Antarctic Glacial Meltwater Impacts the Diversity of Fungal Parasites Associated With Benthic Diatoms in Shallow Coastal Zones.

Doris Ilicic,Hans-Peter Grossart,Hans-Peter Grossart,Alexandra Livenets,Thomas Wichard,Gabriela Laura Campana,Gabriela Laura Campana,Jason Woodhouse,Jonas Zimmermann,Jonas Zimmermann,Maria Liliana Quartino,Silke Van Den Wyngaert,Ulf Karsten

doi:10.3389/fmicb.2022.805694

Abstract

Aquatic ecosystems are frequently overlooked as fungal habitats, although there is increasing evidence that their diversity and ecological importance are greater than previously considered. Aquatic fungi are critical and abundant components of nutrient cycling and food web dynamics, e.g., exerting top-down control on phytoplankton communities and forming symbioses with many marine microorganisms. However, their relevance for microphytobenthic communities is almost unexplored. In the light of global warming, polar regions face extreme changes in abiotic factors with a severe impact on biodiversity and ecosystem functioning. Therefore, this study aimed to describe, for the first time, fungal diversity in Antarctic benthic habitats along the salinity gradient and to determine the co-occurrence of fungal parasites with their algal hosts, which were dominated by benthic diatoms. Our results reveal that Ascomycota and Chytridiomycota are the most abundant fungal taxa in these habitats. We show that also in Antarctic waters, salinity has a major impact on shaping not just fungal but rather the whole eukaryotic community composition, with a diversity of aquatic fungi increasing as salinity decreases. Moreover, we determined correlations between putative fungal parasites and potential benthic diatom hosts, highlighting the need for further systematic analysis of fungal diversity along with studies on taxonomy and ecological roles of Chytridiomycota.

Highlights

With this study it was intended to highlight the prevalence of fungi in Antarctic benthic environments, determine the impact of glacial meltwater on benthic diatoms and their associated fungal communities and to identify correlation in their presence
Relative proportions of fungal amplicon sequence variants (ASVs) in dataset containing only fungal community (FunLSU) confirmed differences observed in dataset containing whole eukaryotic community (EukSSU) and 51.3% of sequences were classified as fungi in marine, 73.2% in brackish and 69.3% in limnic environments
Our work suggests that salinity has a major impact in shaping eukaryotic microbial communities in shallow coastal waters of Antarctica

Summary

Introduction

They constitute a wellfounded component of terrestrial ecology due to more than 100 years of research that has highlighted their role in biogeochemical cycling and promoting biodiversity (Peay et al, 2016). There is increasing evidence that fungal diversity in aquatic ecosystems is greater and more important than previously considered (Shearer et al, 2007; Amend et al, 2019; Grossart et al, 2019). Despite sampling efforts of fungi in aquatic habitats being low compared to terrestrial environments (Rojas-Jimenez et al, 2017), molecular analyses of environmental DNA samples reveal a great diversity of novel fungal sequences, the so-called Dark Matter Fungi (Grossart et al, 2016). Recent advances in DNA-sequencing technology have revealed that fungi are highly abundant in marine environments (Comeau et al, 2016; Taylor and Cunliffe, 2016; Tisthammer et al, 2016; Hassett et al, 2019a; Banos et al, 2020), their ecological functions and interactions with other microorganisms remain largely unexplored and missing from current general concepts (Amend et al, 2019; Richards et al, 2021)

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