Seasonal Dynamics of Pelagic Mycoplanktonic Communities: Interplay of Taxon Abundance, Temporal Occurrence, and Biotic Interactions

Abstract

Marine fungi are an important component of pelagic planktonic communities. However, it is not yet clear how individual fungal taxa are integrated in marine processes of the microbial loop and food webs. Most likely, biotic interactions play a major role in shaping the fungal community structure. Thus, the aim of our work was to identify possible biotic interactions of mycoplankton with phytoplankton and zooplankton groups and among fungi, and to investigate whether there is coherence between interactions and the dynamics, abundance and temporal occurrence of individual fungal OTUs. Marine surface water was sampled weekly over the course of 1 year, in the vicinity of the island of Helgoland in the German Bight (North Sea). The mycoplankton community was analyzed using 18S rRNA gene tag-sequencing and the identified dynamics were correlated to environmental data including phytoplankton, zooplankton, and abiotic factors. Finally, co-occurrence patterns of fungal taxa were detected with network analyses based on weighted topological overlaps (wTO). Of all abundant and persistent OTUs, 77% showed no biotic relations suggesting a saprotrophic lifestyle. Of all other fungal OTUs, nearly the half (44%) had at least one significant negative relationship, especially with zooplankton and other fungi, or to a lesser extent with phytoplankton. These findings suggest that mycoplankton OTUs are embedded into marine food web chains via highly complex and manifold relationships such as parasitism, predation, grazing, or allelopathy. Furthermore, about one third of all rare OTUs were part of a dense fungal co-occurrence network probably stabilizing the fungal community against environmental changes and acting as functional guilds or being involved in fungal

Mycoplankton Biome Structure and Assemblage Processes Differ Along a Transect From the Elbe River Down to the River Plume and the Adjacent Marine Waters

“…The comparative analysis as PCoA including communities of this study and the one of Banos et al (2020) monitoring mycoplankton communities at Helgoland Roads over a year showed a grouping of samples 20-24 (marine samples) with the samples of Banos et al (2020), while the sample group structure of groups I and II remained intact and well separated from the rest (Supplementary Figure 4).…”

“…Sequences were analyzed with a phylogeny-based approach following the pipeline of Banos et al (2020). Shortly, quality-controlled sequence reads were passed on for classification.…”

Diversity and biomass dynamics of unicellular marine fungi during a spring phytoplankton bloom

“…The low number of temporally dominant OTUs seems to be a general pattern of mycoplankton communities in coastal environments (Taylor and Cunliffe, 2016; Picard, 2017), where they can peak in abundance several times a year and be categorized according to such patterns (Banos et al ., 2020). The fluctuations can be attributed to a direct or indirect effect of periodically changing environmental conditions, typical of coastal environments (Jeffries et al ., 2016; Taylor and Cunliffe, 2016; Duan et al ., 2018; Banos et al ., 2020). Important factors include periodic transport of water masses with riverine inputs, tidal mixing, wind forcing and sediment resuspension (Tian et al ., 2009).…”

“…Sequence analysis followed the protocol of Banos et al . (2020). In short, quality controlled reads were aligned to the non‐redundant SILVA SSURef_NR99_132 database (Quast et al ., 2013), using the SINA aligner v.1.2.11 (Pruesse et al ., 2012) in ARB (Ludwig et al ., 2004), with the default settings.…”

“…The structure of these communities appears to vary with latitude and local influences, with evidence suggesting a dominance by members of the Dikarya (Ascomycota and Basidiomycota) or the Chytridiomycota (Comeau et al ., 2016; Hassett et al ., 2016; Tisthammer et al ., 2016; Duan et al ., 2018). Time‐series data have also highlighted the impact of seasons on community composition and more specifically, changes in nutrients, temperature and, with respect to certain taxa, phytoplankton (Taylor and Cunliffe, 2016; Duan et al ., 2018; Banos et al ., 2020). To understand these driving factors further, a few studies have tried to elucidate ecological roles for the dominant fungal taxa and revealed the presence of parasitism and saprotrophism within the water column (Gutiérrez et al ., 2016; Scholz et al ., 2016; Cunliffe et al ., 2017).…”