Microplastic Contamination of Holothuria (Thymiosycia) arenicola Semper, 1868, Holothuria pardalis Selenka, 1867, Sediments and Seawater From Karachi Coast, Northern Arabian Sea, Pakistan

Microplastics (MPs) are posing an increasing threat to the marine environment, affecting marine ecosystems and posing potential risks to human health through the food chain. This study aims to investigate the MP contamination of Holothuria (Thymiosycia) arenicola Semper, 1868, Holothuria pardalis Selenka, 1867, sediments and seawater from Buleji coasts of Karachi, Pakistan. The MP contamination was determined in the different body parts of sea cucumber species and both seawater and sediment samples were contaminated with microplastics. The results show that H. arenicola contains more microplastics than H. pardalis. In terms of shape and colour, fibres were the most common form of MPs (>99%), with black being the predominant colour. The highest to the lowest amount of MPs was determined as gut (52±26 pieces/individual in H. arenicola and 31±14 pieces/individual in H. paradis), coelomic fluid (18±10 pieces/individual in H. arenicola and 26±15 pieces/individual in H. paradis), respiratory tree (22±11 pieces/individual in H. arenicola and 14±9 pieces/individual in H. paradis and tentacles (13±8 pieces/individual in H. arenicola and 10±5 pieces/individual in H. paradis), respectively. Determination of MP pollution in these sea cucumbers and their surrounding environment is very important in terms of the importance of these organisms in the marine ecosystems. The biological impacts of MPs on sea cucumbers and other marine organisms can eventually affect humans through the food chain. Therefore, the paper advocates for the development of policies to monitor and reduce MP pollution in marine ecosystems.