Combined effects of food shortage and oxygen deficiency on life history characteristics and filter screens of Daphnia

Daphnia magna were reared in environments with different concentrations of food and dissolved oxygen, and their life history characteristics and filter-screen areas were analyzed. Both low food concentration and low oxygen concentration degraded Daphnia fitness (as measured by individual growth and reproduction), and synergism was detected statistically for the effects of the two factors together. Low food concentration induced the development of large filter screens in Daphnia, but this development was suppressed by low oxygen concentration, suggesting that low oxygen concentration reduces the filtering rate of Daphnia in a food-limited environment. Therefore, energy uptake by Daphnia seems to be reduced by food shortages and oxygen deficiencies jointly, and this reduction in energy uptake may be a possible mechanism causing the synergistic effects of the two environmental stresses on the life history of Daphnia.