Microbial activity during a coastal phytoplankton bloom on the Western Antarctic Peninsula in late summer

• Published in: FEMS Microbiology Letters
• Main Authors: Alcamán Arias, María E., Farías, Laura, Verdugo, Josefa, Alarcón Schumacher, Tomás, Díez, Beatriz
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press 2018
• Subjects: Antarctic microbial communities; Phytoplankton bloom; Bacterioplankton; C and N assimilation pathways; Metatranscriptomics; Antarctic; Antarctic Peninsula; Austral; Inach; Antarc*
• Online Access: https://doi.org/10.1093/femsle/fny090; https://repositorio.uchile.cl/handle/2250/159222

Phytoplankton biomass during the austral summer is influenced by freezing and melting cycles as well as oceanographic processes that enable nutrient redistribution in the West Antarctic Peninsula (WAP). Microbial functional capabilities, metagenomic and metatranscriptomic activities as well as inorganic C-13-and N-15-assimilation rates were studied in the surface waters of Chile Bay during two contrasting summer periods in 2014. Concentrations of Chlorophyll a (Chla) varied from 0.3 mg m(-3) in February to a maximum of 2.5 mg m(-3) in March, together with a decrease in nutrients; however, nutrients were never depleted. The microbial community composition remained similar throughout both sampling periods; however, microbial abundance and activity changed with Chla levels. An increased biomass of Bacillariophyta, Haptophyceae and Cryptophyceae was observed along with night-grazing activity of Dinophyceae and ciliates (Alveolates). During high Chla conditions, HCO3- uptake rates during daytime incubations increased 5-fold (>2516 nmol C L-1 d(-1)), and increased photosynthetic transcript numbers that were mainly associated with cryptophytes; meanwhile night time NO3- (>706 nmol N L-1 d(-1)) and NH4+ (41.7 nmol N L-1 d(-1)) uptake rates were 2- and 3-fold higher, respectively, due to activity from Alpha-/Gammaproteobacteria and Bacteroidetes (Flavobacteriia). Due to a projected acceleration in climate change in the WAP, this information is valuable for predicting the composition and functional changes in Antarctic microbial communities. Chilean Antarctic Institute INACH T_15-10 Programa de Cooperacion Internacional (PCI)-Comision Nacional de Investigacion y Tecnologia (CONICYT) DPI20140044 Fondo de Financiamiento de Centros de Investigacion en Areas Prioritarias (FONDAP)-CONICYT 15110009 Fondo Nacional de Desarrollo Cientifico y Tecnologico (FONDECYT postdoctoral) -CONICYT 3170807