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Publication Date

8-2016

Date of Final Oral Examination (Defense)

4-28-2016

Type of Culminating Activity

Thesis - Boise State University Access Only

Degree Title

Master of Science in Biology

Department

Biology

Supervisory Committee Chair

Kevin Feris, Ph.D.

Supervisory Committee Member

Marcelo Serpe, Ph.D.

Supervisory Committee Member

Erik R. Coats, Ph.D.

Supervisory Committee Member

Deborah T. Newby, Ph.D.

Abstract

Mass cultivation of microalgae has the potential to increase the global supply of sustainable liquid fuels, plastics, animal feeds, and other renewable bioproducts. Increases in annual productivity and stability as well as efficient utilization of waste nutrients are necessary to enhance the economics of mass algal cultivation for such products. Previous research indicates that functional diversity of algae can increase both productivity and stability in algal cultures grown in defined media. Our study represents the first systematically designed assessment of algal diversity effects in dairy wastewater (anaerobic digester effluent). We employed 28 unique species combinations across four species richness levels to identify effects of both species richness and species combination on productivity. We then conducted a grazing experiment to test stability in terms of grazing resistance to a freshwater rotifer (Philodina sp.), and used trait-based modeling to determine key algal traits that most affected grazing resistance. On average, greater species richness led to increases in productivity (up to 70%) and grazing resistance index (up to 140%) relative to average monocultures, however both effects were highly dependent upon species composition. A trait-based model partially explained differences in grazing resistance among algal consortia (R2 = 0.56); grazing resistance increased with increasing cell size (p < 0.0001) and variation in cell size (p < 0.0001), and decreased with increasing C:N ratio (p = 0.05) and carbohydrate content (p = 0.01). A larger scale cultivation experiment (720 L total volume) using the two most productive and stable algal communities showed that they were both consistently productive and effective at removing nutrients from the wastewater under continuous cultivation. However, the algal community with a greater Shannon diversity index had a more favorable biomass profile and a slightly greater yield and nutrient removal efficiency. These results may help inform polyculture selection strategies and provide insight into how ecologically-informed engineering approaches could further optimize productivity and stability of wastewater-based algal cultivation for next generation biofuels and bioproducts.

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