At Åbo Akademi University, across the Archipelago Sea and Åland Islands, we maintain a research infrastructure network for community-scale experimental research.

Manipulating community composition, as well as diverse underwater climates, including their extremes (such as marine heatwaves), allows us to glimpse into the future ocean.

Mesocosms represent a tool to bridge laboratory (Petri-dishes to aquaria) and field experiments and provide the advantage that any underwater climates can be manipulated synchronously (common garden) and replicated.

Two mesocosm systems, of 20 600 L tanks each, are located at the Archipelago Centre Korpoström by the Archipelago Sea (images 1 and 2) and at Husö Biological Station at Åland Islands (images 3 and 4).

The systems mimic most natural conditions in nutrients and organic matter and daily fluctuation of abiotic factors such as water temperature, salinity, pH, and oxygen, as well as light.

Setup information

Each system comprises 20 600 L polyethylene tanks (Schwer-PALOXE 1130 x 930 x 600 mm) supplied with a constant flow-through of unfiltered seawater from a water depths of 2 m (Korpoström: GRUNDFOS SP 5A-12 R 5 from around 20 m from the tank system; Husö: Isku-Jet 3RP from around 300 m from the tank system).

Experiments can be run flexibly, in full 600 L tanks or in experimental (semi-independent), for example 20 L, subunits (vinyl buckets PP Plastex®).

Constant and equal inflow of water is achieved by custom-made INFLOW units (with adjustable flow rates) or HEADER tanks (10 L buckets PP OrthexTM above the water level distribute water passively among the experimental units via 90 cm long silicon tubes – 4 mm diameter, Versilic Silicon Tubing #760320).

Natural light conditions are maintained through shading nets at ~440 µmol photon m-2 s-1 (Li-Cor model Li-1400 data logger), representative of 3 m water depth in the area during summer.