Heme b in marine phytoplankton and particulate material from the North Atlantic Ocean

Honey, David J., Gledhill, Martha, Bibby, Thomas S., Legiret, François-Eric, Pratt, Nicola J., Hickman, Anna E., Lawson, Tracy and Achterberg, Eric P. (2013) Heme b in marine phytoplankton and particulate material from the North Atlantic Ocean. Marine Ecology Progress Series, 483, 1-17. (doi:10.3354/meps10367).

Abstract

Concentrations of heme b, the iron containing prosthetic group of many hemoproteins, were measured in six species of marine phytoplankton (Dunaliella tertiolecta, Emiliania huxleyi, Thalassiosira weissflogii, Thalassiosira oceanica, Phaeodactylum tricornutum and Synechococcus sp. WH7803) subjected to variations in iron concentration. Changes in heme b in response to reduced light and nitrate were also examined for E. huxleyi and T. oceanica. Results from laboratory cultures are compared with heme b determined in particulate material in the North Atlantic. In cultures, heme b was found to make up 18 ± 14% of the total iron pool. Reduced iron and nitrate concentrations resulted in a decreased intracellular heme b concentration, expressed per mole carbon. Chlorophyll a (chl a) to heme b ratios in E. huxleyi and D. tertiolecta increased in response to limited light and nutrient availability, but slightly decreased or did not change in the diatoms and the cyanophyte Synechococcus sp. WH7803. The heme b:particulate organic carbon (POC) and chl a:heme b ratios in the North Atlantic were within the range observed in phytoplankton cultures. In the surface mixed layer, decreases in heme b:POC were linked to decreases in nutrient concentrations. Chlorophyll a to heme b ratios increased with depth and were thus primarily affected by light availability. Relative relationships between heme b, chl a and POC in the North Atlantic likely represented a change in the ability of cells to undertake cellular processes driven by chl a (light harvesting) and heme b (e.g. electron transport) according to ambient light and nutrient conditions.

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Contributors

Author: Nicola J. Pratt

Author: Anna E. Hickman

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