Chapter 16 - Impacts of mesoplastics and microplastics on marine biodiversity

Abstract

Microplastics (MPs) and mesoplastics pose significant threats to the marine environment, potentially affecting marine biodiversity through multiple routes. The contaminants in these debris’ derivatives interfere with the food web and circulate back to humans, inflicting health problems. With their unique circulation patterns in oceans, they form the most invasive human-made material in the ecosystem, distributed from surface water to deep water, from the high tidal to the abyssal zone. The sources of mesoplastics and MPs are plentiful in the Anthropocene, including in agriculture, textiles, construction, aquaculture and fisheries, and shipping and offshore industries. In addition, single-use plastics used in households as cutleries, plates, containers, and plastic bags, as well as microbeads in hygiene and personal care products, are essential sources of mesoplastics and MPs. While the ingestion of MPs and mesoplastics is expected in the feral environment, laboratory studies reiterate their frequent intake, especially in zooplankton, arthropods, mollusks, and worms. The synergistic impacts on the ecosystem exemplify phytoplankton interactions, with MPs affecting sedimentation rates. Plastic ingestion may vary among consumers; primary consumers such as bacterivorous, herbivorous, detritivorous, and deposit-feeding species specialize in foraging for particulate matter and have a greater chance of ingesting MP particles. Herbivores and secondary consumers directly consume MPs, while apex predators are prone to indirect ingestion via prey (food web). Food intake and entry of MPs into marine fauna depend on complex interactions between biotic (e.g., feeding type, physiological state, competition, food size, and availability) and abiotic (e.g., temperature) factors. Both MPs and mesoplastics are more prone to the adsorption of chemicals and toxic substances from the environment due to their higher surface areas. Due to their smaller size, microparticles can be easily ingested by microscopic zooplankton, enter the gills, and cause respiratory disorders in aquatic organisms. These plastic particles also cause much damage, as once organisms have ingested them, they become clogged in the digestive system, bruise the system as they move along, and create a feeling of satiety, resulting in the death of animals due to starvation. Several harmful pathogenic strains of microorganisms colonize MPs and pose a threat to many aquatic organisms. These MPs, along with the chemicals in them like PCBs, PAHs, heavy metals, and additives like phthalates, plasticizers, surfactants, and other endocrine disruptors, can penetrate the cells and interact with molecules at cellular and tissue levels and enter the circulatory system, altering endocrine disruption, gene expression, and liver toxicity. They also act as vectors that transfer contaminants to other organisms and cause detrimental effects like reduction in feeding capacity, behavioral changes, oxidative stress, and reduced growth and reproductive function. In addition, they lead to biomagnification as they move to higher trophic levels. Here lies the major problem, as these MPs and mesoplastic ingested by organisms reach humans via seafood like fish, clams, and oysters and cause harmful effects. Once they reach humans, they may penetrate cells and tissues and cause several problems. This chapter provides information about the marine biodiversity impacts of MPs and mesoplastics, modes of plastic particle ingestion, species and ecosystem-level impacts, and transfers of effects through the food chain.