Fungal communities in sediments along a depth gradient in the Eastern Tropical Pacific

Abstract

Deep waters represent the largest biome on Earth and the largest ecosystem of Costa Rica. Fungi play a fundamental role in global biogeochemical cycling in marine sediments, yet, they remain little explored. We studied fungal diversity and community composition in several marine sediments from 16 locations sampled along a bathymetric gradient (from a depth of 380 to 3474 m) in two transects of about 1500 km length in the Eastern Tropical Pacific (ETP) of Costa Rica. Sequence analysis of the V7-V8 region of the 18S rRNA gene obtained from sediment cores revealed the presence of 787 fungal amplicon sequence variants (ASVs). On average, we detected a richness of 75 fungal ASVs per sample. Ascomycota represented the most abundant phylum with Saccharomycetes constituting the dominant class. Three ASVs accounted for ca. 63% of all fungal sequences: the yeast Metschnikowia (49.4%), Rhizophydium (6.9%), and Cladosporium (6.7%). Although we distinguished a cluster dominated by yeasts and a second cluster dominated by filamentous fungi, we were unable to detect a strong effect of depth, temperature, salinity, dissolved oxygen, and pH on the composition of fungal communities. We highlight the need to understand further the ecological role of fungi in deep-sea ecosystems.

Intercomparison of Two Fluorescent Dyes to Visualize Parasitic Fungi (Chytridiomycota) on Phytoplankton

“…Since the pioneering work on chytrids in British lakes [20], chytrids have been primarily studied locally in a few lakes and on a limited number of isolates [6], mostly because their small and inconspicuous thalli are frequently overlooked or misidentified by the untrained eye when using light microscopy. During the last decade, advances in DNA sequencing assays have substantially broadened the observed diversity and distribution of chytrids in aquatic habitats, reaching from high-altitude lakes [21], coastal regions [22,23] to the deep-sea [24,25] across various climate zones [7,[26][27][28][29][30][31]. This recently discovered diversity and biogeography, however, remains to be complemented with direct observations of chytrid abundances and host identities in most of those habitats.…”