The effect of prolonged darkness on the growth, recovery and survival of Antarctic sea ice diatoms

Abstract

While global climate change in polar regions is expected to cause significant warming, the annual cycle of light and dark will remain unchanged. Cultures of three species of Antarctic sea ice diatoms, Fragilariopsis cylindrus (Grunow) Krieger, Thalassiosira antarctica Comber and Entomoneis kjellmanii (P.T. Cleve) Poulin and Cardinal, were incubated in the dark and exposed to differing temperatures. Maximum dark survival times varied between 30 and 60 days. Photosynthetic parameters, photosynthetic efficiency (a), maximum quantum yield (Fv/ Fm), maximum relative electron transport rate (rETRmax) and non-photochemical quenching (NPQ), showed that dark exposure had a significant impact on photoacclimation. In contrast, elevated temperatures had a relatively minor impact on photosynthetic functioning during the dark exposure period but had a considerable impact on dark survival with minimal dark survival times reduced to only 7 days when exposed to 10°C. Recovery of maximum quantum yield of fluorescence (Fv/Fm) was not significantly impacted by temperature, species or dark exposure length. Recovery rates of Fv/Fm ranged from -5.06E-7 ± 2.71E-7 s -1 to 1.36E-5 ± 1.53E-5 s -1 for monthly experiments and from -9.63E-7 ± 7.71E-7 s -1 to 2.65E-5 ± 2.97E-5 s -1 for weekly experiments. NPQ recovery was greater and more consistent than Fv/Fm recovery, ranging between 5.74E-7 ± 8.11E-7 s -1 to 7.50E-3 ± 7.1E-4 s -1 . The concentration of chl-a and monosaccharides remained relatively constant in both experiments. These results suggest that there will probably be little effect on Antarctic microalgae with increasing water temperatures during the Antarctic winter.

Evaluation of Algal Biofilms on Indium Tin Oxide (ITO) for Use in Biophotovoltaic Platforms Based on Photosynthetic Performance

“…F v /F m is often used as an indicator of photosynthetic capacity. Various studies have reported values of F v /F m ranging between 0.1 to 0.65 for natural populations of microalgae [50]. Results in the present study indicated that most samples were in a healthy condition, as the F v /F m values were all above 0.800 except for Synechococcus elongatus UMACC 105 with a F v /F m value of 0.799.…”

Dark survival in a warming world

“…Increased temperature can also raise the compensation point irradiance [35], which might lead to increased mortality and a decrease in biomass. Experiments with polar algae, however, indicate that dark survival rates are not affected at small to moderate temperature increases [36].…”

Dark metabolism: a molecular insight into how the Antarctic sea‐ice diatom Fragilariopsis cylindrus survives long‐term darkness

“…Therefore, it is a useful indicator species for investigations into adaptation and acclimation to the polar sea‐ice habitat (Mock et al ., ). Several studies have described the effect of darkness on the survivability of Antarctic phytoplankton and sea‐ice algae (Bunt & Lee, ; Palmisano & Sullivan, ; Peters & Thomas, ; Baldisserotto et al ., ; Reeves et al ., ), but most research has focused on physiological adaptation rather than the biochemical and molecular drivers behind dark‐induced metabolism. Recent advances in functional genomics has made it possible to examine the molecular processes enabling dark survival (Nymark et al ., ; Bai et al ., ; Mock et al ., ).…”

“…Maintenance metabolism may help to explain why many sea‐ice diatoms are able to rapidly resume photosynthesis and grow rapidly after extended darkness (Peters & Thomas, ; Wulff et al ., ; McMinn et al ., ,b; Reeves et al ., ; Nymark et al ., ). Despite studies indicating strong downregulation of photophysiological processes during prolonged darkness (Peters, ; Peters & Thomas, ; Popels et al ., ; Wulff et al ., ; Reeves et al ., ; Martin et al ., ), a certain level of functionality and structural arrangement must be retained in the dark. This situation infers that cells are actively maintaining some degree of photosynthetic capacity and sustaining constituents of the photosynthetic apparatus in the dark.…”