KOSMOS Mesocosms for studying ocean acidification in the subtropical Atlantic off Gran Canaria. Photo: Ulf Riebesell

Image of the month: July 2019

Mesocosms in action

Our image of the month shows six of the nine KOSMOS mesocosms (Kiel Off-Shore Mesocosms for Ocean Simulations) which were developed at GEOMAR and have been used in various marine regions since 2010. Here they are located in the subtropical North Atlantic off the coast of Gran Canaria, where in 2014 an international team of scientists conducted a KOSMOS experiment as part of the project "Biological Impacts of Ocean Acidification" (BIOACID).

The 20 m long and 2 m in diameter plastic bags held by floatation frames look like oversized test tubes. After deployment the bag unfolds by weights pulling down its lower end to depth, thereby enclosing an undisturbed water column 55 m3 in volume. The bag is then closed at the bottom by a full-diameter sediment trap. In the mesocosms, changes in various environmental factors can be simulated and their effects on marine ecosystems investigated.

This project, led by Ulf Riebesell, Professor of Biological Oceanography at GEOMAR, focused on ocean acidification. Due to the increased CO2 content in the atmosphere, more of the gas is dissolved in the ocean, which lowers its pH value. This has negative effects on many organisms, with the result that some may no longer be able to maintain their competitive fitness and hold their ecological niche. Other species, including some toxic algae, benefit from ocean acidification. The associated changes in marine ecosystems will likely also affect us humans.
The giant test tubes are presently being used off Gran Canaria to simulate and study artificial upwelling of nutrient-rich deep water. The upwelling of deep water increases the growth of phytoplankton at the base of the marine food chain. The Ocean artUp (Ocean Artificial Upwelling) project, which has been funded by the European Research Council with 2.5 million Euros since 2017, investigates how efficiently the stimulated algal growth is used in the food web. The researchers of Ocean artUp also pay special attention to identifying and estimating associated risks and potential side effects of artificial upwelling on the natural community.

Artificial upwelling could naturally fertilize so-called ocean deserts and thereby increase fish production in these nutrient-poor areas. This could help to reduce fishing pressure on already overexploited fish stocks. Given the rising world population, this approach could also help to produce animal protein from renewable energy sources without need for crop fertilizers and precious fresh water.

Further information:

Ocean acidification:


Ocean artUp:

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During their use, the mescosms are checked regularly. Photo: Michael Sswat

During their use, the mescosms are checked regularly. Photo: Michael Sswat

Many people are involved in the deployment of the mescosms in order to put them safely in the right place. Photo: Silke Lischka

Many people are involved in the deployment of the mescosms in order to put them safely in the right place. Photo: Silke Lischka