Photoperiod
was 16:8 L:D supplied by 32 W, 5000 K white T8 fluorescent lamps
(Philips, Somerset, NJ, USA). Light intensity at the water surface was
140 ± 10 μmol photons m−2 s−1 of photosynthetically active radiation
(PAR; Li-Cor Li-1400 with Li-193SA spherical sensor, Lincoln, NE).
pHwas monitored three times daily in thewater inflowandwas always
in the range 7.2 to 7.9.