Microplastic accumulation and impacts on eelgrass (Zostera marina L.) ecosystems throughout coastal Massachusetts, USA

Microplastics have been discovered ubiquitously in marine environments. While their accumulation is noted in seagrass meadows, much work is required to understand microplastic accumulation patterns and mechanisms in this ecosystem, as well as microplastic impacts on seagrass plants and their associated epiphytic and sediment communities. We pursue this effort by quantifying microplastic densities in seagrass blades, sediments, and nearby water columns across nine sites in coastal Massachusetts and exploring their relationships to morphological and anthropogenic variables. Further, we synthesize the potential impacts microplastics have on relevant seagrass plant, epiphyte, and sediment processes and functions. Microplastics were found ubiquitously at all sites regardless of proximity to anthropogenic interference, with plant epibiont density influencing their accumulation on seagrass blades, and bulk density influencing accumulation within sediments. Literature review revealed that microplastics may harm seagrass ecosystems via physical obstruction of epiphytic and plant surfaces, nutrient cycle and sediment characteristic alteration, and sediment organism ingestion, with all impacts exacerbated by seagrasses high trapping efficiency. As microplastics become a permanent and increasing member of seagrass ecosystems it will be pertinent to direct future research towards continuing to explore their impacts and patterns behind their accumulation.