Secondary Production
Carbon or energy that is transferred to consumers
Ultimately from primary producers, could be from other consumers (1o to 2o)
1. Fate of energy and materials in a food web.
a. Energy used and not used.
2. How do we measure components of secondary productivity?
a. Each species is measured separately
b. Gross energy intake measured by feeding rate (observation, loss food)
c. Assimilated or metabolized energy measured laboratory monitor intake
By difference know gross intake & monitor outputs (feces, urine)
Assimilation energy = Gross intake - egested - waste (urine)
d. Respiration rate: confine org. measure respiration (heat, CO2, O2)
i. Basal metabolism
ii. May not represent field metabolic rates different organisms
e. •Field use doubly labeled water-inject animals water 3H2O18 loss rate isotopes H & O
f. Some animals have relationship between field metabolic rate & body mass
i. Different for mammals, birds and reptiles (>dependent on temperature)
g. Use population changes to calculate secondary net production.
3. Problems with estimating Secondary Production of a Community
a. Individuals do not fit into neat trophic levels (upper levels particularly)
Some herbivores can be carnivorous & vice versa
b. What to do with detritus “the decomposer food-web”
c. Dynamics of many communities unrealistic define 2ndary production
Thus, approach is to investigate each species separately-taxonomically
Not try to determine the entire 2ndary Production rate of a Community
4. Ecological Efficiencies of Energy Transfer in Secondary Production-species level
a. View animals as energy transformers
b. Production efficiency = net productivity spp. n/ assimilation of species n
c. Respiration uses up 97 to 99% energy assimilated in mammals/birds d. Thus, only 1 to 3% energy goes to net production
5. Trophic Efficiencies of Energy Transfer in Secondary Production – trophic level
a. Efficiency energy transfer from one trophic level to next
b. Use information to calculate the amount of primary production required
c. Trophic efficiency = net production (NP) at trophic level (TL) i+1/ NP at TL i
d. If trophic efficiencies are ~10%, then each level food chain 10xs loss C
e. How much 1o production can support how much 2ndary production ocean?
Average 8% global aquatic primary production used fisheries catch
Some regions high fish production up to 25% total 1o prod. used
Little margin of error for building up & maintaining populations?
f. Terrestrial Ecosystems Differ Aquatic Systems in Energy Transfer
Majority of the Carbon goes through detritus & decomposers (96%)
g. Comparing among Ecosystems in role of decomposers vs herbivores
Aquatic ecosystems more direct grazing of plants by herbivores
Terrestrial system more plant material goes through detritivores
Results in differences standing crop different systems
6. Eltonian pyramid
a. A result of Ecological Efficiencies
7. What limits Secondary Production?
Direct relationship between 1o and 2ndary Production
> Scatter so other factors also important.
Then question becomes, what limits 1o production
Leads to a focus on nutrient cycling
8. Summary:
Organic matter (C) produced green plants transferred to higher consumers
Majority matter or energy lost as waste & respiration
Warm-blooded vertebrates 98% energy intake used maintenance
Invertebrates & fish typically 60-90% maintenance (still high)
Data on efficiency 2ndary production primarily obtained at species level
More problematic trying determine 2ndary production ecosystem
Each step food chain high loss energy-thus pyramid of mass move up chain
Flow of energy different aquatic (herbivores) vs terrestrial (detritus) systems
Knowing these flows for different environments important management
Nutrient Cycling may be important understand linkage of 1o & 2ndary Prod.