Abstract
Microbial eukaryotes can play prominent roles in the Arctic marine ecosystem, but their diversity and variability is not well known in the ice-covered ecosystems. We determined the community composition of microbial eukaryotes in an Arctic under-ice spring bloom north of Svalbard using metabarcoding of DNA and RNA from the hypervariable V4 region of 18S nrDNA. At the two stations studied, the photosynthetic biomass was dominated by protists >3 μm and was concentrated in the upper 70–80 m, above the thermocline and halocline. Hierarchical cluster analyses as well as ordination analyses showed a distinct clustering of the microbial eukaryote communities according to a combination of water mass and local environmental characteristics. While samples collected in the surface mixed layer differed distinctly between the two sites, the deeper communities collected in Atlantic Water were fairly similar despite being geographically distant. The differentiation of the microbial eukaryote communities of the upper mixed water was probably driven by local development and advection, while the lack of such differentiation in the communities of Atlantic Water reflects the homogenizing effect of water currents on microbial communities.
Highlights
The Arctic spring bloom fuels production in the seasonally ice-covered shelves surrounding the Arctic Ocean
We investigated microbial eukaryote diversity and community compositional differences in an under-ice spring bloom north of Svalbard
The water masses were identified based on their potential temperature— salinity characteristics; Atlantic Water (AW), Polar Water (PW), and Arctic Surface Water (ASW; Aagaard and Carmark, 1989; Cokelet et al, 2008; Figures 2, 3)
Summary
The Arctic spring bloom fuels production in the seasonally ice-covered shelves surrounding the Arctic Ocean. During the last decade, sequencing of 18S rDNA has been used to metabarcode communities of the pico- (0.2–3 μm) and nano- (3–20 μm) sized eukaryotic fraction of Arctic marine systems (e.g., Lovejoy et al, 2006; Comeau et al, 2011; Kilias et al, 2014; Marquardt et al, 2016) as reviewed by Lovejoy (2014). It has been shown that the pronounced Arctic seasonality extends to the succession of microbial eukaryotes (Marquardt et al, 2016; Joli et al, 2017). Molecular data can provide insight into responses of marine microbes to environmental change (Comeau et al, 2011) with potential changes higher up in the marine food web
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