Speaker
Description
In duckweed pond systems established either for biofiltration or biomass production, excessive proliferation of planktonic algae reduces ecosystem services. In this study we revealed those algal related mechanisms resulting duckweed growth inhibition. We isolated 26 algal species from duckweed covered mesocosms and measured their impact on axenic culture of Lemna gibba. At low duckweed coverage (<50%), 18 algal and cyanobacterial species significantly reduced the growth rate of duckweed. The strongest inhibitory effects were exerted by unicellular green algae. When the combined effects of dominant algal species were examined, all tested algae drastically inhibited duckweed growth. The elemental flux between the water, algal biomass and Lemna fronds was followed in time. Algal biomass increase was closely associated with the depletion of nutrients from the water column. In aquarium experiment, under low and moderate nitrogen concentrations together with the absence of algal shading, algae significantly inhibited the growth and chlorophyll content of Lemna by 60-80%. The algal inhibitory effect weakened with increasing nitrogen concentration and under conditions of stronger shading affecting the algae. Laboratory experiments demonstrated that duckweed growth was most strongly inhibited by algal-induced nitrogen deficiency, followed by elevated pH (10.2), phosphorus deficiency, and iron deficiency, resulting in growth inhibition of 72%, 52%, 51%, and 47%, respectively. By the final day of the experiment, both algal-induced nitrogen depletion and high pH completely reduced duckweed growth.
Keywords
algae inhibition competition pH
References
Szabó S, Roijackers R, Scheffer M, Borics G. 2005. The strength of limiting factors for duckweed during algal competition. Archiv für Hydrobiologie 164:127–140.
Szabó S, Braun M, Borics G. 1999. Elemental flux between algae and duckweeds (Lemna gibba) during competition. Archiv für Hydrobiologie 146:355-367.
| Corresponding author email | szabo.sandor@nye.hu |
|---|---|
| Scientific Session | Microbiome & Interactions |
