Benthic macrofauna as a model for assessing the effects of coastal urbanization on sandy beaches: a study case in Baixada Santista, SP
Sandy beach ecosystems are subject to various anthropogenic pressures stemming from urbanization, which can disturb fauna and alter community structures. The impact of this phenomenon varies along the coast in terms of temporal and spatial scales. Some urbanization-related pressures, such as trampling and artificial lighting, are common on urbanized beaches but lack comprehensive information due to their disparate effects. In this context, we conducted an assessment of the benthic macrofauna community structure along an urbanization gradient in Baixada Santista, Brazil. We examined the effects of different trampling intensities and frequencies on macrofauna and investigated the impact of artificial lighting and trampling on the macrofauna community. Our results indicate that less urbanized beaches have higher species richness and abundance compared to highly urbanized ones, and the composition of the fauna varies between these categories. Furthermore, while trampling frequency reduces species abundance and richness, intensity has the opposite effect on richness. The interaction between these factors negatively affects crustaceans but benefits polychaetes with increased trampling frequency. Artificial lighting also affected the macrofauna, with varying responses. One beach exhibited increased abundance in illuminated areas, while another showed reduced species richness, with the presence of Scolelepis sp. being a key factor. Overall, environmental disturbances negatively impacted species diversity, highlighting the importance of effective conservation and management while considering factors such as beach length. These findings underscore the need to protect and preserve sandy beach ecosystems in the face of urbanization threats, as well as the necessity of public policies and environmental education programs for this purpose.