Large and interacting effects of temperature and nutrient addition on stratified microbial ecosystems in a small, replicated, and liquid dominated Winogradsky column approach

Abstract

Aquatic ecosystems are often stratified, with cyanobacteria in oxic layers and phototrophic sulfur bacteria in anoxic ones. Changes in stratification caused by global environmental change are an ongoing concern. Understanding how such aerobic and anaerobic microbial communities, and associated abiotic conditions, respond to multifarious environmental changes is an important endeavor in microbial ecology. Insights come from observations of naturally occurring stratified aquatic ecosystems, and from theoretical models of ecological processes. Here we complement such studies with an experimental approach in the laboratory, using a novel aquatic micro-ecosystem, with distinct oxic/anoxic strata. Our two main objectives are to 1) describe the features of this promising micro-ecosystem and 2) report how the microbial community composition (full-length 16S rRNA-sequencing) and the abiotic conditions responded to two globally relevant environmental changes (temperature and nutrient addition). The composition of the strongly stratified microbial communities was highly affected by temperature and by the interaction of temperature and nutrient addition. Dissolved oxygen and pH responded to the treatments, with differences in effect between the oxic and anoxic zone. Further research with this experimental system could focus on effects of environmental change on spatial distribution and on stability of the communities to press and pulse perturbations.

Contrasting resistance and resilience to light variation of the coupled oxic and anoxic components of an experimental microbial ecosystem

“…Sediment and water samples were taken from a pond (Zurich, Switzerland, 47°23'51.2"N 8°32'33.3"E) and eight micro-ecosystems were set-up as reported previously [17]. In short, 1.5 cm sediment (with 0.5 % crystalline cellulose, 0.5 % methyl-cellulose, 1 % CaSO4, 0.2 % CaCO3, 0.01 % NH4H2PO4) were covered with 16 mL pond water and incubated for 35 days at 24 °C under a light-dark-cycle of 16:8 h (gradient of light).…”

“…To understand microbial response behavior of aerobic and anaerobic communities within one ecosystem to a major disturbance, we study functional and compositional responses to light removal in recently developed dynamic (phototrophic) oxic-anoxic micro-ecosystems [6]. These micro-ecosystems are analogs of aquatic inland ecosystems, like lakes and ponds, which harbor highly diverse functional groups of microorganisms that are dependent on light for oxygenic and anoxygenic photosynthesis.…”

“…We analysed the responses of aerobic and anaerobic aquatic communities (4 snapshots of 16S rRNA full-length sequencing) in combination with high frequency and resolution measurements of the oxygen state of the system. Sediment and water samples were taken from a pond (Zurich, Switzerland, 47°23'51.2"N 8°32'33.3"E) and eight micro-ecosystems were set-up as reported previously [6]. In short, 1.5 cm sediment (with 0.5 % crystalline cellulose, 0.5 % methyl-cellulose, 1 % CaSO4, 0.2 % CaCO3, 0.01 % NH4H2PO4) were covered with 16 mL pond water and incubated for 35 days at °C under a light-dark-cycle of 16:8 h (gradient of light).…”

“…500 µL liquid sample were taken on day 8 (prior-to-stressor), day 15 (stressor-sample), day 19 (short-term recovery) and day 35 (longterm recovery), respectively, at the height of the top and bottom oxygen sensor. DNA extraction and 16S rRNA full-length sequencing (PacBio) were performed as reported previously [6].…”

“…Here we studied the response of mixed aerobic-anaerobic communities to light deprivation within a single ecosystem with a recently developed dynamic phototrophic oxicanoxic micro-ecosystem [17]. These micro-ecosystems are analogs of freshwater ecosystems, like lakes and ponds, which harbor highly diverse functional groups of microorganisms, tightly connected through the oxygen state of the aquatic environment, which are dependent on light for oxygenic and anoxygenic photosynthesis.…”