Edinburgh Napier University

  Emergent macrophytes, like Scilpus 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 SCilPUS 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 Scilpus. 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 /-Lg L-1 and 4000 /-Lg 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. HPLCUV
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