Population dynamics of Brachionus calyciflorus (Rotifera : Brachionidae) in waste water from food-processing industry in Mexico

Waste water from Mexico's largest food processing industrial sector (based on maize, nejayote water) was used for growing Brachionus calyciflorus isol ated from Lake Chapultepec in the Federal District of Mexico (D.F). Nejayot e water was collected from Colonia Providencia, D.F Experiments were conduc ted at 25 degrees C in 25 mi capacity vials with 20 ml of medium into which we introduced B. calyciflorus at an initial density of 1 ind ml(-1). The e xperimental design consisted a total of 33 test vessels (2 food combination s X 5 densities X 3 replicates = 30 plus 3 replicates as controls that cont ained only algae). Experiments were terminated after day 16. Waste water in original concentration did not support rotifers. However, when diluted to 5 concentrations (ranging from 2% to 32% and pH adjusted to 7.0), rotifer d ensity increased with increasing concentration of waste water. Green algae (at constant density of 2 X 10(6) cells ml(-1) of Chlorella) in combination with waste water resulted in a higher abundance of rotifers only at higher concentrations (above 8%) of waste water. The maximum peak density of roti fers (238 +/- 50 ind ml(-1)) was obtained at 16% dilution of waste water an d with addition of Chlorella. The rate of population increase per day (r) ( mean +/- SD) varied from 0.355 +/- 0.059 to 0.457 +/- 0.048 depending on fo od combination and concentration.