Sediment quality assessment as potential tool for the management of tropical estuarine protected areas in SW Atlantic, Brazil

Abstract

Marine Protected Areas (MPAs) represent a tool for conservation that is intended to protect marine and estuarine habitats, biodiversity, and ecological processes. Many MPAs, some of which include estuarine zones, are affected by contamination sources; the discharge of chemicals into aquatic systems results in sediment contamination, risks to benthic systems, and consequent negative effects on ecological function. This study evaluated sediment quality in estuaries located within the Mosaic of Marine Protected Areas of São Paulo State, Brazil (MMPASP) in austral winter and summer: the Verde River (RV), the Una do Prelado River (BU), the Guaraú River (GU), the Preto River (RP), and the Itanhaém River (ITA). Data on sediment chemistry (major and trace metals, as well as hydrocarbons) and whole-sediment toxicity in copepods and amphipods were associated with ecological indices of macrobenthic infaunal organisms in a weight-of-evidence approach meant to estimate the effects at the community level. Results revealed low-to-moderate levels of contamination, with higher concentrations detected at sites influenced by domestic effluent discharges (RP, ITA). Site-specific chemical contamination guidelines were in accordance with biological responses than threshold levels from international benchmarks, indicating a failure of these international criteria to predict effects. Sediments were toxic, and benthic descriptors corroborated these findings. The results reflected a pattern of environmental quality that ranged from relatively good conditions (RV, BU, GU) to poor environmental quality (RP, ITA). We concluded that benthic environments in the estuaries of the Central Shore Marine Protected Area (APAMLC) exhibit a good ecological status in general, but some sites are directly impacted by human activities and exhibit contamination levels associated with biological effects, thereby showing that some portions of these MPAs may be damaged by contamination. Environmental assessments based on the sediment quality triad (SQT) method provide suitable and reliable information on pollution within MPAs and can assist in establishing additional policies to control pollution sources and achieve conservation goals.