Thus, a decrease in pH increases metal availability, lending itself to greater metal uptake by organisms. The ammonium ion is non-toxic and not of concern to organisms. Experiments have shown that a pH decrease of 1.4 units of pH can disturb the aquatic community. Acidification of aquatic systems also inhibits microbial activity in the benthos, reducing decomposition and nutrient cycling. This may lead to a reduction of the invertebrates and plankton that are a vital part of the food chain.
Some amphibians are very sensitive to acid inputs, especially during reproductive periods.
Effluent water that is treated for industrial use may be more acidic or more alkaline than the receiving water body. If the water has a pH different from that of the solution within the probe, an electric potential results that registers on the meter. Acid may be carried to surface water bodies via overland or subsurface flow.