Plankton biomass decomposition enriches for methanogenic archaea in near-shore waters of Puget Sound
Streaming Media
Presentation Abstract
Aerobic marine surface waters are typically oversaturated with the greenhouse gas methane. This phenomenon is known as the “ocean methane paradox” because of the existing paradigm that methanogenesis is restricted to anaerobic environments. As a result, the ocean emits large quantities of methane to the atmosphere. Near-shore and coastal waters are responsible for the majority of oceanic methane emissions. Yet the biological sources of methane remain poorly characterized. Resolving the biological underpinnings of coastal methane production is important for assessing its sensitivity to ocean change and predicting future contributions of coastal waters to global methane emissions. We explored decaying plankton biomass as a potential source of methane in near-shore waters of the Puget Sound. We hypothesized that anaerobic conditions, promoted by the active microbial decomposition of biomass, would support microorganisms with the capability for methanogenesis. Aerobic surface water and plankton were collected from a floating dock in Old Town Tacoma (Washington, USA), sealed gas-tight, and left to decay. To evaluate possible methane precursor substrates, samples were enriched with trimethylamine (TMA) and dimethyl sulfide (DMS), two common marine metabolites produced by algae that are significant carbon sources in the ocean and are present and degradable in aerobic and anaerobic environments. Through continuous monitoring of dissolved oxygen concentrations during plankton decomposition, we found that methane production was associated with anaerobic metabolism of TMA and DMA. Using metagenomic analysis we found that methanogenic Archaea of the family methanosarcinaceae were more abundant in the decomposing plankton samples that produced methane. Further metagenomic reconstruction of the genomes of archaeal and other microbial populations enriched during plankton decomposition will resolve the genes and biochemical pathways required for TMA and DMS conversion to methane. These results implicate water column microbial decomposition of plankton biomass as an important source of methane in coastal ecosystems.
Session Title
Poster Session 3: Land - Water Connections
Conference Track
SSE14: Posters
Conference Name
Salish Sea Ecosystem Conference (2022 : Online)
Document Type
Event
SSEC Identifier
SSE-posters-361
Start Date
27-4-2022 4:00 PM
End Date
27-4-2022 4:30 PM
Type of Presentation
Poster
Genre/Form
conference proceedings; presentations (communicative events); posters
Subjects – Topical (LCSH)
Methanobacteriaceae--Washington (State)--Puget Sound; Methanobacterium--Washington (State)--Puget Sound; Marine plankton--Washington (State)--Puget Sound
Geographic Coverage
Puget Sound (Wash.)
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Type
Text
Language
English
Format
application/pdf
Included in
Fresh Water Studies Commons, Marine Biology Commons, Natural Resources and Conservation Commons
Plankton biomass decomposition enriches for methanogenic archaea in near-shore waters of Puget Sound
Aerobic marine surface waters are typically oversaturated with the greenhouse gas methane. This phenomenon is known as the “ocean methane paradox” because of the existing paradigm that methanogenesis is restricted to anaerobic environments. As a result, the ocean emits large quantities of methane to the atmosphere. Near-shore and coastal waters are responsible for the majority of oceanic methane emissions. Yet the biological sources of methane remain poorly characterized. Resolving the biological underpinnings of coastal methane production is important for assessing its sensitivity to ocean change and predicting future contributions of coastal waters to global methane emissions. We explored decaying plankton biomass as a potential source of methane in near-shore waters of the Puget Sound. We hypothesized that anaerobic conditions, promoted by the active microbial decomposition of biomass, would support microorganisms with the capability for methanogenesis. Aerobic surface water and plankton were collected from a floating dock in Old Town Tacoma (Washington, USA), sealed gas-tight, and left to decay. To evaluate possible methane precursor substrates, samples were enriched with trimethylamine (TMA) and dimethyl sulfide (DMS), two common marine metabolites produced by algae that are significant carbon sources in the ocean and are present and degradable in aerobic and anaerobic environments. Through continuous monitoring of dissolved oxygen concentrations during plankton decomposition, we found that methane production was associated with anaerobic metabolism of TMA and DMA. Using metagenomic analysis we found that methanogenic Archaea of the family methanosarcinaceae were more abundant in the decomposing plankton samples that produced methane. Further metagenomic reconstruction of the genomes of archaeal and other microbial populations enriched during plankton decomposition will resolve the genes and biochemical pathways required for TMA and DMS conversion to methane. These results implicate water column microbial decomposition of plankton biomass as an important source of methane in coastal ecosystems.
