Loskop crocs will track acid mine spill
Scientists worry that Thungela Resources’ toxic mine drainage will have long-term effects
As soon as their ropes were removed, the three large crocodiles launched themselves into the cool water of their new home in a wilderness area of the Loskop Dam Nature Reserve in Mpumalanga.
The trio, each measuring about 3m from snout to tail, were among the nine crocodiles introduced to the reserve last week. They were fitted with satellite transmitters, marking a first-of-its-kind project on the reserve to monitor crocodile movements.
“They walked off, went in the water and swam away,” grinned Hannes Botha, a herpetofauna (amphibian and reptile) scientist, who led the effort, together with colleagues from the Mpumalanga Tourism and Parks Agency (MTPA) and the University of Pretoria’s veterinary faculty at Onderstepoort. “We switched on the receiver, and it picked all three crocodiles up.”
For Botha and his team, the satellite transmitters will give them greater insight into the crocodiles, their habitat and how they move around in it.
“We want to see, from the point where we released them, where they travel to and how long they stay in particular areas of the dam and where they spend most of their time. This will give us an idea of which areas in the dam they prefer, where they are happy and where they will stay around. Most importantly, it’s about the habitat where they are so that we can keep that intact.
“We would want to try and see if they hang around where we let them go now, if they perhaps move upriver, which will bring them closer to where the acid spill was — we could adapt our management of these crocodiles because we wouldn’t want them to move to areas that will be hazardous to their health.”
On 14 February, a single bricklined concrete seal at the south shaft of thermal coal business, Thungela Resources’ old Kromdraai coal mine upstream failed. It decanted millions of litres of toxic acid mine drainage into the river system. The mine, which was last operational in 1966, is part of Thungela’s Khwezela Colliery, outside emalahleni.
The acidic water flowed uncontrolled into the Kromdraaispruit, then the Saalboomspruit and the Wilge River, which leads into the Olifants River, until it reached the inlet to Loskop Dam, affecting 95km of the river system. Within days, tonnes of fish were wiped out by the extremely low ph values and metal toxicity of the acid water.
Acid mine drainage, which has a low ph and is high in acidity, occurs when water reacts with pyrite in mining cavities beneath the Earth’s surface. It is rich in iron, lead and other metals — many of which are present in toxic concentrations — and also contains high concentrations of sulphate.
Mpumi Sithole, Thungela’s executive head of corporate affairs, said it purchased four satellite tracking tags at the request of the MTPA to assist with their crocodile reintroduction project.
“The purpose of the tracking units is to simplify tracking, locating and therefore monitoring of the crocodiles,” she said, adding that several employees of Thungela joined the crocodile reintroduction.
Botha explained that fitting the satellite transmitters is essentially about monitoring how the crocodiles could potentially be affected by the spill.
“Although we appreciate the contribution to getting the satellite tracking in place and running, this all happened because of something that was allowed to happen that should never have happened,” he added.
Over the past 18 months, 38 crocodiles were introduced into the nature reserve, but Botha and his colleagues are seeing fewer signs of them. “We’ve been keeping an eye on them for a year and half and they were doing well and then they just suddenly started not doing well.”
The spill reached the inlet of the Loskop Dam and “surely it must have had some kind of influence on the system”, he said. “We haven’t seen dead animals but we’re seeing less than half of the crocodiles that were released.”
Before the spill, they were operating at 80% resightings. “You release them and every time you see them again you mark that down as a resighting and we’re now down to around 40%.
“So, we’re seeing less than half of the population that we reintroduced since then and there must be a reason for that. I can’t really say now that there’s a definite connection between the acid spill and us seeing less of the crocodiles, but what I can tell you is we saw much more of them before the spill than after the spill and we’re constantly seeing less of them.”
Such a spill would affect the entire
food chain. “We know for a fact because we did the work that the whole system is connected to the crocodiles ... So the fish eat the invertebrates, for instance, and the crocodiles eat the fish. So what the fish eat, and what the invertebrates eat, ends up in the crocodile … So it stands to reason then that if there’s a problem, say at the source point in this chain, then it will probably end up in the crocodiles, and you will only see it when the big things start dying … by the time you notice that, the whole system is in trouble.”
Almost 20 years ago, the Loskop Dam’s crocodile population was virtually wiped out after an outbreak of pansteatitis, a condition which causes their fat bodies to harden. There is still, however, no satisfactory answer for their demise.
“It’s very difficult to connect things to each other. We picked up pollutants in the blood of crocodiles from this area that could possibly be connected to something like a pansteatitis outbreak. So, where does a pollutant in the blood of the crocodile come from? The environment.”
In May, Mail & Guardian reported that the department of forestry, fisheries and the environment and the department of water and sanitation had launched a criminal investigation into Thungela Resources over the spill.
Albi Modise, a spokesperson for the environment department, said environmental management inspectors from both departments have not yet finalised their criminal investigation.
“Once the investigation has been finalised, the criminal docket will be submitted to the relevant director of public prosecutions who will decide whether or not there is sufficient evidence to pursue a prosecution and which parties should be charged.”
According to Sithole, the sampling of macroinvertebrates (including insects in various stages, snails, worms, crayfish and clams), fish, dia
toms (photosynthesising algae) and riverine habitats to determine the low flow ecostatus of the river system was carried out from 15 to 19 August. This work was conducted by Thungela’s appointed biodiversity experts, the Biodiversity Company, under the supervision of senior scientists from the MTPA.
“Both affected portions of the rivers as well as non-affected tributaries were sampled,” she said.
“Results from the fieldwork are currently being collated and samples have been sent away for laboratory analysis. Once the results are available, a workshop will be held with a panel of experts to determine rehabilitation actions that should be taken.”
The expert panel includes members of the MTPA, Thungela, the water and sanitation department, the Biodiversity Company and recognised scientific leaders in the fields of ecotoxicology, riverine health and other aquatic biosciences. Sithole said Thungela, has made “good progress” in the rehabilitation of the Kromdraai area.
But Francois Roux, an aquatic scientist at the MTPA, shook his head. “We’re doing biomonitoring results for fish and macroinvertebrates and at present, it doesn’t look good.”
Botha agreed. “If you take that information and add it to the fact that we’re seeing less than 40% of the animals [crocodiles] that we put back in, there’s that circumstantial thing now. There was a spill, we’re seeing less crocodiles and seeing less fish — there must be some kind of connection.”
Roux worries that the toxic aftermath of the spill will linger in the river system for decades. “We’re going to feel the impact on this river in 50 years. The heavy metals and all that stuff is sitting in the deposits in the sand — it’s really very early days.
Botha added: “The problem isn’t the fish we lost now and the crocodiles we lost now. It’s going to be the population that struggles to maintain itself in 10, 20 and 50 years from now.”