Capybaras in Entre Ríos Province dyed Hulk green by algae

First a river ran blood red. Now Argentina's beloved giant rodent, the capybara, has been coated in Hulk-green slime as pollution turns the country's waterways traffic light colours.

The capybara, also known as a carpincho or chiguire, is the world's largest rodent, measuring up to 1.35 meters (four feet four inches) in length and weighing up to 80 kilogrammes (176 pounds).

An AFP photographer snapped several of the tufty creatures that had been stained pea green along the Uruguay River north of Buenos Aires on Thursday where a rotten smell hangs in the air and dead fish lay strewn on the banks.

Each year, bacteria cause a thick greenish layer to coat the shores around the Salto Grande hydroelectric dam, on Argentina's border with Uruguay. The phenomenon has increased in intensity in recent years.

These cyanobacteria "are photosynthetic organisms that perform an important function in the ecosystem," Diego Frau, a biologist at the National Institute of Limnology told AFP.

But in high concentrations they can be destructive and toxic, he said.

High temperatures and high levels of nutrients in the water, partly driven by livestock farming, causes the algae to spread.

Climate change is causing the green tide, which can last for several weeks, to become "increasingly recurrent," damaging ecosystems, he said.

In people, mild exposure to the bacteria can cause skin conditions or "flu-like symptoms" such as diarrhoea, vomiting and headaches, Martin Novoa, a biologist at the Faculty of Food Sciences at the National University of Entre Ríos, told AFP.

Prolonged exposure can lead to liver and nervous system complications, he added.