A study was carried out on algal phosphatase activity and water chemistry in zinc-contaminated streams in the Northern Pennine Orefield. Fourteen field sites were studied; They ranged from low contaminated to high-zinc sites (0.1 mg 1(^-1) to 19.4 mg 1(^-1) with 7 of the 14 above 1 mg 1(^-1) Zn). Phosphate concentrations were low in the majority of sites (2.2 µg 1(^-1) to 22.8 µg l(^-1) with 13 of the 14 sites below 7.7 µg l(^-1) TFP and 1.8 µg l(^-1) to 8.5 µg 1(^-1) with 13 of the 14 sites below 4.9 µg l(^-1) FRP). Phosphatase activity was tested over a broad pH range (3.0 -11.0) using at least two different buffers at each pH value. Phosphatase activity of samples tested showed different responses to pH. Most of the samples exhibited enzyme activity in the alkaline range. High phosphatase activity was observed in samples with Mougeotia and Stigeoclonium populations. Possible relationships between phosphatase activity and selected environmental variables were examined. Phosphatase activity was significantly correlated with Zn (+ve), TFP (-ve) and FRP (-ve) in the water. The role of phosphatases in these high-zinc environments is discussed
