Limitation of marine phytoplankton reproductive rates by zinc, manganese, and iron

The reproductive rates of 21 species of marine phytoplankton were measured in media in which free zinc, manganese, and iron ion activities were controlled at different levels using EDTA-trace metal ion buffer systems. In general, the reproductive rates of neritic species were limited by zinc activities below $10^-11.5 M$, while those of oceanic species were either not limited or only slightly limited at the lowest zinc activity attained in the experiment, ca. $10^-13M$. The reproductive rates of oceanic coccolithophores were either not limited or only slightly limited by the lowest manganese ion activity attained, ca. $10^-11M$, but those of a neritic coccolithophore an all diatoms, both neritic and oceanic, were limited below a manganese activity of $10^10 M$. Neritic species had reduced reproductive rates in media containing $