Water quality and the distribution of some fishes in an area of acid sulphate soils, Kalimantan, Indonesia

Abstract

The drainage from acid sulphate soils severely affects water quality, with pH values commonly around 3, and toxic concentrations of ferrous iron and aluminium. The water quality in an area of acid sulphate soils on the southern coastal plain of Kalimantan, Indonesia, was examined and an inventory of fish species was made. The ionic composition of the water can be described as a simple dilution series of the hypothetical mineral Fe(II)4Na8Ca2Mg6Al4H10(SO4)27, originating from the oxidation of pyrite and weathering products of clay minerals. The oxygen concentrations were variable, ranging from 100% saturation, without a clear relation to ionic concentrations. Fish were encountered over the entire pH range of 2.8–5.2. Although species distribution showed some correlation with water quality, the species showed widely overlapping ranges, and they are not suitable for use as indicator organisms on the present detailed scale. The most likely explanation for the poor correlation between fish distribution and water quality are seasonal and local fluctuations in quality. These presumably eliminated the more sensitive species, and only those with a high acidity tolerance were found in the area.