COVID-19 pandemic has emphasized the essential role of plastic in modern society especially in healthcare sector and public health safety (Parashar & Hait, 2021). As plastics are lightweight, flexible and durable, global plastic production has increased drastically to 368 million tons in 2019 (Plastics Europe, 2020) and by 2050 it is predicted that around 12000 metric tons of plastic debris will end up in dumping ground and in the surrounding environment (Geyer et al., 2017). With the widespread indiscriminate use of plastic products and improper disposal of plastic litter (Silva et al., 2020) during COVID-19 pandemic it has become a global and emerging pollution crisis that must be addressed by powerful and effective plan of action (United Nations Environmental Program, 2021). Recent research predicted that around 14.4 million tons of microplastic have made its way into the world’s ocean floor Barrett et al. (2020).
Microplastic are plastic fragments with a diameter <5 mm as defined by U.S. National Oceanic and Atmospheric Administration in 2008 (Betts, 2008). In the natural environment, microplastic are released as primary or secondary microplastic. Primary microplastic are discharged into the environment in their original form which may be from washing of clothes and as microbeads which are used in beauty and personal care products. Likewise, secondary microplastic are formed by the fragmentation of macroplastic items which may be generated from the weathering of plastic debris or disintegration of car tire (UNEP, 2018). Microplastic are ubiquitous in the aquatic environment. This is of increasing concern as it is associated with various ecotoxicological effects (Akdogan & Guven, 2019) which includes reduction in food intake (Cole et al., 2015; Watts et al., 2015) decline in reproductive capacity (Au et al., 2015; Sussarellu et al., 2016), growth delay (Au et al., 2015; Watts et al., 2015), and enzyme alteration (Avio et al., 2015; Gambardella et al., 2017; Jeong et al., 2017).
Likewise, Green (2016) demonstrated that when benthic fauna was exposed continuously to a higher concentration of microplastic, it decreased the overall abundance of benthic assemblage structure and triggered the species accumulation. Similarly, microplastic are medium for transferring toxic chemicals to the biota and other contaminants into the aquatic ecosystem (Brennecke et al., 2016; Koelmans et al., 2019). Microplastic enter the freshwater environment through domestic wastewater effluent (Browne et al., 2011), runoff from agricultural lands and overflow of drains during storm or rain event (Eriksen et al., 2013; Galgani et al., 2015), factory spillage (Gasperi et al., 2014) and atmospheric fallout (Allen et al., 2019; Negrete Velasco et al., 2020). Microplastic is an emerging pollutant which has been intensely studied in marine environment (Thompson et al., 2004), but recently only freshwater studies have received scientists attention (Campanale et al., 2020). Freshwater bodies act as a carrier of microplastic and transport network of microplastic to the marine environment (Jiang et al., 2018). The country Nepal is blessed with rich water resources which have been providing important services (like drinking water source, generation of hydropower, irrigation, aquaculture and recreation) but due to weak implementation of pollution law and poor waste management strategy, freshwater resources are fast degrading.
The study area, Phewa Lake is the second largest lake and one of the main tourist destinations of Nepal. The panoramic view of Manaslu and Annapurna Mountain range and the refection of Machhapuchhre Mountain on the lake attracts tourist. The lakeshore is encroached by hotels and restaurants to capture the scenic beauty of the lake which has increased the pollution load of the lake. Till date no study on microplastic has been reported previously from the proposed study area. Therefore, the objective of this study was to compare the microplastic concentration in different seasons for Phewa Lake with regards to surface water. Thus, this study will bridge the gap to generate abundance and spatial distribution of microplastic from lake surface water for the first time. Further, this study will provide a baseline data on microplastic so the local authority could take action to protect the lake ecosystem before it is too late.