From NIMS-AQ to
an Application Example
Calculating
River Metabolism:
The case of a river confluence
River Metabolism:
Primary Productivity and Community Respiration
-Primary productivity (GPP): Rate of formation of organic matter from inorganic carbon
by photosynthesizing organisms and represents the conversion of solar energy to
reduced chemical energy.
6CO2
 12H 2O 
photons  6O2
 C6 H12O6
 6 H 2O
Carbon dioxide (g) + water (l) + photons  oxygen (g) + glucose (aq) + water (l)
-Respiration (R): Portion of that fixed energy is lost through autotrophic respiration
C6 H12O6
 6O2  6CO2
 6H 2O  energy
Glucose + oxygen  carbon dioxide + water + energy
Then, photosynthesis stores energy, and respiration releases it for use in functions
such as reproduction and basic maintenance.
We calculate Primary Productivity and Respiration in lotic
ecosystems because:
-They help to determine ecosystem biomass (i.e. how much energy is
available to support an ecosystem).
-They help to understand the trophic structure, thus to evaluate the
potential for competition for food.
-They serve as indicators of river health when compared with
undisturbed sites or when comparing over periods of time (e.g.
changes in Net Primary Productivity can be symptomatic of stresses).
Some Key terms:
Gross Primary Productivity, the total fixed energy, is the sum of the portion of energy
stored in biomass (Net Primary Productivity) + the portion that is lost through
autotrophic respiration (Ra).
GPP  NPP  Ra
-Community Respiration is the sum of the autotrophic and heterotrophic respiration.
We use it because so far it’s not possible to measure them separately.
CR  Ra  Rh
-While NPP is the net amount of primary production after the costs of plant respiration
are included, Net Ecosystem Production (NEP), Net Community Production (NCP), or
Net Daily Metabolism (NDM) is the amount of primary production after the costs of
respiration by autotrophs and heterotrophs are all included.
NEP  GPP  CR
NDM  GPP  CR24
(instantaneous)
(daily)
The open-system dissolved oxygen (DO) change method
Metabolism
Q  PRD A
M L2 T 1
Q : Rate of change of DO per area
P : Rate of GPP per area
R : Rate CR per area
D : Diffusion rate per area
A : GW accrual per area (usually assumed negligible)
q  pr d a
3
ML T
1
Modified from Odum (1956)
Single-station Method:
Q or q: is the rate of DO change between two consecutive sampling times.
The open-system O2 change
q  p  r  din  a  M L3 T 
Observed diel (24 h) DO cycle
Light penetration
Rate of change of DO per hour
Community respiration
Diffusion in or out of the stream water according to
water DO saturation
q  p  r  din
-Undersaturated: O2 in,
-Supersaturated: O2 out, q  p  r  dout
- Gross primary productivity
River Lark (England). Source: Odum (1956)
p  q  r  din
p  q  r  dout
Calculation of river metabolism using NIMS data
The confluence by the time of the experiment
Calculation of river metabolism using NIMS data
* Upstream view
Dissolved Oxygen
(mg / L)
Merced River zone
Mixing zone
San Joaquin River
zone
Temperature (C)
Merced River Zone
San Joaquin River Zone
Day 1
Day 2
Day 3
Units: gr/m2-min
Pink line: average
community respiration
(CR24)
Green line: Gross
Primary Productivity
(GPP)
hour
hour
Zone 1: Merced River zone
Zone 2: Mixing zone
Zone 3: San Joaquin River zone
Future Directions:
-Evaluation of the effects of irrigation returns at a river reach.
- Groundwater-surface water interactions and their effect on river biota.
-Association of those distributed physicochemical parameters to
Ecosystem diversity?