Biogeochemical measurements associated to deep-sea wood falls

DOI

Large organic food falls to the deep sea - such as whale carcasses and wood logs - support the development of reduced, sulfidic niches in an otherwise oxygenated, oligotrophic deep-sea environment. These transient hot spot ecosystems may serve the dispersal of highly adapted chemosynthetic organisms such as thiotrophic bivalves and siboglinid worms. Here we investigated the biogeochemical and microbiological processes leading to the development of sulfidic niches. Wood colonization experiments were carried out for the duration of one year in the vicinity of a cold seep area in the Nile deep-sea fan (Eastern Mediterranean) at depths of 1690 m. Wood logs were deployed in 2006 during the BIONIL cruise (RV Meteor M70/2 with ROV Quest, Marum, Germany) and sampled in 2007 during the Medeco-2 cruise (RV Pourquoi Pas? with ROV Victor 6000, Ifremer, France). Wood-boring bivalves played a key role in the initial degradation of the wood, the dispersal of wood chips and fecal matter around the wood log, and the provision of colonization surfaces to other organisms. Total oxygen uptake measured with a ROV-operated benthic chamber module was higher at the wood (0.5 m away) in contrast to 10 m away at a reference site (25 mmol m-2 d-1 and 1 mmol m-2 d-1, respectively), indicating an increased activity of sedimentary communities around the wood falls. Bacterial cell numbers associated with wood increased substantially from freshly submerged wood to the wood chip/fecal matter layer next to the wood experiments, as determined with Acridine Orange Direct Counts (AODC) and DAPI-stained counts. Microsensor measurements of sulfide, oxygen and pH were conducted ex situ. Sulfide fluxes were higher at the wood experiments when compared to reference measurements (19 and 32 mmol m-2 d-1 vs. 0 and 16 mmol -2 d-1, respectively). Sulfate reduction (SR) rates at the wood experiments were determined in ex situ incubations (1.3 and 2.0 mmol m-2 d-1) and fell into the lower range of SR rates previously observed from other chemosynthetic habitats at cold seeps. There was no influence of wood deposition on phosphate, silicate and nitrate concentrations, but ammonium concentrations were elevated at the wood chip-sediment boundary layer. Concentrations of dissolved organic carbon were much higher at the wood experiments (wood chip-sediment boundary layer) in comparison to measurements at the reference sites, which may indicate that cellulose degradation was highest under anoxic conditions and hence enabled by anaerobic benthic bacteria, e.g. fermenters and sulfate reducers. Our observations demonstrate that, after one year, the presence of wood at the seafloor had led to the creation of sulfidic niches, comparable to what has been observed at whale falls, albeit at lower rates.

Supplement to: Bienhold, Christina; Pop Ristova, Petra; Wenzhöfer, Frank; Dittmar, Thorsten; Boetius, Antje (2013): How deep-sea wood falls sustain chemosynthetic life. PLoS ONE, 8(1), e53590

Identifier
DOI https://doi.org/10.1594/PANGAEA.802516
Related Identifier https://doi.org/10.1371/journal.pone.0053590
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.802516
Provenance
Creator Bienhold, Christina ORCID logo; Pop Ristova, Petra ORCID logo; Wenzhöfer, Frank; Dittmar, Thorsten ORCID logo; Boetius, Antje ORCID logo
Publisher PANGAEA
Publication Year 2012
Funding Reference Seventh Framework Programme https://doi.org/10.13039/100011102 Crossref Funder ID 226354 https://cordis.europa.eu/project/id/226354 Hotspot Ecosystem Research and Mans Impact On European Seas; Sixth Framework Programme https://doi.org/10.13039/100011103 Crossref Funder ID 511234 https://cordis.europa.eu/project/id/511234 Hotspot Ecosystem Research on the Margins of European Seas
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Representation
Language English
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 11 datasets
Discipline Earth System Research
Spatial Coverage (30.352W, 32.533S, 30.356E, 32.535N)
Temporal Coverage Begin 2007-11-10T17:25:40Z
Temporal Coverage End 2007-11-13T06:15:51Z