The Otago Regional Council advised against swimming in Lake Hayes a fortnight ago after cyanobacteria scum was found, and at Frankton Bay last Friday after high levels of E. coli were found. ORC environmental scientist Rachel Ozanne said the cause of the E. coli reading was still under investigation.
Last Friday the regional council said testing revealed a level of 921 E. coli per 100ml of water.
The water was tested again on Monday, the results showing it had dropped to 16 E. coli per 100ml.
Warning signage was removed from there and Lake Hayes yesterday.
At Lake Hayes initial testing last month showed the bio-volume of cyanobacteria was 3.96cu mm per litre - under government water quality guidelines for recreational swimming areas, water with more than 1.8cu mm per litre posed a health risk.
Ms Ozanne said the latest results showed the cyanobacteria level had reduced to 1.05cu mm per litre.
Weekly monitoring would continue, but people who frequented Lake Hayes should familiarise themselves with the scum and know what to look for before going swimming or exercising dogs in and around the lake.
