Mangroves threatened by microplastic infiltration

A recent study highlighted by a Mongabay-India report offers insights into the extent of infiltration of microplastics detected in a mangrove in south-western India. Micro plastic contaminants are described by the United Nations Environment Programme as one of the “long-lived legacies of plastic pollution”, as the Mongabay-India report warns. The study found that fibres, mostly measuring less than a millimetre, emerged as the most abundant category across all samples studied from the mangrove in a coastal village Kota in Udipi district of Karnataka state, by researchers from the Manipal Institute of Technology and Universidad del Atlántico, Colombia.  The mangrove forest at Kota is about three kilometres long and has over 10,800 people residing there. They found all categories — from fragments to foam, fibres, films and pellets — in surface water samples from the Kota mangrove. Fibres were the most abundant, followed by films, fragments and foam. The scientists report that the concentrations were the lowest during the monsoon season, which could be attributed to enhanced flow rates, which facilitate the transport of microplastics from the mangroves to the Arabian Sea. The higher levels seen post-monsoon could be due to tourism activities.

The study, published in the ‘Regional Studies in Marine Science’, investigates the seasonal variations in microplastic contamination, specifically those ranging in size from 0.1 mm to 5 mm, within the tropical mangroves of Kota, South-western India. Its Introduction states that environmental stressors – be they biological, chemical, or physical – facilitate the degradation of mismanaged plastic debris. These degraded fragments, along with industrially produced particles of size 1 µm-5 mm, are collectively termed ‘microplastics’. Emerging evidence has confirmed the pollutant potential of microplastics, categorizing them as pollutants of emerging concern.

The Introduction goes on to point out, using several studies to reinforce its argument, that mangrove ecosystems occupy a substantial 152,000 square kilometres of the Earth’s surface, with 42% located in Asia. These vital ecosystems perform multiple ecological functions, supporting a diverse range of flora and fauna. Among various types of anthropogenic debris found in mangroves, plastics are the most prevalent. Plastic pollution poses a significant threat to mangrove ecosystems. When buried in sediment over multiple tidal cycles, plastics can induce anoxic conditions that are detrimental to mangrove trees. Marine plastic litter is primarily delivered to mangrove areas by waves and currents. Notably, mangroves have been observed to contain eight times more microplastics than non-mangrove environments. Previous studies from Asia also have shown the prevalence of microplastics in mangroves in Asia which is home to 42% of mangroves.

As the United Nations Environment Programme warns, one of the most damaging and long-lived legacies of the plastic pollution crisis is microplastics, a growing threat to human and planetary health. These tiny plastic particles are present in everyday items, including cigarettes, clothing and cosmetics. Among various types of anthropogenic debris found in mangroves, plastics are the most prevalent. Plastic pollution poses a significant threat to mangrove ecosystems. When buried in sediment over multiple tidal cycles, plastics can induce anoxic conditions that are detrimental to mangrove trees (Smith, 2012). Marine plastic litter is primarily delivered to mangrove areas by waves and currents (Martin et al., 2019). Notably, mangroves have been observed to contain eight times more microplastics than non-mangrove environments.

Further UNEP research shows that continuous use of some of these products increases microplastics’ accumulation in the environment. Microplastics, which can be up to five millimetres in diameter, enter the ocean from marine plastic litter breaking down, run-off from plumbing, leakage from production facilities and other sources. When ingested by marine life such as birds, fish, mammals and plants, microplastics have both toxic and mechanical effects, leading to issues including reduced food intake, suffocation, behavioural changes and genetic alteration. In addition to entering the food chain through seafood, people can inhale microplastics from the air, ingest them from water and absorb them through the skin. Microplastics have been found in various human organs, and even in the placenta of newborn babies. Earlier, a UNEP’s 2021 report had warned that chemicals in microplastics “are associated with serious health impacts, especially in women”. These can include changes to human genetics, brain development and respiration rates, among other health issues.