Mesozooplankton community development at elevated CO2 concentrations: results from a mesocosm experiment in an Arctic fjord

• Published in: Biogeosciences
• Main Authors: Niehoff, B., Schmithüsen, T., Knüppel, N., Daase, M., Czerny, J., Boxhammer, T.
• Format: Other/Unknown Material
• Language: English
• Published: 2018
• Subjects: Arctic; Svalbard; Kongsfjord*; Kongsfjorden; Copepods
• Online Access: https://doi.org/10.5194/bg-10-1391-2013; https://www.biogeosciences.net/10/1391/2013/

The increasing CO 2 concentration in the atmosphere caused by burning fossil fuels leads to increasing p CO 2 and decreasing pH in the world ocean. These changes may have severe consequences for marine biota, especially in cold-water ecosystems due to higher solubility of CO 2 . However, studies on the response of mesozooplankton communities to elevated CO 2 are still lacking. In order to test whether abundance and taxonomic composition change with p CO 2 , we have sampled nine mesocosms, which were deployed in Kongsfjorden, an Arctic fjord at Svalbard, and were adjusted to eight CO 2 concentrations, initially ranging from 185 μatm to 1420 μatm. Vertical net hauls were taken weekly over about one month with an Apstein net (55 μm mesh size) in all mesocosms and the surrounding fjord. In addition, sediment trap samples, taken every second day in the mesocosms, were analysed to account for losses due to vertical migration and mortality. The taxonomic analysis revealed that meroplanktonic larvae (Cirripedia, Polychaeta, Bivalvia, Gastropoda, and Decapoda) dominated in the mesocosms while copepods ( Calanus spp., Oithona similis , Acartia longiremis and Microsetella norvegica ) were found in lower abundances. In the fjord copepods prevailed for most of our study. With time, abundance and taxonomic composition developed similarly in all mesocosms and the p CO 2 had no significant effect on the overall community structure. Also, we did not find significant relationships between the p CO 2 level and the abundance of single taxa. Changes in heterogeneous communities are, however, difficult to detect, and the exposure to elevated p CO 2 was relatively short. We therefore suggest that future mesocosm experiments should be run for longer periods.