Fungal planktonic community related to salinity and temperature in an oligotrophic sea.

Marine fungi play a crucial role in carbon cycling and food webs by acting as saprophytes or parasites and shaping host communities. However, our knowledge of these fungi in the marine ecosystem remains limited. To address this gap, we conducted a study to investigate the diversity of planktonic fungal communities in the Red Sea, a warm and oligotrophic sea. We collected water samples from the photic layer at six sites along the Red Sea basin and analyzed the fungal community by targeting the 28S rRNA gene. Our results showed that Chytridiomycota dominated these communities, accounting for 85% of reads, followed by members of the divisions Basidiomycota (4.7%) and Cryptomycota (4.13%). Interestingly, we found that fungal communities did not exhibit significant changes with depth or chlorophyll concentration. However, they did vary with the latitudinal gradient in environmental conditions, which is characterized by high temperature (ranging from 22.3 to 27.0°C) and salinity (ranging from 38.0 to 40.4 PSU). Specifically, the proportions of Chytridomycetes and Neocallimastigomycetes (the two dominant classes of Chytridiomycota) were negatively correlated between themselves. Chytridomycetes exhibited a negative correlation with temperature (R