Widespread microplastic pollution in Peruvian mangrove sediments and edible mangrove species

3 May 2024

Previous field studies have demonstrated that microplastic debris can become trapped in aerial roots or the interior scrub zone of the mangrove. There is also an indication that microplastics can accumulate in the underlying sediments, and be ingested by or adhere to a wide range of aquatic organisms, including commercially-important species.

The edible mangrove crab and black ark (a filter-feeding shellfish) are of highest commercial value in Tumbes mangroves and support the nutrition and socio-economic wellbeing of inhabitants in the region. Research has shown the presence of microplastics in the gills and digestive tract of 30 mangrove crabs collected from local markets in the city of Tumbes and raised the question of whether this poses a risk to food security in the area.

To help answer this question, a team of scientists from the Universidad Científica del Sur, Instituto del Mar del Peru (IMARPE) and Plymouth Marine Laboratory (PML), set out to establish the prevalence of microplastics in the sediments and in the commercially-important mangrove crab and black ark of the mangrove ecosystem of Tumbes, as well as estimate the dietary exposure to microplastics in local populations.

The study, supported by the Global Challenges Research Fund (GCRF) project ‘Reducing plastic waste in the Galapagos and Eastern Pacific’, revealed that microplastics were identified in all sediment samples tested with concentrations ranging from 138 to 1462 plastics per kg.

In the black ark, microplastic concentrations were between 2.7- 7.1 particles per individual and in the mangrove crab, between 4.7-10.9 particles per individual. Across all sites the mangrove crabs showed significantly greater microplastic concentrations in their gills and stomach than observed in the soft tissues of the black ark.

The microplastics comprised microbeads, fragments, fibres and films, with fibres and films the most common categories of microplastics in the black ark (fibre 80.6%, film 11.1%), mangrove crab (82.3%, 6.6%) and sediment (33%, 63%).

The ingestion of microplastics by local inhabitants from consuming black ark and mangrove crab was estimated as 431 microplastics per person per year. Consumers that eat microplastic-contaminated food, especially organisms that are consumed whole (i.e. including the gills and digestive tract where microplastics are prevalent) are at high risk of consuming microplastics. In Peru, both the edible mangrove crab and the black ark are consumed whole in traditional dishes, such as ceviche and parihuela.

The risks posed to humans from consuming microplastics may include oxidative stress, impacts upon gene expression and cell morphology, aggravating allergic diseases and genotoxic and neurotoxic effects.

In addition to the direct environmental and human health impacts, there is concern that microplastics may act as vectors for disease, such as cholera, through bacterial colonization on particle surfaces, and help provide an ideal habitat for parasites and viruses, such as Dengue and Zika.

Lead author, Angelica Aguirre Sanchez, who visited Plymouth Marine Laboratory (PML) to conduct the analysis, said:

“Thanks to this wonderful project in collaboration between PML and IMARPE, I travelled to Tumbes, where I learned to understand the area’s needs such as the scarcity of water, resource limitations, and the lack of wastewater treatment. This not only results in numerous contaminants in the environment, such as microplastics, but also emphasizes the importance of conducting research in an environmentally friendly manner. Therefore, in the future, I would love to focus on investigating solutions to this problem. Despite Tumbes being one of the smallest regions in Peru, it has a great variety of ecosystems such as mangroves, dry forest, tropical forest, and the Grau tropical Sea. Having found microplastics in the mangrove sediment and in two economically representative species such as the black ark and mangrove crab during our research, we expected that this will contribute to decision-making by local authorities, raise awareness about the plastic issue among citizens, and serve as well as a base investigation for future research in the region.”

“Likewise, thanks to the Pacific Plastics Science to Solutions (PPSS) project I had the opportunity to complete the research by performing the FT-IR analysis in PML. The support and friendship of the microplastics team at PML has been essential to enrich my knowledge, overcome obstacles and open me to new opportunities. I will always be grateful for all the experience that has contributed to my growth as a researcher”.

Dr Matthew Cole, Senior Marine Ecologist and Ecotoxicologist at PML and co-author on the paper, commented:

“Activities, such as improper waste disposal, tourism, farming and shipping contribute to the widespread distribution of microplastics throughout the region, which is accumulating in sediments throughout the Tumbes mangrove. Notably, microplastic concentrations within the mangroves represent some of the highest microplastic concentrations in Peru, indicating that these mangroves are accumulating microplastics more readily than unvegetated habitats. The outcomes of this work highlights the risks this microplastic contamination may pose to the marine food web and food security in the area, which needs to be addressed urgently".

 

Related information

Full paper: Prevalence of microplastics in Peruvian mangrove sediments and edible mangrove species
 

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