Interactions of aquatic microphytes and epiphytes and epiphytic algae in freshwater ecosystems
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The distribution, population dynamics, photosynthesis and nutrition
of epiphytic algae were investigated in natural and artificial
freshwater ecosystems, with special reference to interactions between
the algae and their macrophytic substrata.
The distribution of epiphyton in the littoral zone of Windermere
was related to light shading effects of dense emergent vegetation. The
distribution of epiphyton in the phyllosphere of Lemna minor in a small
pond and in culture media was related to the rate of multiplication, age,
topography, and exudates of the fronds, and to tactic responses of motile
algal propagules.
The population dynamics of epiphytic algae on Lemna minor in a
small pond were correlated with seasonal changes in light and temperature,
the growth cycle of Lemna minor,
and with depletions of dissolved substances associated with primary production.
Standing crops of epiphyton which accumulated on Lemna minor in
culture media in the laboratory were related to the topography and rate
of multiplication of the fronds, and to the inorganic nutrient concentrations
in the media. Calothrix brevissima reduced the multiplication rate
of fronds. The accumulation of Calothrix was correlated with an increase
in the pH of the media to values which inhibited multiplication and
photosynthesis in Lemna.
Photosynthetic rates and yields of epiphytic algae were reduced in
nitrogen deficient culture media. Photosynthesis and yields of Lemna minor
were not severely reduced under nitrogen deficient conditions. Competition
for nitrogen between Lemna and algae was proposed.
Lemna minor excrete
14C labelled substances into axenic culture
media. Epiphytic algal and bacterial populations assimilated the substances
excreted by Lemna minor. Evidence for the excretion of antibiotic
substances by Lemna minor was not conclusive.
Authors
Bowker, David WilsonCollections
- Theses [3706]