Mangrove microbial diversity and the impact of trophic contamination

► The impact of nutrient increases on biofilm microbial communities is investigated in a tropical mangrove. ► Microbial communities were sampled using a colonization device in the mangrove. ► Their structure and diversity were shaped by the nutrient load level. ► Microbial communities may play a key role in the fate of nutrients. Mangroves are threatened ecosystems that provide numerous ecosystem services, especially through their wide biodiversity, and their bioremediation capacity is a challenging question in tropical areas. In a mangrove in Mayotte, we studied the potential role of microbial biofilm communities in removing nutrient loads from pre-treated wastewater. Microbial community samples were collected from tree roots, sediments, water, and from a colonization device, and their structure and dynamics were compared in two areas: one exposed to sewage and the other not. The samples from the colonization devices accurately reflected the natural communities in terms of diversity. Communities in the zone exposed to sewage were characterized by more green algae and diatoms, higher bacteria densities, as well as different compositions. In the area exposed to sewage, the higher cell densities associated with specific diversity patterns highlighted adapted communities that may play a significant role in the fate of nutrients.