Effects of CO 2 concentration on a late summer surface sea ice community

• Published in: Marine Biology
• Main Authors: McMinn, A, Muller, MN, Martin, A, Ugalde, SC, Lee, S, Castrisios, K, Ryan, KG
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer-Verlag 2017
• Subjects: Biological Sciences; Microbiology; Microbial Ecology; Scott Base; Antarc*; Antarctica; Sea ice
• Online Access: https://doi.org/10.1007/s00227-017-3102-4; http://ecite.utas.edu.au/116493

Annual fast ice at Scott Base (Antarctica) in late summer contained a high biomass surface community of mixed phytoflagellates, dominated by the dinoflagellate, Polarella glacialis . At this time of the year, ice temperatures rise close to melting point and salinities drop to less than 20. At the same time, pH levels can rise above 9 and nutrients can become limiting. In January 2014, the sea ice microbial community from the top 30cm of the ice was exposed to a gradient of pH and CO 2 (5 treatments) that ranged from 8.87 to 7.12 and 5215mol CO 2 kg −1 , respectively, and incubated in situ. While growth rates were reduced at the highest and lowest pH, the differences were not significant. Likewise, there were no significant differences in maximum quantum yield of PSII ( F v / F m ) or relative maximum electron transfer rates (rETR max ) among treatments. In a parallel experiment, a CO 2 gradient of 26230mol CO 2 kg −1 (5 treatments) was tested, keeping pH constant. In this experiment, growth rates increased by approximately 40% with increasing CO 2 , although differences among treatments were not significant. As in the previous experiment, there was no significant response in F v / F m or rETR max . A synchronous grazing dilution experiment found grazing rates to be inconclusive These results suggest that the summer sea ice brine communities were not limited by in situ CO 2 concentrations and were not adversely affected by pH values down to 7.1.