The study was performed using three concentrations containing 1.0, 10 and 100 mg/L (nominal). Incubation time (test system Desmodesmus subspicatus) was 72 hours. The cell concentration of each replicate was determined by measuring the absorption of the solutions at 440 nm every 24 hours with a spectral photometer. The cell density of the cultures was calculated based on the correlation curve between the adsorption and the cell density of the cultures determined by microscope counts. Growth rate μ and the yield1 were determined from the cell densities at the respective observation times.

Significant inhibition of algal growth was observed at all tested concentrations.

In the highest test item concentration 100 mg/L, due to the test items properties the test solutions were clouded and therefore photometric measurement biased.

Because no alga cell could be detected via microscopic observation at the concentration 100 mg/L, inhibition was stated as 100 % in this treatment.

The EC50s of potassium dichromate were tested in a separate reference test. The values lay within the normal range of the laboratory.

The following results for the test item GREENQUAT® BT (Polyglyceryl-3 Betainate Acetate) were determined:

Table 1-a Results of the test item

  Endpoint   NOEC   LOEC   EC50
  Growth Rate < 1.0 mg/L 1.0 mg/L
10 – 100 mg/L
  Yield < 1.0 mg/L 1.0 mg/L < 1.0 mg/L

 

PURPOSE AND PRINCIPLE OF THE STUDY

This study was performed in order to evaluate the toxicity of GREENQUAT BT (Polyglyceryl- 3 Betainate Acetate in Desmodesmus subspicatus.This freshwater green alga was chosen as a typical species of phytoplankton.
The system response was the reduction of growth in a series of algal cultures (test units) exposed to various concentrations of a test item. The response was evaluated as a function of the exposure concentration in comparison with the average growth of replicate, unexposed control cultures. For full expression of the system response to toxic effects (optimal sensitivity), the cultures were allowed unrestricted exponential growth under nutrient sufficient conditions and continuous light for a sufficient period of time to measure reduction of the specific growth rate.