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. https://doi.org/10.3897/aiep.53.102643

Conversation on the shore: Interview with ecologist & geographer Kremena Burkhard

Kremena’s work on local coastal ecosystems in Germany aims to develop approaches and methodologies which can be applied in an international context.

The shore is a mutual caress. More than just a place of encounter between land and water, it is one of the physical and imagined thresholds between humans and the other-than-human world. This place of touch - through thoughts, actions, interconnections, and affect - is the inevitable crossing at the beginning and end of every inquiry into the world’s bodies of water. 

In the context of the UN’s Decade of Ocean Science for Sustainable Development, the Decade of Ecosystem Restoration and the recent historic High Seas Treaty to establish Marine Protected Areas in international waters, the world looks into the deep blue. Let us, however, linger on the way there for a moment. Let us breathe, and let the shore catch our breath.


This moment on the shore leads us to a conversation with Kremena Burkhard – a researcher at the Ludwig Franzius Institute of Hydraulic, Estuarine and Coastal Engineering at the Leibniz University Hannover, Germany. Kremena’s work focuses on the co-benefits and risks of carbon sequestration in coastal ecosystems. 

Late last year, she presented her most recent work at the 4th European conference of the Ecosystem Services Partnership (ESP), which won her one of the Best Poster Talk awards. 


I find the idea of improving the understanding of how ecosystems – and more generally the natural world – contribute to our well-being to be very inspiring and refreshing in a high-tech profit-oriented world,

she says to explain how she stays motivated in her research work.

To communicate this knowledge to policy- and decision-makers, as well as the general public is key, especially when we consider the threats of climate change and the fact that our deep dependency on nature seems to be largely undervalued,

she adds.
Kremena highlights the role of nature-based solutions:

When utilising conventional and  nature-based solutions, the focus is often on a single benefit that is demanded in a certain area, time and situation. 

In contrast to conventional solutions, nature-based solutions provide additional co-benefits. These may include biodiversity protection and other ecosystem services that address broader societal demands and are more sustainable in the long term.

As part of the CDRmare research mission “Marine carbon sinks in decarbonisation pathways” of the German Marine Research Alliance, Kremena’s work on coastal ecosystems aims to develop approaches and methodologies which can be applied in an international context.

Our project sea4soCiety focuses on the carbon storage capacity and co-benefits of four coastal vegetated ecosystems which play a key role as carbon sinks around the world and thus contribute to climate regulation. The analysis and methods developed in the project contribute scientifically to the studied topics and have an international relevance.

The German coast is representative of three coastal ecosystems, namely seagrass, salt marsh and macroalgae. The fourth ecosystem – that of mangrove forests in the tropics, is also investigated within the project as a key ocean carbon sink of global relevance.

But climate regulation is only one of the multiple services that these ecosystems provide. Coastal protection, water purification, food and material provision and recreation are among the key services of coastal ecosystems, the benefits of which are used and highly appreciated by the local communities and have significant role in the local safety, economy and culture. 

Kremena’s winning poster presented at the 4th European conference of the Ecosystem Services Partnership (ESP) (Crete, Greece 2022)
What are the strategies for mitigating or further analysing the risks of carbon sequestration in coastal ecosystems?

We prioritise conservation and restoration of coastal vegetated ecosystems, which are often heavily degraded, and we identify the most suitable areas for establishment of new ecosystems. This reduces the risk of carbon release and provides additional carbon sink capacity. 

Further risks are related to unknown climate change impacts. The sea temperature and hydrodynamics are changing, and we are not sure how those changes of habitat will impact the coastal ecosystems. We are studying their reaction in laboratory environments and in the field, identifying thresholds for their functionality and capacity to supply ecosystem services. 

Finally, the identification and mitigation of conflicts with other users of those ecosystems is also key to reduce the social risks for all beneficiaries, including labour, human rights, public health issues, and political uncertainty.

When it comes to stakeholders and non-experts, is science communication around the topic of carbon sequestration in coastal ecosystems effective?

On a national and international level, Germany seems to be on track with setting targets and planning actions to become climate neutral through the Climate Action Programme 2030.

The CDRmare research mission and in particular the sea4soCiety project on carbon sequestration in coastal ecosystems are in a way part of that effort, receiving funding to provide the knowledge base for the action programme. Thus, to some extent, the science communication on that level is working and the action plan is based on scientific knowledge. 

The shortcomings are in the implementation phase. Local governments are often lacking established mechanisms that allow and support the implementation of action plans related to the national targets.

Such regulated implementation strategies should operationalise the uptake of scientific knowledge in the management of coastal ecosystems and by the local communities, and also in all fields of policy and management.

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