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Secondary production and consumer energetics. The consumer energy budget Determinants of energy flow Ecological efficiencies Definition of secondary production Measurement of secondary production Predicting secondary production For individual populations For guilds of consumers

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secondary production and consumer energetics
Secondary production and consumer energetics
  • The consumer energy budget
  • Determinants of energy flow
  • Ecological efficiencies
  • Definition of secondary production
  • Measurement of secondary production
  • Predicting secondary production
    • For individual populations
    • For guilds of consumers
    • For the entire community of consumers
slide4

I = A + E

Ingestion (I)

Assimilation (A)

Egestion (E)

slide5

I = A + E

A = R + P (+ U)

Respiration (R)

Ingestion (I)

Assimilation (A)

Growth (G), or Production (P)

Egestion (E)

(Excretion (U))

slide6

I = A + E

A = R + P (+U)

Respiration (R)

=loss of useful energy

Ingestion (I)

=loss to prey

population

Assimilation (A)

=energy available to consumer

Growth (G), or Production (P)

=energy available to predators

Egestion (E)

=input to detritus

(Excretion (U))

metabolic rates are evolutionarily flexible
Metabolic rates are evolutionarily flexible

Data on flatworms from Gourbault 1972

ecological efficiencies
Ecological efficiencies

A/I = assimilation efficiency

P/A = net growth efficiency

P/I = gross growth efficiency

introduction to secondary production
Introduction to secondary production
  • “All non-photosynthetic production (growth), regardless of its fate”
  • NOT the same as biomass accumulation
  • NOT just the production of herbivores
  • Much better studied than other parts of the consumer energy budget
    • Easier to measure
    • Historically considered more important
secondary production is aquatic and empirical
Secondary production is aquatic and empirical
  • 167 papers published on subject in 2005
  • 52% marine or estuarine, 35% freshwater, 3% terrestrial
  • 55% microbial, 39% invertebrate, 7% vertebrate
  • Very little theoretical work
  • Are generalizations about secondary production really generalizations about aquatic ecosystems?
how do we estimate secondary production
How do we estimate secondary production?
  • Tracer methods
  • Demographic methods
  • Turnover methods
  • Empirical methods
controls on prediction of secondary production
Controls on/prediction of secondary production
  • Individual populations
  • Guilds of consumers
  • Entire communities
predicting secondary production 1 individual populations
Predicting secondary production:(1) individual populations
  • Marine benthic invertebrates
  • Log10(P) = 0.18 + 0.97 log10(B)
  • - 0.22 log10(W) + 0.04 (T)
  • – 0.014 (T*log10depth)
  • R2 = 0.86, N = 125

Tumbiolo and Downing 1994

predicting secondary production 1 individual populations1
Predicting secondary production:(1) individual populations
  • Marine benthic invertebrates
  • Log10(P) = 0.18 + 0.97 log10(B)
  • - 0.22 log10(W) + 0.04 (T)
  • – 0.014 (T*log10depth)
  • R2 = 0.86, N = 125

Tumbiolo and Downing 1994

predicting secondary production of individual populations
Predicting secondary production of individual populations
  • Feasible if you know mean annual biomass, body size, and temperature
  • Very imprecise
  • If you’re going to measure mean annual biomass, why not just estimate production directly?
predicting secondary production 2 guilds
Predicting secondary production: (2) guilds

(aquatic bacterial production as a function of phytoplankton production – Cole et al. 1988)

predicting secondary production 2 guilds1
Predicting secondary production: (2) guilds

(aquatic invertebrate production in experimentally manipulated streams (Wallace et al. 1999)

predicting secondary production 2 guilds2
Predicting secondary production: (2) guilds

(terrestrial animal production as a function of primary production – McNaughton et al. 1991) (V=vertebrates, I=invertebrates)

predicting secondary production or ingestion 2 guilds
Predicting secondary production (or ingestion): (2) guilds

Aquatic is white (left) or blue (center and right); terrestrial is black (left) or green (center and right)

(Cebrian and Lartigue 2004)

terrestrial aquatic differences
Terrestrial/aquatic differences
  • Herbivores ingest a higher proportion of NPP in aquatic systems (higher nutrient content of NPP)
  • Herbivore production possibly much higher in aquatic systems (higher ingestion, higher assimilation efficiency?, less homeothermy so higher net growth efficiency)
predicting secondary production of guilds
Predicting secondary production of guilds
  • Predictable (and linear?) from resource supply
  • Too imprecise to be very useful as a predictor
  • Maybe strong terrestrial/aquatic differences arising from nutrient content of primary producers
  • Nutrients as well as energy affect guild production
predicting secondary production 3 entire communities1
Predicting secondary production: (3) entire communities

S = R + L, so R = S – L

(S = net supply of organic matter, L = non-respiratory losses)

predicting secondary production 3 entire communities2
Predicting secondary production: (3) entire communities

S = R + L, so R = S – L

εng = P/(P + R), so P = εng(P + R)

(εng = net growth efficiency,

S = net supply of organic matter, L = non-respiratory losses)

predicting secondary production 3 entire communities3
Predicting secondary production: (3) entire communities

S = R + L, so R = S – L

εng = P/(P + R), so P = εng(P + R)

Therefore, P = εng(P + S – L)

predicting secondary production 3 entire communities4
Predicting secondary production: (3) entire communities

S = R + L, so R = S – L

εng = P/(P + R), so P = εng(P + R)

Therefore, P = εng(P + S – L);

Rearranging, P(1- εng) = εng(S – L)

predicting secondary production 3 entire communities5
Predicting secondary production: (3) entire communities

S = R + L, so R = S – L

εng = P/(P + R), so P = εng(P + R)

Therefore, P = εng(P + S – L);

Rearranging, P(1- εng) = εng(S – L)

And P = (S – L)εng/(1 – εng)

predicting secondary production 3 entire communities6
Predicting secondary production: (3) entire communities

P = (S – L) εng/(1 – εng)

A = (S – L)/(1 – εng)

I = (S – L)/(εa(1 - εng))

εa = assimilation efficiency, εng = net growth efficiency,

S = net supply of organic matter, L = non-respiratory losses

predicting secondary production of entire communities
Predicting secondary production of entire communities
  • Secondary production is large compared to primary production (if NGE=30%, secondary production = 43% of NPP)
  • Decomposers see a lot of consumer tissue (not just plant tissue)
  • Secondary production is larger in systems dominated by heterotherms than in systems dominated by homeotherms
  • Energy available for ingestion and assimilation by consumers is greater than primary production (if NGE=30% and AE = 20%, A=143% of NPP, I = 714% of NPP)
conclusions
Conclusions
  • It’s easier to predict the secondary production of an entire community than a single population
  • Consumer activity is tightly linked with other processes that control the movement and fate of organic matter
  • When considered at the community level, secondary production (maybe) is controlled by the same factors that control primary production: supply of energy and nutrients, and their retention
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