Iron supply regulates nutrient utilization by phytoplankton
2002
Takeda, S. (Tokyo Univ. (Japan))
Iron has many functions within a phytoplankton cell, including major roles in photosynthesis and respiratory electron transfer processes as well as nitrogen metabolism. Studies in highnutrinet, Iow-chlorophyll (HNLO waters suggest that increased iron availability results in an in-crease in phytoplankton biomass and major nutrient (N, P, Si) utilization. The diatoms are one of the phytoplankton groups which responses dramatically to iron supply in the HNLC waters. An increasing number of studies report that iron-stress may regulate the ratio of the silicate:nitrate utilization by phytoplankton. However, the physiological basis for iron effects on diatom silicon metabolism is poorly understood compare to its role on nitrogen metabolism Under iron-stress, the most common responses of diatoms are increase in silicate:nitrate consumption ratio, but in some species cellular Si/N ratio is nearly invariant with iron. Iron-stress alteres the kinetics of silica production and inhibits the uptake of silicate. These results suggest that iron affects silicon metabolism in a more complex manner than simply an iron requirement for silicate utilization. The understandings of physiological responses to iron-stress has further implications for the estimate of the efficiency of the biological CO2, pump using biogeochemical models as well as in paleoproductivity reconstruction.
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