Spatial distribution of aquatic marine fungi across the western Arctic and sub‐arctic

Abstract

Fungi are important parasites of primary producers and nutrient cyclers in aquatic ecosystems. In the Pacific-Arctic domain, fungal parasitism is linked to light intensities and algal stress that can elevate disease incidence on algae and reduce diatom concentrations. Fungi are vastly understudied in the marine realm and knowledge of their function is constrained by the current understanding of fungal distribution and drivers on global scales. To investigate the spatial distribution of fungi in the western Arctic and sub-Arctic, we used high throughput methods to sequence 18S rRNA, cloned and sequenced 28S rRNA and microscopically counted chytrid-infected diatoms. We identified a broad distribution of fungal taxa predominated by Chytridiomycota and Dikarya. Phylogenetic analysis of our Chytridiomycota clones placed Arctic marine fungi sister to the order Lobulomycetales. This clade of fungi predominated in fungal communities under ice with low snowpack. Microscopic examination of fixed seawater and sea ice samples revealed chytrids parasitizing diatoms collected across the Arctic that notably infected 25% of a single diatom species in the Bering Sea. The Pezizomycotina comprised > 95% of eukaryotic sequence reads in Greenland, providing preliminary evidence for osmotrophs being a substitute for algae as the base of food webs.

Diversity and Hidden Host Specificity of Chytrids Infecting Colonial Volvocacean Algae

“…), the Artic and Subartic Sea (Hassett et al. ). This cluster, constitutes a novel clade (SW‐I) within Lobulomycetales.…”

“…) and Arctic sea ice (Hassett et al. ) in a separate, novel clade, sister to the order Lobulomycetales (Simmons et al. ).…”

“…Interestingly, the arctic sea ice clones most likely represent parasitic chytrids of diatoms, since microscopic observations by Hassett et al. () indicated that a substantial portion of large pennate diatoms in the arctic sea ice were infected by chytrids during the sampling period. Morphologically these arctic chytrids also shared the feature of an apical operculum with A. stechlinensis .…”

Comparison of sterol and fatty acid profiles of chytrids and their hosts reveals trophic upgrading of nutritionally inadequate phytoplankton by fungal parasites

“…chytrids). These true fungi are commonly found in freshwater, brackish and marine pelagic environments (Lepère et al, 2016;Hassett et al, 2017;Maier and Peterson, 2017). Chytrid fungi display a characteristic free-living life stage as flagellated zoospores.…”

Chytridiomycosis of Marine Diatoms—The Role of Stress Physiology and Resistance in Parasite-Host Recognition and Accumulation of Defense Molecules

“…Conversely, chytrid infections of marine microalgae and cyanobacteria and in particular diatoms (Bacillariophyceae), have only been considered in recent years (e.g., [5,6,7,8]). Although latest molecular surveys have shown that chytrids are ubiquitous and common in marine environments around the globe (e.g., [9,10,11,12]), the biology and eco-evolutionary role of marine aquatic parasites in general, and chytrids in particular remain largely unstudied.…”