Assessing the Potential of QBR Index in Predicting Instream Habitat Quality; A Comparison with Macrobenthos Diversity Indices in Wathurawa Stream, Deniyaya, Sri Lanka

Abstract

Most riparian ecosystems have been degraded due to human activities such as removing forests for cultivation in Sri Lanka. Therefore, effective management is urgently needed with reliable and rapid assessment methods. Macrobenthos diversity is a widely used, reliable instream habitat quality assessment tool that is labor and time-consuming. The QBR index is a rapid riparian habitat quality assessment tool but hardly any record in the Sri Lankan context. Hence, the present study aimed to assess the applicability of the QBR index to evaluate the instream habitat quality in the Wathurawa stream, Deniyaya, and macrobenthos diversity as a reference. Five sampling sites were selected starting from the less disturbed forest reserve (S1). The remaining sites (S2-S5) were in the deforested area for tea and paddy cultivation. Macrobenthos were sampled and the QBR score was recorded with key water quality parameters such as Dissolved Oxygen, pH, Electrical conductivity, TDS, and Temperature at each sampling site. The Shannon-Weiner diversity index and EPT index were used as a measure of habitat quality across five sampling sites with different levels of riparian disturbance. pH and Temperature were not significantly different among the sampling sites while Conductivity, TDS, and DO significantly differ between S1 and S5 (p<0.01). The QBR index was strongly correlated to macrobenthos diversity (r = 0.91, p<0.05). More sensitive taxa, such as Ephemeroptera, Trichoptera, and Plecoptera, were abundant in the less-disturbed areas where the QBR index was high (QBR index; 78.9±8.6). The poorest QBR index (20.0±6.5) was observed at highly degraded riparian area (S5) where the macrobenthos diversity and EPT index were the lowest. The results showed that the QBR index is a valuable indicator for rapid habitat assessment. Sites in poorer QBR showed lower species richness and were dominated by pollution-tolerant species, whereas sites with high QBR index showed healthier and more diverse communities. These results suggest that the inclusion of the QBR index as a rapid assessment tool into conservation methodologies could further enhance habitat monitoring and assist in prioritization within riparian ecosystems.

Keywords: Diversity index, Deforestation, QBR index, Habitat quality, Sensitive taxa