Rapid Manipulation in Irradiance Induces Oxidative Free-Radical Release in a Fast-Ice Algal Community (McMurdo Sound, Antarctica)

Abstract

Sea ice supports a unique assemblage of microorganisms that underpin Antarctic coastal food-webs, but reduced ice thickness coupled with increased snow cover will modify energy flow and could lead to photodamage in ice-associated microalgae. In this study, microsensors were used to examine the influence of rapid shifts in irradiance on extracellular oxidative free radicals produced by sea-ice algae. Bottom-ice algal communities were exposed to one of three levels of incident light for 10 days: low (0.5 μmol photons m−2 s−1, 30 cm snow cover), mid-range (5 μmol photons m−2 s−1, 10 cm snow), or high light (13 μmol photons m−2 s−1, no snow). After 10 days, the snow cover was reversed (either removed or added), resulting in a rapid change in irradiance at the ice-water interface. In treatments acclimated to low light, the subsequent exposure to high irradiance resulted in a ~400× increase in the production of hydrogen peroxide (H2O2) and a 10× increase in nitric oxide (NO) concentration after 24 h. The observed increase in oxidative free radicals also resulted in significant changes in photosynthetic electron flow, RNA-oxidative damage, and community structural dynamics. In contrast, there was no significant response in sea-ice algae acclimated to high light and then exposed to a significantly lower irradiance at either 24 or 72 h. Our results demonstrate that microsensors can be used to track real-time in-situ stress in sea-ice microbial communities. Extrapolating to ecologically relevant spatiotemporal scales remains a significant challenge, but this approach offers a fundamentally enhanced level of resolution for quantifying the microbial response to global change.

Net heterotrophy in High Arctic first-year and multi-year spring sea ice

“…An alternative to estimating primary production, as in a majority of studies, relies upon a radioisotope tracer to estimate the rate of carbon fixation by photosynthesis (i.e., 14 C) for samples of ice algae collected from a given point (ice core) location, after the sample has been removed from the sea ice environment. Measurements of production, the balance between respiration and photosynthesis at the community level (Rysgaard and Glud, 2004;Rysgaard et al, 2008), and algal stress (Kennedy et al, 2020) can also be assessed using in situ or in vivo O 2 -based technologies. These studies have shown net heterotrophic conditions (net O 2 uptake) during the initial spring bloom period in FYI due to high respiration (Campbell et al, 2017).…”

Screening and Genetic Network Analysis of Genes Involved in Freezing and Thawing Resistance in DaMDHAR—Expressing Saccharomyces cerevisiae Using Gene Expression Profiling

“…The high accumulation of ROS generates oxidative stress [11]. ROS can induce DNA damage, protein oxidation, membrane lipid peroxidation and pigment destruction [2,6,12]. Therefore, a considerable amount of research has been conducted to explore the correlation between ROS scavenging and plant stress tolerance under extreme temperatures [13][14][15].…”

Antarctic sea ice over the past 130,000 years, Part 1: A review of what proxy records tell us

“…Importantly, the consideration of a phytoplankton biomarker alongside IPSO25 helps to avoid the misinterpretation of the absence of the sea-ice biomarker in a sediment sample which may result from ice-free conditions or perennial sea ice and/or ice shelf cover, both conditions inhibiting any ice algae productivity (Lamping et al, 2021). Therefore, while the PIPSO25 index seems a promising tool, further investigations of other environmental parameters such as nutrient and light availability that affect bottom-ice algal growth (Kennedy et al, 2020), and of ice-shelf processes such as the formation and accretion of platelet ice that offer habitat to IPSO25-synthesizing diatoms, are required to obtain more information on the production and fate of IPSO25 and better constrain its applicability as an Antarctic sea-ice proxy (Lamping et al, 2021). Further attempts to calibrate the PIPSO25 index against observational (i.e., satellite) sea-ice data also require higher circum-Antarctic spatial coverage of HBI analyses conducted on well-dated, ideally by 210 Pb and 14 C, surface sediments.…”