Occurrence of Priming in the Degradation of Lignocellulose in Marine Sediments

Abstract

More than 50% of terrestrially-derived organic carbon (terrOC) flux from the continents to the ocean is remineralised in the coastal zone despite its perceived high refractivity. The efficient degradation of terrOC in the marine environment could be fuelled by labile marine-derived material, a phenomenon known as “priming effect”, but experimental data to confirm this mechanism are lacking. We tested this hypothesis by treating coastal sediments with 13C-lignocellulose, as a proxy for terrOC, with and without addition of unlabelled diatom detritus that served as the priming inducer. The occurrence of priming was assessed by the difference in lignocellulose mineralisation between diatom-amended treatments and controls in aerobic sediment slurries. Priming of lignocellulose degradation was observed only at the initial stages of the experiment (day 7) and coincided with overall high microbial activity as exemplified by total CO2 production. Lignocellulose mineralisation did not differ consistently between diatom treatments and control for the remaining experimental time (days 14–28). Based on this pattern, we hypothesize that the faster initiation of lignocellulose mineralisation in diatom-amended treatments is attributed to the decomposition of accessible polysaccharide components within the lignocellulose complex by activated diatom degraders. The fact that diatom-degraders contributed to lignocellulose degradation was also supported by the different patterns in 13C-enrichment of phospholipid fatty acids between treatments. Although we did not observe differences between treatments in the total quantity of respired lignocellulose at the end of the experiment, differences in timing could be important in natural ecosystems where the amount of time that a certain compound is subject to aerobic degradation before burial to deeper anoxic sediments may be limited.

Effects of zooplankton carcasses degradation on freshwater bacterial community composition and implications for carbon cycling

“…have been used. Although some authors have found support for ROM priming by more labile organic matter, mainly of algal origin (van Nugteren et al, 2009;Guenet et al, 2013;Hotchkiss et al, 2014;Bianchi et al, 2015;Gontikaki et al, 2015), others did not reveal any evidence for a positive priming effect (Bengtsson et al, 2014;Catalán et al, 2015;Dorado-García et al, 2015;Blanchet et al, 2017), or even found a negative priming effect (Gontikaki et al, 2013) with ROM being decomposed slower in the presence of a labile carbon source. Thus, it appears that the absence or presence of the priming effect may strongly depend on specific environmental or experimental conditions, which may also explain the absence of humic matter degradation in our HD treatments using Daphnia carcasses LOM as the primer.…”

Effects of organic matter and low oxygen on the mycobenthos in a coastal lagoon

“…Fungi can represent a major component of the initial microbial community that colonizes freshly bioturbated sediments (Taylor and Cunliffe, 2015) indicating that they are potentially important for seafloor carbon turnover processes. Further evidence for a role of Fungi in estuarine organic matter turnover has been demonstrated by ergosterol-based methods showing that fungi grow on Spartina leaves in salt marshes (Newell et al, 1989;Newell, 1994) and stable isotope probing experiments has shown that mycobenthos utilize lignocellulose as a carbon source in estuarine sediments (Gontikaki et al, 2015). In salt marshes the mycobenthos can account for up to 10% of total detrital biomass indicating they are important members of the ecosystem (Gessner et al, 1997).…”

Bioturbator‐stimulated loss of seagrass sediment carbon stocks

“…In control sediment amended with seagrass, the observed potential negative MPE was equivalent to a > 50% reduction in ROM‐derived CO 2 release, indicating a preferential remineralization of seagrass (LOM) by the microbial community (Gontikaki et al ). Negative priming in seagrass sediments may indeed support the long‐term preservation of sediment C org with the microbial community preferentially remineralizing labile (i.e., proteins, hemicellulose, and soluble carbohydrates; Trevathan‐Tackett et al ) and some recalcitrant lignocellulose seagrass compounds (Gontikaki et al ), over the sediment‐bound C org . However, the extent of the MPE is also related to the added substrate C as a proportion of the microbial biomass (Blagodatskaya and Kuzyakov ), and some of this calculated negative MPE may also be attributed to changes in redox conditions within the sediment, resulting in temporarily higher remineralization rates (Burdige ).…”

“…While previous research has highlighted the MPE in both terrestrial and marine systems (Aller 1994;López et al 1998;Banta et al 1999), the effect of priming on C cycling has recently garnered increased attention in marine systems (Guenet et al 2010;Gontikaki et al 2015;Steen et al 2016), specifically with regard to identifying the sources of C remineralization and release in coastal ecosystems (van Nugteren et al 2009). Indeed, the stimulation of sediment metabolism by bioturbating macrofauna could be a trigger for remineralization of recalcitrant C in deep sediment layers, which could be enhanced by the MPE.…”