Mycobiota of the Bottom Sediments of the White Sea: Metabarcoding and Cultural Method

Knowledge of the composition of fungi in sediments is necessary to understand many biological processes, the decomposition of organic substances in aquatic ecosystems in particular. However, the diversity of fungi in the Arctic seas remains poorly studied, and single studies have been performed, using metabarcoding of DNA from sediments. Such studies for the White Sea are absent, and the composition and structure of fungal communities in its bottom sediments are known only on the basis of inoculation on nutrient media. The aim of this work was to characterize the species diversity and the taxonomic and trophic structure of the mycobiota of bottom sediments in the White Sea obtained by high-throughput sequencing and comparative analysis with the results of cultural methods. Significantly larger number of fungal taxa of all ranks was found in the sediments by the molecular approach as compared to cultural methods. The nucleotide sequences (8030) were classified into 312 OTUs, representing 200 species, 171 genera, 125 families, 69 orders, and 29 classes of ten phyla: Ascomycota, Basidiomycota, Chytridiomycota, Mucoromycota, Mortierellomycota, Glomeromycota, Kickxellomycota, Rozellomycota, Monoblepharomycota, and Aphelidiomycota. The number of OTU and the species richness were the largest in Ascomycota (60% of the total number of OTU) and Basidiomycota (28%), followed by Chytridiomycota (10%) and Mortierellomycota (0.8%), and the total contribution of the other six phyla was 1.2%. According to the FungalTraits database, 18 ecological and trophic groups were identified in the soil microbiome: saprotrophs (soil and litter and on nectar/nectaries and on wood) prevailed, followed by plant and animal pathogens, ectomycorrhizal agents, and endophytes; and the proportion of the rest groups was very small. According to the cultural method, the fungal biota of sediments in the same area of the White Sea was represented by three phyla with a significant predominance of representatives of Ascomycota (90%), as well as of Mucoromycota (8%) and Basidiomycota (2%). The species number revealed by this approach was two times smaller (101). A total of 245 species were identified in the sediments, 15 of which were revealed by both methods. Zoospore fungi and basidial fungi were discovered by metabarcoding. The mycobiota diversity in sediments of the White Sea and the composition of the most widespread fungal inhabitants in them at different depths were more comprehensively assessed based on both approaches.