Today has been more productive than expected: the nine upper parts of the mesocosms have been assembled (it was initially planned to unload the big truck this morning but we did it yesterday)! We spent the day “playing” Lego and fixed the different pieces together with Colson rings. We did it under the sun and a strong wind outside on the deck.
Some explanations about the mesocosms:
The structure we’ll use for the experiment is called a mesocosm and is divided in many parts: the roof to protect from rain, seawater spray, birds, …, the upper part which support the bag and buoys to maintain the structure at the surface, the bag itself and the sediment traps. All the structure has been invented by people from LOV, inspired from another project and adapted for our acidification experiment.
The roof is made out of a plastic tissue that leaves the light passes through. The material of the tissue is important because it doesn’t have to change the spectrum and intensity of the light. Every day we’ll perform light profiles in the mesocosms and outside to see if any difference is caused by the structure.
The upper part, what we did today, is a rigid PVC structure that has to support the bag and will be surrounded by buoys. It’s made with pipes connected together with plastic junctions and attached with Colson rings.
The polyethylene bag has a diameter of 2.3 m, a height of 14 m and a volume of around 50 m3. The material has been selected in order not to “contaminate” the water by passive release from the plastic and the whole upper part plus bags are designed to allow some turbulence generated by swell and currents inside the mesocosm.
The mesocosms end with a sediment trap and a diver will collect the material collected every day.
So, we still have lot of work to do before the mesocosms can be deployed! While we were building the upper parts, the divers (Jean-Michel, Bruno, Grigor and Didier) prepared the installation of the anchors.