Global change drivers including eutrophication, hydrological disturbance, climate change, chemical pollution, overexploitation, invasive species, and land-use change are affecting the function and structure of freshwater ecosystems. South American freshwater ecosystems are especially threatened by the combination of rising human pressures on natural resources (i.e., water use, intensive agriculture, mining, deforestation, and afforestation) and the lack of adequate legislation and economic resources for environmental protection and restoration. We assess the state of freshwater ecosystems in Argentina, Brazil, Chile, Colombia, Ecuador, Uruguay, and Venezuela, focusing on broad categories of human-induced threats grouped into 5 categories: climate change, watershed stressors, hydrological alteration, channel modification, and biological stressors. For most countries, the most severe threats are related to land uses such as mining, agriculture, and urban expansion. Other threats relate to the abstraction or wasteful use of water and the intense regulation of flows, including the effects of large hydraulic infrastructure. There is also an increasing need to empower public organisations that focus on environmental protection, to update or develop an adequate regulatory and legal framework, to provide adequate funding for the implementation of environmental legislation, and not least to implement ecological rehabilitation. Implementation of these steps would reduce the threats to South American aquatic ecosystems and allow progress toward the sustainable development of this region in future decades.

Extracting microplastics from sediment is critical in assessing pollution in freshwater environments. However, this process can be particularly challenging for clayey sediments with a significant organic matter content. This study proposes a simplified method for extracting microplastics from organic-rich clayey sediments and a complete protocol for sediment processing. To evaluate the extraction method, calcined clayey sediment was artificially enriched with varying organic content (20, 40, and 60%). Known quantities of plastic particles with distinct characteristics and compositions (PET, HDPE, PP, PE, and PS) were introduced into these artificial organic sediments, mixed with a saline solution, centrifuged, and then assessed the recovery rate. The recovery rate exceeded 83% for the five selected plastic types. Additionally, the method minimized particle loss by reducing the number of transfers between containers, a common issue in other microplastic extraction protocols. Based on the efficiency of the extraction method, we proposed and applied a protocol for environmental samples. The protocol comprises five key steps: (1) drying sediment samples, (2) density separation, (3) filtering, (4) digestion of organic matter, and (5) visual analysis. This protocol extracted a wide variety of microplastics with diverse shapes, colors, sizes, and polymeric compositions. These results demonstrate that the proposed protocol is both straightforward and effective in extracting plastic particles commonly found in clayey sediments of freshwater systems. Moreover, the protocol employs inexpensive, readily available, and environmentally friendly reagents, making it a more sustainable alternative to other methodologies for extracting microplastics from environmental matrices.