T.M. Huete-Stauffer, N. Arandia-Gorostidi, L. Díaz-Pérez, X. Anxelu G. Morán
FEMS Microbiology Ecology, volume 91, issue 10, (2015)
Marine bacteria, Coastal ocean, Flow cytometry, Activation energy, Carrying capacity, Metabolic theory of ecology
Using the metabolic theory of ecology (MTE) framework, we evaluated over a whole annual cycle the monthly responses to temperature of the growth rates (μ) and carrying capacities (K) of heterotrophic bacterioplankton at a temperate coastal site. We used experimental incubations spanning 6ºC with bacterial physiological groups identified by flow cytometry according to membrane integrity (live), nucleic acid content (HNA and LNA) and respiratory activity (CTC+). The temperature dependence of μ at the exponential phase of growth was summarized by the activation energy (E), which was variable (−0.52 to 0.72 eV) but followed a seasonal pattern, only reaching the hypothesized value for aerobic heterotrophs of 0.65 eV during the spring bloom for the most active bacterial groups (live, HNA, CTC+). K (i.e. maximum experimental abundance) peaked at 4 × 106 cells mL−1 and generally covaried with μ but, contrary to MTE predictions, it did not decrease consistently with temperature. In the case of livecells, the responses of μ and K to temperature were positively correlated and related to seasonal changes in substrate availability, indicating that the responses of bacteria to warming are far from homogeneous and poorly explained by MTE at our site.