Effect of Chromium on the Growth of Unicellular Chlorophyceae and Diatoms

Abstract

In attempts to isolate and culture some of the more abundant algae occurring in the waters of the Bear River Migratory Bird Refuge in Utah, difficulty in growing certain spp. was encountered. Chromium, which has been shown by a number of workers to be toxic to microorganisms, was suspected, inasmuch as acid-dichromate was employed in cleaning the glassware. Seven spp. of Chlorophyceae and diatoms were cultured over a period of 56 days in 2 different basal media in the presence of graded concns. of Cr ranging from 0.0001 to 16 ppm. The algae, on the basis of complete suppression of growth, fell into 3 groups as follows: (a) most tolerant, 3 Chlorococcales 3.2-6.4 ppm. Cr; (b) intermediately tolerant, 2 euglenoid flagellates, 0.32-1.6 ppm. Cr; (c) least tolerant, 2 diatoms, 0.032-0.32 ppm. Cr. The organisms on the basis of ability to make optimum growth showed greater similarity in sensitivity to Cr with 5 of the 7 organisms being unable to develop optimally above 0.32 ppm. Chlorella variegatus grew normally in 1.6-3.2 ppm. while diatom 47 could tolerate no more than 0.032-0.32 depending on the basal medium. Chromium in sub-lethal concns. stimulated the growth of several of the organisms, especially on the synthetic medium. The composition of the basal media, one synthetic, the other non-synthetic containing soil extract, influenced both the growth vigor and sensitivity of the organisms to Cr. Growth vigor and degree of tolerance for Cr were positively correlated.