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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

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Secondary production and consumer energetics

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  1. 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

  2. Ingestion (I) →

  3. I = A + E Ingestion (I) → Assimilation (A) Egestion (E) →

  4. I = A + E A = R + P (+ U) Respiration (R) → Ingestion (I) → Assimilation (A) Growth (G), or Production (P) Egestion (E) → (Excretion (U))

  5. 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))

  6. What affects rates of energy flow?

  7. Temperature affects energetic rates(Q10 ~2) Peters 1983

  8. Body size affects energetic rates(~M-0.25) Peters 1983

  9. Homeothermy/heterothermy affects energetic rates Peters 1983

  10. Metabolic rates are evolutionarily flexible Data on flatworms from Gourbault 1972

  11. Ecological efficiencies A/I = assimilation efficiency P/A = net growth efficiency P/I = gross growth efficiency

  12. Typical values of ecological efficiencies

  13. What affects ecological efficiencies (partitioning of energy)?

  14. Assimilation efficiency depends on food quality Valiela 1984

  15. Bacterial growth efficiency depends on food quality Del Giorgio and Cole 1998

  16. Bacterial growth efficiency depends on temperature Rivkin and Legendre 2001

  17. 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

  18. 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?

  19. How do we estimate secondary production? • Tracer methods • Demographic methods • Turnover methods • Empirical methods

  20. How do we estimate secondary production?

  21. Controls on/prediction of secondary production • Individual populations • Guilds of consumers • Entire communities

  22. 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

  23. 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

  24. Predicting secondary production:(1) individual populations Q10 ~ 2.5 Tumbiolo and Downing 1994

  25. Predicting secondary production:(1) individual populations Tumbiolo and Downing 1994

  26. 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?

  27. Predicting secondary production: (2) guilds (aquatic bacterial production as a function of phytoplankton production – Cole et al. 1988)

  28. Predicting secondary production: (2) guilds (aquatic invertebrate production in experimentally manipulated streams (Wallace et al. 1999)

  29. Predicting secondary production: (2) guilds (terrestrial animal production as a function of primary production – McNaughton et al. 1991) (V=vertebrates, I=invertebrates)

  30. Activity of consumer guilds rises roughly linearly with food supply

  31. Nutrients affect production of guilds Cross et al. 2006

  32. 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)

  33. 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)

  34. 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

  35. Predicting secondary production: (3) entire communities

  36. Predicting secondary production: (3) entire communities S = R + L, so R = S – L (S = net supply of organic matter, L = non-respiratory losses)

  37. 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)

  38. 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)

  39. 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)

  40. 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)

  41. 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

  42. Predicting secondary production: (3) entire communities

  43. 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)

  44. 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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