Comparable in- and outdoor ice-resistant mesocosms

An indoor and outdoor mesocosm system at Umeå Marine Sciences Centre was run in parallel over the 5-month long winter season in the northern Baltic Sea.

One goal was to set boundary conditions and compare the performance of both mesocosm systems in harsh winters including ice formation. Another aim was to study the effects of browning by organic matter substitutes HuminFeed® and a soil extract from the local watershed on the response of the Baltic Sea plankton community relative to a control without additions during winter.

Both the in- and outdoor systems could be operated with ice cover while the ice thickness and transparency differed. Temperature and salinity were similar while light irradiance was lower indoors during spring. Despite some differences between the in- and outdoor facilities, the effects of organic matter treatments were similar for 75% of the variables.

Some differences in the effects of HuminFeed® and the soil extract were observed that should be considered in future experiments. This mesocosm experiment was supported by the AQUACOSM-plus Transnational Access program (WP9) which funded three trainees and seven researchers for a total of 105 person days during the 5 months of performance.

Preliminary results are reported in Deliverable D8.5 at the AQUACOSM-plus website.

View of the outdoor mesocosm in the northern Baltic Sea (left). Indoor mesocosm at Umeå Marine Sciences Centre with a freezer hood facilitating ice cover also indoors (right). Photographer: Kristina Viklund (left) and Markus Nordin (right).