Researchers from Spain, Colombia and Chile issued this warning through a study set to be published later this year in Environmental Pollution. It named three lagoons – Lagos in Nigeria, Sakumo in Ghana and Bizerte in Tunisia – as among the most affected water ecosystems. They pointed out that these three lagoons, all located in Africa, are situated near huge urban centers without waste and sewage treatment systems.
Furthermore, the researchers looked at scientific literature on microplastic pollution in 50 coastal lagoons in 20 countries. Aside from the three African lagoons mentioned, they found maximum concentrations of microplastics in Barnes Sound and other small lagoons in a protected area in the northern part of Florida Bay.
Coastal lagoons are transitional ecosystems between inland and marine aquatic systems, putting them in a position of great significance for biodiversity conservation. They are also the key sources of food and other ecosystem services to communities that rely on them. While about 58 percent of these ecosystems presently have some kind of national or international protection status, they are also affected by human activity.
Study author Ostin Garces-Ordonez of the University of Barcelona said: “In these natural habitats, peak levels of microplastic pollution result from a combination of several factors. For example, the residence time and water renewal rate of lagoons, the presence of large urban and industrial developments with insufficient waste management, river and outfall discharges, seasonal climate fluctuations, natural phenomena and the typology of microplastics.”
He also remarked that coastal lagoons with slow or very slow water turnover rates are the most sensitive to extreme microplastic pollution.
“During the rainy season, the concentration of microplastics also increases in surface water compared to the dry season, a phenomenon that has been observed in the lagoon of Rio Lagarto (Mexico) and in the Ciénaga Grande de Santa Marta (Colombia), with maximum levels in areas where the most intense human activities are recorded,” noted Garces-Ordonez.
High levels of microplastics found in fish
Fish fauna is one of the most-studied groups of organisms in connection with the effects of microplastics.
The study, which examined the effects of pollution on 96 species, discovered a maximum impact on fish in the lagoons of Bizerte and Ghar El Melh in Tunisia, especially the golden gray mullet (Liza aurata) and the Salema porgy (Sarpa salpa), with consumption of up to 65 microplastics per individual.
Mollusks, with levels of up to 17 microplastics per individual, are another of the most impacted groups, with the highest values found in Eastern oysters (Crassostrea virginica) in Florida’s Mosquito Lagoon.
The study also revealed the presence of microplastics in the water column, sediments and fish in the Iberian Peninsula coastal lagoons.
Besides gathering in particular areas of lagoon ecosystems, microplastics can also end up in the sea and exacerbate the problem of ocean pollution. (Related: Microplastic pollution is the REAL threat to our oceans, warn scientists.)
The paper is based on studies that have combined various methodological approaches like direct visual inspection, chemical digestion and density separation to study diverse habitats that may cover coral reefs, seagrass beds, beaches and swamps.
Accomplishing this goal requires a series of collective actions at global, regional, national and local levels.
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