Moi Moi from (one-man) Team Finland
Also “Team Finland” works on answering the question why invasive populations of marine benthic species are often more tolerant to environmental stress than conspecifics in the species’ home range. For this, the archipelago around the Tvärminne Zoological Station in the Gulf of Finland offers conditions, which are rather special compared to the other GAME X study sites. It is a brackish system with a low biodiversity and the fieldwork season is restricted to the short nordic summer beyond 60 ° N.
The first information about Tvärminne Zoological Station I received from my local supervisor Patrik Kraufvelin was that he wrote me that “even the mentally strongest person can get mad in the loneliness in Tvärminne”. Since there are usually two students in each GAME-Team, but not for Finland in 2012, I took this comment seriously. So, I started my work in Finland a bit doubtful in the mid of April after postponing my flight to a later date because of the not unrealistic possibility to find the Baltic Sea covered with ice. Luckily the ice melted early this year and there was only some snow around the station and in the woods left. Also loneliness was not a problem, as many researchers and students from numerous countries like Hungary, Ireland, England, Canada and of course Finland gather here during the short fieldwork season.
Starting work was not easy as the laboratory infrastructure was not ready for use so early in the year.
The tanks that should later serve as water bathes were in a poor condition - standing outside the laboratory in the rain. Furthermore, the climate chamber reserved for the GAME project was still under renovation. However, these problems were solved until early May, so that the first experiments started in time.
The Tvärminne Zoological Station in May 2012.
Patrik Kraufvelin emptying the full trawling-net into a bucket.
For the first experiment, all GAME teams decided to go for mussels (Mytilidae) and the only species from this family that lives in the Gulf of Finland is the blue mussel Mytilus edulis. However, collecting the animals was more difficult than thought, since the winter ice scraped everything off the rocks in the first meters of the water column. Therefore, collecting mussels at the shore as it was done at most of the other GAME stations was not possible. After speaking to local SCUBA divers who knew where to find mussel beds, bottom trawling from a motor-boat with a very small net turned out to be the most effective method. With the help of Patrik (see photo), I gathered hundreds of individuals in a few hours.
The individuals were quite small with a mean length of around 1 cm. Their size together with the low water temperature here made it easy to keep each individual in its own container as oxygen consumption and ammonia production were low throughout the experiments.
When the climate chamber was finally fully equipped at the beginning of May, the mussels were already acclimated to the room temperature of 15 °C. The experiment was then set up fast. One day to prepare the water bathes (see photo) and a second day to measure the length and weight of 210
Size range (maximum, minimum) of the collected blue mussels (Mytilus edulis).
Experimental setup: three heatable water bathes with space for 210 small plastic tanks.
mussels and to put them in their private containers for the next 2 months.
My work during the experiment consisted mainly of doing a manual water exchange every second day in all of the 250 small containers to supply oxygen and to eliminate the produced ammonia.
Furthermore, the mussels had to be fed every day with a mixture of living phytoplankton ordered from an online aquaria shop. When a mussel died during the experiment, I measured its wet weight again. Then I removed the soft body from the shell and obtained the dry weight for both: the shell and the soft body to calculate the body condition index that gives information about the nutritional condition of the mussel.
I ran the first experiment from the beginning of May until the end of June without any further complications. The main idea of the experiment was to mimic transport conditions for “blind passengers” on ship hulls or in ballast water tanks. To facilitate the interpretation of the results only one stressor was applied, in this case heat. During the first stress phase, water temperature was slowly increased to create a mortality of at least 60% among a part of the mussels. This should select the most resistant genotypes among the test mussels. At the same time, another group of 30 individuals was kept at room temperature. The first stress phase was followed by 14 days of recovery and then both groups were stressed and the tolerance towards stress was compared between the two groups. If the group stressed twice would then be more tolerant, selection for robust genotypes during the first stress phase could explain this increased tolerance.
The second experiment started timely at the beginning of July directly after the first one was terminated. It will hopefully be finished by the end of August - before the plane back leaves for Germany. The species I am using in this second approach is the marine isopod Idotea baltica. Animals were collected by shaking the fronds of the bladder wrack (Fucus vesiculosus) over a bucket so that the individuals that clung themselves to the algae fell into the container. As the isopods were not very abundant, it took a whole day to
collect enough of them. I used the same experimental setup and the same stressor (heat) again. However, the handling of isopods turned out to be more difficult than the handling of mussels because they seemed to be more stressed by the lab conditions.
The water in the containers needed to be exchanged manually every day. In contrast to the mussels, which are filter feeders, the isopods are grazers
On my daily way to collect the bladder wrack tips for the isopods in the experiment.
and consumed tips of bladder wrack fronds that were also renewed every day. After some time, there was not much bladder wrack left directly around the station. So it was necessary to go out with the rowing boat every morning to collect 210 fresh bladder wrack tips. When the wind was stronger this was good physical exercise (see photo). However, despite all my careful precautions there was still high mortality among the isopods in the beginning of the experiment. Just before I was so frustrated that I considered switching to another species, the mortality dropped to a reasonable level. Maybe the transfer from the field to the lab was too much stress for some of the individuals in the beginning. Now the experiment is already in its second phase and should be finished in time before September. Then, I will have time for data analyses and thesis writing before the whole GAME X group meets back in Kiel in October.
Greetings from Finland Daniel
Afterglow at Tvärminne Archipelago at 11 o’clock in the evening.
