The cause behind a recent spate of crocodile deaths at Olifants Gorge in the Kruger National Park is still unknown, the Department of Water Affairs and Forestry said on Wednesday.
Various investigations to establish why the crocodiles were dying were under way between the department, officials from the Kruger National Park and the Water Research Commission, said spokesperson Linda Page.
She said some water analysed from sources in the area was found to contain 15 pesticides.
”The concentrations found were well below World Health Organisation drinking-water guidelines, but were in the range where possible accumulation in the food chain is possible,” said Page.
She said endocrine-disrupting effects were possible, especially with long-term exposure.
The department would continue to monitor the pesticide residue levels.
”It is, however, not clear whether these low-level concentrations of pesticides could have contributed to the crocodile deaths in the Olifants River.”
Page said low levels of phthalates — associated with plastics — were found both in the water column and in the sediments.
Sediment of Olifants Gorge also contained traces of polyaromatic hydrocarbons. The hydrocarbons found are associated with low temperature combustion such as from veld fires or coal combustion.
Normal levels of trace metals were found in both sediment and the water column.
Therefore there was no indication that the crocodiles were dying because of metal poisoning.
”What is further puzzling scientists at this stage is that the water is currently visibly clean, with no algal scum.”
Last month at least 30 crocodile carcasses were found in the Olifants River area.
Some carcasses had distinctive yellow-orange hardened fat in the tail.
At the time Kruger National Park’s head of scientific services, Danie Pienaar, said this hardened fat was associated with a condition known as Pansteatitisn which is usually linked with the consumption of rotten or rancid fish.
”We are not sure what caused this condition in the Olifants Gorge as there were no recent fish kills reported,” he said last month.
Pienaar also said the river system was strained beyond its capacity to deal with the level of stress.
It was the most polluted river in the park and the system had experienced further strain from the Massingir Dam that had pushed back into the Olifants Gorge, causing sediment to be deposited. — Sapa