# From NIMSAQ to an Application Example Calculating River

• Slides: 12

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. Carbon dioxide (g) + water (l) + photons oxygen (g) + glucose (aq) + water (l) -Respiration (R): Portion of that fixed energy is lost through autotrophic respiration 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). -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. -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. (instantaneous) (daily)

The open-system dissolved oxygen (DO) change method Metabolism Rate of change of DO per area Rate of GPP per area Rate CR per area Diffusion rate per area GW accrual per area (usually assumed negligible) Modified from Odum (1956) Single-station Method: Q or q: is the rate of DO change between two consecutive sampling times.

The open-system O 2 change 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 -Undersaturated: O 2 in, -Supersaturated: O 2 out, - Gross primary productivity River Lark (England). Source: Odum (1956)

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/m 2 -min Pink line: average community respiration (CR 24) Green line: Gross Primary Productivity (GPP) 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?