Does competition for nanomolar phosphate supply explain the predominance of the cyanobacterium Synechococcus ?

Abstract

Experimental work during a cruise along a W‐E transect in the Mediterranean Sea suggests that (1) orthophosphate concentrations in the upper photic zone show a decreasing trend from the west to the east reaching levels well below 1 nM and (2) microorganisms in the 0.6–2ߝµm size fraction, probably Synechococcus , have, in addition to high affinity for orthophosphate, significantly higher maximum uptake rates than heterotrophic bacteria or eukaryotic algae. These specific advantages concerning orthophosphate uptake at low ( Synechococcus abundance in P‐depleted environments and transient blooms of this species in the open ocean where episodic orthophosphate nanopulse events are likely to occur.

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