Some 86 tonnes of yellowtail, catfish, tilapia and bass, died due to low levels of oxygen in the water, and had to be scooped up in an extensive clean-up by 100 municipal workers over two days.
, Principal Lecturer in the School of Environment and Technology, said the causes of such piscine carnage, known as 'fish kills', were usually a combination of factors linked to not only the geography and hydrology of the water, but also the meteorological conditions.
He said: "It is also the decomposition of biological material such as dead algae and bacteria that most commonly leads to oxygen depletion and mass fish kills. Just before the kill there was heavy rainfall, leading to faecal inputs in the form of run-off from impermeable surfaces. Inputs such as sewer overflows are often high in nutrients (and biological matter) which can stimulate algal (phytoplankton) growth, potentially leading to algal blooms."
Rio de Janeiro's Rodrigo de Freitas lagoon
© REUTERS/Sergio Moraes
"These types of aquatic risk management tools are currently being developed by our 13-strong research group, the Environment and Public Health Research Unit, here at the 91¶¶Òõ."
Dr Ebdon said: "It is sad that tens of thousands of fish have died in this way, but what is yet more tragic is that these fish kill events will continue to occur unless inputs of biological material (dead algae and faecal matter) from sediments, sewage and run-off are better understood and more robustly managed in the future.
Dr Ebdon added: "Despite, significant investment to clean up the lagoon in recent years, there is no guarantee that these scenes of carnage will not be repeated in the not too distant future.
"I imagine that planners and government officials are just hoping that the 2016 Olympic rowing events won’t coincide with periods of extreme, intense rainfall."