Assessing effects of pond effluents on the diversity and abundance of Macroinvertebrates and Zooplankton along selected streams in Wakiso, Central Uganda
Abstract
Uganda is targeting 1,000,000 tonnes from aquaculture only by 2030 since fish farming is now
looked at as a very good economic venture for feeding the estimated 50 million people. Wakiso
District contains several fish farms practising pond culture and was shortlisted among the 31
districts in Uganda that were identified for fisheries and aquaculture development based on both
natural and socio-economic factors. The economic venture pauses ecological threat on the
streams that receive the pond effluents especially species of the aquatic organisms that are so
sensitive to the changes in water parameters. The fluctuations in water parameters along streams
have direct effects on the diversity and abundance of aquatic organisms especially the intolerant
ones.
Shannon index of macroinvertebrates sampled upstream (1.675) was higher than the index of
macroinvertebrates sampled from downstream (1.557). the same diversity index showed that
diversity of zooplankton was generally high upstream (2.386) and downstream (2.414), but lower
in the ponds (2.344). There were significant variations in the means of three physico-chemical
parameters; temperature, dissolved oxygen and PH (p<0.05) at the different sample points.
However, mean conductivity showed no significant difference between the sample points
(p>0.05). The abundance of macroinvertebrate populations was easily recognized at the order
level, whereby Dipterans and Odonatans had higher abundance in the overall population. Aquatic
insects in order Odonata can survive in low oxygen because they have a close tracheal system.
This study has shown that pond effluents has relatively no effects on the downstream ecosystem
as far as diversity and abundance of macroinvertebrates and zooplankton are concerned.
Ecological effects of waste waters from fish farms require frequent research in order to protect
environmental health. Aquaculture subsector in Uganda is intensifying very fast therefore waste
management research is key in order to mimic the environmental effects that may occur.