Microplastic Menace in India’s Pichavaram Mangroves Revealed in New Study

A new study published in Chemosphere by researchers at Bharathidasan University reveals alarming seasonal microplastic (MP) contamination in fish and shellfish from India's Pichavaram Mangroves. This study, led by Rajendran Rajaram from Bharathidasan University in Tamil Nadu, India, shows a seasonal analysis of microplastic ingestion by aquatic species in this habitat.

The Pichavaram Mangrove Forest is an estuarine ecosystem in southeast India. It lies between the Vellar and Coleroon estuaries, forming the Killai backwaters (2). Being one of India’s largest mangrove ecosystems, Pichavaram contains a wide range of habitats and his rich in biodiversity (2). From mangroves to dry evergreen forests to salt marshes, Pachavaram offers many opportunities for locals and visitors to engage in outdoor recreation activities such as kayaking and rowing (2). Acting as a natural bio-shield, the mangroves in Pachavaram protect against erosion and climate impacts, and as part of India’s coastal region, they contribute to shoreline stability (2).

Pichavaram Mangrove Forests. The second largest Mangrove forest in the world, located near Chidambaram in Cuddalore District, Tamil Nadu, India | Image Credit: © Sumit - stock.adobe.com

In their study, Rajaram and his team conducted a comprehensive seasonal analysis of microplastic ingestion by aquatic species in Pichavaram. The study took samples from the aquatic species during four distinct seasonal periods, which were summer, pre-monsoon, monsoon, and post-monsoon. After capturing the temporal dynamics of microplastic accumulation and ingestion across various aquatic species, the researchers determined that the monsoon season recorded the highest microplastic abundance, accounting for 45% of the total MPs found (1). During monsoon season, which encompasses heavy rain, plastic runoff from nearby human settlements and the shoreline move directly into the mangrove ecosystem, which is why the researchers were able to attribute the seasonal variation to the increase in MP concentration (1).

The researchers examined several species in their study. Among the ones studied are finfish Liza tade (mullet) and Etroplus suratensis, as well as shellfish species Portunus sanguinolentus and Scylla serrata. Their study demonstrated that Liza tade (mullet) and Etroplus suratensis showed the highest levels of microplastic contamination, with Liza tade alone registering an average of 13.33 MPs per individual during the summer season (1). This was followed by a sharp decline to 0.77 MPs per individual in the pre-monsoon, and a moderate resurgence in the monsoon (6.3) and post-monsoon (2.67) seasons (1). Portunus sanguinolentus and Scylla serrata were also heavily contaminated, underscoring the widespread impact of MP pollution across different trophic levels (1).

The researchers measured the size of the MPs detected, and they determined that 32% of the MPs were smaller than one millimeter (1). Knowing this information explains the alarming level of MPs in the aquatic species, because smaller MPs are more likely to be ingested by marine organisms. The researchers also found that fibrous MPs were the dominant morphotype, with blue fibers being the most prevalent (40%), followed by red (13%), and smaller proportions of transparent, brown, and yellow particles (1). These color patterns suggest localized pollution sources, possibly from textiles, fishing gear, and household waste (1).

To determine the polymeric composition of MPs obtained from the fish gut samples, the researchers employed advanced μ-Raman spectroscopy. Using this technique allowed for polymer identification. They found that polypropylene (PP) emerged as the most abundant polymer, followed by polyethylene (PE) and polyethylene terephthalate (PET) (1). The prevalence of PP was particularly notable in fibers colored red, white, blue, black, and green. The study also found that the physical characteristics of polymers could affect their likelihood of ingestion and bioavailability to aquatic organisms (1).

What sets this study apart is its comparative analysis with global mangrove ecosystems. Although similar polymers such as PP, PE, and PET are found in other mangrove regions worldwide, the sources, colors, and seasonal trends of microplastics vary significantly (1). These differences underscore the importance of localized environmental monitoring and policymaking to effectively address the plastic pollution crisis (1).

The findings provide a baseline for future conservation and pollution control efforts in mangrove ecosystems, which serve as critical nurseries for marine biodiversity (1). As a result, the researchers concluded their article by stressing the importance of improving waste management infrastructure, public awareness campaigns, and stricter regulations on plastic use and disposal (1). Doing these three things would help safeguard vulnerable ecosystems and the species that reside in them.

References

1. Bhattacherya, S.; Kolandhasamy, P.; Mandal, A.; et al. Ecological Risk Assessment and Ingestion of Microplastics in Edible Finfish and Shellfish Species Collected From Tropical Mangrove Forest, Southeastern India. Chemosphere 2025, 377, 144308. DOI: 10.1016/j.chemosphere.2025.144308
2. Tamil Nadu Wetlands Mission, Pichavaram Mangrove. TNSWA.org. Available at: https://tnswa.org/pichavaram-mangrove (accessed 2025-05-06).