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Sediment anoxia limits microbial-driven seagrass carbon remineralization under warming conditions

journal contribution
posted on 2017-06-01, 00:00 authored by Stacey Trevathan-TackettStacey Trevathan-Tackett, J R Seymour, D A Nielsen, Peter MacreadiePeter Macreadie, T C Jeffries, J Sanderman, J Baldock, J M Howes, A D L Steven, P Ralph
Seagrass ecosystems are significant carbon sinks, and their resident microbial communities ultimately determine the quantity and quality of carbon sequestered. However, environmental perturbations have been predicted to affect microbial-driven seagrass decomposition and subsequent carbon sequestration. Utilizing techniques including 16S-rDNA sequencing, solid-state NMR and microsensor profiling, we tested the hypothesis that elevated seawater temperatures and eutrophication enhance the microbial decomposition of seagrass leaf detritus and rhizome/root tissues. Nutrient additions had a negligible effect on seagrass decomposition, indicating an absence of nutrient limitation. Elevated temperatures caused a 19% higher biomass loss for aerobically decaying leaf detritus, coinciding with changes in bacterial community structure and enhanced lignocellulose degradation. Although, community shifts and lignocellulose degradation were also observed for rhizome/root decomposition, anaerobic decay was unaffected by temperature. These observations suggest that oxygen availability constrains the stimulatory effects of temperature increases on bacterial carbon remineralization, possibly through differential temperature effects on bacterial functional groups, including putative aerobic heterotrophs (e.g. Erythrobacteraceae, Hyphomicrobiaceae) and sulfate-reducers (e.g. Desulfobacteraceae). Consequently, under elevated seawater temperatures, carbon accumulation rates may diminish due to higher remineralization rates at the sediment surface. Nonetheless, the anoxic conditions ubiquitous to seagrass sediments can provide a degree of carbon protection under warming seawater temperatures.

History

Journal

FEMS microbiology ecology

Volume

93

Issue

6

Article number

fix033

Pagination

1 - 15

Publisher

Oxford University Press

Location

Oxford, Eng.

ISSN

0168-6496

eISSN

1574-6941

Publication classification

C Journal article; C1 Refereed article in a scholarly journal

Copyright notice

2017, FEMS