With the help of benthocosms, scientists at GEOMAR investigate how life at the bottom of the Baltic Sea will develop in the coming decades. For this purpose, they simulate environmental conditions that they expect for the future. For this purpose, typical organisms of the Baltic Sea such as bladderwrack, starfish or mussels are cultivated in the benthocosms and exposed to rising temperatures, increased carbon dioxide levels, a growing amount of nutrients, decreasing amounts of oxygen, decreasing amounts of light or other ecological changes that the researchers assume for the coming decades. The researchers' goal is to detect potential structural and functional shifts in biological communities and assess their consequences.
The facility, which has been operating in Kiel since 2013 on a pontoon directly on the Kiel Fjord, consists of six benthocosms, each with two experimental chambers with a water capacity of 1,500 liters. What makes it special is that a powerful computer system can not only continuously measure temperature, salinity, oxygen and pH, but also adjust them and their natural fluctuations to realistically simulate underwater environmental scenarios of the coming decades. The water in the basins comes directly from the Kiel Fjord, allowing for an almost natural environment in the experimental basins. Most of the benthocosms' required energy is generated by solar panels and a small wind turbine.
The focus of the indoor benthocosms in the GEOMAR West Bank Building, which went into operation in 2017, is also on the behavior of individual organisms, as well as smaller biological communities in the Baltic Sea, in response to environmental fluctuations. To this end, parameters such as temperature, salinity, pH and oxygen can be adjusted in a controlled manner in the 12 experimental units, each with a water capacity of 600 liters. The novelty of these experimental units, which were also developed in Kiel, is that they can also simulate environmental fluctuations, i.e. not necessarily average changes that affect organisms and ecosystems in the Baltic Sea, but rather extreme events, from daily fluctuations to weeks-long heat waves in summer. To ensure that the conditions for the experiments are realistic but also reproducible, "real" seawater from the Kiel Fjord is used as a basis. The lighting can be simulated almost true to life in the diurnal and annual cycle via an LED lighting system, so that future underwater lighting regimes can also be simulated.