Biodiversity and disease risk in an algal biofuel system: An experimental test in outdoor ponds using a before-after-control-impact (BACI) design

RESEARCH ARTICLE Biodiversity and disease risk in an algal biofuel system: An experimental test in outdoor ponds using a before-after-control-impact (BACI) design Spenser L. WidinID1☯*, Kia M. Billings1, John McGowen2, Bradley J. Cardinale3☯ 1 School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, United States of America, 2 Arizona Center for Algae Technology and Innovation (AzCATI), Arizona State University, Mesa, AZ, United States of America, 3 Department of Ecosystem Science and Management, Penn State University, University Park, PA, United States of America ☯ These authors contributed equally to this work. * swidin@umich.edu Abstract For outdoor cultivation of algal feedstocks to become a commercially viable and sustainable option for biofuel production, algal cultivation must maintain high yields and temporal stabil- ity in environmentally variable outdoor ponds. One of the main challenges is mitigating dis- ease outbreaks that leads to culture crashes. Drawing on predictions from the ‘dilution effect’ hypothesis, in which increased biodiversity is thought to reduce disease risk in a com- munity, a teste of whether algal polycultures would reduce disease risk and improve feed- stock production efficiencies compared to monocultures was performed. While the positive benefits of biodiversity on disease risk have been demonstrated in various systems, to the best of our knowledge this is the first test in an algal biofuel system. Here, the results a before-after-control-impact (BACI) experimental design to compare mean monoculture

(control) and polyculture (impact) yield, stability, and productivity before and after fungal infection when grown in 400-L outdoor raceway ponds are presented. It has been found that polycultures did not experience a reduction in disease risk compared to monocultures or dif- fer in production efficiencies throughout the course of the 43-day experiment. These results show that polyculture feedstocks can maintain similar levels of productivity, stability, and disease resistance to that of a monoculture. Determining whether these results are general- izable or represent one case study requires additional outdoor experiments using a larger variety of host and pathogen species. Introduction Over the last several decades, renewable microalgal derived biofuels have begun to show increased promise as a replacement for petroleum-based transportation fuels as a way to curb global CO2 emissions. Compared to conventional terrestrial crops (e.g. corn, switchgrass, oil PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0267674 April 28, 2022 1 / 15 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Widin SL, Billings KM, McGowen J, Cardinale BJ (2022) Biodiversity and disease risk in an algal biofuel system: An experimental test in outdoor ponds using a before-after-control-impact (BACI) design. PLoS ONE 17(4): e0267674. https:// doi.org/10.1371/journal.pone.0267674 Editor: Md. Asraful Alam, Zhengzhou University, CHINA Received: November 27, 2021 Accepted: April 12, 2022 Published: April 28, 2022 Copyright: © 2022 Widin et al. This is an open

access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the manuscript and its Supporting Information files. Funding: BJC: U.S. Department of Energy Biotechnology Office Grant (DE-EE0008482) https://www.energy.gov/eere/bioenergy/bioenergy- technologies-office The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist.