Manganese and the Growth of Phytoplankton

Abstract

Inshore water collected near Plymouth during the late summer and autumn of 1945, after enrichment with nitrate, phosphate and iron, did not support continued growth of a species of Chlamydomonas, of Chlorella, of a Cryptomonad and of two species of Chrysomonads.The addition of 0-5-2-0 mg. Mn" or Mnv/m.3 allowed vigorous growth and the production of heavy crops. The effect on Chlamydomonas of adding as little as o-i mg./m.3 was apparent.The growth of Coscinodiscus excentricus varied in waters collected from inshore and from offshore which had been similarly enriched with N, P and Fe. The addition of manganese had only a minor effect.The addition of other microelements to inshore waters enriched with N, P, Fe and Mn did not affect growth rate of Chlamydomonas. Manganese starvation led to the production of small Chlamydomonas cells.Manganese starvation caused a resting condition or lag period in Chlorella. A supply of manganese alone was insufficient for recovery; a period of illumination was also required for internal changes to take place before logarithmic growth was resumed.The addition of manganese was effective when either nitrate or ammonium was supplied as source of nitrogen, in dim, bright, continuous, or discontinuous illumination.Metabolic products which leached out of the cells into the water during the growth of both Chlorella sp. and of Nitzschia closterium acted as a growth stimulant.Manganese at great dilution is rapidly 'collected' from solution by Chlorella. During growth this alga abstracts a material proportion from water containing 5 mg. Mn/m.3Using Chlamydomonas as 'analyst', it was found that added organic detritus, or the corpses of marine bacteria, adsorbed a material proportion of the manganese in sea water containing 1-2 mg. Mn/m.3