Algal Diversity Reduces Invasibility into Open-pond Algal Biofuel Systems

Undergraduate #75
Discipline: Biological Sciences
Subcategory: Ecology

Alexandria Chumney - Washtenaw Community College and Hope College

Algal biofuel is a promising source of energy that has potential to reduce many problems associated with conventional fossil fuels. There are still many challenges to growing algal biofuel at commercial scales that we have yet to overcome. For example, a common problem in outdoor open-pond biofuel systems is that they get invaded by unwanted fungi, bacteria, cyanobacteria and even nuisance algae that outcompete the focal biofuel species and degrade crop yields. Figuring out how to prevent or minimize the impact of invaders is key to developing stable algal biofuel systems. Here we report results of a study that examined the effectiveness of two treatments meant to reduce the prevalence of invaders – physically covering ponds with barriers to invasion, and growing mixture cultures of algae that might outcompete invaders. We set up twelve 1000-L ponds filled with Bold 3N growth media outdoors at the University of Michigan’s E.S. George Reserve in Pinkney, MI. Five ponds were inoculated with a mixture of Selenastrum capricornutum and Scenedesmus acuminatus (two common biofuel species) and five tanks were inoculated with monocultures of S. capricornutum. Tanks were covered with a fine green mesh for varying periods of time (0 – 100% of the experiment), and each week the mono- and bicultures were sampled for algal biomass and invader densities. Covering tanks had no influence on the final densities of invasive species (P > 0.05); however, bicultures had a lower invasibility than monocultures. Both experimental duration (P < 0.01) and focal algal species richness (P < 0.05) significantly affected the number of invasive algal species and the density of invasive algae in the tanks. By the end of the experiment, bicultures had been invaded by fewer species (3.5 vs. 5 for monocultures), and these invaders were held to densities that were 50% lower (106 vs. 206 cells L-1 ). Our results suggest that diversity in algae biofuel tanks help them resist invasion over time, therefore potentially offering a solution to one of algal biofuel’s more prominent problems.

Funder Acknowledgement(s): This work was funded by a Research Experience and Mentoring (REM) supplement to grant 1332342 from NSF’s Emerging Frontiers in Research and Innovation (EFRI) Program. The supplement supported development of an undergraduate internship program co-run by Dr. Bradley Cardinale (University of Michigan) and Dr. Steve Francoeur (Eastern Michigan University).

Faculty Advisor: Bradley Cardinale,