Filling of the mesocosms

Mesocosm filling

Ulf Riebesell by Ulf Riebesell on 6.9.2019

Filling the mesocosm enclosures sets the stage for everything to come. So you want to be sure that the filling is done as smoothly as possible, to minimize damage to the plankton community, particularly to the larger and more fragile organisms. You also want to ensure that the filling is done simultaneously and from a single water source, equally distributed over all mesocosms, to have the same plankton community with identical organism abundances in all enclosures. Also important, the source water should be representative for the type of pelagic ecosystem you are aiming to study. If you mess up the filling, the rest of the experiment can become meaningless. So the day of filling is always a bit tense. Did we forget anything? Is all the equipment functioning well? Does everyone know what they are doing?

Mesocosm filling 1 PLOCAN Uno (in the back) anchored in Melenara Bay, running the massive peristaltic pump delivering the water for filling the mesocosm bags.

It all started with the vessel PLOCAN Uno dropping anchor outside Taliarte harbour at 7:30 a.m. The massive peristaltic pump on board got connected to the 350 m long hose that delivered water from 10 m depth outside the harbour to the mesocosms lined up at the PLOCAN pier. After a long flushing of the filling system and test runs for the team on the pier, the filling of the bags finally started. At a flow rate of about 10 cubic meters per hour, it takes some 6-7 hours to fill the eight mesocosms, each with a volume of ca. 8,000 litres. It all went fairly smoothly, although the flow meters at some of the mesocosms gave some problems. But the bags all unfolded well and were filled to their maximum capacity. By 7:30 p.m. operations ended. A big thank you to our technical team and all who helped setting the stage.

Now we are quite curious what the enclosed plankton assemblage looks like, because it will serve as the seed community for our upwelling experiment during the coming five weeks. Tomorrow’s first sampling will tell us.

Mesocosm filling 2 The filling team overseeing the smooth flow of water into the mesocosms bags.

Mesocosm filling 3 Checking the hoses and flow meters.