Comparison of endpoint respiration/retention (Resp/Ret) values for natural communities present in sea-ice brines from Kanajorsuit Bay in April 2013 (a) and Kobbefjord in March 2014 (b–d) following shifts (down, no, up) in salinity at –1°C. Incubation salinities (ppt) are given above each bar; the no-shift salinity is the in situ brine salinity. A Resp/Ret ratio of 1 implies equal respiration and retention of choline; Resp/Ret > 1 indicates more choline respired than retained; and Resp/Ret < 1 indicates more choline retained than respired. Error bars indicate S.D. of the mean (n = 3 except for (a) where n = 2); where no bar is visible, it falls within the dimensions of the symbol for the mean.