Ecotoxicological Assessment And waterbird Distribution In Selected Alkaline Rift Valley Lakes, Kenya

Abstract

Ecotoxicology is the study of toxic chemical effects on living organisms at ecosystem, community or population levels. Heavy metals such as mercury (Hg), lead (Pb), Cadmium (Cd) and Chromium (Cr) are examples of common toxic chemicals that pollute the environment due to their persistence in the environment and resistance to biodegradation. The persistent pollutants enter water bodies through natural weathering process and anthropogenic activities. Kenya Rift valley lakes are prone to pollution by heavy metals due to increased industrial activities around lakes and the active natural volcanic activity in the area. Pollution is likely to influence the aquatic life including water birds distribution as a result of the effect on health and physiological parameters. The study was carried out in six Kenyan Alkaline Rift Valley Lakes, Bogoria, Nakuru, Magadi, Oloiden, Elementaita and Crater Lake (Sonachi) with the aim to assess the ecotoxicology and its relationship with water bird distribution. The objectives of the study were to determine the levels of metal elements in water and sediment samples, describe the water birds inhabiting the Rift Valley lakes of Kenya and analyze the Kenya Rift Valley flamingo population trend from the year 1990 to 2015 based on secondary data. High levels of lead (42ppm) above EPA 2007 benchmarks (36ppm) were detected in Lake Oloiden. Lakes Bogoria and Elementaita had high levels of Mn (3676.7 ± 6652.3 and 747.55 ± 510.95 respectively) above benchmark levels (631ppm) according to EPA 2007 benchmarks. The mean sediment concentrations for Zn, Pb, Ni, As and Hg were statistically significant (P<0.05) in all the six lakes. Apart from Zn, all other metal elements (Pb, Co, Mn, Cr, Cd, Fe and Cu) significantly varied in all water samples from the six selected lakes (P<0.05). The distribution of the water bird families for lakes Nakuru, Magadi, Elementaita, Oloiden, Bogoria xiii and Crater were 11, 9, 9, 7, 6 and 4 respectively. There was no association between metal elements concentration and water bird distribution in all the selected six lakes (P>0.05). Flamingo population patterns from secondary data showed a great variation between years and between lakes due to inconsistency in annual counts and lack of data for some years. It was concluded that concentration of metals in Kenya Rift Valley lakes has no effect on the distribution of water birds in the lakes; other factors other than metals may be associated with the distribution. Population trends of both lesser and greater flamingos in Kenyan Alkaline Rift Valley lakes are highly variable making future projections of their populations difficult and further studies should be carried out to establish the reasons for changes in flamingo population patterns. Bioaccumulation from the High Mn levels in lakes Bogoria and Elementaita and Pb in Oloiden might cause toxic effects to the aquatic living organisms and humans.