Invasive species as biomonitors of microplastics in freshwater ecosystems?

Microplastics forming the disproportionate amount of plastic garbage, and catfish have become numerically dominant in some ecosystems thanks to their tolerance to pollution and anoxic environments.

Armored catfish (Pterygoplicthys spp.) and microplastics, as invasive species and emerging contaminants, respectively, represent two socio-environmental problems in the globalized world, since both have negative effects on faunistic communities and freshwater habitats, as well as on rural community fisheries and public health.

Non-native invasive species of armored catfish have become numerically dominant in some ecosystems, with efforts to eradicate them a seemingly endless task. Due to this, a possible scenario of biological homogenization in Mesoamerica can be expected, mainly given by the wide dispersion of the Pterygoplichthys species, added to the introduction of other non-native catfish species.

Photo: Miguel Ángel Salcedo. Drawing: Diana Ríos-Hernández.

The omnipresence of plastics in terrestrial and aquatic environments is caused by their excessive use and inadequate management of waste. The discarded plastics are fragmented, degraded, and dissolved by solar radiation, wind, and water, among other agents, to be incorporated into the food web in aquatic environments.

Both persist in the aquatic environment, microplastics forming the disproportionate amount of plastic garbage, and catfish thanks to their tolerance to pollution and anoxic environments, and their ability to survive for several hours breeding atmospheric oxygen. What is the relationship between the two? Microplastics, depending on their origin and composition, are sedimented in the wetlands, where they can be ingested by detritus feeders, such as armored catfish, mainly in areas where there is runoff or discharge of liquid waste.

In this context, we ask ourselves, can armored catfish be used as biomonitors of microplastics deposited in wetlands? Taking the above into consideration, the doctoral student Gabriela Angulo-Olmos under the guidance of the researchers Nicolás Álvarez-Pliego, Alberto J. Sánchez, Rosa Florido, Miguel Ángel Salcedo, Allan K. Cruz-Ramírez and Arturo Garrido Mora from the Laboratorio de Humedales, from the División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco, decided to answer the aforementioned question based on the numerical dominance of armored catfish recorded in the aquatic ecosystems of the Metropolitan Area of Villahermosa (MAV) in the coastal plain of the Gulf of Mexico.

A) Study area; Metropolitan Area of Villahermosa. Map modified from INEGI (2021). B) La Pólvora lake (Satélite Airbus 2023).

The stomach contents of the specimens from a lake located in the MAV were reviewed and the results showed that all the specimens had consumed microfibers. This result corroborated that these organisms can ingest sedimented microplastics due to their benthophagous habits.

Microplastics. Image by Oregon State University under a CC BY-SA 2.0 license.

The use of armored catfish as a resource in the food industry has had positive results, but is still insufficient. Therefore, we propose that another option to control their populations is to subtract and use this organism to verify which are the most frequent and abundant emerging contaminants deposited in the bottoms of urban wetlands.

Research article:

Angulo-Olmos G, Alvarez-Pliego N, Sánchez AJ, Florido R, Salcedo MÁ, Garrido-Mora A, Cruz-Rámirez AK (2023) Microfibers in the gut of invasive armored catfish (Pterygoplichthys spp.) (Actinopterygii: Siluriformes: Loricariidae) in an urban lake in the floodplain of the Grijalva River basin, Mexico. Acta Ichthyologica et Piscatoria 53: 81–88.