The Amazon is the largest drainage basin in the world and contains about 40% of the world’s remaining tropical rainforest, hosting an enormous diversity of terrestrial and aquatic species. Recently, degradation of the amazon forest due to (intentional) fires, agriculture expansion and logging has received international attention. However, much less efforts have been dedicated to describe the presence and spread of contaminants related to agricultural intensification, demographic increase or industrialization in the Amazon basin. This is particularly important since almost all waters leaving agricultural fields and wastewaters generated by urban areas are dumped untreated into the Amazon River.
Awareness about the impact of synthetic chemicals used by modern societies into the environment was initiated back in the 1960s, notably through the publication of the book ´Silent Spring´ by Rachel Carson. This book inspired the environmental movement, which has contributed to the regulation of chemical substances regarding their potential impacts for ecosystem’s and human health. Thanks to this whole movement, today we have advanced monitoring programs and regulatory frameworks to control the chemical status of rivers in many developed nations. However, the presence of contaminants and their potential impacts on many tropical rivers, including the Amazon, have not been evaluated so far. The project SILENT AMAZON, inspired on the environmental movement initiated by Carson, attempts to create the first complete dataset on the chemical status of the Amazon River, which hopefully supports the development of further legislation and management actions to control chemical emissions and protect biodiversity in the region. The SILENT AMAZON project is supported by the National Geographic Society and the IMDEA Water Institute, and will initially run from August 2019 to January 2021.
Objectives and methods
The overarching goal of the SILENT AMAZON project will be to assess how and to what extent current demographic pressure and industrial activities are impacting the Amazonian biodiversity at local and regional scale. This will be achieved by performing the largest chemical monitoring campaign, navigating more than 1,500 km, from the archipelago of Anavilhanas to the Atlantic coast (Brazil), and focusing on the emission of chemicals from the main urban areas (Manaus, Santarém, Belém) . Water, plant and fish samples will be collected for the analysis of a wide range of contaminants, including: pharmaceuticals and life-style compounds, fragrances, persistent organic pollutants, plastics and microplastics, metals and other industrial compounds (PFAS). A full dataset of chemical exposure concentrations in different areas subject to different levels of anthropogenic impact will be created and used to calculate risks for aquatic biodiversity.
Based on the different contaminant groups we will create interactive maps, so that we can easily observe the relationship between urbanization, deforestation, agriculture and industrial hot-spots with the presence of contaminants in the river. Maps of water exposure concentrations will be compared with those obtained with measured concentrations in biota, so that we will assess whether they have a good match in terms of chemical occurrence and concentration, and whether the observed concentrations in biota are mainly related to water exposure or to other factors (e.g. trophic chain transfer, biological migrations). Finally, the dataset on measured chemical concentrations will be used to perform a risk assessment for different taxonomic groups inhabiting Amazonian waters, and to define particular contaminants and mixtures that are impacting biodiversity and that therefore require urgent attention and management.