Lake Turkana and Lake Naivasha: fish as bioindicators for trace element pollution from two contrasting rift valley lakes, Kenya.
- Author(s)
- Christof Plessl, Elick O. Otachi, Wilfried Körner, Annemarie Avenant-Oldewage, Bernhard Keppler, Franz Jirsa
- Abstract
Lake Turkana and Lake Naivasha are two freshwater lakes in Kenya that differ significantly in water chemistry and anthropogenic influence: whereas Lake Turkana is believed to be rather pristine and unpolluted, Lake Naivasha is seen as heavily influenced amongst others due to agricultural activity in the surrounding areas. During the last years a major rise in the water level of the lake has been observed.
This study presents the distribution of selected trace elements in water, sediments and fish tissues from these two lakes. We have included the red belly tilapia Tilapia zillii and the elongated tigerfish Hydrocynus forskahlii from Lake Turkana as well as the blue spotted tilapia Oreochromis leucostictus and common carp Cyprinus carpio from Lake Naivasha.
Sediments and water samples of Lake Turkana did not show any sign of trace element pollution at least for the sample area in the central basin of Lake Turkana, while Lake Naivasha showed slightly elevated levels of most trace elements in the sediments compared to L. Turkana.
In the muscle of H. forskahlii from Lake Turkana and O. leucostictus from Lake Naivasha high levels of cadmium and zinc, amongst others, have been detected, presenting risks for human consumers of these fish.
A positive correlation between cadmium and zinc content in muscle has been observed. This might be due to the blockage of zinc-containing enzymes leading to their enhanced expression and therefore leading to elevated zinc levels in muscle.
Furthermore, the results show that the trace element levels in fish seem to correlate with the intensity of land use around the water bodies or more precisely, the usage of mineral fertilizers, which usually contain elevated levels of several trace elements, including Cadmium; highest levels of Cd and Zn, presenting a high risk for fish consumers, were found in O. leucostictus from Lake Naivasha. Because of the major change in water level we examined C. carpio five years after the sampling of O. leucostictus, which did not show those high levels anymore, leading to the necessity of further investigation.
Second highest levels were present in H. forskahlii from Lake Turkana, which is exposed to heavily influenced waters only seasonally during migration into the highly influenced delta of the Omo River. This clearly points out that knowing migratory pattern of the fish species is one of the basic requirements for evaluating its suitability as a bioindicator for trace element pollution.- Organisation(s)
- Department of Inorganic Chemistry
- External organisation(s)
- University of Johannesburg (UJ), Egerton University
- Pages
- 404
- Publication date
- 07-2016
- Austrian Fields of Science 2012
- 106020 Limnology, 104023 Environmental chemistry
- Sustainable Development Goals
- SDG 15 - Life on Land
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/5612b0cc-b0f6-43db-b41d-71b34b1d99a0