Evaluation of the water and sediment quality of a lotic water-body in the western coastal region of Sri Lanka using Rapid Bioassessment Protocol II (RBP II) of benthic macroinvertebrates

Abstract

The biotic indices used in Rapid Bioassessment Protocol II (RBP II) developed by United States Environmental Protection Agency was used to assess the feasibility of using benthic macroinvertebates as bio-indicators for monitoring water and sediment quality in Ja-Ela stream, which is a lotic water body in the western coastal region of Sri Lanka. Five study sites to cover the entire length of the stream, which are in five different fringing land uses (undisturbed site, agricultural site, industrial discharge receiving site, densely populated urban site and a site close to the mouth of the stream) were sampled for water and sediment quality parameters and benthic macroinvertebrates from April to October 2015. Shannon-Weiner diversity index (H`), Hilsenhoff Family Biotic index (FBI), Taxa richness (TRI), and Ehemeroptera, Plecoptera and Trichoptera (EPT) index were calculated for each site. Results indicated significant spatial variations in BOD5, COD, visibility, nitrate concentration and total phosphorus concentrations in the water, and total organic carbon content and particle size distribution in sediments. The highest mean values for H' (2.38), TR (13.6) and EPT (6.2) were recorded from the undisturbed site. Significantly higher FBI values are recorded from the industrial discharge receiving site (6.97) and the urban site (6.81), indicating that they are the most polluted sites with higher degree of organic pollution than other sites. These biotic index values showed significant correlations with sediment and water quality characteristics of the study sites (R2 >0.5, p<0.05) The H', EPT, FBI and TR values for benthic macro-invertebrate community showed that the upstream portion of this stream is habitable to pollution sensitive taxa, while the downstream areas close to its opening to Negombo estuary are habitable by pollution tolerant taxa. Results of the present study identified the RBP II as a possible bio monitoring protocol to reflect the water and sediment quality in the Ja-Ela stream.

RBP II (Rapid Bioassessment Protocol II) as a tool to assess the sediment and water quality in a treated textile effluent receiving stream ecosystem.

“…Total of 16 species belonging to three phyla were recorded during the study. (Hilsenhoff, 1982;Wijeyaratne and Kalaotuwawe, 2017). According to the FBI based categorization, the water quality in the reference site is in the "excellent category" whereas the treated textile e uent receiving sites is in the "very good" category (Table 4).…”

“…Their metabolic and behavioral activities help to improve the sediment quality. Further, macrobenthos are very sensitive to changes in sediment or water quality and their responses are re ected as changes in the abundance and community structure (Wijeyaratne and Kalaotuwawe, 2017).…”

“…The taxa richness, Ephemeroptera, Plecoptera, and Trichoptera (EPT) index, ratio of EPT and Chironomid abundance (EPT/C), modi ed Hilsenhoff family biotic index (FBI) and percent contribution of dominant taxa are the indices that are commonly used in the RBP II protocol. It is recommended to use at least four of these biotic indices in order to successfully interpret ecosystem health using RBP II (Singh et al, 2019;Wijeyaratne and Kalaotuwawe, 2017). Macrobenthos based RBP have been widely used in many parts of the world as they are cost effective screening tools that can be used to assess the cumulative effects and severity of impairment in the aquatic ecosystems (Bhadrecha et al, 2016;Copatti et studies.…”

“…Macrobenthos based RBP have been widely used in many parts of the world as they are cost effective screening tools that can be used to assess the cumulative effects and severity of impairment in the aquatic ecosystems (Bhadrecha et al, 2016;Copatti et studies. However, in a pilot study conducted by Wijeyaratne and Kalaotuwawe (2017), RBP II has been identi ed as a as a possible bioassessment protocol to predict water and sediment quality in stream ecosystems in Sri Lanka (Wijeyaratne and Kalaotuwawe, 2017).…”

“…showed the highest abundance in treated textile e uent receival sites, indicating their possibility to use as bio monitor of inorganic pollution as well.Shannon Wiener diversity index and the Family Biotic Index did not show signi cant spatial variations among study sites in both seasons. The Shannon-Wiener Index and the Family biotic Index are among the most reliable indices in assessing stream water quality using benthic macroinvertebrates (Ghosh and Kumar Biswas, 2015;Wijeyaratne and Kalaotuwawe, 2017…”