An Assessment of plankton diversity as an water quality indicator in small man-made reservoirs in the Mzingwane catchment, Limpopo basin, Zimbabwe

2.3 Data analysis

Clusters were used for the statistical analysis of the data. The eight reservoirs were grouped in terms of species composition and abundance. Zooplankton and phytoplankton taxa were also grouped as they co-occurred or not in the studied reservoirs. Correlations between all means including the abiotic data were computed. Graphs were drawn and analyses were done using SigmaPlot, SPSS and Statistica softwares.

A Simpson's index of diversity (a measure of diversity which takes account of species richness and evenness⁴, which is 1-D) was calculated using the following formula for D: D = ~ (n/N) ² where: n = the total number of organisms of a particular species; N = the total number of organisms of all species. The value of this index ranges between 0 and 1. The greater the value, the greater the sample diversity. Spearman' s rank correlations were calculated.

⁴ http://www.countrysideinfo.co.uk/simpsons.htm