The uptake and distribution of selected heavy metals in the freshwater crab, Potamonautes perlatus (Milne Edwards), in the Eerste River, Western Cape
Date
1996-12
Authors
Snyman, Reinette Georgenie
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
A number of studies on the general physico-chemical character of the Eerste River, Western
Cape, had previously been done, but the problem of heavy metal pollution had, by 1993, not
been addressed. A study was therefore undertaken from 1993-1995 in order to investigate these
aspects. Since several researchers have shown that freshwater crabs accumulate certain heavy
metals in their bodies and may therefore be used as monitors of environmental heavy metal
pollution, the present study concentrated mainly on metal concentrations (Mn, Zn, Cu, Pb and
Cd) in the local freshwater crab species, Potamonautes perlatus, and its possible use as
biomonitor in the Eerste River.
Two localities in the Eerste River were chosen,. in order to make comparisons, namely a
relatively uncontaminated site in the Assegaaibosch Nature Reserve, Jonkershoek, and a visibly
polluted site downstream from Stellenbosch, behind Stellenbosch Farmers' Winery (SFW).
Crabs, water and sediment samples were collected seasonally at both localities, and metal
concentrations thereof determined by atomic absorption spectrophotometry.
The results showed that the Eerste River down to the SFW locality is still relatively unpolluted
in terms of heavy metals. It was, however, clear that runoff from the Stellenbosch municipal,
industrial and agricultural areas do have an influence on other physico-chemical features of the
river. The concentrations of heavy metals in whole crabs, tissues and carapace showed that Zn
concentration was well regulated in P. perlatus from both localities, Mn and Cu were
accumulated in individuals from SFW, and Pb and Cd accumulated in both populations.
Compartmentalization of heavy metals was shown to occur in P. perlatus: the carapace was
found to be the most important storage site for Mn, Zn and Pb, the carapace and gonads equally
important for Cd storage, and the digestive gland the most important site for Cu storage.
Whereas gender was shown, generally, to be of little importance in heavy metal uptake in P.
perlatus, crab body size and seasonality were both shown to influence heavy metal uptake to
some extent. However, only summer peaks in whole crab, carapace and tissue manganese
concentrations were shown to correlate with peaks in environmental Mn concentrations.
It was concluded that P. perlatus would possibly only be a Suitable monitor of environmental
Mn, Pb and Cd pollution, although there is no guarantee that the crab body would accurately
reflect environmental concentrations. It was also ascertained that, since a study of the sperm
ultrastructure of P. perlatus showed a significantly larger number of abnormal spermatozoa in
male crabs from ,SFW, and since these observed differences could possibly be related to heavy
metal exposure, the sperm of this species might be a more reliable indicator of heavy metal
pollution. It was finally concluded that more intensive research need to be undertaken on various
aspects, especially the use of the spermatozoon as indicator of environmental heavy metal
pollution, and that the results of the present study could serve as a basis for future studies.
Description
Thesis (MScAgric (Zoology))--University of Stellenbosch, 1996.
Keywords
Crabs, Effect of heavy metals on - South Africa - Stellenbosch, Crabs, Effect of pollution on - South Africa - Stellenbosch, Eerste River (South Africa : River), Heavy metals - Environmental aspects - South Africa - Stellenbosch, Dissertations -- Zoology, Theses -- Zoology