Evidence for the Priming Effect in a Planktonic Estuarine Microbial Community

Abstract

The "priming effect," in which addition of labile substances changes the remineralization rate of recalcitrant organic matter, has been intensively studied in soils, but is less well-documented in aquatic systems. We investigated the extent to which additions of nutrients or labile organic carbon could influence remineralization rates of 14 C-labeled, microbially-degraded, phytoplankton-derived organic matter (OM) in microcosms inoculated with microbial communities drawn from Grove Creek Estuary in coastal Georgia, USA. We found that amendment with labile protein plus phosphorus increased remineralization rates of degraded, phytoplankton-derived OM by up to 100%, whereas acetate slightly decreased remineralization rates relative to an unamended control. Addition of ammonium and phosphate induced a smaller effect, whereas addition of ammonium alone had no effect. Counterintuitively, alkaline phosphatase activities increased in response to the addition of protein under P-replete conditions, indicating that production of enzymes unrelated to the labile priming compound may be a mechanism for the priming effect. The observed priming effect was transient: after 36 days of incubation roughly the same quantity of organic carbon had been mineralized in all treatments including no-addition controls. This timescale is on the order of the typical hydrologic residence times of well-flushed estuaries suggesting that priming in estuaries has the potential to influence whether OC is remineralized in situ or exported to the coastal ocean.

Sequential bioavailability of sedimentary organic matter to heterotrophic bacteria

“…Coffin et al ., ; Pearson et al ., ; Brady et al ., ; Mills et al ., ; Whaley‐Martin et al ., ); however, it only provides a snapshot and is unable to resolve the potential selectivity that may occur over the short time span of hours to days. Other experiments performed over these shorter intervals used isotopically‐labelled substrates (Benner et al ., ; Sun and Wakeham, ; Gontikaki et al ., ; van Nugteren et al ., ; Steen et al ., ). However, these studies added compounds of known accessibility at elevated concentrations and may not reflect their utilization at natural concentrations, or the accessibility of other compounds found in the sediment.…”

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

“…Recently, a number of studies have investigated the prevalence of a priming effect in aquatic ecosystems (e.g., van Nugteren et al ., ; Guenet et al ., ; Kuehn et al ., ; Steen et al ., ). Various types of ecosystems (marine, lentic, lotic) and habitats (pelagic, hyporheic, sediments) have been tested, as well as different sources of LOM (carbohydrates, algae leachate, gastropod mucus, etc.)…”

Dissolved Organic Carbon Turnover in Permafrost-Influenced Watersheds of Interior Alaska: Molecular Insights and the Priming Effect

“…The timescale over which priming is measured is important when considering the quantitative relevance of priming with respect to DOC mineralization and CO 2 fluxes from aquatic ecosystems. Many aquatic studies on the priming effect that have reported evidence of priming describe the phenomenon as "apparent" or "transient" because, although they observed initial differences in DOC consumption between unamended and primed treatments, ultimately the amount of DOC consumed after about 1 month is not significantly different from background consumption (Steen et al, 2016;Textor et al, 2018).…”