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Structure and function of microbial communities in urban freshwater across a pollution
gradient

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1,2 Mamun Abdullah Al*, Xue Yan, Zijie Xu, Kexin Ren, Yuanyuan Xue, Huihuang Chen,
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1 Jun Zuo, Jun Yang
1

1 Aquatic Eco-Health Group, Fujian Key Laboratory of Watershed Ecology, Key Laboratory of
Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences,
1799 Jimei Road, Xiamen 361021, China
2 University of Chinese Academy of Sciences, Beijing 100049, China

* Corresponding author: abdullah@iue.ac.cn

Abstract:
Urban freshwater ecosystems have important ecosystem functions, provide habitats for diverse
microbial communities and are susceptible to multiple interconnected factors such as
environmental pollution. In recent decades, increasing anthropogenic impact and growing
urbanization effects on urban ecosystem services. Despite the ecological significance of bacteria
and microeukaryotes, little is known about factors affecting them in urban aquatic ecosystems. In
this study, water and sediment samples were collected from 20 urban waterbodies along a pollution
gradient in Wuhan City, central China. Those were comprising 6 shallow rivers, 11 open channels
(wastewater carrying drains to rivers), 1 lake/reservoir and 1 tributary, while the non-urban drinking
water reservoir was Mulan Lake. Here, we measured six types of environmental stressors including
water physicochemical parameters, primary productivity, water nutrients, water heavy metals,
water dissolved gasses and sediment nutrients to investigate the impact of anthropogenic effects on
microbial community structure and function. Using, environmental DNA-based approaches, our
results showed that bacterial and microeukaryotic diversity and community composition differed
significantly between water and sediment habitats across pollution gradients. The heterogeneity of
environmental conditions has significant negative effects on community composition. Our results
showed that urban pollution significantly affected microbial community functions, particularly
heavy urban pollution increased the N-cycle regulatory bacteria and pathogenic bacteria, and
parasitic and heterotrophic microeukaryotes. Further, microbial network analysis revealed complex
structure, while more positive interactions of bacteria-microeukaryotes-environmental factors in
sediment than in water. Stochastic processes were more important in water, whereas deterministic
processes were more important in sediment, indicating contrasting environmental vulnerabilities
and preferences between the two habitat types. This study provides significant insights into the
response of bacterial and microeukaryotic community structures and functions to urban pollution,
and the ecological processes structuring microbial community dynamics across habitat types under
anthropogenic disturbances.

Keywords: Microeukaryotes, Bacteria, Anthropogenic pollution, Urban ecosystems, Ecosystem
function