A review of microplastic impacts on seagrasses, epiphytes, and associated sediment communities.

Microplastics have been discovered ubiquitously in marine environments. While their accumulation is noted in seagrass ecosystems, little attention has yet been given to microplastic impacts on seagrass plants and their associated epiphytic and sediment communities. We initiate this discussion by synthesizing the potential impacts microplastics have on relevant seagrass plant, epiphyte, and sediment processes and functions. We suggest that microplastics may harm epiphytes and seagrasses via impalement and light/gas blockage, and increase local concentrations of toxins, causing a disruption in metabolic processes. Further, microplastics may alter nutrient cycling by inhibiting dinitrogen fixation by diazotrophs, preventing microbial processes, and reducing root nutrient uptake. They may also harm seagrass sediment communities via sediment characteristic alteration and organism complications associated with ingestion. All impacts will be exacerbated by the high trapping efficiency of seagrasses. As microplastics become a permanent and increasing member of seagrass ecosystems it will be pertinent to direct future research towards understanding the extent microplastics impact seagrass ecosystems.