Microplastics in seagrass ecosystems: A review of fate and impacts

Abstract

Microplastics have been detected in seagrass ecosystems, raising concerns about their potential impacts on the ecological functions of seagrasses. Seagrass meadows are biodiversity hotspots as they provide habitats to diverse fish and invertebrates. They also play a crucial role in nutrient cycling, capturing carbon, and buffering coastal erosion. This review aims to present the fate of microplastics in seagrass ecosystems and their impacts on the ecosystems. A total of 66 scientific articles have been reviewed. The review highlights that seagrass meadows intercept microplastics, though the relevant results are currently inconclusive. Some microplastics attach to the epiphytes on seagrass blades or the seagrass blades while some accumulate in the seagrass sediment, causing enrichment of microplastics in seagrass meadows. Nonetheless, a few studies did not observe such intercepting effects. Microplastic enrichment, where observed, could be due to near-bed turbulent kinetic energy that entraps denser sinking microplastics. Microplastics can directly affect seagrasses by blocking light and nutrient transfer, affecting their shoot or leaf turnover, degenerating root and causing oxidative stress. However, a study on Zostera marina L. found that short-term exposure to microplastics did not significantly impact bicarbonate utilization and photosynthetic efficiency. Microplastic additives, particularly bisphenol A reduced chlorophyll and caused peroxide accumulation in Cymodocea nodosa. The presence of biodegradable plastics in the sediment might alter the distribution and interaction of seagrass species. Seagrasses could be affected indirectly through the potential impacts of microplastics on seagrass epiphytes but more studies are needed to confirm this. Desorption of pollutants sorbed on microplastics could negatively affect seagrass meadows. Further research could focus on the impacts of microplastic accumulation on the seagrass ecosystem and the processes therein, including nutrient cycling. Disintegration-oriented techniques and alternatives to conventional plastics are two strategies to mitigate microplastic prevalence in the environment.