Characterization of macro- and micro-invertebrates and assessment of water quality in dams and rivers of Qwaqwa

Abstract

This study was aimed at assessing water quality status and documentation of waterborne invertebrate organisms in freshwaters (rivers and dams) of Qwaqwa area of Maluti-A-Phofung municipality. Water samples were collected seasonally from rivers and dams to test water quality parameter levels and the variability of the South African scoring system (SASS) bioassessment method. Variable parameters were assessed using the multiparameter equipment and spectrophotometer for water quality and nutrient assessment respectively in all sampled rivers, namely; Metsimatsho, Namahadi, Khoptjwane, Kollatshwene and Elands as well as in two dams namely; Metsimatsho and Fikapatso. The mean electrical conductivity (EC) levels were the highest in Kollatshwene (0.268 μS/cm); Elands (0.231 μS/cm) and Khoptjwane (0.214 μS/cm) rivers between February and June 2014. The EC levels varied widely across the rivers ranging from 0.017 to 0.298 μS/cm in spring. Therefore there were no significant differences (p > 0.05) of the EC levels between the rivers. The EC levels of Fikapatso dam have been higher than those of Metsimatsho dam throughout the sampling period. The pH levels between the rivers were slightly significantly different (p ≤ 0.06). There were no significant differences (p > 0.05) on the temperature levels between the rivers. The salinity and TDS levels between the rivers were significantly different (p < 0.001). The highest winter temperature level was observed in Namahadi river (9.07 ºC) with the lowest winter temperature observed in Kollatshwene river (6.22ºC) which is the highest elevated sampled river (1675m). Meanwhile, with Fikapatso Dam (8.13 ºC) compared to Metsimatsho dam (9.07 ºC) is the opposite since temperature levels were relatively higher than those of most rivers. The pH average levels were high in the Elands river (7.57) than in Kollatshwene river (7.12) being the least of them all. On the other hand, pH average levels were high in Metsimatsho dam (7.42) than Fikapatso dam (7.25). The highest salinity levels between rivers and dams were observed in Metsimatsho river (0.223 mg/l) as compared to 0.01 mg/l in Metsimatsho dam. Lastly, the TDS levels were high in rivers ranging from 21 mg/l (Metsimatsho river) to 297 mg/l of Elands river; than that of dams ranging from 13 to 60 mg/l in both dams. Of the various macroinvertebrate diversity indices, the South African scoring system version 5 (SASS5) index and the average score per taxon (ASPT) were the most consistently used among all biotopes. On the other hand, of the biotopes examined the Gravel/Sand/Mud (GSM) and vegetation combination is the most variable with respect to the SASS score and number of taxa encountered. The comparative SASS scores among the sampled sites were the highest in Metsimatsho Dam (SASS score = 125; No. of Taxa = 20 and the ASPT = 6.3) followed by Elands River (SASS score = 118; Number of Taxa = 21 and ASPT= 4.8); Metsimatsho River (SASS score = 117; No. of Taxa = 17 and ASPT = 6.8); and the least was Kollatshwene River (SASS score = 64; No. of Taxa = 14 and ASPT = 4.8). The lowest ASPT score of 4.8 was observed in both Kollatshwene and Elands rivers and was indicative of poor ecological category, hence poor water quality. Aquatic insects were identified to family level. The most occurring taxa was Baetidae with 102/298 (34.22%) and was the found in all sites; followed by Corixidae with 36/298 (12.08%) and the least being Ceratopogonidae 18/298 (6.04%). Occurrence of macroinvertebrates in water sources depends on their sensitivity to water pollution, while microinvertebrates (total and faecal coliforms) are tolerant to water pollution. Of many sampled sites, Kollatshwene, Elands and Khoptjwane rivers had the highest percentage occurrence of tolerant families (71.4%; 61.9% & 60.0% respectively). The coliform bacteria such as Escherichia coli, Aeromonas hydrophila, Acinetobacter baumanii, Serratia marcescens, Vibrio fluvialis, Pseudomonas putida, Enterobacter cloacae, and Burkholderia cepacia were also identified from Qwaqwa waters. Organisms like fish and frogs (Ameitia spp) as well as ,crabs (Potamonantes spp) occurred in water sources with good water quality mainly in Fikapatso dam since they are highly sensitive to high levels of water pollution. All studied parameters classify the Qwaqwa river water quality status to be poor as compared to the potable water from Fikapatso and Metsimatsho dams.