Microplastic distribution in urban vs pristine mangroves: Using marine sponges as bioindicators of environmental pollution

Sessile benthic organisms are considered good bioindicators for monitoring environmental quality of coastal ecosystems. However, these environments are impacted by new pollutants such as microplastics (MPs), where there is limited information about organisms that can be used as reliable bioindicators of these emerging contaminants. We evaluated MP concentrations in three compartments: surface sediment, water and in three marine sponge species (Haliclona implexiformis, Halichondria melanadocia and Amorphinopsis atlantica), to determine whether these organisms accumulate MPs and reflect their possible sources. Results showed MPs in all three compartments. Average concentrations ranged from 1861 to 3456 items kg of dry weight in marine sponges, 130 to 287 items L in water and 6 to 11 items kg in sediment. The maximum MP concentration was in the sponge A. atlantica, which registered 5000 items kg of dry weight, in water was 670 items L and in sediment was 28 items kg, these values were found in the disturbed study area. The three sponge species exhibited MP bioaccumulation and showed significant differences between disturbed and pristine sites (F = 11.2, p < 0.05), suggesting their use as bioindicators of MP.