António obtained a MSc in Cell and Molecular Biology at FCUP-U. Porto and is now a Bioinformatician at Instituto Gulbenkian de Ciência.

MSc Thesis

Title: Arctic microbiome and N-functions during the winter-spring transition

Supervisor: Catarina Magalhaes; co-supervisors: Luis Torgo and Pedro Duarte

MSc in Cell and Molecular Biology

Finished: Nov/2017

Abstract

One of the most prominent manifestations of climate change is the changing Arctic sea-ice regime with a reduction in the summer sea-ice extent and a shift from thicker, perennial multiyear ice towards thinner, first-year ice. Microbial communities are a key component when evaluating the ecological impact of the Arctic’s changing ice regime, as they constitute the basis of Arctic marine food webs and biogeochemical cycles. During the Norwegian young sea ICE expedition (N-ICE2015), that took place in drifting pack ice north of Svalbard between January and June 2015, seawater was collected, at 5, 20 or 50 and 250 m depth in 9th March, 27th April and 16th June, together with physical and biogeochemical data. Through the massively parallel sequencing of small subunit ribosomal RNA (SSU rRNA) amplicon as well as environmental DNA (i.e., metagenomics) we got a snapshot of the Arctic’s microbiome diversity, structure and key N-cycling functions through the winter-spring transition. Results show that, at compositional level, Alpha- (30.7%) and Gammaproteobacteria (28.6%) are the most abundant across the prokaryotic N-ICE2015 collection, and also the most phylogenetically diverse. Winter to early summer trends are quite evident regarding thaumarchaeotes abundance in the under-ice water column in springtime, and nearly absent towards summer. Moreover, the emergence of Flavobacteria and the SAR92 clade in late spring might be associated to the degradation of an early spring bloom of Phaeocystis. Surprising it was found a great representativeness and high relative abundance of hydrocarbonoclastic bacteria, particularly Marinobacter (6.3%) and Alcanivorax (54.3%). This phylotypes supports evidence of an Arctic’s unexpected biosphere, prone to degrade petroleum-derived hydrocarbons and probably associated to natural oil seepage. In addition, not just thaumarchaeal ammonia oxidizers (TAO) have a high frequency of occurrence in the subsurface waters underneath of winter-spring pack ice (5 and 50 m depth), but also nitrite-oxidizing bacteria (NOB). However, they are nearly absent close to summer, suggesting active nitrifying activity underneath of winter-spring pack ice. Urease and AMO encoding genes are positively correlated with total dissolved nitrogen (N), which includes urea, suggesting that both pathways, ureolysis and aerobic ammonia oxidation, are coupled. Urease encoding gene increases along depth suggesting that distinct TAO Arctic microbiome and N-functions during the winter-spring transition populations found in the water column of the Arctic Ocean have different genomic potential to carry out ureolysis. In spite of the sequence effort made, it was not found genomic evidences to support nitrogen fixation, anammox and denitrification pathways. The microbial and metagenomic libraries from N-ICE2015 collection analysed in the present study provides comprehensive new knowledge about the microbiota and N-cycling communities and pathways in the Arctic Ocean winter to spring transition.