[8] As a diazotrophic cyanobacterium that has oxygen-evolving photosystem II, one of the ways by which Crocosphaera watsonii protects its nitrogenase from oxygen is through the adaptation of a diel rhythm.

Consistent with this, many genes involved in nitrogen fixation and photosynthesis show variation in transcription between day and night.

Another method by which Crocosphaera watsonii protects its nitrogen fixing enzyme complexes, which is unique to this species, is through its ability to shut down photosystem II.

[12] Crocosphaera watsonii also slows its electron transfer rate closer to the dark period, and the cell transitions itself to shut down its photosystem.

[13] Regulating photosystem II in Crocosphaera watsonii is a fast process, and it can be inactivated or activated immediately when needed.

Crocosphaera watsonii, which contributes significantly to oceanic nitrogen fixation,[14][15][16][17] is limited by iron as is also the case for other marine diazotrophs.

[14][22][5] To overcome the challenge of iron scarcity, Crocosphaera watsonii has come up with a unique mechanism that involves reduction of metalloenzyme inventories.

Because Crocosphaera watsonii lives in oligotrophic waters, it can be limited by a variety of nutrients, including dissolved inorganic phosphate.

[3][25] During times of phosphorus stress, Crocosphaera watsonii is shown to have increased levels of pstS transcription.

PstS transcript levels in Crocosphaera watsonii instead correspond to the diel cycle, peaking at the end of the light phase.

[24][25][1] Another method to measure phosphorus stress in Crocosphaera watsonii is to look at arsenic concentrations within the cell.

As a response, Crocosphaera watsonii will upregulate arsB levels, which will remove the excess arsenic from within the cell.