Nitrogen is a major limiting factor in seaweed cultivation and when nitrogen becomes limiting nori loses its
pigmentation and can even bleach. Nitrogen depletion often leads to an increased flow in the products of photosynthesis
being turned into carbohydrates and lipids. Furthermore, it is important to remember that the pigmentation
of nori is closely linked with the availability of nitrogen. In recirculating systems, nitrogen will be
supplied in the form of ammonia (if the fed crop is fish or shrimp), which will then be taken up by the nori and
converted into phycobilin pigments and other nitrogenous compounds. In the absence of adequate nitrogen,
nori can mobilize phycobilins as nitrogen stores for use in photosynthesis and other metabolic functions, resulting
in a loss in pigmentation.