A glimpse into the biogeography, seasonality, and ecological functions of arctic marine Oomycota

Abstract

High-latitude environments are warming, leading to changes in biological diversity patterns of taxa. Oomycota are a group of fungal-like organisms that comprise a major clade of eukaryotic life and are parasites of fish, agricultural crops, and algae. The diversity, functionality, and distribution of these organisms are essentially unknown in the Arctic marine environment. Thus, it was our aim to conduct a first screening, using a functional gene assay and high-throughput sequencing of two gene regions within the 18S rRNA locus to examine the diversity, richness, and phylogeny of marine Oomycota within Arctic sediment, seawater, and sea ice. We detected Oomycota at every site sampled and identified regionally localized taxa, as well as taxa that existed in both Alaska and Svalbard. While the recently described diatom parasite Miracula helgolandica made up about 50% of the oomycete reads found, many lineages were observed that could not be assigned to known species, including several that clustered with another recently described diatom parasite, Olpidiopsis drebesii. Across the Arctic, Oomycota comprised a maximum of 6% of the entire eukaryotic microbial community in Barrow, Alaska May sediment and 10% in sea ice near the Svalbard archipelago. We found Arctic marine Oomycota encode numerous genes involved in parasitism and carbon cycling processes. Ultimately, these data suggest that Arctic marine Oomycota are a reservoir of uncharacterized biodiversity, the majority of which are probably parasites of diatoms, while others might cryptically cycle carbon or interface other unknown ecological processes. As the Arctic continues to warm, lower-latitude Oomycota might migrate into the Arctic Ocean and parasitize non-coevolved hosts, leading to incalculable shifts in the primary producer community.

Phylogeny and cultivation of the holocarpic oomycete Diatomophthora perforans comb. nov., an endoparasitoid of marine diatoms

“…As shown in this study, their clade designated as OOM_1 corresponds to the genus Miracula (Buaya et al 2017), with their sequences designated as OOM_1-1 being not genetically differentiated with M. helgolandica, and are probably conspecific with that species. Miracula helgolandica seems to be a very widespread species, especially in higher latitudes (Hassett et al 2019). The clade designated by Garvetto et al (2018Garvetto et al ( , 2020 as OOM_2 corresponds to the genus Diatomophthora, with one sequence derived from a specimen with Licmophora (Garvetto et al 2020) probably corresponding to an individual belonging to D. drebesii.…”

“…Oomycete parasitoids of diatoms are ubiquitous in the aquatic environment (Karling 1942;Sparrow 1960). Despite their widespread occurrence (Garvetto et al 2018;Hassett et al 2019), little is known about the biology and ecology of these holocarpic organisms, especially in marine habitats (Sparrow 1936;Scholz et al 2015;Hassett et al 2019). However, these parasitoids are known to play a significant role in breaking down blooms of their host diatoms, and might also play a role in the marine food web (Skovgaard 2014;Scholz et al 2015).…”

Salinity, pH and temperature growth ranges of Halophytophthora isolates suggest their physiological adaptations to mangrove environments

“…Unknown Halophytophthora species were also isolated from the Wadden Sea (Denmark), the Dutch Delta area (the Netherlands) and Thau lagoon (France), suggesting that species of this genus are not restricted to tropical/subtropical locations but have a much wider worldwide distribution than previously thought (Man in ’t Veld et al 2019 ). Hassett et al ( 2019 ), using a high throughput sequencing technique, detected sequence signatures of Halophytophthora in the Arctic. Distribution of Halophytophthora and related taxa worldwide might have been overlooked; alternatively, Halophytophthora species can disperse through recent events, e.g.…”

Taxonomy and phylogeny of Aphanomycopsis bacillariacearum, a holocarpic oomycete parasitoid of the freshwater diatom genus Pinnularia

“…Protist pathogens of photosynthetic eukaryotes are widely distributed in aquatic environments (Chambouve et al 2019;Markussen Bjorbaekmo et al 2019;Hassett et al 2019). These biotrophic parasites and parasitoids are diverse and infect wide varieties of hosts, especially marine and freshwater diatoms (Kühn 1998;Scholz et al 2016;Guinder et al 2017;Chambouve et al 2019).…”

“…These biotrophic parasites and parasitoids are diverse and infect wide varieties of hosts, especially marine and freshwater diatoms (Kühn 1998;Scholz et al 2016;Guinder et al 2017;Chambouve et al 2019). However, the biology and ecological importance of these inconspicuous organisms are still widely unknown and understudied despite their abundance also during diatom blooms (Hanic et al 2009;Thines et al 2015;Hassett et al 2019). Many of the oomycete parasitoids of freshwater diatoms were documented in studies from more than half a century ago (Karling 1942;Sparrow 1960) and were classified into various genera, mainly Aphanomycopsis (Scherffel 1925), Ectrogella (Zopf 1884), Lagenidium (Zopf 1878), and Olpidiopsis (Cornu 1872).…”