Amazonian Fish Threatened by Climate Change and Pollution
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Loading... - Rosy Klein
- 18 Oct 2024
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In a "room of the future" at the National Institute of Amazonian Research (INPA) in Brazil, scientists are simulating the extreme conditions predicted by the Intergovernmental Panel on Climate Change (IPCC). Here, researchers explore how rising temperatures, increased CO2 levels, and pesticide contamination will affect Amazonian fish—with alarming results.
The experimental setting mimics a temperature increase of 5°C (9°F) above the average in Manaus, the capital of Amazonas, with CO2 levels reaching 708 ppm, far beyond today’s atmospheric level of 420 ppm. The study, led by biologist Samara Souza, focuses on Tambaqui (Colossoma macropomum), a vital Amazonian freshwater fish, exposing it to these climatic extremes along with a mix of pesticides commonly found in the region’s rivers and lakes.
Climate Change and Pollution
Adalberto Val, coordinator of INPA’s Adapta program, emphasizes the need to look beyond rising temperatures:
"We must evaluate how increased temperature and CO2 concentrations interact with other environmental stressors like pesticides, creating dangerous synergies."
In her study, Souza subjected 36 juvenile tambaquis to two scenarios—one with current climate conditions and another under extreme climate projections—for 96 hours. In both cases, the fish were exposed to common regional agrochemicals, including Chlorpyrifos (insecticide), Malathion (insecticide), Atrazine (herbicide), Carbendazim (fungicide).
While these pesticide concentrations are typically non-lethal, their combined effects were harmful. The tambaquis exhibited liver damage, nervous system dysfunction, and partial paralysis. However, the damage worsened significantly under the extreme climate scenario, highlighting the interaction between pollutants and environmental stressors.
Metabolism Under Stress
The study found that higher temperatures and elevated CO2 levels impair the fish’s ability to metabolize and expel harmful compounds. The stress of increased metabolism required to adapt to warmer conditions left the tambaquis more vulnerable to pesticide toxicity.
For example, organophosphate insecticides like chlorpyrifos inhibit acetylcholinesterase (AChE), an enzyme essential for transmitting nerve impulses. The fish also struggled with depleted antioxidant defenses in the gills, making it harder for them to cope with the combined stress of heat and toxins.
"The fish exposed to high temperatures and elevated CO2 levels became more susceptible to agrotoxins because their metabolisms couldn’t handle the additional burden," Souza explained. "This resulted in more severe damage than in today’s climate conditions."
The combination of extreme climate conditions and pesticide exposure caused irreversible liver damage and DNA damage in blood cells, indicating a grim future for Amazonian fish populations.
“The results showed that a future of climate change combined with pesticides will have devastating effects on Amazonian fish, potentially leading to biodiversity loss,” Souza warned.
