The effect of road salt (NaCl) treatment on the hatching success of
Daphnia magna and Thamnocephalus platyurus.
Salinization is an emerging problem for freshwater biodiversity. Road
salt treatment results in salinization of local freshwater, influencing
its entire ecosystem throughout the year. The present study examines the
impact of road salt on the hatching success of two zooplankton species,
Daphnia magna and Thamnocephalus platyurus, using pure laboratory lines
from MicroBioTest. Hatching success was determined without incubation
(T0) and after 3, 7 and 28 day of incubation at 5°C (T3, T7 and T28,
respectively). The number of hatchings decreased with increasing NaCl
concentration for T. platyurus, and decreased rapidly after a crucial
value of 7 600 mg NaCl/L for D. manga. At the second hatching (eggs
washed after first incubation and put into standard freshwater), D.
manga demonstrated a low hatching rate regardless of NaCl concentration,
while most T. platyurus hatchings were observed at the highest NaCl
concentration; hence, the highest (15 200 mg/L) and lowest (1 900 mg/L)
NaCl concentrations resulted in similar total hatching for the two
species. The incubation time (T0, T3, T7 and T28) in NaCl at 5°C had no
significant impact on hatching success; however, T28 resulted in
significantly lower hatching success at all NaCl concentrations and
controls. No significant differences in hatching success were noted if
the eggs were first washed after incubation in NaCl and then put into
the standard freshwater for hatching.