 Dunaliella parva

Dunaliella parva is a unicellular green member of the algae adapted to saline environments, making it an experimental example of a halophile. Its ability to adjust intracellular glycerol connects a change in external salinity to a measurable cellular response.^[ref]

In 1973, Ami Ben-Amotz and Mordhay Avron measured cellular volume and glycerol content. For cells cultured in $1.5\mathrm{M}$ sodium chloride, they estimated an intracellular glycerol concentration of about $2.1\mathrm{M}$. Increasing or decreasing the external salt caused corresponding glycerol adjustments, reaching a new balance in about90minutes. Above the reported salt threshold, leakage did not explain the changes, supporting synthesis and breakdown as a mechanism of osmoregulation.^[ref]

The experiment compares distinct quantities: salt outside the cell and glycerol inside it. Their numerical concentrations should not be equated as if they alone specified equal osmotic pressure; sodium chloride dissociates and other cellular solutes also contribute. The informative result is the regulated response to a controlled environmental change, not a universal concentration ratio for all halophiles.