Benthic microbes in shallow temperate systems experience substantial daily and seasonal temperature fluctuations, but whether changing temperatures couple or decouple microbial processes involved in carbon remineralization is not well understood. Here, we measured temperature effects (along a 40°C range) on rates of enzymatic activities (cell-free vs. cell-present) and aerobic respiration in surface sediments of a shallow estuary. Temperature effects under cell-free vs. cell-present conditions differed and suggests a decoupling at certain temperatures. Varying temperature effects on enzyme activities and aerobic respiration were evident across seasons, but show complex relationships with in-situ temperature and microbial counts. Temperature effects on these processes were also consistently decoupled across seasons, with enzymatic activities relatively more stimulated than aerobic respiration with increasing temperatures. Thus, periods when temperature fluctuates substantially in shallow oxic sediments likely exhibit dynamic elemental cycles, altering the pools of organic and inorganic carbon in these systems. The highly complex nature of temperature effects on microbial function may be difficult to capture with simple equations and warrant empirical measurements across time and diverse conditions and microorganisms. Nevertheless, disentangling temperature effects on different diagenetic processes is necessary to understand impacts of weather, climate, and anthropogenic stressors for the biogeochemical function of coastal systems.

Primary Presenter: Silje Pedersen, University of Southern Denmark (silpe17@student.sdu.dk)

Authors:

Silje Waaler Pedersen, University of Southern Denmark  (siljewaaler.p@gmail.com)

John Paul Balmonte, University of Southern Denmark  (jpbalmonte@biology.sdu.dk)

Devangi Sathe, University of Southern Denmark  (devangi@biology.sdu.dk)

Ronnie Glud, University of Southern Denmark  (rnglud@biology.sdu.dk)