Tests carried out

ASSESSMENT OF ALGAECIDAL ACTIVITY AT 10% Dilution

Method 1: Inhibition of Algal Growth
1ml of test product was added to sterile nitrocellulose or Whatman number 1 filters. The filters were placed on Bolds Basal Agar (Bolds Basal Broth with 10g/l agar). Two ‘sprays’ from a pump containing the algal suspension were sprayed onto the surface of the agar over the filter papers. The plates were then incubated in an algal incubator at 20°C for 10 days. The test product was compared to a control with the test product replaced with synthetic hard water.

A growth control was also included to demonstrate that the agar supported the growth of the algae.

Results: There was inhibition of algal growth on the filter papers treated with test product but no inhibition of growth on the paper treated with synthetic hard water (control). There were small zones of inhibition around the filter papers treated with test product but not around the control papers.

Method 2: Killing of Algae on a Surface (Bolds Basal Agar). The test organisms were grown up on Bolds Basal Agar (Bolds Basal Broth with 10g/l agar). Two ‘sprays’ from a pump containing the test product were sprayed onto centre of the surface of the agar. The plates were then incubated in an algal incubator at 20°C for 4 days. The effects of test product on the algae were compared to a control where the test product was replaced with synthetic hard water. A growth control was also included to demonstrate that the agar supported the growth of the algae.

Results: A change in colour or the algae in the centre of the plate were the test product had been sprayed compared to the colour of the algae on the control plates was noted. Colour changed from dark green to lime green indicating the death of the algae. The areas where the product had been applied and colour change had been noted were sub cultured onto Bolds Basal Agar (Bolds Basal Broth with 10g/l agar) and incubated for 10 days in an algal incubator at 20°C. There was no growth of the algae indicating that the algae had been killed by the test product.

Method 3: Killing of Algae in a Solution (Bolds Basal Medium)
The test organisms were grown up on Bolds Basal Medium. Two concentrations of test product were tested. The first concentration was 1ml of neat product added to 9ml of algal suspension. This gave a final product concentration of 10%.

The second concentration was 1ml of a 10% product solution added to 9ml of algal suspension. This gave a final product concentration of 1%. The suspensions were then incubated in an algal incubator at 20°C for 4 days. After incubation the suspensions were sub cultured onto Bolds Basal Agar to determine whether the algae were dead. The plates were incubated for 10days in an algal incubator at 20°C for

Results: After addition of the test product the solutions were observed for colour change as an indicator of algal death. Gloeocapsa atrata with the 10% test product changed from green to yellow in 2 minutes. Gloeocapsa atrata with the 1% test product changed from green to yellow in 10 minutes. Nostoc commune var. flagelliforme with both the 1% & 10% test product changed from green to yellow in 10 minutes. Stichococcus bacillaris did not show a colour change. There was no growth on any of the sub-culture plates indicating that the algae were not viable.