Toward a mechanistic understanding of how natural bacterial communities respond to changes in temperature in aquatic ecosystems

Abstract

We examine how heterotrophic bacterioplankton communities respond to temperature by mathematically defining two thermally adapted species and showing how changes in environmental temperature affect competitive outcome in a two-resource environment. We did this by adding temperature dependence to both the respiration and uptake terms of a two species, two-resource model rooted in Droop kinetics. We used published literature values and results of our own work with experimental microcosms to parameterize the model and to quantitatively and qualitatively define relationships between temperature and bacterioplankton physiology. Using a graphical resource competition framework, we show how physiological adaptation to temperature can allow organisms to be more, or less, competitive for limiting resources across a thermal gradient (2-34 1C). Our results suggest that the effect of temperature on bacterial community composition, and therefore bacterially mediated biogeochemical processes, depends on the available resource pool in a given system. In addition, our results suggest that the often unclear relationship between temperature and bacterial metabolism, as reported in the literature, can be understood by allowing for changes in the relative contribution of thermally adapted populations to community metabolism.

Depth Dependent Relationships between Temperature and Ocean Heterotrophic Prokaryotic Production

“…Long term (years) heating experiments in soils have shown that microbial activity returns to pre-warming values within a few years, likely due to a depletion of labile organic matter pools and/or thermal adaptation of the microbial community to the increased temperatures (e.g., Bradford et al, 2008;Rousk et al, 2012). Microbial temperature adaptation has also been demonstrated in lakes (Hall and Cotner, 2007;Hall et al, 2008) and similar mechanisms could also be at play in the ocean, but experimental data to support this are still missing.…”

Variation in cell volume and community composition of bacteria in response to temperature

“…In a model, it has been shown that the effect of increasing temperature on bacterial community composition and bacterially mediated biogeochemical processes is linked to the resource stoichiometry of a given aquatic system (Hall et al 2008). It is possible that changes in size in relation to temperature also depend on the resource stoichiometry of the aquatic system.…”

Geographic distribution pattern of low and high nucleic acid content bacteria on a river-catchment scale

“…It was reported that warm-adapted bacteria could have lower minimal P cell quotas than do coldadapted bacteria (Hall et al 2008), which would confer an advantage to cells with low nucleic acid content (because nucleic acids are an important intracellular source of P) in warm-temperature and resource-limited environments (Van Wambeke et al 2011). The change of temperature, coupled with regional-scale latitudinal gradients or sometimes local weather contingencies, will affect microbial activity, metabolism and growth rate, and hence the abundance of LNA and HNA.…”