Diversity, Abundance, and Ecological Roles of Planktonic Fungi in Marine Environments

Abstract

Fungi are considered terrestrial and oceans are a “fungal desert”. However, with the considerable progress made over past decades, fungi have emerged as morphologically, phylogenetically, and functionally diverse components of the marine water column. Although their communities are influenced by a plethora of environmental factors, the most influential include salinity, temperature, nutrients, and dissolved oxygen, suggesting that fungi respond to local environmental gradients. The biomass carbon of planktonic fungi exhibits spatiotemporal dynamics and can reach up to 1 μg CL−1 of seawater, rivaling bacteria on some occasions, which suggests their active and important role in the water column. In the nutrient-rich coastal water column, there is increasing evidence for their contribution to biogeochemical cycling and food web dynamics on account of their saprotrophic, parasitic, hyper-parasitic, and pathogenic attributes. Conversely, relatively little is known about their function in the open-ocean water column. Interestingly, methodological advances in sequencing and omics approach, the standardization of sequence data analysis tools, and integration of data through network analyses are enhancing our current understanding of the ecological roles of these multifarious and enigmatic members of the marine water column. This review summarizes the current knowledge of the diversity and abundance of planktonic fungi in the world’s oceans and provides an integrated and holistic view of their ecological roles.

Profiling Analysis of Filter Feeder Polypedilum (Chironomidae) Gut Contents Using eDNA Metabarcoding Following Contrasting Habitat Types—Weir and Stream

“…It was apparent that the presence of different planktonic fungal clusters denoted the involvement of fungi in the decomposition of organic matter and aggregation. A similar relation between fungi and sediments in the aquatic environment is inferred in other reports also [ 61 , 63 , 69 , 70 ]. The ratio of protozoa in this study symbolizes the feeding of chironomids at different layers in the habitats, even in the anoxic zones [ 53 , 71 , 72 ].…”

“…Notably, we recorded diverse fungal groups in the diet profile ( Table 3 ). Fungal content in the diet resembles the enzymatic synthesis linked to metabolizing activities in the gut [ 59 , 60 ] by converting detritus into more nutritious and readily digestible products [ 4 , 61 ].…”

“…The fungal groups in the gut content typically determined the sediment conditions since the diverse fungal species in previous studies have been identified in the sediments of water habitats. This is a critical interpretation of the coexistence of the fungal population in planktons and their interaction distinctly in biogeochemical cycling in the water and sediment layers [ 61 , 68 ]. It was apparent that the presence of different planktonic fungal clusters denoted the involvement of fungi in the decomposition of organic matter and aggregation.…”

Different Geographic Strains of Dinoflagellate Karlodinium veneficum Host Highly Diverse Fungal Community and Potentially Serve as Possible Niche for Colonization of Fungal Endophytes

“…Fungi are persistent in marine ecosystems; however, they are understudied compared with their terrestrial counterparts [ 9 , 10 ]. As an integral component of marine microbiomes, fungi are ubiquitously found in nearly every marine habitat, from coastal areas to the deep ocean [ 9 ].…”

“…As an integral component of marine microbiomes, fungi are ubiquitously found in nearly every marine habitat, from coastal areas to the deep ocean [ 9 ]. Although considerable efforts have been made to explore fungus–biota interactions in terrestrial systems, much less endeavor has been undertaken to elucidate the paralleled interactions in aquatic, and particularly, marine environments [ 9 , 10 , 11 ]. In a few field studies in open-ocean and coastal ecosystems, the authors demonstrated positive correlations between phytoplankton and fungal abundance [ 4 , 5 , 6 , 7 , 12 , 13 , 14 , 15 , 16 ].…”