Spatiotemporal Distribution and Assemblages of Planktonic Fungi in the Coastal Waters of the Bohai Sea

Abstract

Fungi play a critical role in the nutrient cycling and ecological function in terrestrial and freshwater ecosystems. Yet, many ecological aspects of their counterparts in coastal ecosystems remain largely elusive. Using high-throughput sequencing, quantitative PCR, and environmental data analyses, we studied the spatiotemporal changes in the abundance and diversity of planktonic fungi and their abiotic and biotic interactions in the coastal waters of three transects along the Bohai Sea. A total of 4362 ITS OTUs were identified and more than 60% of which were unclassified Fungi. Of the classified OTUs three major fungal phyla, Ascomycota, Basidiomycota, and Chytridiomycota were predominant with episodic low dominance phyla Cryptomycota and Mucoromycota (Mortierellales). The estimated average Fungi-specific 18S rRNA gene qPCR abundances varied within 4.28 × 106 and 1.13 × 107copies/L with significantly (P < 0.05) different abundances among the transects suggesting potential influence of the different riverine inputs. The spatiotemporal changes in the OTU abundance of Ascomycota and Basidiomycota phyla coincided significantly (P < 0.05) with nutrients traced to riverine inputs and phytoplankton detritus. Among the eight major fungal orders, the abundance of Hypocreales varied significantly (P < 0.01) across months while Capnodiales, Pleosporales, Eurotiales, and Sporidiobolales varied significantly (P < 0.05) across transects. In addition, our results likely suggest a tripartite interaction model for the association within members of Cryptomycota (hyperparasites), Chytridiomycota (both parasites and saprotrophs), and phytoplankton in the coastal waters. The fungal network featured several hubs and keystone OTUs besides the display of cooperative and competitive relationship within OTUs. These results support the notion that planktonic fungi, hitherto mostly undescribed, play diverse ecological roles in marine habitats and further outline niche processes, tripartite and co-occurrence interaction as the major drivers of their community structure and spatiotemporal distribution in the coastal water column.

Fungal diversity in deep-sea sediments from the Magellan seamounts as revealed by a metabarcoding approach targeting the ITS2 regions

“…Nevertheless, Chytrids was found to dominate Arctic marine fungal communities and might change primary production patterns rapidly with increased light penetration through the Arctic Ocean (Hassett and Gradinger 2016 ). In marine habitats, Chytridiomycota, Mortierellomycota, and Mucoromycota have been characterised as decomposers of pollens and leaves (Phuphumirat et al 2016 ) or pathogens of marine algae and animals (Scholz et al 2016 ; Wang et al 2018 ). These discoveries suggest that these fungi played a wide array of ecological roles potentially in the marine environment.…”

“…Our present knowledge of deep-sea fungal diversity is largely based on the identification of the fruiting body, culturing surveys and conventional sequencing of the internal transcribed spacer (ITS) of rRNA gene clones (RaghuKumar et al 2004 ; Bass et al 2007 ; Nagano et al 2010 ; Singh et al 2011 , 2012 ; Xu et al 2014 , 2016 ; Zhang et al 2016 ). High-throughput sequencing (HTS) of DNA amplification from marine environments is a powerful approach for screening fungal communities with better capacity for detecting rare species, the taxa that present only as vegetative mycelia and cannot be cultured (Zhang et al 2016 ; Nagano et al 2017 ; Wang et al 2018 ; Xu et al 2018b ). A few of studies have been conducted to detect fungal assemblages present in bathypelagic and abyssopelagic zones and other specialised deep environments including hydrothermal systems, methane-dominated regions, and deep subsurface sediments (Bass et al 2007 ; Lai et al 2007 ; Takeshita et al 2007 ; Jebaraj and Raghukumar 2009 ; Le Calvez et al 2009 ; Nagano et al 2010 ; Nagahama et al 2011 ; Singh et al 2011 , 2012 ; Thaler et al 2012 ; Xu et al 2014 , 2016 , 2017 ).…”

Cryptic fungal diversity revealed in deep-sea sediments associated with whale-fall chemosynthetic ecosystems

“…Later, some of these unknown basal fungal lineages reported from deep-sea environments were affiliated within a novel fungal phylum, Cryptomycota (Jones et al 2011 ) and NCLC (Novel-Chytrid-Like-Clade) groups (Richards et al 2015 ). The presence of Cryptomycota and unknown basal fungal lineages, such as NCLC are more recognised and have been reported in recent years from many environments, including land, freshwater, sea ice, shallow to deep marine, with more extensive reporting from aquatic environments (both fresh and marine) (Jones et al 2011 ; Lazarus and James 2015 ; Ishii et al 2015 ; Richards et al 2015 ; Comeau et al 2016 ; Hassett and Gradinger 2016 ; Picard 2017 ; Rojas-Jimenez et al 2017 ; Wang et al 2018 ; Lepere et al 2019 ). Picard ( 2017 ) reported that marine benthic sediments harboured high proportion of novel sequences, which were assigned to early-diverging fungal groups and could not be assigned beyond phylum with statistical support, suggesting they belong to unknown lineages.…”

Diversity, Ecological Role and Biotechnological Potential of Antarctic Marine Fungi

“…In the last years, culture-dependent and molecular techniques have allowed us to describe a large number of fungal taxa in seawater [ 33 , 34 ]. Likewise, fungi have been identified in several polar environments [ 35 , 36 , 37 ].…”