Microplastics are tiny plastic particles less than 5 millimetres in size, as small or smaller than a grain of sand. They originate from various sources, such as personal care products like face scrubs, the breakdown of larger plastic waste, the wear and tear of car tyres, and even clothes made from synthetic fibres like polyester. Once these small pieces enter the environment, they are challenging to remove and can spread through ocean currents, winds, and tides. Microplastics that have found their way into marine environments worldwide are wreaking havoc on ecosystems.
A recent study by ICAR-Central Institute of Fisheries Education, Mumbai, and King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia, has documented and categorized the types of microplastics found in the mangrove sediments of Mumbai, India. The study aims to understand the sources of the microplastics and identify ways to mitigate them.
Mumbai is one of the most populous cities in India, with over 21 million residents. The city's mangroves play critical roles in the ecosystem. They act as buffers against natural disasters, provide habitats for marine life, and help sequester carbon (absorb carbon from the atmosphere and store it in the soil).
Unfortunately, Mumbai also releases untreated sewage into the sea, which, coupled with urban runoff, results in high levels of pollutants entering these vital natural barriers. By studying the sediments (the muck and soil where the mangroves root themselves) in these areas, researchers can measure how big of a problem microplastics truly are in this setting.
The research team collected samples from 30 random sites across six different zones within Mumbai's mangrove ecosystem. They identified more than 2,000 types of microplastic particles in the collected sediments, with a staggering average of 6,730 microplastic pieces per kilogram of dry sediment weight. The Versova region had the highest concentration, suggesting heavy urban activity and poor waste management practices there, while the lowest was in Sewri.
The study categorized these particles by shape, size, and colour and then, using a technique called micro-Fourier transform infrared spectroscopy, the scientists identified the most common plastics in these sediments. The majority (56.1%) were fibres, like the kind that are shed from synthetic clothing. Polyethylene, often used in plastic bags and bottles, was the most prevalent polymer, comprising 36.91% of the total particles. This was followed by polyester and polyamide -- materials found in clothing and industrial applications. Relatively small particles, less than 100 micrometres (about the diameter of a human hair), made up 38.5% of the microplastics discovered. Various colours were observed, but translucent or transparent particles were prominent, complicating detection.
The presence of fibres is particularly alarming as these can look like food particles to small fish, which consume these microplastics. This can lead to bioaccumulation, where organisms that consume these fish accumulate the microplastics within them. This accumulation can quickly travel up the food chain and soon show up in human stomachs.
While this study provided valuable insights, it also had some limitations. For example, the sediment sampling depth was restricted to 15 centimetres, missing potential older microplastic deposits deeper down. The study also focused on specific sampling areas and timeframes, which means it might not completely capture seasonal fluctuations or the whole picture across all of Mumbai's mangroves.
Furthermore, while the research noted the presence of microplastics, it didn't delve deeply into their broader impacts on the ecosystem or local organisms. Understanding how these particles affect local wildlife, especially fish, benthic organisms like crabs and bivalves, and even birds such as flamingos, is essential. This would deepen our understanding of how microplastics travel through food webs and potentially impact human health.
Understanding the type and concentration of microplastics in sediment is crucial. It highlights the environmental impact of human activities and serves as a wake-up call for better waste management practices. Additionally, identifying the types of plastics present can help develop targeted strategies for cleaning and preventing further contamination. The research is a key stepping stone for Mumbai to launch more effective conservation and waste management policies, which can protect the mangroves that serve vital ecological and economic roles by supporting marine life and providing natural protection against weather events.
This research news was partly generated using artificial intelligence and edited by an editor at Research Matters