Occurrence and pathways of microplastics, quantification protocol and adverse effects of microplastics towards freshwater and seawater biota

Plastic has become one of the major contributors to the world’s pollution. As it may degrade into smaller particles known as microplastics (<5 mm), which has become a new threat towards marine ecosystems. Due to their size, microplastics can easily enter the food chain due to seafood consumption, entering the digestive system. Moreover, microplastics also bring negative impact towards freshwater biota and sea life. Despite the extensive studies on microplastic contamination in the marine environment, research on microplastic in seafood and freshwater environments, specifically regarding ingestion and effect of microplastics in aquatic organisms, freshwater biota as well as human health along the supply chain are still scarce. Microplastic ingestion in aquatic animals causes health hazards such as leaking gut, transferring pathogenic bacteria into the blood and increasing toxic levels in the body. This scenario could potentially introduce similar hazards to human health if consumed. This paper reviewed the sources, detection method, allocation and adverse effects of microplastics contamination in seafood and freshwater ecosystems. The focus of this review is on biota which includes samples of aquatic animals as well as seawater samples from various sources including riverine (river), lacustrine (lake) and wastewater treatment plants (WWTPs) throughout the world. Since microplastics are related to synthetic substances from waste, there is an alarming concern regarding their physical and chemical compounds that might be present in the aquatic life and food supply chain. Therefore, recommendations and improvements on future studies of microplastic contamination in marine ecosystems regarding identification and quantification protocol along with the study on microplastics towards the freshwater organism also are addressed in this paper.