The relative influence of diffuse- and point-source disturbances on a small upland stream in East Java,Indonesia: a preliminary investigation

The relative effects of a diffuse disturbance (alteration of land use from forest to plantation) and a point-source disturbance (a village and its associated coffee-processing plant, within the plantation) on longitudinal variation in water chemistry and macroinvertebrate community composition were assessed in Kali Dinoyo, a small upland stream in East Java, Indonesia. Four sites were sampled. The catchments of the two most-upstream sites were covered primarily by rainforest, while the two lower sites fell within a coffee plantation. The lowest site was downstream of a small village and its associated coffee-processing plant. Most of the variance in all water quality variables and in several community composition measures was explained by the difference between plantation and forest sites. Comparatively small differences in total suspended solids and macroinvertebrate community composition were observed downstream of the village. Diffuse disturbances associated with land clearance and plantation agriculture therefore appear to have a larger impact on the ecology of Kali Dinoyo than the point source impacts associated with the village. More robust and powerful study designs to formally test these findings are discussed.