Temporal dynamics of marine fungi on epiphytic protist assemblage on macroalgae: demonstration of a parasitoid chytrid-dinoflagellate association

Abstract

The field of marine fungal diversity and ecology remains largely unexplored. This study provides new and valuable insights into the diversity, ecology, and temporal dynamics of epiphyte protist and fungal assemblages on coastal Mediterranean macroalgae during the summer season. The temporal sampling results showed that dinoflagellates become the most abundant taxonomic group, and its structure and relation with fungi, especially on Chytridiomycota, were evaluated in detail. The study revealed that temporal dynamics of the chytrid community are significantly impacted by the assemblage of epiphytic dinoflagellate species. The Chytridiomycota group was found to be primarily represented by Dinomyces arenysensis and a Lobulomycota representative yet to be described. The relative abundance of chytrids was at its highest following the peak of the dinoflagellate Ostreopsis sp. proliferation with D. arenysensis being the dominating chytrid, having a maximum infection prevalence of 2%. The results of laboratory experiments showed a low prevalence of D. arenysensis over its host Ostreopsis and a stable coexistence. Moreover, although the chytrid demonstrates a preference for parasitizing dinoflagellate cells, it has been shown to utilize pollen as a resource to sustain viable infections demonstrating a facultative and generalist parasite. The study underscores the diversity and potential impact of marine chytrids on epiphyte protist communities, bringing attention to the presence of zoosporic parasites in this understudied benthic habitat