摘要：The assessment of the impact of volcanic mud discharge into a river based on several quality indices including habitat quality index (HQI), water quality index (WQI) and fish biotic integrity (FIBI) using the case study of Lusi in Sidoarjo-Indonesia, was undertaken from January 2011 to February 2012. Compared to the data collected at the control station (HQI= 21; WQI= 59-75; FIBI=75), the siltation caused by the Lusi discharge adversely affected several factors. Firstly, the declining value of stream covers and aesthetics resulted in lower HQI (10-13); secondly, the increasing concentration of total suspended solids (TSS), biochemical and chemical oxygen demand (BOD and COD) resulted in low WQI, primarily in the dry season (22.3-49.3); and thirdly, the limited supporting habitat for cyprinids and the mud-intolerant native fish species lowered the FIBI score (60-65). The abundance of mud-tolerant species revealed that the downstream aquatic communities have the ability to adjust to the volcanic mud contamination. However, since there was a strong positive correlation between HQI and FIBI, the expected long term exposure to Lusi will be followed by more habitat degradation, thus limiting the life of fishes that are not tolerant to the mud and lowering of the quality indices permanently. Further investigations using Mystus gulio as the bioindicator for Lusi mud contamination is proposed, as follow-up research.
