Our project is going on and each new sampling point is a possibility for new innovative methods, some are time consuming, some are funny and others really expensive! The results are always a surprise either a positive one or a disappointing one. Here I will share with you 2 “case studies” of our first experiences on the project! But don´t get too excited…the heading says.
In February 2013, we had hardly started the project, but yet we were under high pressure to design an experiment of our BIO2008 students, which had already started the semester and needed to be linked to our project. As the project deals with combined stresses of both the environment (salinity, temperature…) and pollution (oil, heavy metals), we designed a exposure to look into the effect of both salinity and oil….assuming that our mussels in their natural habitat here in “Kvalsundet” were mainly exposed to high salinities. During the experiment, we acclimated the organisms slowly over 2 weeks, from an in situ salinity of 33 psu to 20 psu. Literature review had advised us that below 15psu, we may kill the animals.
The experiments went just fine, but the results did not show any amazing differences in responses between the salinities. A bit surprising. We left the matter there.
Now, having recorded light, temperature and salinity for the last 4 months, we got a surprise to see that the mussels were during certain periods daily exposed to extreme fluctuations in salinity. The figure below is one example: temperature in the air increased in the end of February, exposing the mussels to almost freshwater (5 psu) from snow melt during low tides.
This kind of results demonstrated how our salinity stress experiment with 20 psu was in fact far from what mussels in situ may experience in real…..
Now we will be much more prepared for the next years experimental work…
BINGO… or not
In our search for a method to measure growth of mussels in the field, we had several options, some good, some less good.
Our first choice was to measure the morphometrics of a group (n>100) of individuals of all size ranges that would be marked and caged. They would then be followed and measured again every 2 or 3 months. This was a tiresome methods and the marking and caging of each individual shell was not that straight forward, especially with the desire to avoid any confounding factors through for instance placing them in single small bags, which may create unnatural conditions…
The best way to mark them, we figured out, was to give them numbers with a marker. Black on black was unreadable, so a small white paint drop was used in order to have the contrast!
In the mean time, we also wanted a second, more accurate way to measure them and opted for a calcein bath: extremely simple, quick and reliable. The disadvantage is that you do not get the data out before you actually sample the animal and analyze the shells…a year later.
We combined both methods on the same animals and got quite funny looking shells then baptized the “BINGO” shells (in the calcein bath on the figure).
They were placed back in their cages for a month. Last time I went out, the mussels had lost their numbers! That was not a BINGO!
Well, the project is still at its infancy….we still have good time to improve!!!