The Distribution and Role of Active Fungi in the Marine Subsurface Across Different Oceanic Provinces

Ginny Edgcomb, Geology & Geophysics
William Orsi, Geology & Geophysics



Little is known about which microorganisms have the most impact on biogeochemical cycles in the marine subsurface, and practically nothing is known about microbial eukaryotes in these ecosystems.   We have produced the first survey of active subsurface microbial eukaryotes across a globally distributed sample collection of sediments from up to 48 meters below seafloor (mbsf).   The data reveal an unexpected dramatic increase in fungal diversity with increasing sediment depth.   Unique communities of fungi inhabit different locations and are selected for as a result of geographic isolation and differential responses to in situ geochemical conditions.   We hypothesize 1) that the diversity of subsurface fungi increases substantially with sediment depth, and 2) that fungi play an important role in large scale elemental cycling and organic substrate turnover in the marine subsurface.   This project aims to test these hypotheses by 1) conducting a more detailed profile of fungal diversity at 5 depths in Iberian Margin sediments spanning 10-120 mbsf using RNA-based approaches to target active fungi, and 2) sequencing two metatranscriptomes for analysis of fungal derived message RNA coding for functional proteins in Peru Margin (IODP site 1229) sediments from 5 and 50-mbsf.   Gene expression studies will provide insights into the important role that fungi may play in large scale elemental cycling and organic substrate turnover in the marine subsurface.