Response of aquatic macro-invertebrate diversity to environmental factors along the Lower Komati River in Swaziland

This paper assessed macro-invertebrates diversity as an indicator of aquatic ecosystem health in the Lower Komati River. It also investigated whether this diversity is a function of physico-chemical water quality parameters along an area with major agricultural activities. Bio-assessment of aquatic macro-invertebrates present in the Lower Komati River was carried out at seven sites on the river over 3 months. Water samples were also collected at these sites and analysed for pH, dissolved oxygen, electrical conductivity, turbidity, nitrates, ammonia and ortho-phosphates according to standard methods. It was found out that species diversity along agricultural fields was not significantly different (p > 0.05) between successive sites. However, nitrate and turbidity among the physico-chemical parameters indicated a significant variation of mean values (p < 0.05) between sites. With the exception of turbidity, no significant relationship (p > 0.05) was found between diversity and water quality parameters. Principal Component Analysis also demonstrated the influence of turbidity in the sub-catchments as it was the only parameter that showed a significant loading in all Principal Components. Turbidity seems to be the main parameter influencing aquatic macro-invertebrate diversity in the Lower Komati River at the time of study. The study recommends further studies to determine the seasonal variation of the impact of water quality on macro-invertebrates diversity.