High‐resolution monitoring reveals dissolved oxygen dynamics in an Antarctic cryoconite hole

Abstract

Abstract:This study presents the first high-resolution dataset of dissolved oxygen (DO) measurements in an ice-lidded cryoconite hole on Canada Glacier, McMurdo Dry Valleys, Antarctica. Fibre optic DO minisensors were installed in a cryoconite hole prior to seasonal internal melting and hydrological connection to the subsurface drainage system. Oxygen air saturation in the cryoconite hole typically ranged from 50 to 80%, in broad agreement with previous single measurements, indicating net respiration (R). This is consistent with results of simple incubation experiments performed in the field. Simultaneous time series for electrical conductivity, water temperature, and DO over the four-week study period provide information regarding the connectivity of cryoconite holes with the near-surface drainage system. The main driver of the observed variations in DO is likely to be periodic melt-freeze cycles. We conclude that automated sensing techniques, such as those described here, when used in conjunction with physical measurements, have great potential for high-resolution monitoring of the factors that perturb biogeochemical processes in cryospheric surface aquatic ecosystems.

Processes controlling carbon cycling in Antarctic glacier surface ecosystems

“…1), in that both sets of incubations show unequivocal net heterotrophy over timescales of ~8 days. This is consistent with other studies which use 24 hr incubation of cryoconite from Antarctica (Hodson et al, 2010a,b;Bagshaw et al, 2011;Hodson et al, 2013). However, the longer term incubations suggest that more complex interactions control the overall C balance, with net heterotrophy shifting to net autotrophy over timescales of >~20 days.…”

“…The DO concentrations begin to diverge after 380 hr (16 d), with the light bottles eventually becoming supersaturated after 1000 hr (40 d). The DO concentrations in the light bottles increase to 140 % saturation after 250 hr, a value that has been observed in cryoconite holes on Canada Glacier Bagshaw et al, 2011). The dark bottles become increasingly undersaturated, falling to values of 23 %.…”

“…Standard cryoconite incubation methods using oxygen microoptodes were employed (Hodson et al, 2010b;Telling et al, 2010;Bagshaw et al, 2011), with experiment durations of one week for field incubations and 150 days for laboratory experiments. We equate dissolved oxygen concentration with carbon production (Telling et al, 2010).…”

“…Reported rates of P range from 1.3 (Bagshaw et al, 2011) to 2.4 µg C g -1 d -1 (Hodson et al, 2010b), compared with 20.9 µg C g -1 d -1 (Telling et al, 2010) to 208 µg C L -1 d -1 (Anesio et al, 2009) in cryoconite on Svalbard glaciers. Telling et al (2010) elaborate on some of the methodological differences between these experiments.…”

“…2). Some studies find that P exceeds R in cryoconite holes (Anesio et al, 2009), whilst others find that R exceeds P during the melt season (Stibal and Tranter, 2007;Bagshaw et al, 2011).…”