More than 100 shallow lakes extending across roughly 1,000 kilometers of coastline in southern Brazil and Uruguay could become one of the world’s most valuable natural laboratories for studying how climate change and human activity transform freshwater ecosystems. An international research team has identified this vast, understudied network as a unique opportunity to track biodiversity loss, pollution, water-quality decline and the capacity of ecosystems to recover from environmental stress.
The findings, published in One Ecosystem, represent the first comprehensive assessment of what the researchers call the Southern American Coastal Shallow Subtropical Lakes. These lakes form one of the largest continuous coastal shallow-lake systems on Earth, stretching along the Atlantic coast of Rio Grande do Sul in Brazil and into Uruguay. Despite their size and ecological diversity, they have received considerably less scientific attention than many better-known lake systems in Europe and North America.
“Most of what we know about lakes comes from the Northern Hemisphere,” says lead author Mariana Kluge of the Swedish University of Agricultural Sciences. The southern coastal lakes offer a crucial opportunity to test whether established ecological theories apply under different climatic, geological and biological conditions. Their subtropical setting, shallow water columns and close connection to coastal environments create a combination of characteristics rarely represented in global freshwater research.
Unlike deep lakes, shallow lakes can shift rapidly between clear-water states dominated by aquatic plants and turbid states in which algae and suspended sediments reduce water transparency. This sensitivity makes them particularly useful for detecting environmental change. Nutrient enrichment from sewage, agricultural runoff and urban development can trigger eutrophication, a process in which excess nitrogen and phosphorus stimulate algal growth, deplete oxygen and disrupt aquatic food webs. In extreme cases, these changes can produce harmful algal blooms and conditions unsuitable for fish, wildlife or human recreation.
The lake network is already under pressure from expanding cities, agricultural pollution, wastewater discharges and emerging contaminants, including pharmaceuticals and microplastics. Increasingly intense rainfall and flooding can wash pollutants into the lakes while altering salinity, sediment transport and nutrient cycles. The region is also strongly influenced by the El Niño–Southern Oscillation, a climate phenomenon that periodically changes rainfall patterns, temperature and hydrological conditions across South America. These overlapping pressures make the lakes valuable indicators of how ecosystems respond when several disturbances occur at the same time.
The researchers describe the lakes as “sentinel ecosystems”: natural observatories that can reveal early signs of environmental deterioration before damage becomes irreversible. Their proposed monitoring system would combine microbial ecology, environmental DNA, water chemistry, remote sensing and long-term ecological surveys. Environmental DNA allows scientists to detect traces of genetic material released by organisms into the water, offering a rapid way to measure biodiversity and identify species that may be difficult to observe directly. Remote sensing, meanwhile, can track changes in water colour, vegetation, algal blooms and shoreline development across hundreds of kilometers.
Microorganisms may be among the most sensitive indicators in this system. Bacteria, archaea, microscopic algae and other microbes respond quickly to shifts in oxygen, nutrients, salinity, temperature and toxic compounds. By analysing changes in microbial communities, researchers may be able to identify pollution or ecosystem stress before larger organisms show visible effects. The same approach could eventually help detect contaminants associated with public-health risks, including antibiotic-resistant microorganisms and chemical compounds that persist in wastewater.
“Our vision is to establish an internationally coordinated monitoring network that not only benefits South America, but also improves our understanding of freshwater ecosystems worldwide,” says Haig, a professor at the Federal University of Rio Grande do Sul. The researchers argue that data collected from these lakes could be compared with observations from freshwater systems on other continents, helping scientists distinguish global environmental trends from responses that are specific to subtropical coastal ecosystems.
The study grew out of an international workshop hosted by the Pontifical Catholic University of Rio Grande do Sul and the Federal University of Rio Grande do Sul in Porto Alegre. Researchers from Brazil, Uruguay, Germany and Sweden identified four representative lake regions that capture major environmental differences across the system. These sites could form the foundation of coordinated long-term observation, allowing scientists to track ecological change across urban, agricultural, rural and relatively undisturbed landscapes.
As climate change intensifies and demand for freshwater resources increases, the Southern American coastal lakes may become an essential testing ground for conservation and environmental management. Protecting them would preserve biodiversity and regional water resources, but studying them could also produce monitoring tools applicable far beyond South America. By treating these shallow lakes as living sensors of planetary change, scientists hope to detect ecosystem disruption earlier, understand how resilience is gained or lost, and develop more effective strategies for safeguarding freshwater worldwide.
Subject of Research: Southern American coastal shallow subtropical lakes and their potential for monitoring climate change, pollution, biodiversity and human-driven ecosystem change
Article Title: Coastal subtropical Southern American shallow lakes as unique ecosystems for monitoring anthropogenic induced ecosystem changes
News Publication Date: 14-Jul-2026
Web References: https://doi.org/10.3897/oneeco.11.e186107
References: Kluge M, Shubeita A, Uchaikina A, Alonso C, Herrman B, Menegotto-Silva C, Lopes C, Pagani D, Marques D, Moreira-Silva E, Kristiansson E, Quintana I, Cavalcanti J, Fleck J, Ribeiro K, Varghaei L, Oliveira L, Rodrigues LR, Ramilo L, Crossetti L, Stockenreiter M, Cabezudo M, Lima M, Gonçalves NP, Mazzeo N, Schneider R, Utz LP, Bertilsson S, Wurzbacher C, They NH, Medina-Silva R (2026). “Coastal subtropical Southern American shallow lakes as unique ecosystems for monitoring anthropogenic induced ecosystem changes.” One Ecosystem 11: e186107.
Image Credits: CECLIMAR Collection (Acervo CECLIMAR)
Keywords: shallow lakes, freshwater ecosystems, climate change, biodiversity, eutrophication, environmental DNA, microbial ecology, pollution, microplastics, South America, ecosystem monitoring, El Niño–Southern Oscillation
