Complications in the determination of the nutrient status of the marine environment.

How much of the organic matter in the oceans is truly bioavailable under in situ conditions? This bioavailability may be altered by perturbation, priming, bottle (surface or confinement) effects, and air contaminants. Measured free organic matter may not be free in situ but may depend on method of analysis. We have yet to determine the threshold energy for growth of microbes and their energy of maintenance under in situ conditions.