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 3,474 m) in two transects of about 1,500 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%). We distinguished a cluster composed mainly by yeasts, and a second cluster by filamentous fungi, but we were unable to detect a strong effect of depth and the overlying water temperature, salinity, dissolved oxygen (DO), and pH on the composition of fungal communities. We highlight the need to understand further the ecological role of fungi in deep-sea ecosystems.

Evolutionary Relationships, Phylogeographic Patterns, and a Hypothesis for Air- and Sea-driven Global Spread of Chromoblastomycosis by Etiological Fonsecaea Agents

“…Filamentous fungi and ascomycetes can grow in both natural and arti cial seawater media. Salinity, water temperature, dissolved oxygen, and pH in seawater do not strongly affect growth of fungal communities, even of mycelia resting over long periods (Mouton et al, 2012;Manohar & Raghukumar, 2013;Rédou et al, 2015;Wijesekera et al, 2017;Grossart et al, 2019;Rojas-Jimenez et al, 2020). Fungi have been discovered in practically every marine ecosystem studied (Gladfelter et al, 2019;Grossart et al, 2019), including deep subsurface sediments (Rédou et al, 2014;Gladfelter et al, 2019;Vargas-Gastélum & Riquelme, 2020), coastal plankton (Taylor & Cunliffe, 2016), wood (Rämä et al, 2016;Lee et al, 2019;Rahaman et al, 2020), and marine animals (Wainwright et al, 2017;Amend et al, 2019) at depths ranging from the deep sea to surface waters (Amend et al, 2019).…”

Fungal diversity in sediments of the eastern tropical Pacific oxygen minimum zone revealed by metabarcoding

“…Fungal communities in surface sediments sampled along a bathymetric transect have generally shown large variations in their composition [ 29 – 31 ]; in contrast, surface sediments along the South China Sea showed similarity to each other [ 32 ]. Overall, fungal diversity figures are higher at nearshore than offshore benthic sites [ 33 , 34 ], perhaps because of the sediment source, geographic distance, or site-specific environmental factors [ 32 , 33 , 35 , 36 ].…”

“…In these sediments, fungi have been considered the dominant eukaryotic kingdom [ 30 ] and the third most abundant microbial component (after Bacteria and Archaea; [ 38 ]). Within vertical gradients, fungal composition can be highly variable at the small-scale (<100 cm below seafloor; [ 29 , 41 ]) and the large-scale (>100 cm below seafloor; [ 30 , 32 , 38 ] by the possible influence of site-specific conditions. However, to the extent of our knowledge, fungal diversity in the Mexican OMZ remains unexplored, resulting in a limited understanding of the community structure and its importance in the ecosystem.…”

Diversity of Deep-Sea Echinoderms From Costa Rica

“…Recent studies estimated that over 60% of the total area of the country is below 2,000 m depth, and over one-third below 3,000 m (Cortés and Benavides-Varela, in prep.). Eastern Tropical Pacific (ETP) deep waters (below 200 m) constitute a particularly important ecosystem in Costa Rica, since they represent about 90% of the whole territory and the last frontier in the international scientific agendas (Cortés, 2019;Rojas-Jiménez et al, 2020;Azofeifa-Solano and Cortés, 2021).…”