DIFFERENT DISSOLVED ORGANIC MATTER SOURCES SUSTAIN MICROBIAL LIFE IN THE SUBTERRANEAN ESTUARY OF A HIGH-ENERGY BEACH

In subterranean estuaries (STEs), microbial life is fueled by dissolved organic matter (DOM) introduced with meteoric groundwater and seawater. In high-energy beaches with dynamic porewater advection, microbes face frequent changes in groundwater composition, even at several meters depth. However, the distribution of DOM in the deep STE and its processing by microbes is poorly understood. We incubated sediment with deep (6 m) STE groundwater of low (1.6) and high (29.1) salinity from a high-energy beach on Spiekeroog Island, Germany. We quantified dissolved organic carbon (DOC) and analyzed DOM,and microbial community composition. Ultra-high resolution mass spectrometry revealed that both groundwater types contained mainly reworked DOM; however, meteoric groundwater had a more terrestrial DOM signature. During incubation, DOC concentrations increased primarily due to leaching of sedimentary organic matter, providing an additional carbon source. The DOM composition changed significantly from start to end and similarly for both groundwater types. Some molecular formulas (MF) were lost during incubation, indicating continuous degradation of recalcitrant DOM in the deep STE. Characteristics of newly detected MF in both groundwater types were indicative of labile DOM and some of them were also identified in sediment-leachates. The contribution of sediment-derived DOM as a potential substrate for deep STE microbial communities was confirmed in a study of a continuous 24 m long core at the same site.

Presentation Preference: Oral

Primary Presenter: Grace Abarike, Carl von Ossietzky Universität Oldenburg (grace.abarike@uol.de)

Authors:

Grace Abarike, Institute for Chemistry and Biology of the Marine Environment (ICBM), School of Mathematics and Science, Carl von Ossietzky Universität Oldenburg  (grace.abarike@uol.de)

Simone Brick, Institute for Chemistry and Biology of the Marine Environment (ICBM), School of Mathematics and Science, Carl von Ossietzky Universität Oldenburg  (simone.brick1@uol.de)

Bert Engelen, Institute for Chemistry and Biology of the Marine Environment (ICBM), School of Mathematics and Science, Carl von Ossietzky Universität Oldenburg  (bert.engelen@uol.de)

Jutta Niggemann, Institute for Chemistry and Biology of the Marine Environment (ICBM), School of Mathematics and Science, Carl von Ossietzky Universität Oldenburg  (jutta.niggemann@uol.de)