|Transformation and fate of microphytobenthos carbon in subtropical, intertidal sediments: potential for long-term carbon retention revealed by 13C-labeling|
|B. D. Eyre1  J. M. Oakes1 |
|Centre for Coastal Biogeochemistry, Southern Cross University, Lismore, Australia|
|Others : 985660
DOI : doi:10.5194/bg-11-1927-2014
【 摘 要 】Microphytobenthos (MPB) are ubiquitous in coastal sediments, but the fate oftheir production (carbon biomass) is poorly defined. The processing and fateof MPB-derived carbon in subtropical intertidal sediments was investigatedthrough in situ labeling with 13C-bicarbonate. Of the added 13C,100% was fixed within ~ 4 h, suggesting that MPBproductivity was limited by inorganic carbon availability. Although therewas rapid transfer of 13C to bacteria (within 12 h), a relatively smallfraction of 13C was transferred to heterotrophs (up to 12.5% oftotal fixed 13C into bacteria and 0.01% into foraminifera). MPB wasthe major reservoir for 13C throughout the study, suggesting thatproduction of extracellular polymeric substances was limited and/or MPBrecycled 13C. This retention of 13C was reflected in remarkablyslow estimated turnover times for the MPB community (66–100 d). Over 31 d,~ 70% of the 13C was lost from sediments. This wasprimarily via resuspension (~ 55%), enhanced by elevatedfreshwater flow following rainfall. A further ~ 13% waslost via fluxes of dissolved inorganic carbon during inundation. However,13C losses via dissolved organic carbon fluxes from inundated sediments(0.5%) and carbon dioxide fluxes from exposed sediments ( 30 d, despite highresuspension, demonstrates the potentially substantial longer term retentionof MPB-derived carbon in unvegetated sediments and suggests that MPB maycontribute to carbon burial ("blue carbon").
© Author(s) 2014. This work is distributedunder the Creative Commons Attribution 3.0 License.
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