Abstract
Abstract. The increasing CO2 concentration in the atmosphere caused by burning fossil fuels leads to increasing pCO2 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 CO2. However, studies on the response of mesozooplankton communities to elevated CO2 are still lacking. In order to test whether abundance and taxonomic composition change with pCO2, we have sampled nine mesocosms, which were deployed in Kongsfjorden, an Arctic fjord at Svalbard, and were adjusted to eight CO2 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 pCO2 had no significant effect on the overall community structure. Also, we did not find significant relationships between the pCO2 level and the abundance of single taxa. Changes in heterogeneous communities are, however, difficult to detect, and the exposure to elevated pCO2 was relatively short. We therefore suggest that future mesocosm experiments should be run for longer periods.
Highlights
Kongsfjorden, an Arctic fjord at Svalbard, and were adjusted solves in seawater, it reacts with water to form carbonic acid to eight CO2 concentrations, initially ranging from 185 μatm to 1420 μatm
This mesocosm experiment is the first that describes the development of a mesozooplankton community at elevated pCO2
The copepod species, i.e. Oithona similis, Calanus spp., Acartia longiremis and Microsetella norvegica, we found in the upper 12 m water column are typical for Kongsfjorden (e.g. Weslawski et al, 1991)
Summary
M sphere caused by burning fossil fuels leads to increasing pCO2 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 CO2. In order to test whether abundance and taxonomic composition change with pCO2, we have sampled nine mesocosms, which were deployed in concentrations have increased and future scenarios predict ufpSromctoiea1b0no0uc0teμ2as8t0mtoby38t0heμaetmnd, of this century (IPCC, 2007). This present study was part of the EPOCA CO2 enrichment mesocosm experiment conducted in Kongsfjorden (78◦56.2 N and 11◦53.6 E) in Ny-Alesund, Svalbard, in June/July 2010. Samples taken prior to the manipulation (for mesozooplankton t−2 in the water column and t−1 in the sediment traps) reflect the initial status of the pelagic community
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