We measured the elemental composition of single cells from six strains of marine Prochlorococcus and two strains of marine Synechococcus by X‐ray microanalysis in the transmission electron microscope (TEM), which allows measurements of all major elements in cells without any fixation or staining. The mean carbon : volume ratios ranged from 136 to 280 fg µm −3 in Prochlorococcus and 138 to 290 fg µm −3 in Synechococcus . Using...

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...

An enclosure experiment was performed in the brackish layer of a Norwegian fjord, a system where both phytoplankton and bacterial growth have previously been hypothesized to be phosphorus (p) limited. All enclosures had a succession pattern characterized by an initial autotrophic phase with positive net community production, increasing phytoplankton primary production, and chlorophyll, followed by a heterotrophic phase with de...