Aquatic macroinvertebrates as water quality bioindicators in Chicu river, Cundinamarca, Colombia

Background: Studies carried out in the last decade identified an evident environmental disturbance of the Chicu river on the basis of demographic increase in the zone and activities as agriculture and livestock rearing that exert anthropic pressure over the water source through waste water discharges. Goals: Determine the water quality of the Chicu river with the help of biotic indexes (BMWP, ASPT and ABI) based on aquatic macroinvertebrates and analyze their relationship with physical and chemical parameters monitored in the same biological sampling sites. Methods: Sampling took place in four sites distributed along the river and in three intensity-based rainy seasons (low-rain season, middle-rain season, and high-rain season). Biotic indexes (BMWP-Col, ASPT and ABI), and diversity indexes were calculated, and physicochemical parameters in the water were analyzed. Canonical Correspondence Analysis were applied to determine the correlation between indexes, families and parameters. Results: Nine orders, 16 families and 7,094 individuals were identified in the sampling sites, it was found that the highest abundance of individuals belongs to the families Sphaeriidae (49,71%) and Physidae (21,83%). The values of the indexes BMWP and ABI showed that the water quality averaged from "moderately polluted" to "strongly polluted"; canonical correspondence analysis showed a specific grouping of dissolved oxygen and pH with some identified families. Conclusions: Water quality in the Chicu river had a decreasing trend from the high (site 1 of sampling) to the low zone (site 4 of sampling) of the basin. The parameters dissolved oxygen and pH are the ones that reflect a higher sensitivity to adaptability of some families of aquatic macroinvertebrates in the river.