In order to represent an algae pond susceptible to predation, the rotifer and alga were co-cultured
to determine the toxic effect of QS on B. calyciflorus in the presence of algae. The same setup as
in Section 3.2 was used, except rotifers were added to the algae cultures. Two experiments were
conducted with different QS concentrations (0.6, 7.7, 15.3 and 25.5 M) in triplicate. Initial rotifer
densities averaged six rotifers per mL. One positive control with algae, rotifers, and no QS was
conducted in triplicate. The initial OD of the algae was 0.2. Rotifers were counted each day over
8 days. Rotifers were counted in 1 mL samples in a well plate under the stereomicroscope. If the
number of rotifers per 1 mL sample was greater than 40, the field of view of the well plate was divided
into four quarters and each quarter was counted and multiplied by four to get the rotifer number per
1 mL sample in the co-cultures; this rotifer count multiplied by 100 is rotifer number in the flask. If the
rotifer count in each quarter exceeded 40, a smaller sample size of 0.2 mL was used and the number of
rotifers was then multiplied by 500 to obtain the rotifer number in in each flask. The relative mortality
of the rotifers and the growth of algae were calculated using the positive controls when the rotifer
concentrations were at their peak according to: Abs (1 (rotifer # in the experiment/positive control
rotifer #)) 100 (see Equation (1)), which # stands for the count of rotifer number. The standard
deviation is the average standard deviation of each experiment/positive control rotifer # 100
(see Equation (2)).