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

[摘要] The increasing CO₂ concentration in the atmosphere caused by burningfossil fuels leads to increasing pCO₂ and decreasing pH in the worldocean. These changes may have severe consequences for marine biota,especially in cold-water ecosystems due to higher solubility of CO₂.However, studies on the response of mesozooplankton communities to elevatedCO₂ are still lacking. In order to test whether abundance and taxonomiccomposition change with pCO₂, we have sampled nine mesocosms, whichwere deployed in Kongsfjorden, an Arctic fjord at Svalbard, and were adjustedto eight CO₂ concentrations, initially ranging from 185 μatmto 1420 μatm. Vertical net hauls were taken weekly over about onemonth with an Apstein net (55 μm mesh size) in all mesocosms andthe surrounding fjord. In addition, sediment trap samples, taken every secondday in the mesocosms, were analysed to account for losses due to verticalmigration and mortality. The taxonomic analysis revealed that meroplanktoniclarvae (Cirripedia, Polychaeta, Bivalvia, Gastropoda, and Decapoda) dominatedin the mesocosms while copepods (Calanus spp., Oithonasimilis, Acartia longiremis and Microsetella norvegica)were found in lower abundances. In the fjord copepods prevailed for most ofour study. With time, abundance and taxonomic composition developed similarlyin all mesocosms and the pCO₂ had no significant effect on the overallcommunity structure. Also, we did not find significant relationships betweenthe pCO₂ level and the abundance of single taxa. Changes inheterogeneous communities are, however, difficult to detect, and the exposureto elevated pCO₂ was relatively short. We therefore suggest thatfuture mesocosm experiments should be run for longer periods.

[学科分类] 地球化学与岩石