental for them if they are inhibited from allocating energy to byssus production. This is, for instance, the case when they are stressed and therefore need to invest energy in the compensation of stress effects. If ALAN is a stressor for mussels, it could impair the water cleansing service that mussels provide and from which also we as humans benefit.

Carmen will add a predator treatment to test whether there is an interaction between ALAN and the presence of a predator. The chemical cue that is released by a predator and which Carmen will inject into the experimental containers will function as an additional stressor that will be combined with the different light treatment levels. Although, it is our first and foremost goal to assess whether or not ALAN affects mussels in any way, it is also interesting to see whether the effects of other stressors change under the influence of nightly illumination. Carmen will be using the mud crab, Rhithropanopeus Harrisii, as a predator, which is an invasive species in the Baltic Sea. Relative to other possible predators of mussels, it is easy to catch and to maintain in a laboratory environment. 

However, first, we have to do pilot studies to explore the mussels’ biorhythm and their sensitivity to red light, which our mussels will be subjected to when we capture photographs of them in darkness. In Finland, summer nights are short, so a day-night cycle of 12h + 12h is not realistic, and therefore we must adjust our period of darkness in the lab accordingly, which we achieve by connecting a dimmer to the lights.

Experimental setup at Husö.

I – Carmen – was the first one of us to travel. Even though I had a lot of luggage with me (it is 6 months of experiments in a foreign country!), the trip itself was extremely nice and even kind of relaxing. Covid restrictions have been lifted in most places in Finland and life almost felt normal again. The only part that was stressful about this long trip was the planning. What do I need? How do I pay for everything? How do the new country and its laws differ from ours? In the end, everything went far smoother than anticipated, which I have been very grateful for. Living abroad for half a year can be a scary concept, but all the collaborating institutes and stations work tirelessly to make the process as easy as possible for the foreign students. During my travel preparations I have been in constant contact with the Husö station’s employers. They have helped me figuring out how to best travel to Husö, what I would need to bring with me and how life at the station works. An additional help had been the previous year’s German GAME participant Helen who gave me an insight into her time abroad in Finland. GAME is a collaboration between many institutes and therefore, a helping hand can be found anywhere. Something I haven’t considered, though, is getting vaccinated for Tick-Born Encephalitis. Something that I am currently fixing by getting the vaccination shots here in Åland.

We have been at Husö for over six weeks now. When we arrived at the end of April, it was still around 10°C, while for this week, forecasts show temperatures from 28 up to 32 degrees, so summer has begun here in Finland. We were eager to start the project right after arriving and finishing the introductory course. Unfortunately, there were delays in getting all the necessary equipment, such as everything we need for starting our own microalgae culture, and there was not much we could do about this but wait. In the meantime, we built the setup, since we were lucky enough to have the necessary tools and competent help at site. We have, furthermore, done the pilot study in which we explore the biorhythm of the mussels. For this, we did time-lapse photography of 4 mussels for 24 h to see when they are most active during the day-night cycle. Unfortunately, we did not analyze the results yet since we had thought we had to wait for a cable to arrive that transfers the pictures to a computer. It then turned out that all you need is an app and wifi. However, we are planning to do the pilot study again anyway, since one of the mussels in our previous attempt was found dead. The mussel individuals we used were also small, under 1 cm in length, what makes it difficult to work with them. During the second time that we went out in the field to collect mussels, we managed to find mussels over 2 cm. Using bigger mussels has the advantage that the siphon area is easier to see. 

In general, our mussels are smaller than in other locations due to the brackish water, i.e., the combination of saltwater and freshwater, in the Baltic Sea, which is a stressor and makes the animals allocate their resources to osmoregulation instead of growth. The Baltic Sea is less saline due to the numerous rivers that flow into the Baltic Sea from 14 surrounding countries. The surface water in the central Baltic Sea and the Åland region has a salinity of approximately 7, while the salinity of oceans is 35. 

One of the best aspects of biology is fieldwork. We collected our mussels in the waters of the Åland islands and got to the mussel beds by boat. Additionally, we collected mud crabs that will provide the predator cue in Carmen’s experiment.

Collection of mussels in the Åland archipelago.

What GAME has taught us so far is the following: expect the unexpected. In March, all teams of this international project spent a month together, supervised by Mark Lenz, preparing themselves for running the experiments at the different stations. We went through every single detail we could think of that might become an issue while conducting our experiments, and yet, more and more challenges have arisen that need to be solved. In science you can spend an infinite amount of time planning your experimental work and still not foresee everything that will happen once you get started. 

Our team supervisor, associate professor Christian Pansch-Hattich, has been a great help to us so far. Whenever we have any questions, he is there for us to discuss possibilities and look for solutions. He helped us acquire the necessary equipment for our microalgae culture that we need for feeding the mussels, and now we can finally start with the next part of our work, which is studying the feeding behavior of the mussels. Our mussels will be fed with the microalgal species Rhodomonas salina, which we will cultivate in large quantities in the lab, from the starter culture that we received. 

Since the culture’s cell concentration has gotten dense, we will need to start a new culture soon. So far, maintaining the microalgae culture feels like the most challenging part of the project, since there are a lot of different aspects – like keeping everything sterile, adding vitamins and medium at the right time, keeping them at the right salinity, etc. – that need to be considered when cultivating microalgae. Even though it is a slight challenge for us right now, once we get into the routine, we will surely also solve this problem. Luckily, we have weekly meetings, together with the other GAME teams and Mark Lenz, in which we exchange ideas and discuss the complications and challenges we face, and at the same time, these meetings help us keep motivated. 

Rhodomonas culture at Husö.

Since we have not been all too busy yet, we have taken the opportunity to enjoy our time here at Husö. The station is in a beautiful location right by the sea. A wood-fired sauna is warm twice a week, and in between enjoying the warmth, we go swimming or sip a drink outside, which is very relaxing. On other days we have also gone kayaking and biking and have visited a neighboring farm to take their two horses for a stroll. Later in the evening, we might gather for board games or a movie, and when there are enough people at the station, we can also play volleyball together.

Kayaking in the waters of the Åland archipelago.

To summarize, although it has taken an unexpectedly long time to get started, we have now acquired all the missing equipment, meaning that we can finally begin our experiments. We are grateful for our supervisors and everyone else who is helping.

Team Finland: Sofia (left) and Carmen (right).

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