The role of bio-geomorphic feedbacks in shaping microplastic burial in blue carbon habitats

Coastal sediments are considered as hotspots of microplastics (MPs), with substantial MPs stocks found in blue carbon habitats such as mangroves and tidal marshes, where wave-damping vegetation reduces sediment erosion and en-hances accretion. Here, we examined the effects of such bio-geomorphic feedbacks in shaping MPs burial, through a year-round field study in a mangrove habitat along the coast of South China. The results revealed that MPs abundance decreased significantly with the increase of cumulative sediment erosion as the strength of bio-geomorphic feedbacks declined. More shapes and colors of MPs were found at locations with weaker waves and less sediment erosion, where the average particle size was also higher. Our findings highlight the importance of bio-geomorphic feedbacks in affect-ing both the abundance and characteristics of the buried MPs. Such knowledge extends our understanding of MPs transport and burial from the perspective of bio-geomorphology, which is essential to assess and predict MPs accumu-lation patterns as well as its impacts on ecosystem functioning of the blue carbon habitats.

Automated summary

This year-round field study in a mangrove habitat along the coast of South China reveals the significant effects of bio-geomorphic feedbacks on the burial of microplastics. As the strength of these feedbacks declines, the abundance of microplastics decreases, and locations with weaker waves and less sediment erosion have more diverse shapes and colors of microplastics with larger average particle size. These findings highlight the importance of bio-geomorphic feedbacks in shaping the abundance and characteristics of buried microplastics.