∗ Low Concentrations of Deuterium Oxide and the Growth of Marine Diatoms

Abstract

Summary

A consistent lag of about 16% (quotient of total mean into D mean, Table III) in the growth rate of Nitzschia bilobata in the dilute heavy water is unmistakably apparent from a survey and mathematical analysis of the data in Table I.

The data in Table II show a trend of the opposite character, particularly in the earlier times, but are not sufficiently numerous for a conclusive interpretation. Any effects must, therefore, be very slight.

That heavy water may be without detected physiological effects, or may exert influences of either a stimulative or retarding character is certain, but the situation is somewhat analogous to that of the hydrogen ion concentration in that the nature and extent of observed influences depend upon the organism or other biochemical system under investigation, the concentration of heavy isotope, and probably a host of other physical and chemical factors.

Gratitude is expressed to the members of the 1934-35 Committee on Grants-in-Aid of the National Research Council, whose generosity toward the senior author's project made possible the acquisition of the heavy water.

While the problem arose in the physiological laboratory where other research on heavy water was being carried on, the identification and cultural isolation of the diatoms were the work of E. E. Cupp, of the Phytoplankton section here; she also made the population counts. G. F. McEwen, of the section of Physical and Dynamic Oceanography, performed the mathematical analyses and wrote the discussion of their significance.