PS 8-100 - CANCELLED - Aeration effects on microbial diversity and function in the context of nitrification in wastewater management

Abstract: Although Biodiversity-Ecosystem Function relationships (BEF) have been central to ecology for several decades, there are gaps in our ability to explain, predict, and manage ecosystem functions mediated by microbial communities. This study investigates the BEF relationship between microbial diversity and ammonia removal at the Arcata Wastewater Treatment Facility (AWTF). The AWTF uses constructed wetlands for its secondary natural wastewater treatment. Water quality management at the AWTF requires nitrification of ammonia, therefore we sought to explain the general effects of added aeration on the potential enhancement of microbial driven nitrification and water purification. We conducted a laboratory-controlled microcosm experiment manipulating aeration to determine direct effects on microbial diversity and its ammonia removal functionality. Microcosms were filled with wastewater from the AWTF wetlands and exposed to various degrees of added aeration. Treatments included (1) added homogeneous aeration, (2) added heterogeneous aeration and (3) a control of ambient air. Based on classical BEF research and wastewater treatment studies, we expected a positive relationship between biodiversity and function, anticipating higher nitrification in the treatments with homogeneous oxygen addition. We measured microbial community diversity via next generation sequencing with richness and evenness as the biodiversity metrics. We used an electrode to determine the change in ammonia concentration over time. We found that DO concentration had a positive relationship with evenness and a negative relationship with richness. We found a negative correlation between evenness and nitrification (negative BEF) but no significant relationship with richness. The lower evenness values associated with higher ammonia removal suggests this ecosystem function is most efficient when fewer species dominate the microbial communities in wastewater nitrification. Moving forward, BEF studies should aim to generalize which ecological processes can best promote or disrupt diversity and function relationships. Potential studies include:; identifying the specific taxa driving nitrogen cycling and the mechanism behind functional decrease in diverse communities (co-occurrence network analyses or competitive assays), and (2) diversity relationships with nitrification and denitrification gene abundance (qPCR assays). Importantly, this research can be applied to other sections of the nitrogen cycle in aquatic systems, and other biogeochemical cycles in terrestrial systems, with the objective to understand the role of microbial communities in driving the Earth’s ecosystems.