Benthic communities play a vital role in ecosystem functioning, closely linked to sediment characteristics and potentially affected by microplastic (MPs) contamination. This study presents the first characterization of macrofaunal and meiofaunal distribution patterns on three Vietnamese sandy beaches with differing morphodynamics and management regimes, in order to examine the influence of environmental gradients and local MP pollution. Environmental variables (Chlorophyll a, total organic matter, grain size) and MPs (concentration, polymer types) were measured across high-, mid-, and low-tide zones. Benthic assemblages differed markedly between dissipative and reflective beaches. On the dissipative Bai Sau beach, a clear spatial zonation pattern was evident for both faunal groups, with the mid- and low-tide zones hosting the highest diversity and abundance. Reflective beaches exhibited less distinct zonation. Distribution patterns varied between macrofauna and meiofauna, underscoring the importance of including multiple faunal groups in ecological assessments. Microplastic polymer types (PP, PET, and PS) were associated with community composition differences for both benthos groups in addition to food availability and grain size. Our findings underscore the need for continued investigation into the effects of MPs on benthic fauna and the underlying mechanisms, particularly ecophysiological implications for organism fitness. Moreover, spatio-temporal variations in feeding plasticity and ingestion-egestion dynamics in relation to local pollution dynamics, as well as species’ roles in bioaccumulation in the food web need to better understand, before their potential of beach invertebrates as bioindicators of MP pollution can be considered. In addition, the protection of beach ecosystems calls for targeted management measures that mitigate pollution sources across coastal, riverine, and marine systems in concert with the natural processes governing MP deposition in sediments. |
