Role of protozoan grazing in relieving iron limitation of phytoplankton

Article Abstract:

Model systems of protozoan grazers, dead bacteria, diatoms and iron colloids were conducted to determine the role of protozoans on the bioavailability of colloidal iron for iron-deficient phytoplanktons. The increase in cell densities of diatoms and the corresponding chlorophyll a concentrations indicated that protozoans did have a role in producing iron from ferrihydrite colloids. The mechanism was illustrated as a digestion of the colloidal iron in food vacuoles of protozoans. pH was also found to have no effect in the colloid consumption.

Food chains (Ecology), Food chains, Protozoa, Protozoans

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Competition among marine phytoplankton for different chelated iron species

Article Abstract:

Dissolve-iron availability is important in controlling phytoplankton growth in oceans. The uptake of siderophore- and porphyrin-complex (super55)Fe by phytoplankton was compared, using both cultured organisms and natural assemblages. The importance of siderophores and cell-breakdown products as iron sources may change from place to place in the euphotic zone. The results suggest that the chemical nature of organically complexed Fe will affect the outcome of competition for Fe between picoplanktonic cyanobacteria and diatoms.

Observations, Oceanographic research, Chelates

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Iron acquisition by photosynthetic marine phytoplankton from ingested bacteria

Article Abstract:

Incubation experiments have been used to show that the common photosynthetic flagellate Ochromonas sp. from the Pacific Ocean obtains iron in particulate form through the ingestion of bacteria. 30% of the ingested ration is assimilated to maintain a fast growth rate. Iron flux via mixotropic flagellates can be as much as 35-58% of total Fe uptake and results indicate that the bacterial ingestion may be an efficient adaptive method for such organism to obtain iron in iron-limited areas of the sea.

Bacteria, Ingestion, Iron, Iron (Metal)

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