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Title: Microbial diversity-ecosystem function in canals across a gradient of urban intensification in Suzhou, China
Author: Yuan, Tianma
ISNI:       0000 0004 7970 4843
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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Urbanization is increasing worldwide and is happening at a rapid rate in China in line with rapid and continuing economic development. Although urbanization accelerates economic and social development, it can also lead to major changes to freshwater environments such as eutrophication, loss of biodiversity, and chemical and microbiological contaminations due to domestic, industrial and agricultural discharges. Suzhou is a good example for urbanization with its development in recent decades therefore, this project aimed at assessing the impact of urbanization on water quality and microbial diversity-ecosystem function using Suzhou canals as a model system. Nine sampling locations covering three urban intensity classes (High, Medium and Low) in Suzhou were selected and field studies were carried out in winter and summer over a two-year period (2015 and 2016). Three sampling locations in natural reserve mountains in Huangshan were added as control locations in summer 2016. Water samples were collected from each location for physico-chemical, microbiological and molecular analyses (microbial abundance and diversity) and leaf bag experiments were carried out to assess the organic matter (OM) breakdown and leaf associated microbial communities. The water quality results showed that pH, electrical conductivity (EC), total nitrogen (TN), total phosphorous (TP), ammonium nitrogen (NH4-N), phosphate (PO4-P), total viable count (TVC), total coliforms (TC) and fecal coliforms (FC) varied with urban intensification, whereas water temperature (WT), EC, TN, PO4-P, nitrate-N (NO3-N), nitrite-N (NO2-N), chlorophyll a (Chl a) and FC showed seasonal variations. Higher levels of nutrients and microbial load were observed in the high urbanization locations as compared to medium and low urbanization, and the results correlated well with land use classification and anthropogenic activities. The OM breakdown rate was significantly affected by the seasons as compared to urbanization and high temperature was found to accelerate OM breakdown. The results of bacterial and fungal community diversity studied by next-generation sequencing of specific target genes (16S rRNA and ITS1, respectively) revealed that the water associated communities were distinct from leaf associated communities and obvious variations in the composition with seasons were also observed. The bacterial and fungal communities also varied among the sampling locations, but no clear trend was observed. However, the bacterial / fungal communities in water / leaf samples collected from Suzhou were very distinct from the samples collected at control locations in Huangshan. The phylum Proteobacteria was dominant (20- 80%) in almost all the water and leaf samples tested and Burkholderiales was dominant (5-50%) in most samples at order level. Some of the bacterial genera (Arcobacter, Massilia and Acinetobacter) which are typically found in wastewater or associated with human / animal microbiomes were represented at high percentages at high and medium urban intensification areas. In the fungal community, the phylum Ascomycota was dominant (2-99%) in most samples and the order Pleosporales was dominant (1-99%) in most leaf samples. Fungal genera like Trichothecium associated with pathogens / microbiomes and human health were represented at high percentages in high urban intensification areas, whereas natural fungal flora (e.g. Alternaria) associated with decomposition / ecosystem function were represented at high percentages at low urban intensification areas and also at control locations. In microcosm studies, the influence of temperature, nutrients and heavy metals on OM breakdown rate and bacterial diversity were studied. The results revealed that the temperature was a key factor that affects the composition of bacterial community, whereas nutrients had fewer effects on the community but accelerated the OM breakdown rate in the short term. The heavy metals such as Cu had potential effects on the shifts in bacterial community, especially the high concentrations of Cu reduced the diversity and also OM breakdown rate. Selected fecal (total, human and avian-associated) markers and bacterial pathogens were quantified by qPCR by using the DNA extracted from water samples. The effect of urbanization was observed with total and human-associated fecal markers (BacUni and HF183) and these markers were observed in higher levels at high urbanization locations. Among the bacterial pathogens tested, Enterococcus spp. were the most frequently detected pathogens in water samples (100%), followed by Arcobacter butzleri (74%), Shiga toxin-producing Escherichia coli (STEC) (41%), Shigella sp. (36%), whereas Campylobacter jejuni and Salmonella spp. were least frequently detected (10%). The overall results indicated that urbanization impacts the water quality with high level of nutrients, microbial contaminations including pathogens. The microbial community composition was affected by the season, and high levels of nutrients and temperature were found to be the key factors which affect both the microbial diversity and OM breakdown rate.
Supervisor: Raju, Sekar ; McCarthy, Alan ; Zhang, Yixin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral