Effects of microplastics pollution on the abundance and composition of interstitial meiofauna/Efectos de la contaminacion por microplasticos en la abundancia y composicion de la meiofauna intersticial

Introduction: Pollution by microplastics is a global problem in marine environments, which impacts microorganisms and ecosystems at several spatial levels. Sandy beaches are depositional environments where microplastics tend to accumulate in large quantities. The co-occurrence of interstitial meiofauna and microplastics in sand grains raises the question on whether the accumulation of microplastics in the sediments affects the abundance and composition of the meiofaunal communities. Objective: To test the hypothesis that microplastics affect the meiofauna of urban sandy beaches. Methods: We studied the three main urban sandy beaches of Santa Marta, Colombia: El Rodadero, Santa Marta Bay, and Taganga. All are similar in morphology and external pressures, and differ from other beaches in the region. In April 2019 we collected 81 sand samples, equally distributed in the intertidal zone (upper, mid, and lower intertidal levels). We applied generalized linear models to abundance, and multivariate permutational tests to community composition. Results: We identified 17 taxonomic groups of meiofauna, and microplastic particles (mainly 45-500 micron fibres) evenly distributed across beaches and intertidal levels. There was more meiofauna at the mid intertidal level, and in fine and medium grain sediment. At the lower intertidal level, sites with more microplastics had less meiofauna. Abundance of microplastics explained 39% of the variation in meiofaunal community composition at lower intertidal levels. Conclusions: The accumulation of microplastics might have a negative impact on these meiofaunal interstitial communities. This is not surprising: if microplastics occupy the same physical space as these animals, they might presumably modify the structure of sediments and the composition of interstitial water. Key words: benthos; coastal zone; meiofauna abundance; microplastic abundance; pollution effect; sandy beaches. Introduccion: La contaminacion por microplasticos es un problema global en los ecosistemas marinos, con impacto sobre microorganismos y ecosistemas en varios niveles espaciales. Las playas arenosas son ambientes de deposicion donde se tiende a acumular gran cantidad de microplasticos. La co-ocurrencia de meiofauna intersticial y microplasticos en granos de arena plantea la pregunta de que si la acumulacion de microplasticos en sedimentos afecta la abundancia y composicion de comunidades de meiofauna. Objetivo: Probar la hipotesis de que microplasticos