Temporal and spatial variation of benthic macroinvertebrates on the shoreline of Guarujá, São Paulo, Brazil, under the influence of urban surface runoff

Abstract

In recent decades, the management of urban surface runoff in coastal regions has become a global priority. However, in Brazil, whose coastline is 8,500 km, these actions are still scarce. This study aimed to characterise, for the first time, the structure of the benthic assemblages near urban drainage channels, whose waters flow permanently to four beaches of Guarujá, São Paulo, Brazil. Collection of sediments took place between October 2017 and August 2018. Macroinvertebrate fauna were identified in a certified laboratory using international standard methodologies. The data showed that although the species richness was in general low, a great abundance and density of taxa tolerant to organic pollution was observed (e.g. Oligochaeta, Gastropoda and, mainly Insecta: Ceratopogonidae, Chironomidae, Chironomus and Culicidae) during the period of greatest tourist influx (rainy season/summer). Furthermore, the results of water quality indexes (in all channels) suggested heavily polluted environments: (i) Shannon-Wiener: H’ < 1; (ii) Biological Monitoring Working Party: BMWP’ < 12 and (iii) Average Score per Taxon: ASPT < 2. Therefore, it is urgent to adopt management measures to improve the environmental water quality and to prevent human health risks associated with tourism activities taking place in the recreational coastal waters of Guarujá municipality.