Do SASS5 scores vary with season in the South African highveld? A case study on the Skeerpoort River, North West province, South Africa

Abstract

Macroinvertebrate assemblages can vary with season as a result of changing environmental conditions and phenology of individual species. The objective of this study was to determine whether results from the South African Scoring System version 5 (SASS5) are affected by season. The standard SASS5 protocol was used to sample three sites on the Skeerpoort River, South Africa, in autumn, winter and spring 2013, and summer 2014. At each site, stream morphology was characterised and physico-chemical variables were measured. Two-way analysis of variance (ANOVA) was used to compare SASS indices in relation to site and season, and a one-way ANOVA was used to test the effect of season using both current and historical data. Macroinvertebrate assemblage similarity of sites was determined using non-metric multidimensional scaling ordination, followed by analysis of similarity. Whilst macroinvertebrate assemblages differed between seasons and sites, there was no seasonal variation in the values of SASS indices, but they did differ between sites. SASS5 appears to be robust to seasonal variation in macroinvertebrate assemblage and seems suitable for use throughout the year in a perennial river draining the South African highveld region.

Keywords:

• aquatic macroinvertebrates
• bioassessment
• seasonal variation
• water quality