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Microplastics in the marine and freshwater ecosystems

Name: Sayan Dutta
Name of supervisor: Prof. Amritanshu Shriwastav
Department: Environmental Science and Engineering

Topic of research: Microplastics in the marine and freshwater ecosystems

Description of research work:

Microplastics in the marine and freshwater ecosystems

Microplastics can be defined as synthetic plastic particles or polymeric matrix of either primary or secondary manufacturing origin with a typical size range from 1 µm to 5 mm. The freshwater ecosystems act as carriers for transporting them and other pollutants into the marine waters. Once ingested by the aquatic biota it has negative effects such as reduced rates of respiration and reproduction, obstruction of the digestive tract, and disruption of the endocrine system. In humans, scientists have speculated that microplastics with size < 20 µm have the potential to access all organs and translocation of blood-brain, cell membrane, and placental barrier.

This is the first study of its kind which aimed at determining the abundance, morphological and spatio-temporal variation of microplastics in the water column of selected marine and freshwater ecosystems of Mumbai and to present a comparison of the two ecosystems based on microplastic contamination level. The potential anthropogenic activities responsible for the pollution were also identified. The laboratory analysis involved sieving through 5 mm sieve, oven-drying at 700C, density separation using zinc chloride salt solution, Fenton’s oxidation, Nile Red staining, and observation under a fluorescence microscope.

In the seawater column, the average microplastic abundance was 100 ± 7 particles/L ranging from 15 particles/L to 260 particles/L while in the surface water of lakes the mean concentration was 232 ± 14 particles/L ranging from 0 to 720 particles/L. The abundance of microplastics spatially shows an increasing trend towards the south with Girgaon Chowpatty beach displaying the highest plastic abundance for the marine environment and Powai lake for the freshwater ecosystem. Located in the outskirts and isolated from the main city Aksa beach is cleaner and has relatively less microplastic contamination. Beads and fragments were found to be predominantly present in both marine and freshwater ecosystems whereas fibers were the least abundant. In terms of size, particles lied mostly in the range between 0-500 µm in both environments thereby highlighting the fact that small-sized microplastic litter dominated the waterbodies in Mumbai.

The results indicate that microplastics are ubiquitous in aquatic environments. The potential anthropogenic factors are the tourist activities, fishing, and riverine activities and municipal and industrial wastewater being released into rivers which eventually gets mixed with the ocean. To maintain the aesthetic appeal frequent beach cleanup activities and tourist awareness programs need to be conducted in large scales across the country.



Spatio-temporal variation of microplastics in a) marine water b) freshwater lakes