Abstract
Of growing concern to the ecological status of freshwaters are the increasing volumes of sewage effluent entering rivers (Noacco et al., 2017). Effluent can contain high concentrations of microbial biomass (Garnier, Servais and Billen, 1992), and thousands of chemical compounds (He et al., 2021). Therefore, effluent has the potential to alter the dissolved organic matter (DOM) and the microbial communities of the receiving river. These changes could have implications on freshwater biogeochemistry as DOM and microbes are essential for biogeochemical processes (Cole et al., 2007; Arnosti et al., 2014). However, molecular-level studies on the impacts of effluent on DOM using high resolution-mass spectrometry (HRMS) are limited, and studies on the effects on microbial activity are scarce despite microbial activity being essential for community involvement in biogeochemical processes (Arnosti et al., 2014).This study used HRMS to investigate the impacts of sewage effluent on freshwater DOM and investigated the impacts of effluent on microbial community composition and activity. To understand how periods of high- and low-flow may influence effluent’s impact, three rivers across two seasons were compared. Also, a protocol for bioorthogonal non-canonical amino acid tagging (BONCAT) combined with fluorescent-activated cell sorting (FACS) was optimised to understand how sewage effluent impacts the composition of the active microbial community.
The magnitude and nature of the impact of sewage effluent on DOM and microbial community composition and activity was shown to vary between seasons of high- and low-flow. Notably, some measured microbial activities were almost completely diminished. The first use of BONCAT-FACS to study the impact of effluent on microbial communities was performed. It was shown that effluent altered the active and total population of the river, including changing the most dominant phyla in the active population. The complexity and magnitude of the impact of sewage effluent on freshwater DOM and microbial communities was highlighted in this work.
| Date of Award | 13 May 2025 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Richard P Evershed (Supervisor) & Penny J Johnes (Supervisor) |