The Ecotoxicological Effects of Microplastics on Primary Producers in the Marine Environment

Abstract

Plastic debris is an emerging environmental threat all over the world. But its effect and distribution in the marine ecosystem is barely known. Microplastics abundance in the marine vegetated area is about 2 to 3 times higher than the bare site in the ocean. Although seagrass meadows trap huge amount of microplastics over the ocean floor, a considerable amount of microplastics are also sink incorporating with the marine aggregates from the epipelagic zone of the ocean. Scavenging of microplastics by diatom aggregation decreases the sinking rate of them rather than cryptophyte. As we know, marine snow is the leading carbon source for zoobenthos, but the ubiquitous presence of microplastics damages cell of different microalgae which may alter the food webs of marine ecosystems. Additionally, microplastics releases immense amount of dissolved organic carbons (DOC) in the surrounding seawater that stimulates the growth of heterotrophic microorganisms as well as their functional activity. Plastic debris result in outbreaks of disease in the marine environment and coral reefs are highly affected by it. When coral reef comes in contact with microplastics, the disease infestation rate of the reef increases massively. Three major disease viz., skeletal eroding band, white syndrome and black band of coral reef causes approximately 46% of reef mortality due to microplastics consumption. Due to complex structure and size, the corals accumulates huge amount of microplastics that increases growth of pathogens by hampering the coral immune system. Existing scientific evidence presents that exposure of microplastics in aquatic environments triggers a wide variety of toxic insult from feeding disruption to reproductive performance, disturbances in energy metabolism throughout the ocean. The present review focused on the ecotoxicological effect of microplastics on primary producers of ocean, its uptake, accumulation, and excretion, and its probable toxicity with risk assessment approaches.