Microbial dynamics in Manaus river, Brazil

Abstract

Rivers, which are vital ecosystems that support a variety of life forms and provide many ecosystem services, have been degraded by human activities, such as urbanization, pollution, and overexploitation. Habitat restoration projects have been implemented in different parts of the world to restore the ecological health and functioning of degraded rivers. The microbial community that forms biofilms on various substrates is one of the key components of river ecosystems. Organic matter is decomposed and carbon dioxide is produced by these biofilms, which affects the oxygen levels and nutrient cycles in the water. However, the effects of habitat restoration on the biofilm microbial community are not well understood. High-throughput DNA sequencing was used in this study to compare the bacterial composition of biofilms in three types of rivers: degraded urban rivers, urban rivers with restored habitats, and forested rivers that serve as reference conditions. The following questions were aimed to be answered: (i) How is the biofilm bacterial community composition affected by habitat restoration? (ii) How does bacterial diversity change in restored rivers compared to degraded and reference rivers? (iii) What are the environmental factors that influence the biofilm bacterial community composition? It was found that water quality was improved by habitat restoration by increasing the dissolved oxygen and reducing the organic pollutants in urban rivers. A decrease in bacterial diversity and a shift in the biofilm bacterial community structure towards that of the reference forested rivers were accompanied by this. This suggests that the biofilm microbial community can be altered by habitat restoration and its role in processing organic pollutants can be enhanced. However, it was also found that there was still a significant difference in the biofilm bacterial community between the restored and reference rivers, indicating that more time and effort are needed to achieve a similar ecological quality as the natural forested rivers.