Four
replicate sterile Petri dishes were each filled with 30 mL
of
1.0% (distilled water) agar (Merck 1614) as the basal layer,
which
was dried with sterile air. Macrophyte extracts (100 L) were
pipetted
onto the basal solidified basal agar layer; the extract was
confined
to a small area in the middle of each Petri dish (1% agar
and
distilled water), dried with sterile air then incubated for 3 h to
allow
the methanol to evaporate. The basal layer was then covered
by
a second agar layer (0.2% agar, BG-11 as the culture medium)
inoculated
with either target organism. BG-11 was also used as the
medium
for S. quadricauda (Makarevi
ˇ
cien
˙
e et al., 2011). Controls
were
made with 100 L 98% methanol to eliminate the possible
toxic
effects of the solvent. Sixteen treatments (four replicates for
each
macrophyte and microalgal combination) and eight controls
were
set up, resulting in 24 plates in total. Plates were incubated
in
the CT room for 10 d. Clearing zones of the target organisms
were
measured every two d for 10 d. Clear areas were quantified
by
placing a gridded square (1 cm × 1 cm) on top of each Petri dish
and
measuring the areas that appeared clear to the naked eye.