Pioneering research by ecophysiologist Adalberto Luis Val in Brazil's Amazon rainforest is revealing the impact of climate disruption through the study of the tambaqui fish. Val, a leading investigator at the National Institute for Amazonian Studies (INPA), has found that tropical fish are highly sensitive to fluctuations in heat, humidity, and water chemicals.
The tambaqui (Colossoma macropomum), a large freshwater fish, has an evolutionary adaptation that allows it to breathe oxygenated surface water using a protruding lower lip. This behaviour is observed when rising temperatures cause water-oxygen levels to drop and carbon dioxide to increase. Val's work indicates that monitoring the tambaqui could be a key method for assessing the Amazon forest's resilience.
Laboratory experiments conducted by Val and his team at INPA, simulating future climate impacts, showed that excessive warming depletes water-oxygen levels and harms the vascular systems, metabolism, and physiology of river fish. Beyond the lab, observations have linked prolonged dry seasons and record droughts in 2023 and 2024 to significant fish and river dolphin die-offs across the Amazon basin. Brazil's biodiversity authority, ICMBio, has added the tambaqui to its list of species at risk of extinction.
Val's research also highlights how human activities, such as forest clearing, burning, mining, and plantation agriculture, contribute to habitat disturbances. Chemical runoff from these activities pollutes waterways, contaminates fish, and can sicken humans. The combined effects of climate disruption and human impact threaten the 40 million people in the Amazon Basin, many of whom rely on freshwater fish for a significant portion of their diet.