In Puerto Narino, Colombia, researchers waist-deep in the Amazon River carefully trap river dolphins with mesh nets.
They tighten the nets gradually as silver fish leap to escape the splashy enclosure.
The team hauls each dolphin into a boat, where it thrashes before researchers carry it to the riverbank.
On the sandy bank, scientists place the dolphins on mats and limit handling to 15 minutes.
Careful Handling Protects Dolphins
Marine biologist Fernando Trujillo shields each dolphin’s eyes with a cloth and speaks in gentle tones to calm them.
He says, “Taking a dolphin out of the water is a kind of abduction,” while resting a hand lightly on it.
Team members count breaths, wet the skin with sponges, and perform multiple health tests on each dolphin.
The Omacha Foundation, led by Trujillo, coordinates these evaluations with veterinarians, fishermen, and local assistants after months of planning.
Dolphins Reveal Mercury Pollution in the Amazon
Trujillo collects blood and tissue samples to measure mercury levels, using dolphins as indicators of river health.
Illegal gold mining and deforestation wash mercury into waterways, contaminating fish and dolphins.
Miners use mercury to separate gold, then release toxic sludge into the river, worsening pollution as gold prices rise.
Mercury damages the brain, kidneys, lungs, and immune system, causing memory loss, muscle weakness, and mood changes.
Pregnant women and children face the highest risk, with prenatal exposure affecting development and cognitive function.
Trujillo reports dolphins in the Amazon carry 20–30 times the safe mercury limit, with some reaching 42 milligrams per kilogram.
High mercury levels threaten dolphins with neurological and organ damage similar to humans.
