Response of halocarbons to ocean acidification in the Arctic

[摘要] The potential effect of ocean acidification (OA) on seawater halocarbons inthe Arctic was investigated during a mesocosm experiment in Spitsbergen inJune–July 2010. Over a period of 5 weeks, natural phytoplankton communitiesin nine ~ 50 m³ mesocosms were studied under a range ofpCO₂ treatments from ~ 185 μatm to ~ 1420 μatm. In general, the response of halocarbons to pCO₂ wassubtle, or undetectable. A large number of significant correlations with arange of biological parameters (chlorophyll a, microbial plankton community,phytoplankton pigments) were identified, indicating a biological control onthe concentrations of halocarbons within the mesocosms. The temporaldynamics of iodomethane (CH₃I) alluded to active turnover of thishalocarbon in the mesocosms and strong significant correlations withbiological parameters suggested a biological source. However, despite apCO₂ effect on various components of the plankton community, and astrong association between CH₃I and biological parameters, no effect ofpCO₂ was seen in CH₃I. Diiodomethane (CH₂I₂) displayed anumber of strong relationships with biological parameters. Furthermore, theconcentrations, the rate of net production and the sea-to-air flux ofCH₂I₂ showed a significant positive response to pCO₂. Therewas no clear effect of pCO₂ on bromocarbon concentrations or dynamics.However, periods of significant net loss of bromoform (CHBr₃) werefound to be concentration-dependent, and closely correlated with totalbacteria, suggesting a degree of biological consumption of this halocarbonin Arctic waters. Although the effects of OA on halocarbon concentrationswere marginal, this study provides invaluable information on the productionand cycling of halocarbons in a region of the world's oceans likely toexperience rapid environmental change in the coming decades.

[学科分类] 地球化学与岩石