Abstract:
This study was conducted in the KVRS to; evaluate the seasonal eco-toxicity of water, soil and
sediment samples; establish the suitability of using temperate biotest batteries in tropical
systems; classify the toxicity of samples using Fuzzy Rules to estimate potential ecological risks.
143 water, sediment, and soil samples were collected during dry and rainy seasons in plantation
areas. Pseudokirchneriella subcapitata, Aliivibrio fischeri and Arthrobacter globiformis bioassays
were used to assess the toxicity of the samples. Results were categorized and classified
into toxicity classes.
Dry season presented a significantly higher mean inhibition of 31% than 5% shown by rainy
season samples (p < 0.001) in the bacterial bioassays, indicating a lower concentration of
contaminants due to flooding and increased surface runoff. A few sediment samples resulted
into 100% inhibition of A. globiformis, implying organisms were physiologically inactive upon
exposure to contaminants. Seventy-three percent of samples posed little or no toxic potential
risk, 25% posed critical risk and 1% posed elevated critical risk, implying the KVRS ecosystem
might be at risk if the extensive usage of pesticides in the area is not well managed and
monitored. The temperate micro-biotests can be used in tropical systems, but with further
research on suitable organisms and standardized methods.
