Evaluating the performance of freshwater macroalgae in the bioremediation of nutrient-enriched water in temperate environments
Algal bioremediation can significantly improve the quality of wastewater by assimilating nutrients. However, the efficiency and stability of this approach depends on identifying suitable algae based on their biomass productivity and ability to outcompete less desirable algae. Here, we compare the productivity and competitive ability of three taxa of filamentous macroalgae under the seasonal light and temperature conditions experienced in temperate environments, including extremes of heat and cold. Specific growth rate was greatest for the tropical isolate of Oedogonium under summer conditions (36–40%; P < 0.05); however, it had lower growth under cooler (autumn, winter) conditions than the temperate algae of Stigeoclonium and Hyalotheca. Overall, Stigeoclonium and Hyalotheca had the most stable production across all treatments. A 5-week competition experiment found that each algae grew fastest in monoculture compared with bi-culture and poly-culture treatments. While all three genera showed a considerable level of competitive dominance depending on algae composition and environmental conditions, no single genus outperformed all others under all conditions. Oedogonium was dominant in warmer conditions, Stigeoclonium in cooler conditions (> 90% for both) and, in its absence, Hyalotheca also dominate over Oedogonium. Our results suggest that rather than finding an optimal taxon for all four seasons, the best decision for maximising stable biomass production will require either seasonal rotation of algae, or bi-cultures of the most dominant ones. Further, prioritising competition over production when selecting freshwater algae for wastewater bioremediation is likely to prove the most successful strategy.
KeywordsAlgae Biomass Competition Growth Species dominance Oedogonium
We thank Maria Martínez, Rebecca Lawton and Tine Carl for their assistance with experiments and Melbourne Water and Melbourne City Council for allowing collection of algae from their ponds. This research is part of the Pacific Biotechnology (previously MBD Industries Ltd) Research and Development program for the Integrated Production of Macroalgae.
Funding was provided by the Australian Research Council through a Future Fellowship (TD) and by the Victorian Goverment through the Port Phillip Bay fund (SS).
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