USE OF FISH BIOMARKERS TO ASSESS MICRO- POLLUTANT EXPOSURE AND EFFECTS IN LAKE KANYABOLI, KENYA
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Date
2016-11
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Abstract
A lot of research in ecotoxicology is currently focused on identifying and developing
suitable biomarkers for use in assessing environmental pollution. This study, set out to
evaluate the use of a suite of biomarkers in Clarias gariepinus in assessing micropollutant exposure and effects in Lake Kanyaboli from November 2013 to April 2014.
Fish were collected with the aid of a gill net of mesh size 4” and 5” whereas bottom
sediment was collected by ErkMan crab sampler. The concentrations of Cadmium,
Chromium, Zinc, Copper, and Lead in lake sediment and in the liver of Clarias
gariepinus were determined using Flame Atomic Absorption Spectrophotometry (AAS).
A necropsy-based health assessment index (HAI), the condition factor, hepatosomatic
index (HSI), and splenosomatic index (SSI) were measured in fish from all the sampling
stations. Fish were semi-quantitatively sampled from which an organ index was
calculated to examine the micro- pollutant exposure and effects in fish from all the study
stations. Metals concentrations were significantly (Fα, v1, v2 = 7.16; p < 0.05) higher in
station 2 than at the other stations. The mean heavy metal concentration in Clarias
gariepinus liver were Cd (nd-0.22±0.01), Cr (0.37 ± 0.01 - 1.67 ± 0.03), Zn (7.12 ± 0.03 -
13.40 ± 0.32), Cu (2.12 ± 0.12 - 4.16 ± 0.12) and Pb (1.63 ± 0.33 - 14.40 ± 0.58). Zn
exhibited a significance difference between the stations (Fα, v1, v2 = 7.79; p < 0.05).
Redundancy ordination analysis (RDA) revealed positive linear relation between heavy
metals in sediments and fish liver except for Zinc concentration in sediments and fish
liver which showed a negative relationship. The mean of the biomarkers were HAI (20.61
± 1.01 - 47.43 ± 1.12), Condition factor (0.60 ± 0.03 - 0.91 ± 0.29), HSI (0.53 ± 0.03 -
0.67 ± 0.03), SSI (0.08 ± 0.00 - 0.12 ± 0.01) and Semi-quantitative histological
assessment index (8.3 ± 0.41 - 17.63 ± 0.36). The multivariate analysis of the histology –
based fish health assessment index (HBFHAI) showed that these biomarkers are being
influenced by the concentration of heavy metals in sediments as well as fish liver and
therefore qualified as biomarkers for assessing pollutant exposure and effects. It is
concluded that histology-based fish health assessment index biomarkers can be used to
assess the health of aquatic organisms and ecological health of Lake Kanyaboli and other
aquatic habitats within the Lake Victoria Basin. However, a more comprehensive
chemical analysis of water and sediments samples including the measurements of
endocrine disrupting chemicals is recommended for future studies to further investigate
possible causative agents regarding liver alterations identified.