A study led by researchers from the UB and the Marine and Coastal Research Institute (INVEMAR) in Colombia warns of the impact of microplastic pollution and pathogenic bacteria in the Ciénaga Grande de Santa Marta in Colombia. Credit: Ostin Garcés-Ordóñez (UNIVERSITY OF BARCELONA – INVEMAR). CC BY.

New research has shown how bacterial contamination and microplastics are threatening Colombia’s largest and most productive coastal lagoon.

A study led by researchers from the University of Barcelona and the Marine and Coastal Research Institute (INVEMAR) in Colombia warns of the presence of potentially pathogenic bacteria in microplastics extracted from water, sediments and the digestive tract of fish in the 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 known as plastispheres, ecosystems associated with plastic waste that are highly resistant to environmental changes.

Microplastics have also been found in fish consumed by the local population, posing an even greater risk to the entire natural ecosystem and human health.

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

The study opens a new perspective on the micro-organisms that colonise microplastics in coastal lagoons, an area still little explored by the scientific community.

The findings also provide unpublished data on the interactions between microplastics and potentially pathogenic bacteria in ecosystems under increasing environmental pressure.

The Ciénaga Grande de Santa Marta is seriously threatened by high microbiological contamination and microplastics that affect the water, sediments and organisms. Credit: Ostin Garcés-Ordóñez (UNIVERSITY OF BARCELONA – INVEMAR). CC BY.

Local population

Covering 1,321 km², the Ciénaga Grande de Santa Marta is a shallow (1-1.8m) lake ecosystem that receives freshwater from four rivers and seawater through a channel connecting it to the Caribbean Sea.

Flanked by mangroves, it is home to two national parks — recognised as a Ramsar site — and is a strategic lagoon complex for biodiversity conservation. In this ecoregion of rich fauna and flora, fishing is essential for the livelihoods of local communities.

Despite its ecological value, “the Ciénaga Grande de Santa Marta is seriously threatened by high microbiological contamination and microplastics that affect the water, sediments and organisms. These pollutants alter the quality of the habitat and fishery products and, ultimately, the food security of the local population”, said researcher Ostin Garcés-Ordóñez, a member of the UB’s Consolidated Research Group in Marine Geosciences and INVEMAR’s Marine Environmental Quality Research Group.

The study identified nineteen potentially pathogenic bacterial species in the microplastics tested.

The most prevalent species, Aeromonas caviae, can cause gastroenteritis and was found together with Pantoea sp. in microplastics extracted from water samples, sediment samples and the digestive tract of commonly consumed fish.

Garcés-Ordóñez said: “Enterobacter roggenkampii and Pseudomonas fluorescens species, which can also cause infections, were found on microplastics extracted from water and on fish.

“The bacterium responsible for cholera — Vibrio cholerae — was the second most abundant bacteria, although it was only found on microplastics in water.

“To find out whether these bacteria are capable of triggering outbreaks of disease in fish and humans around the Ciénaga Grande de Santa Marta, the presence of the virulence genes needed to do so would have to be confirmed, so this would be one of the lines of research to be pursued in future studies.”

Early Warning System

Establishing an Early Warning System (EWS) could help identify risk situations and forecast them well in advance.

Rapid communication and emergency protocols — involving scientists, health workers and local communities — could warn of potential infectious disease outbreaks in the area.

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

The experts noted: “Our diagnosis of the situation underlines the need to implement integrated environmental management and public health strategies.

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

The experts, who are also authors of a previous study (Environmental Pollution, 2022) that warned about the alarming situation caused by microplastic pollution in 50 coastal lagoons around the world, said the Ciénaga Grande de Santa Marta represents an ideal model for analysing a health and environmental problem that affects many lagoons around the world.

They concluded: “Studying this system will help not only to generate new knowledge, but also to develop effective strategies to manage the environmental risks associated with these types of pollution, as well as to extrapolate strategies to improve the environmental status of affected coastal lagoons in other regions of the world.”

The study is published in the Journal of Hazardous Materials.