Respiration and bacterial carbon dynamics in Arctic sea ice

Bacterial carbon demand, an important component of ecosystem dynamics in polar waters and sea ice, is a function of both bacterial production (BP) and respiration (BR). BP has been found to be generally higher in sea ice than underlying waters, but rates of BR and bacterial growth efficiency (BGE) are poorly characterized in sea ice. Using melted ice core incubations, community respiration (CR), BP, and bacterial abundance (BA) were studied in sea ice and at the ice–water interface (IWI) in the Western Canadian Arctic during the spring and summer 2008. CR was converted to BR empirically. BP increased over the season and was on average 22 times higher in sea ice as compared with the IWI. Rates in ice samples were highly variable ranging from 0.2 to 18.3 μg C l⁻¹ d⁻¹. BR was also higher in ice and on average ~10 times higher than BP but was less variable ranging from 2.39 to 22.5 μg C l⁻¹ d⁻¹. Given the high variability in BP and the relatively more stable rates of BR, BP was the main driver of estimated BGE (r ² = 0.97, P < 0.0001). We conclude that microbial respiration can consume a significant proportion of primary production in sea ice and may play an important role in biogenic CO₂ fluxes between the sea ice and atmosphere.