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Macroalgal blooms trigger the breakdown of seagrass blue carbon
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posted on 2020-01-01, 00:00 authored by Songlin Liu, Stacey Trevathan-TackettStacey Trevathan-Tackett, Carolyn Jane Ewers Lewis, Xiaoping Huang, Peter MacreadiePeter MacreadieIntensive macroalgal blooms, a source of labile organic carbon (LOC) induced by coastal nutrient loading in some seagrass ecosystems, create ideal conditions for enhanced recalcitrant organic carbon (ROC) loss via the cometabolism effect. Here, we carried out a 62-day laboratory experiment to see if density-dependent addition of macroalgal biomass can influence the seagrass decomposition process, including seagrass detritus carbon chemistry, greenhouse emissions, and bacterial communities. We found that higher density macroalgal addition stimulated microbes to decompose ∼20% more of the seagrass biomass compared to other treatments, which was also reflected in enhanced (∼twofold) greenhouse gas emissions. Although the composition of the seagrass-associated microbiome communities was unaffected by the addition of macroalgae, we showed that high macroalgal addition caused a relative depletion in the ROC as lignin and lipid compounds, as well as δ13C depletion and δ15N enrichment of the seagrass detritus. These results suggest that macroalgal blooms may stimulate the remineralization of recalcitrant components of seagrass detritus via cometabolism, possibly through providing available energy or resources for the synthesis of ROC-degrading enzymes within the resident microbial population. This study provides evidence that cometabolism can be a mechanism for leading to reduced seagrass blue carbon sequestration and preservation.
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Journal
Environmental science & technologyVolume
54Issue
22Pagination
14750 - 15760Publisher
American Chemical SocietyLocation
Washington, D.C.Publisher DOI
ISSN
0013-936XeISSN
1520-5851Language
engPublication classification
C1 Refereed article in a scholarly journalUsage metrics
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