Mesocosms: The Middle World

Mesocosms- or a “medium world”- are at the heart of our fieldwork. Mesocosms are large enclosures that allow researchers to study the environment over a certain time period in a controlled way. The mesocosms we are working with are large bags, filled with natural seawater from the Norwegian fjord. The bags are closed off from the surrounding water and can be manipulated to test different hypotheses about how marine microbial communities function and respond to environmental factors. Mesocosm studies are useful tools to link patterns we see in laboratory cultures to the real world. Mesocosms truly represent a middle world for scientists!

One of our first tasks upon arriving to Norway was to setup and deploy the mesocosm bags. The bags are made of a thick, string reinforced plastic that are attached to floating frame and get filled from the bottom. The bags also have a detachable cone at the bottom 1 meter that will allow divers to collect sediments that have settled out (more on the importance of sediments later!). The cones were installed by professional commercial divers. The video below was captured by one of the divers during the time of deployment.

In Oceanography, you have to always expect the unexpected. During the mesocosm deployment, we had difficulty getting the bags, and the bottom settling cone, to sink. We had to come together to think of a quick solution to this problem. After trying several methods, taking multiple trips to the hardware store for weights,  and drilling several holes in the hoop frames, we were able to get the proper deployment!

Once the bags were deployed, we added nutrients (goodies for the phytoplankton!) to help give a jumpstart to a phytoplankton bloom. Three bags were excluded from nutrient additions (these are our control bags). Each bag was then equipped with bubblers to help mix the nutrient throughout the bag. Now we wait!


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