Since 2008, large numbers of Nile crocodile (Crocodylus niloticus) carcasses were found in the
Kruger National Park (KNP), South Africa. Most of the crocodile carcasses were found in the Olifants
Gorge, which is situated below the Letaba and Olifants river confluence, before the Mozambique
border and Massingir Dam. The Massingir Dam is an important resource and it plays a significant
role in the welfare of the local Mozambican population.
Autopsies performed on the crocodiles indicated that the adipose tissue colour changed from normal
white to yellow and this is usually a sign of pansteatitis. Pansteatitis is caused by lipid peroxidation in
an organism and it is characterised by the lack of vitamin E. This disease is recognisable by the
hardening of the fatty tissue and yellow discolouration, and is mostly associated with aquatic
organisms from polluted ecosystems. There are speculations that the crocodile fatalities may be
associated with the Massingir Dam that backed up into the Olifants Gorge after flooding. After the
dam was reconstructed, it flooded the Olifants Gorge, causing it to act like a localised sediment trap
as the water flow slowed down and as a result, caused pollutants to build-up.
Sediment samples were collected from selected rivers and ponds within the KNP. These samples
were analysed for selected elements, persistent organic pollutants (POPs), and polycyclic aromatic
hydrocarbons (PAHs). The sediment samples were analysed in Norway for POPs and PAHs with the
use of a high-resolution gas chromatography/mass spectrometry (GC/MS) and the heavy metals were
analysed in South Africa with the use of inductively-coupled plasma mass spectrometry (ICP/MS).
In order to identify which elements may have affected the health of the crocodiles, a series of
sediment quality indices were used. These indices made it possible to determine which elements
may have been involved. The order of probability of heavy metals causing harm was
Se>As>Ni>Cr>Cu>I>V>Mn>Co>Fe>Cd>Hg>Zn>Pb>Ba>U.
The data was compared to selected international guidelines. All the information was used to
determine which of the sampled sites had the highest contamination. The sites sampled with the
highest concentrations were in the Crocodile, Nkomati, Olifants, and Letaba Rivers. Concentrations
of the elements, POPs, and PAHs were also quantifiable in the Olifants Gorge.
The following elements (Fe, Co, Cu, Cr, Pb, V, As, and Ni) were quantified at elevated levels and may
therefore have caused negative effects on the crocodiles in the Olifants Gorge. These elevated
concentrations, in combination with the dramatic change in the physical environment due to the dam,
could have added additional stress that may have contributed to the observed crocodile mortalities in
the Olifants Gorge. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/15685 |
| Date | January 2015 |
| Creators | Van Gessellen, Annemarie |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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