Protecting Open-Air Microalgal Culture Ponds from Zooplankton Contamination

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Lawler, Sara
Algae is being studied for its interconnections with biofuel production, ability to remediate pollution (including CO_2), and as a food source for animals and humans. One of the major issues to scaling up algae culture is the open-air culture ponds becoming contaminated with organisms from the ambient environment. This includes, but is not limited to, zooplankton contaminants feeding on the algae. Large-scale solutions to preventing contamination can be costly, and need to not harm the growth of the algae or inhibit its downstream use. Presently, solutions are being investigated on a lab-scale, where algae are being fed to several Daphnia species as test species of zooplankton. Of interest are the growth rates of the Daphnia fed different amounts of algae, induction and hatching from the dormant ephippial stages, and reproductive rates. A search of the scientific literature is being conducted to identify potential zooplankton inhibitors. Since both Daphnia magna and the algae Selenastrum capricornutum have been used for biological toxin testing, their response to numerous chemicals is known. We are looking for a chemical at a specific concentration that is not deleterious to humans nor algae but greatly inhibits Daphnia at some point in their life cycle. Zinc, for example, across a narrow concentration range appears to have minimal effects on S. capricornutum and negative effects on D. magna. We hope to identify other examples which can be used safely to allow us to make progress on decreasing zooplankton contamination, thus benefiting the developing algae industry.