Response of sea-ice microbial communities to environmental disturbance: an in situ transplant experiment in the Antarctic

• Published in: Marine Ecology Progress Series
• Main Authors: Martin, A, Anderson, MJ, Thorn, C, Davy, SK, Ryan, KG
• Format: Article in Journal/Newspaper
• Language: English
• Published: Inter-Research 2011
• Subjects: Mathematical Sciences; Pure Mathematics; Lie Groups; Harmonic and Fourier Analysis; Antarctic; Southern Ocean; The Antarctic; Antarc*; Sea ice
• Online Access: https://doi.org/10.3354/meps08977; http://ecite.utas.edu.au/78004

Sea-ice microbial communities are integral to primary and secondary production in icecoveredregions of the Southern Ocean, but few studies have characterised the heterogeneity ofmicrobes within the ice or determined whether habitat variability influences community dynamics.We examined the response of sea-ice microbes to key physicochemical variables by conducting an18 d reciprocal transplant experiment within Antarctic fast-ice. A series of ice cores were extractedfrom 2.6 m annual ice and reinserted upside down to expose resident microbial assemblages to significantlydifferent light, temperature and salinity regimes. The abundance and community compositionof bacteria, microalgae and protozoa was subsequently determined within 3 sections of each core(top, middle and bottom) and compared with experimental controls. Results demonstrate that iceassociatedmicrobes are finely attuned to discrete microhabitats within the sea-ice matrix. Positivegrowth and a shift in community composition was observed for microalgae moved from the top to thebottom of the ice, but significant bleaching of photosynthetic pigments resulted in zero net growth forbottom-ice communities exposed to the surface. Although bacteria may have been less vulnerable toinitial change in their microenvironment, there was no significant increase in the average abundanceof cells at either end of the flipped cores after 18 d, despite a presumed increase in algal-derived dissolvedorganic matter. This suggests a significant lag in the response time of bacteria to availablegrowth substrates and a temporary malfunction of the microbial loop.