Salinity levels of some freshwater systems have been altered by humans, posing a threat to aquatic life. We hypothesized that a Daphnia magna population pre-treated with a low concentration of NaCl would develop greater salinity tolerance than an untreated population. Two Daphnia magna cultures with 60 individuals each were established, one started with 1.00 ppt NaCl and increased by 0.20 ppt weekly, and the other with pure spring water. After 4 weeks, 40 neonates from each culture were individually placed in a solution of 2.30 ppt NaCl (separately determined to be the LC50) for 48 hours. Survival was significantly greater for the experimental group (LR = 7.5, df = 1, P < 0.05) and significantly exceeded the expected 50% survival rate (χ2 = 6.4, df = 1, P < 0.05). This finding suggests that Daphnia populations can evolve or acclimatize to increase their survival in high salinity habitats.
Dr. Rick Kopp
Parlato, Brady P. and Kopp, Rick
"Adaptive Tolerance to Sodium Chloride in Daphnia magna,"
Kentucky Journal of Undergraduate Scholarship: Vol. 4
, Article 2.
Available at: https://encompass.eku.edu/kjus/vol4/iss1/2