3 woman sampling a mesocosm

Back in the game

Ulf Riebesell by Ulf Riebesell on 6.11.2018

It has been a week of intense repairs at the mesocosms by our divers. The leaks in the flotation pylons have been sealed, the water that leaked into the pylons has been blown out and the sunken mesocosms are now floating again. In addition, metal sheets have been fixed on all pylons at the level where the steel rings could touch them, to protect them from any damage should the unfortunate combination of strong currents and heavy easterly swell hit us again. In parallel, the divers cleaned the outside of the enclosure walls as well as the sediment traps and installed extra flotation bodies on each mesocosm frame. It was amazing to see how the group planned and executed the salvage of our sunken mesocosms. A fantastic team effort, above all by our great squad of divers.

While the repairs were on-going, the enclosure bags were kept open for a complete exchange of water with the Atlantic. No trace of our first experimental trial should be left in the enclosures. Depth profiles of the water inside the bags with our multi-sensor probe – which returned in time after a successful repair by the manufacturer – revealed that there was no indication of any “left-overs” in our mesocosms. Everything is ready for a restart.

This was the sign for closing the mesocosms by pulling the top ends above the surface and shutting the sediment traps. A net with 3 mm mesh size connected to our inner-wall cleaning ring was pulled through the entire water column to take out large predators, which may have invaded during the open-cosm days.

The first sampling of our newly established mid-sized worlds (meso = mid-sized, cosm = world) started early this morning. Fingers crossed for a successful second round.

First-day sampling Several teams are working in parallel to get all the samples needed

First-day sampling Water sampling with the depth-integrating samplers

Zooplankton net sampling Zooplankton net sampling