The Biotic Integrity of Ciliwung River in West Java under Multiple Urban Stressors

Based on its imperviousness, most of the sub-watersheds in the lower part of Ciliwung watershed in West Java are classified as urban drainage. High imperviousness in the urban environment will cause multiple stressors among others on the discharge, water quality and habitat condition, those supposedly support the presence of macroinvertebrates. Macroinvertebrates are commonly used as markers of the biotic integrity of aquatic ecosystem. The aim of the study is to explore the extent of causal relationship between imperviousness, as trigger for the emergence of stressors on biotic integrity, which is represented by Family Biotic Index. The Family Biotic Index is considered as response variables, while imperviousness, discharge, water quality and habitat condition are as explanatory variables. Significance correlation tests among explanatory and response variables from 23 sub-watersheds of Ciliwung using Spearman Rank-order Correlation show that they are correlated. Influence of multiple urban stressors on the biotic integrity was assessed using several alternatives of multiple linear regression model, which is determined based on backward elimination procedure. The standard error of estimate ranges between 0.8563 and 0.9096 are less than standard deviation amounted 1.0876, therefore the models are acceptable for predicting the response variable, the FBI. Although they have not yet fully represented the observed FBI values, especially for the lowest and the highest one, possibly due to very limited data. This can be seen from the low value of the coefficient of determination, R2 ranging from 33,23% up to 43.86%, and from the juxtaposed between model results and the observed values.