Appendix I Processes: phyto biomass rates
The rates that determine the temporal evolution of a phytoplankton group’s biomass are primary productivity, respiration, exudation and settling. In general terms these processes can be thought of as follows:
- Primary productivity is the consumption of carbon and the generation of oxygen and carbohydrate due to photosynthesis. Photosynthetically active radiation catalyses this process so it occurs only during daylight hours. This process is also referred to as growth or gross primary productivity
- Respiration is the consumption of oxygen and stored carbohydrate and the production of carbon. This can be thought of as the reverse of primary productivity. Respiration dominates phytoplankton dynamics during nighttime hours, although it generally still operates during the daytime
- Exudation (also referred to as photo exudation) is the loss of phytoplankton biomass as a result of primary productivity
- Settling is the physical settling of phytoplankton, including motility
The general form of the phytoplankton flux relationship for any given computational cell is therefore given by Equation (I.1).
\[\begin{equation} F^{phy} = \text{Primary productivity} - f(\text{Respiration, Exudation}) - \text{Settling} \tag{I.1} \end{equation}\]
\(f\) represents functions described in Appendix L. The fundamental rates in Equation (I.1) - primary productivity, respiration, exudation and settling - are described following.