Water Chemistry and Phosphatase Activity of the Blue-Green Alga Rivularia in Upper Teesdale Streams

Abstract

(1) Rivularia colonies are abundant and sometimes dominant in many streams in Upper Teesdale, northern England. In three stream systems chosen for intensive survey the alga was restricted to sites combining drainage from both peat and limestone. (2) Water chemical variables were measured monthly over a year (March 1981-February 1982). Most changes at the main Rivularia sites were probably due to varying combinations of drainage from peat, limestone and ores rich in zinc, lead or barium. (3) Mean concentration of filtrable phosphate (as P) from three main sites was 87 μ g 1-1. Less than 3% of this phosphate was reactive; the remainder (hydrolysed by persulphate digestion method) was apparently organic. (4) Most of the phosphorus passed down the streams in March-May, with `filtrable organic' phosphate (as P) reaching 1.0 mg 1-1 in two streams in May. In contrast, both organic and reactive phosphate were near or below detection limits (3 μ g 1-1, 1 μ g 1-1 respectively) for the other months (June-February). (5) Rivularia colonies were shown by two independent methods to have marked alkaline phosphatase activity. The response of the phosphatase to pH was the same for populations from all three streams. Stream water contained active phosphatase. (6) Because the morphology of Rivularia trichomes indicates that the alga is growing under phosphate-limited conditions, it is suggested that one important reason for its success in these streams is its ability to hydrolyse organic phosphates.