Thousands of Dead Fish Mysteriously Floating in Rio's Olympic Bay

Thousands of dead fish are mysteriously floating in the polluted Rio bay, a smelly snag considering the famous city will be host to the 2016 Olympics, including sailing events that will take place in the bay.

Pollution would seem the likely cause - Guanabara Bay's sewage-infested waters have already been the subject of concern amongst future sailing competitors - but scientists say it still doesn't explain this phenomenon.

"Tests showed that this is not a matter of chemical or toxic water pollution," Rio do Janeiro State University oceanographer David Zee told the Agence France-Presse (AFP).

So then what is it? Scientists suggest either predatory fishing or high water temperatures, but they still aren't sure. Regardless, the International Olympic Committee (IOC) expects that Guanabara will be clean and fish free in time for the games, which are less than two years away.

Using a bulldozer, about 200 tons of dead sabalo fish - from the Clupeidae family of herrings and sardines - as well as four dead sea turtles have been recently removed from the bay. People of Paqueta Island were the first to smell the foul stench of these rotting carcasses back in October. And though scientists insist that chemical pollution is not to blame, residents are pointing the finger at the petrochemical activities of state giant Petrobras.

The most probable cause, according to Zee, is what's called "thermal pollution," characterized by a lack of oxygen.

"Sabalo are very sensitive to any lack of oxygen," he explained. "Warm water temperatures such as those recorded several days ago - ranging from 27 to 30 degrees Celsius (81 to 86 Fahrenheit) - in shallow water decrease the solubility of oxygen."

Paqueta is particularly vulnerable to high temperatures given that the bottom of the Rio bay has poor water circulation - a trend exacerbated by the low tide.

Rio de Janeiro earlier this year took steps to clean the already disgusting bay by installing barriers at the mouth of the river and "eco-boats" to scoop up waste, though a report by Bloomberg indicates that the bay still won't be clean for the 2016 Olympics. However, Rio de Janeiro Mayor Eduardo Paes notes that the sailing competition will be held in unpolluted waters, either outside the bay or at its entrance.

Until then, researchers hope to solve the dead fish conundrum at least. Five of the fish were sent Tuesday to the Federal University of Rio de Janeiro's biology department for analysis, the results of which will be announced in a week.