Baseline metal levels in Clarias gariepinus & Crocodylus - - PowerPoint PPT Presentation

Baseline metal levels in Clarias gariepinus & Crocodylus niloticus in the Kruger National Park in relation to pansteatitis – preliminary findings

Roger Dixon, David Huchzermeyer, Herman Espach & Fritz Huchzermeyer.

Reason

• The death in the Olifants River Gorge between 2008 and 2010 of crocodiles

suffering from steatitis has resulted in a coordinated, multidisciplinary approach by various investigators and organisations to find the cause or causes.

• Many different vectors have been postulated as the cause of the steatitis,
• bserved not only in the crocodiles, but also in the barbel, a major food source for

the crocodiles.

• Included amongst these are toxicological causes which could be ascribed to the

cumulative effects certain groups of chemicals, such as pesticides from agricultural use, and heavy metal accumulation from mining activities.

• A number of studies have been launched to determine which are the causative
• factors. This study addresses the potential problem of heavy metals, considering

the presence of active mines upstream.

Sampling

• As part of the ongoing investigation, many tissue samples have

been collected from Clarias gariepinus from a number of localities within the Kruger National Park, including the highly polluted traversing rivers.

• For comparative purposes samples were collected from an

unpolluted dam fed entirely from streams arising within the park.

• Further comparative samples were collected from farmed

specimens at a locality outside the Park.

• Similarly, tissue samples have been collected from Crocodylus

niloticus.

Sampling in the Olifants Gorge

Clarias gariepinus

Results

• Wet liver samples of Clarias gariepinus were digested

in nitric acid, and analysed by ICP-MS for 65 elements

• The elements shown are those detected, and an

average value is presented for three sites:

– Olifants Gorge – damned river, natural? diet, pansteatitis – Reenvoel Dam – earth dam, natural diet, healthy fish – Lunsklip fish farm – earth dam, unnatural diet (fish slaughterhouse waste), severe pansteatitis

2000 4000 6000 8000 10000 12000 14000 Na Mg Fe K Ca

Relative abundance of major elements in Clarias gariepinus

Reenvoel Dam Olifants Gorge Lunsklip

10 20 30 40 50 60 Ti Cu Zn Se Mo Ag Hg Pb Al

Relative abundances of trace elements in Clarias gariepinus

Reenvoel Dam Olifants Gorge Lunsklip

Conclusions so far…

• The high Fe level in the livers of the Lunsklip fish is very different

from those in the Olifants and Reenvoel fish – reflective of different initiating causes of pansteatitis

• Ag & Hg are attributed to mining activities - a possible trigger

initiating redox cycling and lipid peroxidation (Kelly et al. 1998).

• Cu & Zn are correlated with local geology
• Al, Mo & Se are attributed to the food source
• Pb & Ti are anthropogenic

Still to do...

• Analysis of barbel samples from other rivers
• Analysis of crocodile samples from across

Kruger

• Comparison of barbel metal levels on western

and eastern borders

• Determine whether the metal contents in the

fish have a similar distribution in the crocodiles