Emerging threats of microplastics on marine environment: A critical review of toxicity measurement, policy practice gap and future research direction

The concentration of microplastics (MPs) in the ocean is increasing at an alarming rate, which has created numerous hazardous issues for the marine animals and micro-organisms, including coral reef ecosystems and the overall marine environment. The ecotoxicological impacts and invisible threats of MPs on marine animals stimulate the marine scientists and researchers to think about reducing the concentration of MPs in the ocean and ensuring the healthy growth of marine animals. Industrial plastic products, coastal tourism, fishing, shipping, and mismanaged waste dumping in the seas and oceans were the major sources of MPs on the ocean surface. More than 75% MPs were found as marine debris in the coastal and deep-sea sediments. Basically, the ecosystem, ecology, and the overall environment of the coastal regions shallow seas and ocean were highly affected by MP's toxic effects rather than the deep sea and ocean areas worldwide. Hence, the present review focused on toxicological threats of MPs on marine animals, ecosystems, and the overall marine environment along with policy recommendations by applying the PRISMA guidelines. The current review highlighted that different marine animal species, such as fishes, corals, mussels, and turtles were immensely threatened due to the high concentration, extreme exposure, and ingestion of MPs as food in the marine environment. Among different MPs polymers, PP, PE, PET, and PVC were the predominant polymers that were abundantly noticed throughout the world ocean among reviewed articles regarding ocean MPs pollution. Blockage of the digestive tract, genetic damage, malfunction of the immune system, and immature death of marine animals were the major toxic effects of MPs in the marine environment. To minimize the concentration of MPs and its severity on the marine animals, different world organizations such as UNEP, IUCN, FAO etc. have initiated numerous policies, but those were not successful in the true sense. Therefore, it is necessary to implement strict legislation and laws at international, national as well as regional scales. And at the same time, collaborative work of governmental and nongovernmental organizations are recommended for sustainably managing the MPs waste in the seas and oceans to ensure the healthy growth of marine plants, animals, and micro-organisms.