Eukaryotic microbes, principally fungi and labyrinthulomycetes, dominate biomass on bathypelagic marine snow

Abstract

In the bathypelagic realm of the ocean, the role of marine snow as a carbon and energy source for the deep-sea biota and as a potential hotspot of microbial diversity and activity has not received adequate attention. Here, we collected bathypelagic marine snow by gentle gravity filtration of sea water onto 30 μm filters from~1000 to 3900 m to investigate the relative distribution of eukaryotic microbes. Compared with sediment traps that select for fast-sinking particles, this method collects particles unbiased by settling velocity. While prokaryotes numerically exceeded eukaryotes on marine snow, eukaryotic microbes belonging to two very distant branches of the eukaryote tree, the fungi and the labyrinthulomycetes, dominated overall biomass. Being tolerant to cold temperature and high hydrostatic pressure, these saprotrophic organisms have the potential to significantly contribute to the degradation of organic matter in the deep sea. Our results demonstrate that the community composition on bathypelagic marine snow differs greatly from that in the ambient water leading to wide ecological niche separation between the two environments.

Global diversity and geography of planktonic marine fungi

“…There are currently between 120,000 and 143,273 accepted fungal species (Hawksworth and Lucking 2017, www.indexfungorum.org); of these, 1255 species have been recovered from the marine realm (Jones et al , 2019. Even though fungi comprise substantial quantities of biomass in the marine realm (Gutiérrez et al 2011, Bochdansky et al 2017, Hassett et al 2019, their activity is not represented in marine ecosystem models (Worden et al 2015).…”

Highlighting patterns of fungal diversity and composition shaped by ocean currents using the East China Sea as a model

“…Concerning microbial eukaryotes, differences in the community distribution among bathypelagic samples from the Atlantic, Pacific and Indian Oceans were also mostly explained by water masses (Pernice et al., ). Fungi represent an important group of microbial eukaryotes in a wide diversity of marine habitats ranging from coastal waters, for example, off Hawaii (Gao, Johnson, & Wang, ) or Chile (Gutiérrez, Pantoja, Tejos, & Quiñones, ), to bathypelagic marine snow (Bochdansky, Clouse, & Herndl, ), where fungi appeared dominant among microeukaryotes. Fungal occurrence is well correlated with organic matter, suggesting important roles as recyclers in the ocean (Jones, ; Richards et al., ).…”

Models of Plankton Community Changes during a Warm Water Anomaly in Arctic Waters Show Altered Trophic Pathways with Minimal Changes in Carbon Export

“…Metfies et al (2016), analyzing data for this region, did not detect many fungi (OTUs) in the water column; they were found only occasionally in waters dominated by diatoms. Fungi seem to be mainly associated with marine snow (Bochdansky et al, 2017) and in sediment-trap material (Metfies, in prep.). Increasing the lower limit of DOC production in the model can force more carbon through the DOC compartment which might decrease other loss terms, such as detritus production during and after the warm water event, presumably channeling more carbon through the microbial loop.…”