Effects of Arsenate on Growth and Phosphorus Metabolism of Phytoplankton1,2

The response to arsenate in growth and phosphate uptake by five algae in culture varied considerably. The growth rates of Melosira granulata var. angustissima O. Müll, and Ochromonas vallesiaca Chodat were depressed by 1 μM arsenale. Chlamydomonas reinhardtii Dang. required 10 μM for the same degree of depression, while the growth rules of Cryptomonas eroasa Ehr. and Anabaena variabilis Kütz. were unaffeted up to 100 μM. However, following depletion of phosphate, cultures of the later two algae began to die at the higher concentrations of arsenale tested. Growth of C. reinhardtii in the presence of 35 μM arsenate resulted in characteristics of P deficiency. Comparison of rates of photosynthesis, respiration, and phosphate uptake between cultures of C. reinhardtii which had grown in the presence and absence of arsenate showed little evidence after 16 doublings that it had adapted to arsenale.