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Cadmium: A nutrient for the marine diatom Thalassiosira weissflogii
Author(s) -
Lee Jennlfer G.,
Roberts Samantha B.,
Morel Franqois M. M.
Publication year - 1995
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1995.40.6.1056
Subject(s) - thalassiosira weissflogii , cadmium , carbonic anhydrase , diatom , zinc , seawater , nutrient , chemistry , biochemistry , biology , enzyme , environmental chemistry , botany , ecology , phytoplankton , organic chemistry
Although cadmium is known to be very toxic, it exhibits nutrientlike vertical concentration profiles in the open ocean. Recent work has shown that under conditions of zinc limitation, cadmium enhances the growth of the marine diatom Thalassiosira weissflogii. Here, we conclusively demonstrate that Cd is a nutrient for T. weissflogii at inorganic Zn and Cd concentrations typical of surface seawater, although Cd cannot completely replace Zn. Over a wide range of external Cd and Zn concentrations, Cd uptake kinetics are regulated and the intracellular Cd quotas are maintained at relatively constant levels. The same low level of inorganic Cd that enhances the growth rate of Zn‐limited cells restores the activity of carbonic anhydrase (CA), thought to be the key enzyme limiting growth of T. weissflogii at low Zn. Cd also coelutes with some of the isoforms of CA, indicating that Cd substitution in CA is likely partly responsible for the nutritional role of Cd. The substitution of Cd for Zn in CA links the geochemical cycle of Cd to those of Zn and C.