Bacterial contamination and microplastics threaten Colombia’s largest and most productive coastal lagoon

A study led by researchers from the University of Barcelona and the Institute of Marine and Coastal Research (INVEMAR) in Colombia warns of the presence of potentially pathogenic bacteria in microplastics extracted from water, sediment and soil. digestive tract of fish from Ciénaga Grande de Santa Marta. , the largest and most productive coastal lagoon system in the Colombian Caribbean.

Bacteria form biofilms on the surface of microplastics and give rise to what are called plastispheres, ecosystems associated with plastic waste that are highly resistant to environmental changes. Microplastics have also been found in fish consumed by local people, posing an even greater risk to the entire natural ecosystem and human health.

These findings are now revealed in an article from Hazardous Materials Logled by researchers Ostin Garcés-Ordóñez and Miquel Canals, from the Consolidated Research Group in Marine Geosciences of the Faculty of Earth Sciences of the UB.

The study opens a new perspective on the microorganisms that colonize microplastics in coastal lagoons, an area still little explored by the scientific community. The results also provide novel data on the interactions between microplastics and potentially pathogenic bacteria in ecosystems subject to increasing environmental pressure.

Plastics and bacteria which also threaten the local population

Covering 1,321 km²The Ciénaga Grande de Santa Marta is a shallow (1–1.8 m) lake ecosystem that receives fresh water from four rivers and sea water via a canal connecting it to the Caribbean Sea.

Flanked by mangroves, it is home to two national parks, recognized Ramsar sites, and constitutes a strategic lagoon complex for the conservation of biodiversity. In this ecoregion with its rich flora and fauna, fishing is essential to the livelihood of local communities.

Despite its ecological value, “the Ciénaga Grande de Santa Marta is seriously threatened by high microbiological contamination and microplastics that affect water, sediments and organisms. These pollutants alter the quality of habitat and fishery products and, ultimately, the food security of local populations,” explains researcher Ostin Garcés-Ordóñez, member of the Consolidated Marine Geosciences Research Group of the UB and the INVEMAR marine environmental quality research group.

The study identified 19 potentially pathogenic bacterial species in the microplastics tested. The most common species, Aeromonas caviae, can cause gastroenteritis and has been found with Pantoea sp. in microplastics extracted from water samples, sediment samples, and the digestive tract of commonly consumed fish.

“The species Enterobacter roggenkampii and Pseudomonas fluorescens, which can also cause infections, were found on microplastics extracted from water and on fish. The bacteria that causes cholera, Vibrio cholerae, was the second most abundant bacteria, even if it was only found on microplastics in water,” says Garcés-Ordóñez.

“To know if these bacteria are capable of triggering epidemics in fish and humans around the Ciénaga Grande de Santa Marta, it would be necessary to confirm the presence of the virulence genes necessary for this effect, so this would be one of the guidelines research to be pursued in future studies.

Plastisfera: Plastics that facilitate genetic exchanges between bacteria

In the Ciénaga Grande de Santa Marta, microplastics harbor a great bacterial diversity. Analyzes identified a total of 65 bacterial phyla predominant in marine and coastal environments, with the most abundant being Proteobacteria (52%), Firmicutes (15%), and Bacteroidetes (8%).

A total of 1,760 bacterial genera were also identified, with a predominance of Aeromonas (9%), Romboutsia (6%) and Acinetobacter (6%).

“The most abundant microbial taxa varied according to the environmental matrix analyzed: Aeromonas predominated in the waters, Rhodocyclaceae in the sediments and Romboutsia in the fish. However, genera like Acinetobacter, Pseudomonas and Aeromonas, which include potentially pathogenic species, have also been found in microplastics. in water, sediments and fish”, explains Professor Miquel Canals, from the Department of Land and Ocean Dynamics at UB.

“These microorganisms form biofilms that facilitate the interaction between bacterial species and the exchange of genes that may be linked to virulence and antibiotic resistance,” the experts note.

These coastal lagoons are particularly vulnerable to microplastic pollution. With limited water circulation and shallow depth, they are exposed to a constant influx of pollutants via rivers, sewage discharges or direct spills which promote the accumulation of plastics and the proliferation of potentially pathogenic bacteria in the natural environment.

“Positively buoyant microplastics – polyethylene, polypropylene, etc. – can facilitate bacterial growth because they maintain colonies in the water column or near the surface, where they have ready access to oxygen, light and to nutrients. Their specific density is different from that of natural microplastic particles, allowing them to act as vectors and facilitate the flow of bacteria from water and sediment to the fish which ingest them.

Seeking solutions for coastal lagoons around the world

Setting up an early warning system (EWS) could help identify risky situations and predict them well in advance. Rapid communication and emergency protocols, involving scientists, health workers and local communities, could warn of possible infectious disease outbreaks in the region.

Governance must also be strengthened, sanitation and health care infrastructure improved, as well as education and training of different social actors for long-term monitoring.

“Our diagnosis of the situation highlights the need to implement integrated environmental management and public health strategies,” note the experts, also authors of a previous study (Environmental pollution2022) which warned of the alarming situation caused by microplastic pollution in 50 coastal lagoons around the world.

“This new study presents a conceptual model of environmental risks to the lagoon and surrounding human communities. This is a very vulnerable scenario because it is a semi-closed system, with a limited economy, care poor health and heavy dependence on fisheries resources.

Experts say that the Ciénaga Grande de Santa Marta represents an ideal model for analyzing a health and environmental problem that affects many lagoons around the world.

“The study of this system will not only help generate new knowledge, but also develop effective strategies to manage the environmental risks associated with these types of pollution, as well as extrapolate strategies to improve the environmental state of lagoons coastal areas affected in other regions of the world”, concludes the team.