The article presents the possible methods of interpretation of
Shannon-Wiener index values determined for communities of wastewater saprobes and calculated on species abundances (H) or abundances of morphological-functional groups (H∗). To calculate the index, the species richness index ΔSr (or morphological–functional group richness index Δ∗) and nT value (total individual number) as well as abundances of particular species (or groups) ni (or n∗i) are needed. It is also possible to determine the index Hmax = logzΔSr (or H∗max = logzΔ∗) based on ΔSr values (or Δ∗ values). The value of Hmax(or H∗max) can be used for calculation of the evenness index, V.
The value of this index can, after multiplication by 100, express a percentage “evenness deficiency” in relative abundances of species (or morphological–functional groups). Having the value of the H index (or H∗ index) it is possible to calculate Mac Arthur's index E = zH (or E∗ = zH∗). In fact, the E index (or E∗ index) represents a value of the species richness index ΔSr (or group richness Δ∗) for a community in which all species (groups) have the same abundances (thus relative abundances − Π
i
are also the same) and the calculated H value (or H∗ value) is Hmax (or H∗max). Using the E index (or E∗) it is possible to calculate “proportionality” index P = E/ΔSr · 100 (or P∗ = E∗/Δ∗ · 100), expressing in percent, taxa “number shortage.” For the complete characterization of a community, not only the calculated H (H∗) values, but also the values of ΔSr (Δ∗), V (V∗) and P (P∗), should be presented.
