The effects of natural and anthropogenic factors on microbes decomposing the emerging macrophyte Scirpus lacustris in prairie aquatic systems.

Emergent macrophytes, like Scirpus lacustris, are the foundation of the very high biological productivities of wetlands in the Northern Prairies of North America. Fungi and bacteria are the primary organisms that sequester carbon and nutrients from these macrophytes. Almost nothing is known about the process of microbial decomposition and how natural environmental factors and anthropogenic pollutants may impact the microbes associated with Scirpus as it decays while standing and after it falls into the water. Pond 50, located at the St. Denis National Wildlife Area, Saskatchewan, Canada, was chosen as the study site because it is a wetland that typifies the prairie ecozone. First, a procedure to extract ergosterol, a molecule used to estimate living fungal biomass, from various environmental matrices was developed. Ergosterol was detected by high-pressure liquid chromatography with a UV detector (HPLC-UV) and corroborated by mass spectrometry analysis. Seasonal variations in fungal biomass and fungal production, the latter measured by the incorporation of [1-14C] acetate into ergosterol, associated with Scirpus stems, both above and below water, were determined. Changes in fungal biomass and productivities on freshly cut green Scirpus stems decaying in the water under either natural solar radiation (UV+) or protected from ultraviolet (UV−) radiation, were followed over the summer. Several experiments measuring the impact of temperature on fungal biomass and production on Scirpus decaying in pond water were conducted in the laboratory. In view of antibiotics being detected in surface waters, tetracycline was chosen to determine its effects on the microbes that decompose Scirpus. Prior to this experiment, tetracycline's adsorptive characteristics in distilled, river and pond water were measured. Tetracycline's photolytic and microbial rates of degradation were determined in the three mentioned waters in the laboratory in the light and dark and also in natural sunlight (UV+) or protected (UV−) from UV radiation in non-sterile waters. The effects of tetracycline on protein production in planktonic bacteria in river and pond water were experimentally measured. Lastly, confocal laser microscopy (CLSM) was used to study the microbial colonization on Scirpus stems immediately after submersion in river and pond water, in the absence or presence of 500 μg L⁻¹ and 4000 μg L⁻¹ tetracycline. Saponification in a hot water bath for 30 mins followed by toluene extraction was the most ideal method to extract ergosterol from environmental samples. HPLC-UV detections of ergosterol, compared to detections by mass spectrometry, were found to be reliable with all matrices except water. Fungal decomposition began and was the greatest in the spring despite low water temperatures. There was no significant difference in biomass or production on aerial versus submerged portions of Scirpus. Water temperature was correlated to fungal production (r = 0.7, P < 0.005) for aerial stem pieces but not for submerged pieces. However, in laboratory experiments water temperature had a measurable effect on both biomass and production in submerged stem pieces. With respect to Scirpus decaying under UV+ or UV− in pond water, there was no significant difference in either fungal biomass (P = 0.76) or production (P = 0.96) between the two treatments. There were significant differences (P...