Endangered pink river dolphins face a rising mercury threat in the Amazon

PUERTO NARINO, Colombia (AP) — A flash of pink breaks the muddy surface of the Amazon River as scientists and veterinarians, waist-deep in the warm current, patiently work a mesh net around a pod of river dolphins. They draw it tighter with each pass, and a spray of silver fish glistens under the harsh sun as they leap to escape the net.

When the team hauls a dolphin into a boat, it thrashes as water streams from its pink-speckled sides and the crew quickly ferries it to the sandy riverbank where adrenaline-charged researchers lift it onto a mat. They have 15 minutes — the limit for how long a dolphin can safely be out of the water — to complete their work.

Fernando Trujillo, a marine biologist leading the effort, kneels beside the animal’s head, shielding its eye with a small cloth so it can’t see what’s happening. He rests his hand gently on the animal and speaks in low tones.

“They’ve never felt the palm of a hand. We try to calm them,” said Trujillo, sporting a pink dolphin bandana. “Taking a dolphin out of the water, it’s a kind of abduction.”

One person counts the dolphin's breaths. Another wets its skin with a sponge while the others conduct multiple medical tests that will help show how much mercury is coursing through the Amazon’s most graceful predators.

Trujillo directs the Omacha Foundation, a conservation group focused on aquatic wildlife and river ecosystems, and leads health evaluations of river dolphins. It's a painstaking operation involving experienced fishermen, veterinarians and locals that takes months of planning and happens a couple of times a year.

“We take blood and tissue samples to assess mercury,¨ Trujillo told The Associated Press from the Colombian riverside town of Puerto Narino. “Basically, we’re using dolphins as sentinels for the river’s health.”

Mercury contamination comes mainly from illegal gold mining — a growing industry across the Amazon Basin — and forest clearing that washes mercury that naturally occurs in soil into waterways.

The miners use mercury to separate gold from sediment, then dump the sludge back into rivers, where it enters fish eaten by people and dolphins. Rising global gold prices have fueled a mining boom, and mercury pollution in remote waterways has increased.

Mercury can damage the brain, kidneys, lungs and immune system and cause mood swings, memory loss and muscle weakness in people, according to the World Health Organization and the U.S. Environmental Protection Agency. Pregnant women and young children are most at risk, with prenatal exposure linked to developmental delays and reduced cognitive function.

“The maximum any living being should have is 1 milligram per kilogram,” Trujillo said. “Here, we’re seeing 20 to 30 times that amount.”

In previous years, his team found 16 to 18 milligrams per kilogram of mercury in dolphins, which can suffer the same neurological damage, organ damage and other problems as humans. In Colombia’s Orinoco River, levels in some dolphins have reached as high as 42, levels scientists say are among the most extreme ever recorded in the species.

Trujillo said it's difficult to prove the toxin is directly killing dolphins. Further studies are underway, he added, noting that “any mammal with a huge amount of mercury will die.”

When Trujillo and his team tested their own blood three years ago, his results showed more than 36 times the safe limit — 36.4 milligrams per kilogram — a level he attributes to decades working in mercury-affected areas and a diet heavy in fish. With medical assistance, his levels have dropped to about 7 milligrams.

“Mercury is an invisible enemy until it builds up to a sufficient amount, then it starts to affect the central nervous system,” Trujillo told AP after his team managed to capture and test four pink dolphins. “We’re already seeing evidence of it in Indigenous communities.”

A series of scientific studies and reports — including work by the International Pollutants Elimination Network and academic researchers — have found high mercury exposure among Indigenous peoples across the Amazon, including in Brazil, Peru, Colombia, Suriname and Bolivia. Hair samples showed averages well above WHO's safe threshold of 1 part per million, with one Colombian community registering more than 22 milligrams per kilogram.

Dolphin populations in this part of the Amazon have plunged, with Trujillo’s monitoring showing a 52% decline in pink dolphins and a 34% drop in gray river dolphins, a different species, in recent decades. The International Union for Conservation of Nature listed the pink dolphin as endangered in 2018. Trujillo said exact numbers for the Amazon are unknown, but his organization estimates 30,000 to 45,000 across the basin.

Pink river dolphins also face threats from overfishing, accidental entanglement in nets, boat traffic, habitat loss and prolonged drought.

Colombia says it's tackling illegal mining and mercury pollution. It banned mercury use in mining in 2018, ratified the Minamata Convention aimed at reducing mercury in the environment and submitted an action plan in 2024. Authorities cite joint operations with Brazil and recent enforcement sweeps, but watchdogs say efforts remain uneven and illegal mining persists across much of the country.

Other Amazon nations say they’re stepping up. Brazil has launched raids and moved to restrict satellite internet used by illegal gold-mining camps that use mercury, aiming to disrupt logistics and supply lines. Peru recently seized a record 4 tons of smuggled mercury. Ecuador, Suriname and Guyana have filed action plans to cut mercury use in small-scale gold mining.

The dolphin testing operation relies on José “Mariano” Rangel, a charismatic former fisherman from Venezuela. He leads the charge when it’s time to haul the animals — which can weigh as much as 160 kilograms (about 353 pounds) — into the small boats. It's a moment that can end with a stinging blow to the jaw as the dolphins thrash to break free.

“The most difficult part of the captures is enclosing the dolphins,” Rangel said.

A portable ultrasound machine scans lungs, heart and other vital organs for disease. The team checks for respiratory problems, internal injuries and signs of reproduction, photograph the animals' skin and scars, swab blowholes and genital openings for bacterial cultures, and collect tissue for mercury testing. Microchips are implanted so researchers can identify each animal and avoid duplicating tests.

Omacha has recorded antimicrobial resistance — bacteria that can’t be killed by common medicines — and respiratory problems. They have also identified possible emerging diseases, such as papilloma virus, that could pose risks to both dolphins and humans.

After a long morning hauling and testing dolphins, the scientists return to a laboratory in Puerto Narino that's covered with posters of dolphins and manatees and the bones and skulls of dolphins and other animals. They test some samples, prepare others to send to larger facilities and end their day repairing nets and refilling kits to do it all again at dawn.

For Trujillo, each capture, scan and blood test is part of a larger fight.

“We are one step away from being critically endangered and then extinct,” Trujillo said.

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Scientists and veterinarians free a pink river dolphin after a health check in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

Scientists and veterinarians weigh a pink river dolphin after a health check in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

Scientists examine blood samples that were drawn from pink river dolphins in the Amazon River to determine mercury levels in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

A veterinarian draws a blood sample in a pink river dolphin in the Amazon River during health checks in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

Veterinarian Maria Jimena Valderrama implants a microchip into a pink river dolphin after a health check in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

Scientists and veterinarians examine a pink river dolphin in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

Scientists and veterinarians examine a pink river dolphin in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

Scientists and veterinarians capture a pink river dolphin in the Amazon River for health checks in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

Scientists and veterinarians capture a pink river dolphin in the Amazon River for health checks in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

Scientists and veterinarians capture a pink river dolphin in the Amazon River to perform health checks in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

Fishers help scientists and veterinarians to capture pink river dolphins in the Amazon River for health checks in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

Scientists and veterinarians examine a pink river dolphin in Puerto Narino, Colombia, Sunday, Sept. 7, 2025. (AP Photo/Fernando Vergara)

After a frenetic few months of congressional redistricting efforts, President Donald Trump’s plan to reshape voting districts for partisan advantage ahead of this year’s midterm elections stands at an important juncture.

Will Republican- and Democratic-led states ramp up their remapping of U.S. House districts as new legislative sessions get underway? Or will the mid-decade redistricting frenzy fade away following Indiana’s resounding rejection of Trump’s pressure-packaged campaign?

“We’re at a crossroads to see if the mid-decade redistricting movement gains more speed or was simply an attempt by Donald Trump to impact elections that in many states fizzled,” said Jeffrey Wice, director of the Elections, Census and Redistricting Institute at New York Law School.

Virginia and Florida are two key states to watch. Democrats who lead Virginia and Republicans who lead Florida could try to swing multiple seats in their party’s favor by an aggressive redistricting. Virginia’s legislative session begins Wednesday. Florida Gov. Ron DeSantis plans to call a special session in April on congressional redistricting.

What happens next in Democratic-led Illinois and Maryland and in Kansas' Republican-led Legislature also could affect the GOP’s ability to maintain a narrow House majority in the face of political headwinds that typically favor the party out of power in midterm elections. Key lawmakers in all three of those states remain opposed to redistricting.

Trump kick-started an unusual redistricting plan in July by calling on Texas Republicans to redraw their congressional map to create more favorable districts for the party — even though there was no new census data to base it upon. That triggered a mid-decade redistricting battle the likes of which has not been common since the late 1800s.

Texas, Missouri and North Carolina all approved new Republican-friendly House districts. Ohio, which had to redistrict because of its state constitution, used the opportunity to enact a more favorable House map for Republicans.

But Ohio’s action on Oct. 31 marked a turning point. That same day, Virginia’s Democratic-led legislature took a first step toward redistricting. Then in November, California voters approved new House districts helping Democrats, Kansas Republicans dropped plans for a special session on redistricting, and a Utah judge adopted a new House map that benefits Democrats.

Trump suffered a stunning setback Dec. 11, when Indiana’s Republican-led Senate defeated a redistricting plan that could have helped the GOP win all nine of the state’s U.S. House seats, up from their current seven.

The net result from the 2025 jockeying could be three additional seats for Republicans. But even that is in question, because legal challenges remain in some states, and there is no guarantee that parties will win the districts they redrew.

When the Virginia General Assembly begins its annual session, the agenda will include a proposed constitutional amendment allowing mid-decade redistricting in response to other states.

The amendment, which received first-round approval in the fall, would also need to pass a statewide vote before the new districts could be implemented. Quick action would be necessary to get all that accomplished in time for candidates to run in redrawn districts later this year.

Democrats, who currently hold six of the state’s 11 U.S. House seats, have not unveiled what those new districts would look like. But some have talked of trying to gain as many as four additional seats.

Virginia Gov.-elect Abigail Spanberger has embraced the redistricting effort but has not committed to a particular plan.

“I will look at any map that is kind of reasonable and keeping communities compact and together,” Spanberger, a Democrat, told The Associated Press. “But ultimately, it’s up to the people of Virginia to choose whether or not to move forward with the referendum.”

Republicans currently hold 20 of Florida’s 28 U.S. House seats. That advantage could grow if districts are reshaped during a special session.

Although Florida’s regular legislative session starts Tuesday, DeSantis said he is waiting until April to call a special redistricting session to allow time for a possible U.S. Supreme Court ruling on a key provision of the federal Voting Rights Act. If the court rules in a Louisiana case that race cannot be the predominant factor in creating voting districts, it could open the way for several Republican-led states to redraw districts represented by Black or Hispanic lawmakers who are Democrats.

DeSantis said the high court's ruling could affect “at least one or two” Florida districts.

But any redistricting that aids Republicans could face a court challenge. A voter-approved Florida constitutional provision prohibits drawing district boundaries to favor or disfavor a political party or incumbent.

Some Democrats seeking to counter Trump have urged lawmakers in Illinois and Maryland to redraw their already heavily Democratic districts to try to gain one additional seat in each state. But the plans appear to lack traction as legislative sessions begin this week in both states.

Illinois House Speaker Pro Tem Kam Buckner said “there is no active push” for congressional redistricting.

“There is no appetite to reopen something that will consume enormous time, energy and, frankly, political capital without a compelling justification,” Buckner, a Democrat, told the AP.

Democratic Maryland Gov. Wes Moore has created a special commission to recommend a new congressional map. But Democratic Senate President Bill Ferguson remains opposed and insists that a majority of residents also do not want new districts.

In Kansas, some Republicans want to redraw U.S. House districts to try to gain an additional seat. But House Republicans have failed to gain the two-thirds support needed to override a likely veto by Democratic Gov. Laura Kelly.

House Speaker Dan Hawkins told reporters that he has no plans to hold a vote on congressional redistricting during the annual legislative session that starts Monday.

“I do not have the votes,” Hawkins said.

Associated Press reporters Olivia Diaz, John Hanna, Mike Schneider and Brian Witte contributed to this story.

President Donald Trump points to the crowd as he walks off stage after speaking to House Republican lawmakers during their annual policy retreat, Tuesday, Jan. 6, 2026, in Washington. (AP Photo/Evan Vucci)

FILE - Opponents of Missouri's Republican-backed congressional redistricting plan display a banner in protest at the State Capitol in Jefferson City, Missouri, Sept. 10, 2025. (AP Photo/David A. Lieb, File)

FILE - ndiana Lt. Gov. Micah Beckwith announces the results of a vote to redistrict the state's congressional map, Dec. 11, 2025, at the Statehouse in Indianapolis. (AP Photo/Michael Conroy, File)

FILE - This photo taken from video shows organizers rallying outside of the Ohio Statehouse to protest gerrymandering and advocate for lawmakers to draw fair maps in Columbus, Ohio, Sept. 17, 2025. (AP Photo/Patrick Aftoora-Orsagos, File)