DRI researchers Monica Arienzo and Rachel Kozloski are co-authors of a new study examining the ecological impacts of plastic waste in Cambodia’s Mekong River. The Mekong River, which supports the livelihoods of more than 60 million people, faces significant plastic pollution challenges. Published in the August 2024 issue of Water Research, the study found that bacteria thriving on plastic waste significantly alter water quality and impact ecosystem services, particularly in areas with mismanaged waste. Researchers also observed potentially pathogenic organisms that could affect human health, though further analysis is required.
The consortium behind this research is part of the USAID-funded Wonders of the Mekong project and includes researchers from institutions such as the University of Milano-Bicocca, University of Nevada, Reno; Institute of Technology of Cambodia; Desert Research Institute (DRI), and Royal University of Phnom Penh.
“The combination of studying four different plastics in three different rivers with various measurement types makes this study unique,” said Monica Arienzo, associate research professor at DRI’s Division of Hydrologic Sciences. “Bringing together these data is important for understanding potential impacts of plastics on aquatic ecosystems.”
Rachel Kozloski, a doctoral student in Arienzo’s Microplastics and Environmental Chemistry Laboratory, expressed pride in contributing to the study's methods: “This work advances our understanding of how plastic pollution may affect microbial communities and water chemistry in freshwater systems.”
Phnom Penh, Cambodia — Polluted rivers and lakes worldwide host evolving populations of microorganisms living on plastic waste. This new ecosystem, termed ‘plastisphere,’ causes issues ranging from oxygen depletion to potential disease introduction and alters river system health according to research published in Water Research.
“Rivers provide a broad array of ecosystem services,” said Veronica Nava from the University of Milano-Bicocca and lead author. “Our study shows that small organisms growing on different plastic materials change nutrient cycling in rivers and dramatically reduce oxygen levels.” These changes impact river health and biodiversity support.
The consortium analyzed plastisphere impacts on Cambodia’s Lower Mekong River system by monitoring several health indicators. They found that bacteria on plastic waste significantly altered water quality and impacted ecosystem services. Additionally, potentially pathogenic organisms were observed.
The multifaceted study examined microorganism accumulations on riverine plastic waste while reproducing their growth under lab conditions to understand if waste type affects their productivity.
“The combination makes this study unique,” reiterated Monica Arienzo from DRI. “These data are crucial for understanding plastics' potential impacts on aquatic ecosystems.”
Despite supporting over 60 million people’s livelihoods, the Mekong River faces stress due to dam development, deforestation, overfishing, illegal trade practices involving rare species like giant stingrays nearing extinction, and increasing discarded plastic waste affecting biodiversity.
Professor Sudeep Chandra from UNR highlighted concerns about reduced oxygen levels creating 'dead zones' where aquatic life cannot survive during dry seasons: “If scaled up globally because microorganisms inhabiting floating rafts reduce oxygen levels."
Chandra also noted high plastic pollution might create biogeochemical hotspots for greenhouse gas production within rivers: "We cannot take loading plastics within freshwaters lightly as they control many river features."
Rivers contribute up to 265,000 metric tons annually to oceanic plastic waste; however first-of-its-kind research reveals broader ecological challenges needing addressing protect rivers’ ecosystem services provisioned globally impacting far-reaching implications freshwater plastisphere identified by researchers:
In 2023 Nava-Chandra published Nature article detailing microplastic concentrations freshwater lakes worldwide highlighting surprising interconnections between pollution-aquatic ecosystems emphasizing solutions reducing policies benefiting improved function better fish-water quality emphasized Zeb Hogan UNR-Wonders-Mekong Project director: "Policies reducing benefit improved function better fish-water."