Trace Elements in Water, Sediments and the Elongate Tigerfish Hydrocynus forskahlii (Cuvier 1819) from Lake Turkana, Kenya Including a Comprehensive Health Risk Analysis

Abstract

This study presents the distribution of 17 major and trace elements in surface water, sediments and fish tissues from Lake Turkana, Kenya. Eight sediment and ten water samples from the west bank of the lake, as well as 34 specimens of the elongate tigerfish Hydrocynus forskahlii caught in that region were examined. It is the first report for Li, Rb, Sr, Mo from the lake and the first report on most of the trace elements for this fish species. The concentrations of elements in the water and sediments showed no sign of pollution. In fish muscle, Li, Zn and Cd showed relatively high abundances, with mean concentrations of 206, 427 and 0.56 mg/kg dw, respectively. The calculated target hazard quotient values for Li, Zn, Sr and Cd were 138.7, 1.9, 4.1 and 0.76, respectively; therefore the consumption of these fish poses a health risk to humans in the area.

Fish as bioindicators for trace element pollution from two contrasting lakes in the Eastern Rift Valley, Kenya: spatial and temporal aspects

“…Otachi et al ( 2014 ) were the first to include a variety of trace elements in sediments and the Blue belly tilapia Oreochromis leucostictus . All these studies revealed elevated levels of trace elements, calling for further investigations: For Lake Turkana, the report by Otachi et al ( 2015 ) showed elevated levels for some trace elements in the elongate tigerfish Hydrocynus forskahlii although no elevated levels in the sediment or water were observed from their sampling area in the central region of the lake. The authors hypothesized that H. forskahlii might be exposed to high contaminant levels during its annual migration into the Omo River, which drains a large basin used for agricultural purposes.…”

“…Numerous studies have evaluated trace element levels in fish since awareness of environmental pollution awoke in the late 1960s and early 1970s (e.g., Reichenbach-Klinke 1974 and references therein), mostly from waterbodies in Europe and North America. Data from the African continent are scarce, and only little research has dealt with trace metal levels in fish (e.g., Avenant-Oldewage and Marx 2000 ; Mutia et al 2012 ; Otachi et al 2014 , 2015 ; Lynch et al 2016 ).…”

“…This makes monitoring trace elements very important with regard to food safety. Otachi et al ( 2015 ) delivered the first comprehensive study on trace element levels from water, sediment, and one fish species from the central part of Lake Turkana. Data from Lake Naivasha have been published by Tarras-Wahlberg et al ( 2002 ), Ochieng et al ( 2009 ), Kamau et al ( 2008 ), and others who have already investigated the levels and sources of metals such as Cu, Cd, Zn, Fe, Pb, and Ni in Lake Naivasha.…”

“…The authors hypothesized that H. forskahlii might be exposed to high contaminant levels during its annual migration into the Omo River, which drains a large basin used for agricultural purposes. The assumption is that the water is polluted with, amongst others, contaminants that commonly are found in fertilizers, such as Li and Cd (Otachi et al 2015 ). Nonetheless, it remained unclear whether the findings for the central part of the lake regarding water and sediment were accidental or if they can be confirmed using a stationary fish species as bioindicator, i.e., by a species that does not migrate during its lifetime and therefore gives an integrated depiction of the trace element situation of its habitat.…”

“…Nonetheless, it remained unclear whether the findings for the central part of the lake regarding water and sediment were accidental or if they can be confirmed using a stationary fish species as bioindicator, i.e., by a species that does not migrate during its lifetime and therefore gives an integrated depiction of the trace element situation of its habitat. As a follow-up to the study of Otachi et al ( 2015 ), we chose the red belly tilapia Tilapia zillii from the same sample area to gain further insight into a possible trace element contamination of central Lake Turkana.…”