Changes in Water Hardness Influence Colonization of Saprolegnia diclina

Abstract

Experiments were conducted to determine the effects of different water hardness concentrations on colonization of Saprolegnia diclina in an attempt to explain some of the differences in fungal growth and antifungal chemical effectiveness observed at various fish hatcheries. Fungal growth on nonviable seeds of hemp Cannabis sativa was observed significantly sooner in water where hardness was elevated due to the addition of calcium sulfate dihydrate in each of the experiments. Seeds in test tubes containing water with a hardness of 300 mg/L exhibited fungal colonization in approximately one-half the amount of time observed with seeds in water with hardness less than 150 mg/L. In petri dishes containing inoculated corn meal plugs, the growth of S. diclina was observed at only 24 h on seeds in water with a hardness of 450 mg/L, which was significantly quicker than the 31 h from seeds in water hardness of 150 and 300 mg/L. This, in turn, was significantly quicker than the 35 h required for growth in the 0 mg/L hardness control water. Results were similar in a subsequent experiment where the inoculated plugs were removed from the petri dishes prior to seed placement. The relatively minor changes in pH following the addition of water hardness-altering chemicals did not affect the timing of fungal colonization, as a separate experiment indicated no differences in fungal growth in pH ranging from 3 to 10.