3.2 Simulation Class: Inorganics

3.2.1 Overview

The intent of this simulation class is that it provide a framework for simulating typical water quality conditions where organic matter does not play a significant role in ecosystem processes. For example it might be used to examine basic inorganic nutrient processing in nearshore coastal environments that include relatively unimpacted sandy bed conditions, or mine voids that receive little catchment inflow. This simulation class could equally be applied to smaller, well flushed estuaries that receive relatively little catchment derived organic matter, or to basic studies of lakes and water supply reservoirs. The latter cases (amongst others) might also use this simulation class as a stepping stone towards subsequent and more detailed simulations that include organic matter cycling. This would simply require upgrade from this simulation class to the organics simulation class.

This simulation class includes the oxygen, silicate, inorganic nitrogen, inorganic phosphorus, phytoplankton and (optionally) pathogen model classes.

**Simulation Class: Inorganics (as an estuarine example)**

Figure 3.5: Simulation Class: Inorganics (as an estuarine example)

3.2.2 Model Class: Oxygen

This model class is the same as that described in Section 3.1.2.

3.2.3 Model Class: Silicate

The following constituent models are available to select from within the silicate model class.

3.2.3.1 Constituent Model: Si

The constituent model code and associated variables, processes and potentially interacting simulated quantities are provided in Figure 3.6 and Table 3.4.

**Constituent model: Si**

Figure 3.6: Constituent model: Si

Table 3.4: Constituent model properties: Si
Computed Variables Units Processes Interacting Quantities
Silicate mg/L or mmol/m\(^3\) Sediment Flux \(\cdot\quad\) Water temperature
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Sediment properties

This is a relatively simple model, with the only process requiring parameterisation being the sediment flux of silicate. By default, this process depends on overlying dissolved oxygen concentrations, but this can optionally be turned off if required.

3.2.4 Model Class: Inorganic nitrogen

The following constituent models are available to select from within the inorganic nitrogen model class.

3.2.4.1 Constituent Model: AmmoniumNitrate

The constituent model code and associated variables, processes and potentially interacting simulated quantities are provided in Figure 3.7 and Table 3.5.

**Constituent model: AmmoniumNitrate**

Figure 3.7: Constituent model: AmmoniumNitrate

Table 3.5: Constituent model properties: AmmoniumNitrate
Computed Variables Units Processes Interacting Quantities
Ammonium mg/L or mmol/m\(^3\) Sediment Flux \(\cdot\quad\) Water temperature
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Sediment properties
Nitrification \(\cdot\quad\) Water temperature
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Nitrification parameters
\(\cdot\quad\) Ammonium
Wet Atmospheric Deposition \(\cdot\quad\) Rainfall
Dry Atmospheric Deposition \(\cdot\quad\) Atmospheric parameters
Anaerobic Oxidation of Ammonium \(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Anammox parameters
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Nitrate
Dissimilatory Reduction of Nitrate to Ammonium \(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) DNRA parameters
Nitrate mg/L or mmol/m\(^3\) Sediment Flux \(\cdot\quad\) Water temperature
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Sediment properties
Nitrification \(\cdot\quad\) Water temperature
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Nitrification parameters
\(\cdot\quad\) Ammonium
Denitrification \(\cdot\quad\) Water temperature
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Denitrification parameters
\(\cdot\quad\) Nitrate
Wet Atmospheric Deposition \(\cdot\quad\) Rainfall
Dry Atmospheric Deposition \(\cdot\quad\) Atmospheric parameters
Anaerobic Oxidation of Ammonium \(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Anammox parameters
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Nitrate
Dissimilatory Reduction of Nitrate to Ammonium \(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) DNRA parameters

This is a slightly more complex model than those described previously, and this reflects the complexity of inorganic nitrogenous environmental chemistry. In addition to specification of two computed variables and their respective sediment flux properties, rates and related parameters for nitrification and denitrification are also specifiable. By design, the library defaults for these processes are set to zero so that all processes are initially inactive. Users may activate these processes by specifying non-zero rate parameters.

Whilst dissolved oxygen potentially modifies some processes described to this point (e.g. computed sediment flux rates), nitrification is the first of these processes that also potentially consumes dissolved oxygen. Specifically, if nitrification is simulated (i.e. non-zero rate parameters are specified) and allowed to include the effect of dissolved oxygen (the default), then dissolved oxygen concentrations are drawn down as the process operates.

Table 3.6: Complementary lower order computed variables: AmmoniumNitrate
Computed Variables Units Processes Interacting Quantities
Dissolved Oxygen mg/L or mmol/m\(^3\) Nitrification \(\cdot\quad\) Water temperature
\(\cdot\quad\) Nitrification parameters
\(\cdot\quad\) Ammonium

3.2.5 Model Class: Inorganic phosphorus

The following constituent models are available to select from within the phosphorus model class.

3.2.5.1 Constituent Model: FRPhs

The constituent model code and associated variables, processes and potentially interacting simulated quantities are provided in Figure 3.8 and Table 3.7.

**Constituent model: FRPhs**

Figure 3.8: Constituent model: FRPhs

Table 3.7: Constituent model properties: FRPhs
Computed Variables Units Processes Interacting Quantities
FRP mg/L or mmol/m\(^3\) Sediment Flux \(\cdot\quad\) Water temperature
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Sediment properties
Wet Atmospheric Deposition \(\cdot\quad\) Rainfall

This is a relatively simple constituent model, but one that is critical to the simulation of higher order computed variables such as phytoplankton.

3.2.5.2 Constituent Model: FRPhsAds

The constituent model code and associated variables, processes and potentially interacting simulated quantities are provided in Figure 3.9 and Table 3.8.

**Constituent Model: FRPhsAds**

Figure 3.9: Constituent Model: FRPhsAds

Table 3.8: Constituent model properties: FRPhsAds
Computed Variables Units Processes Interacting Quantities
FRP mg/L or mmol/m\(^3\) Sediment Flux \(\cdot\quad\) Water temperature
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Sediment properties
Wet Atmospheric Deposition \(\cdot\quad\) Rainfall
Adsorption and Desorption \(\cdot\quad\) Suspended solids
\(\cdot\quad\) FRP
\(\cdot\quad\) Adorption parameters
FRP Adsorbed mg/L or mmol/m\(^3\) Adsorption and Desorption \(\cdot\quad\) Suspended solids
\(\cdot\quad\) FRP
\(\cdot\quad\) Adorption parameters
Settling \(\cdot\quad\) Suspended solids
\(\cdot\quad\) Suspended solids settling parameters
Dry Atmospheric Deposition \(\cdot\quad\) Atmospheric parameters

In order for this constituent model to be used, the TUFLOW FV Sediment Transport (ST) Module must be activated to simulate at least one fraction of suspended sediment (several fractions may be so set). A WQ Module simulation will not start if the TUFLOW ST Module is not activated. In order to use this FRPhsAds constituent model therefore, the following must be in place:

  • The TUFLOW FV ST Module must be activated and implemented
  • At least one sediment fraction must be set up and executed within TUFLOW FV via the inclusion of a sediment control file, and specification of either of the following TUFLOW FV commands:

  Include Sediment == 1,0   ! Do not include sediment in density calculations

  or

  Include Sediment == 1,1   ! Include sediment in density calculations

If multiple sediment fractions are specified to be simulated by the ST Module, then TUFLOW FV sends all these fraction concentrations as a sum through the API to the WQ Module, and this sum is used as the sediment concentration against which adsorption is computed. The WQ Module uses this information to compute FRP adsorption and loss of adsorbed FRP through settling. It is recognised that there are limitations of this approach. Future releases of TUFLOW FV and the WQ Module will address some of these limitations and allow for:

  • User control of which ST Module sediment fractions are used in adsorption calculations, and
  • Use of the TUFLOW FV ST Module settling and resuspension routines to dynamically link settling and resuspension of adsorbed FRP

3.2.6 Model Class: Phytoplankton

The following constituent models are available to select from within the phytoplankton model class. The differentiator between constituent models is the treatment of internal (to a phytoplankton cell) nutrient simulation.

3.2.6.1 Constituent Model: Basic

This basic phytoplankton constituent model assumes that the ratios of both internal nitrogen and phosphorus concentrations to internal chlorophyll a (or carbon) concentration are fixed. These internal nutrients are not simulated explicitly, but increase and decrease proportionately with increasing and decreasing carbonaceous biomass, according to the specified (or default) nitrogen-chlorophyll a and phosphorus-chlorophyll a (or their carbon equivalents) ratios. Carbonaceous biomass is simulated dynamically and is the measure of phytoplankton concentration. Internal nutrient concentrations are not required to be specified as initial or boundary conditions, and are not treated as computed variables.

The constituent model code and associated computed variables, processes and potentially interacting simulated quantities are provided in Figure 3.10 and Table 3.9. Silicate interactions only apply if phytoplankton is set to uptake silicate via specification of silicate limitation function parameters (section 4.7.3.5.1). The configuration for phytoplankton simulation presented below applies only to the inorganics simulation class. A different, and expanded, configuration applies when phytoplankton is simulated using this basic constituent model in the organics simulation class. This expanded configuration is described in section 3.3.7.1.

**Constituent model: Basic**

Figure 3.10: Constituent model: Basic

Table 3.9: Constituent model properties: Basic
Computed Variables Units Processes Interacting Quantities
Phytoplankton \(\mu\)g Chl a/L or mmol C/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Nitrate
\(\cdot\quad\) FRP
\(\cdot\quad\) Silicate (if activated)
Respiration \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Dissolved oxygen
Excretion \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Silicate (if activated)
Mortality \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Silicate (if activated)
Settling \(\cdot\quad\) Settling model
\(\cdot\quad\) Cell density

The three processes that govern phytoplankton behaviour are:

  • Primary productivity (the photosynthetic conversion of light and carbon to stored energy and oxygen, also referred to as growth)
  • Respiration (the expenditure of stored energy and oxygen), and
  • Settling

A range of light, temperature, salinity, nitrogen, phosphorus and silicate limitation functions can be parameterised and applied in various combinations to the first two processes above, and a range of settling models are available to tailor the third. By design, the associated library default rates are set to zero so as to render all processes initially inactive. Specification of non-zero rates activates these processes.

The distinguishing property of this phytoplankton constituent model is that internal (phytoplankton cell) nutrient concentrations are considered to be fixed proportions of cell chlorophyll a (or carbon) concentrations. They are therefore not treated as computed variables, but rather as multiples of phytoplankton chlorophyll a (or carbon) (which is treated as a computed variable). The key implication of this is the method of calculation of the nitrogen and phosphorus uptake and limitation functions applied to primary productivity. These calculations depend only on ambient (i.e. external to a phytoplankton cell) water column nitrogen and phosphorus concentrations.

Simulation of phytoplankton dynamics in the inorganics simulation class directly modifies the concentrations of a range of other computed variables. These are listed in Table 3.10. Silicate interactions only apply if phytoplankton is set to uptake silicate.

Table 3.10: Complementary lower order computed variables: Basic
Computed Variables Units Processes Interacting Quantities
Dissolved Oxygen mg/L or mmol/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Nitrate
\(\cdot\quad\) FRP
\(\cdot\quad\) Silicate (if activated)
Respiration \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
Ammonium mg/L or mmol/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Nitrate
\(\cdot\quad\) FRP
\(\cdot\quad\) Silicate (if activated)
Excretion \(\cdot\quad\) FRP
\(\cdot\quad\) Silicate (if activated)
Mortality \(\cdot\quad\) FRP
\(\cdot\quad\) Silicate (if activated)
Nitrate mg/L or mmol/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Silicate (if activated)
FRP mg/L or mmol/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Nitrate
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Silicate (if activated)
Excretion \(\cdot\quad\) Ammonium
\(\cdot\quad\) Silicate (if activated)
Mortality \(\cdot\quad\) Ammonium
\(\cdot\quad\) Silicate (if activated)
Silicate (if activated) mg/L or mmol/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Nitrate
\(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
Excretion \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
Mortality \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP

3.2.6.2 Constituent Model: Advanced

This phytoplankton constituent model directly simulates internal (phytoplankton cell) nitrogen and phosphorus concentrations. These are allowed to vary between upper and lower limits, expressed as ratios to chlorophyll a (or carbon) concentrations. Internal nutrient concentrations (not as ratios) are required to be specified as initial and boundary conditions, and are treated as computed variables.

The constituent model code and associated variables, processes and potentially interacting simulated quantities are provided in Figure 3.11 and Table 3.11. Silicate interactions only apply if phytoplankton is set to uptake silicate. The configuration for phytoplankton simulation presented below applies only to the inorganics simulation class. A different, and expanded, configuration applies when phytoplankton is simulated using this advanced constituent model in the organics simulation class. This expanded configuration is described in section 3.3.7.2.

**Constituent model: Advanced**

Figure 3.11: Constituent model: Advanced

Table 3.11: Constituent model properties: Advanced
Computed Variables Units Processes Interacting Quantities
Phytoplankton \(\mu\)g Chl a/L or mmol C/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Nitrate
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if activated)
Respiration \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
Excretion \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if activated)
Mortality \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if activated)
Settling \(\cdot\quad\) Settling model
\(\cdot\quad\) Cell density
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
Internal Nitrogen mg N/L or mmol N/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Nitrate
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if activated)
Uptake \(\cdot\quad\) Water temperature
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Nitrate
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if activated)
Respiration \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Internal phosphorus
Excretion \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if activated)
Mortality \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if activated)
Settling \(\cdot\quad\) Settling model
\(\cdot\quad\) Cell density
\(\cdot\quad\) Internal phosphorus
Internal Phosphorus mg P/L or mmol P/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Nitrate
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Silicate (if activated)
Uptake \(\cdot\quad\) Water temperature
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Nitrate
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Silicate (if activated)
Respiration \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Dissolved oxygen
\(\cdot\quad\) Internal nitrogen
Excretion \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Silicate (if activated)
Mortality \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Silicate (if activated)
Settling \(\cdot\quad\) Settling model
\(\cdot\quad\) Cell density
\(\cdot\quad\) Internal nitrogen

The three processes that govern phytoplankton behaviour are:

  • Primary productivity (the photosynthetic conversion of light and carbon to stored energy and oxygen, also referred to as growth)
  • Respiration (the expenditure of stored energy and oxygen), and
  • Settling

A range of light, temperature, salinity, nitrogen, phosphorus and silicate limitation functions can be parameterised and applied in various combinations to the first two processes above, and a range of settling models are available to tailor the third. By design, the associated library default rates are set to zero so as to render all processes initially inactive. Specification of non-zero rates activates these processes.

The distinguishing property of this phytoplankton constituent model is that internal (phytoplankton cell) nutrient concentrations are simulated directly. They are therefore treated as computed variables. The key implication of this is the method of calculation of the nitrogen and phosphorus uptake and limitation functions applied to primary productivity. These calculations depend on both internal nutrient stores and ambient (i.e. external to a phytoplankton cell) water column nitrogen and phosphorus concentrations.

Simulation of phytoplankton dynamics in the inorganics simulation class directly modifies the concentrations of a range of other computed variables. These are listed in Table 3.12. Silicate interactions only apply if phytoplankton is set to uptake silicate.

Table 3.12: Complementary lower order computed variables: Advanced
Computed Variables Units Processes Interacting Quantities
Dissolved Oxygen mg/L or mmol/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Nitrate
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if simulated)
Respiration \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
Ammonium mg/L or mmol/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Nitrate
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) FRP
\(\cdot\quad\) Silicate (if simulated)
Excretion \(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if simulated)
Mortality \(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if simulated)
Nitrate mg/L or mmol/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) FRP
\(\cdot\quad\) Silicate (if simulated)
FRP mg/L or mmol/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Nitrate
\(\cdot\quad\) Ammonium
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if simulated)
Excretion \(\cdot\quad\) Ammonium
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if simulated)
Mortality \(\cdot\quad\) Ammonium
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
\(\cdot\quad\) Silicate (if simulated)
Silicate (if simulated) mg/L or mmol/m\(^3\) Primary Productivity \(\cdot\quad\) Water temperature
\(\cdot\quad\) Salinity
\(\cdot\quad\) Light
\(\cdot\quad\) Nitrate
\(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
Excretion \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus
Mortality \(\cdot\quad\) Ammonium
\(\cdot\quad\) FRP
\(\cdot\quad\) Internal nitrogen
\(\cdot\quad\) Internal phosphorus

3.2.7 Model Class: Pathogens (optional)

This model class is the same as that described in Section 3.1.3.

3.2.8 Computed variables

The relationships between all available computed variables and processes is this inorganics simulation class are presented in Figure 3.12. Depending on the constituent model classes deployed, not all of the computed variables and processes shown in the figure will necessarily be active. All network link labels have been removed (other than denoting the relevant phytoplankton model), and optional non-interacting model classes (e.g. pathogens) omitted, for clarity.

**Simulation class: Inorganics**

Figure 3.12: Simulation class: Inorganics