Graduation Date
Spring 2022
Document Type
Thesis
Program
Master of Science degree with a major in Biology
Committee Chair Name
Catalina Cuellar-Gempeler
Committee Chair Affiliation
HSU Faculty or Staff
Second Committee Member Name
Bob Gearheart
Second Committee Member Affiliation
Community Member or Outside Professional
Third Committee Member Name
Mark Wilson
Third Committee Member Affiliation
HSU Faculty or Staff
Fourth Committee Member Name
Paul Bourdeau
Fourth Committee Member Affiliation
HSU Faculty or Staff
Keywords
Arcata Marsh, Biodiversity, Microbial ecology, Wastewater, Wetlands, Ecosystem function, Ammonia removal, Nitrification, Aeration
Subject Categories
Biology
Abstract
Microbial communities play a crucial role in ecosystems, yet we know little about how microbial diversity influences ecosystem functioning. An important gap in our understanding is how environmental change affects microbial Biodiversity-Ecosystem Function relationships (BEF). These complex interactions between microbial biodiversity and ecosystem function can influence major biogeochemical processes, such as the nitrogen cycle in wetland ecosystems, which play an important role in managing wastewater. To address the effect of biodiversity on function, my study investigates the BEF relationships between microbial diversity and the function in terms of ammonia removal from wastewater at the Arcata Wastewater Treatment Facility (AWTF) both spatially and temporally. The AWTF uses several natural treatment systems consisting of Oxidation Ponds and constructed wetlands for secondary wastewater treatment. These natural treatment systems provide a unique opportunity to study microbial community BEF relationships because they are interconnected by the flow of nutrients in the wastewater and are exposed to seasonal changes. First, I conducted a field study where I sampled the AWTF natural treatment system from Autumn to Spring. Based on classical BEF studies, I expected a positive relationship between microbial biodiversity and ecosystem function, but also anticipated a potential effect of seasonal and spatial factors in strengthening or weakening the relationship. Instead, I found a significant negative BEF relationship between microbial community richness and ammonia removal. Ammonia concentration significantly decreased through the wastewater purification system, yet microbial diversity was unrelated to the different locations in the wastewater treatment system. In turn, seasonality significantly affected the microbial community diversity where richness was lower during Spring. Following the field study, I conducted a microcosm experiment to determine the direct effect of an environmental change in terms of dissolved oxygen (DO) concentration on biodiversity and ecosystem function. The DO concentration had a positive relationship with evenness and a negative relationship with richness. In addition to the DO relationships, I observed a negative correlation between evenness and nitrification which reflects the BEF relationship findings from the field study. Because the lower evenness values are associated with more ammonia removal, these results further support that ammonia removal capabilities of the AWTF are most efficient when fewer species dominate the microbial communities in the natural treatment system, regardless of oxygen levels and other environmental factors. By expanding our search for more microbial community BEF relationship scenarios we can further unravel how richness and evenness influence ecosystem processes in natural and humanized systems.
Citation Style
APA
Recommended Citation
Grandmont-Lemire, Sandrine, "Environmental effects on constructed wetland microbial diversity and function in the context of wastewater management" (2022). Cal Poly Humboldt theses and projects. 573.
https://digitalcommons.humboldt.edu/etd/573
Included in
Biodiversity Commons, Bioinformatics Commons, Biology Commons, Sustainability Commons, Water Resource Management Commons