Assessment of heavy metals in water samples and tissues of edible fish species from Awassa and Koka Rift Valley Lakes, Ethiopia

Abstract

The Ethiopian Rift Valley Lakes host populations of edible fish species including Oreochromis niloticus, Labeobarbus intermedius and Clarias gariepinus, which are harvested also in other tropical countries. We investigated the occurrence of six heavy metals in tissues of these fish species as well as in the waters of Lake Koka and Lake Awassa. Both lakes are affected by industrial effluents in their catchments, making them ideal study sites. Mercury concentrations were very low in the water samples, but concentrations in the fish samples were relatively high, suggesting a particularly high bioaccumulation tendency as compared with the other investigated metals. Mercury was preferentially accumulated in the fish liver or muscle. It was the only metal with species-specific accumulation with highest levels found in the predatory species L. intermedius. Lower mercury concentrations in O. niloticus could be attributed to the lower trophic level, whereas mercury values in the predatory C. gariepinus were unexpectedly low. This probably relates to the high growth rate of this species resulting in biodilution of mercury. Accumulation of lead, selenium, chromium, arsenic and cadmium did not differ between species, indicating that these elements are not biomagnified in the food chain. Values of cadmium, selenium and arsenic were highest in fish livers, while lead and chromium levels were highest in the gills, which could be related to the uptake pathway. A significant impact of the industrial discharges on the occurrence of metals in the lakes could not be detected, and the respective concentrations in fish do not pose a public health hazard.

Variability in Levels of Heavy Metals in Water and Fish (Chrysichthys nigrodigitatus) tissues from Badagry Creek, Nigeria

“…In comparison among metals studied in this creek water, Cr concentrations were highest in the water samples. Similar finding was reported in Awassa and Koka Rift Valley Lakes, Ethiopia (Dsikowitzky et al, 2012).…”

Copper, zinc, mercury and arsenic content in Micropogonias furnieri and Mugil platanus of the Montevideo coastal zone, Río de la Plata

“…Because of the feeding behavior of whitemouth croaker, these results suggest some degree of biomagnification for these elements, a phenomenon already observed with Hg in a previous study in the area (VIANA et al, 2005) and in other aquatic ecosystems (KEHRIG et al, 2007). Mercury biomagnification and bioaccumulation in fish depend mostly on the fish's position in the food web and its feeding habits (DSIKOWITZKY et al, 2013). However, As showed contradictory results in the literature in terms of the biomagnification process (DSIKOWITZKY et al, 2013).…”

“…The reproductive status can affect the concentration of metals in the liver (MONSEFRAD et al, 2012). Although VIANA et al (2005) found similar relationships for M. furnieri in this region, it has not been possible to determine the reason for these results (MONSEFRAD et al, 2012;DSIKOWITZKY et al, 2013). More studies of the biomagnification and bioaccumulation processes of metals and metalloids are necessary, considering the importance of both species for the ecosystem and the fisheries.…”

“…Mercury biomagnification and bioaccumulation in fish depend mostly on the fish's position in the food web and its feeding habits (DSIKOWITZKY et al, 2013). However, As showed contradictory results in the literature in terms of the biomagnification process (DSIKOWITZKY et al, 2013). Finally, the functional relationship found with Zn and Hg indicates bioaccumulation in M. furnieri for these elements.…”

Environmental risk assessment of pesticides in Ethiopia : a case of surface water systems

“…Others focus on the heavy metals and organochlorine pesticides present in fish species, sediment and water samples, and the correlations between them (Nigussie et al 2010;Dsikowitzky et al 2012;Yohannes et al 2014). These studies detected e.g.…”