||Ecological stoichiometry integrates elemental fluxes, energy transfer efficiency, and prey selectivity into a comprehensive food web research framework. The central idea of ecological stoichiometry is that the mismatch between resource stoichiometry (elemental carbon:nitrogen:phosphorus ratio; C:N:P) and stoichiometric requirement of consumers hinders the carbon assimilation efficiency of consumers. Because high phytoplankton C:N and C:P ratios are disadvantageous to zooplankton growth, zooplankton would consume prey with preferred C:N:P ratio. In addition to stoichiometry, body size determines metabolic rates, and predator-prey mass ratio (PPMR, body size ratio of predator and its prey) determines food chain length in aquatic systems. Through lab-manipulated incubation experiments, stoichiometry and body size are found potential traits that influence trophic transfer efficiency and prey selection; however, evidence from in situ observations in natural aquatic food webs remains elusive. Furthermore, the interactions between body size and stoichiometry are rarely studied. Here, I examined (1) how prey stoichiometry (C:N:P ratio) influences zooplankton production, (2) how body size determines plankton stoichiometry, and (3) how nutrient and prey stoichiometry alter community PPMR in plankton grazing food webs, by in situ observations and theoretical modeling. I found that prey (phytoplankton) C:N and C:P ratios are indeed negatively correlated with zooplankton production in subtropical marine systems, indicating that N and P are essential to zooplankton. In both subtropical marine and freshwater grazing food webs, I found a unimodal C:N ratio pattern with respect to plankton body size: C:N ratio increases and reaches the maximum at 50 μm autotrophs, and then decreases with body size in heterotrophs. This pattern is explained by the accumulation of C through allometric resource affinity and respiratory C loss in my size-based food web model. The decreasing of C:N ratio with body size and heterotrophy suggests that predators prefer large prey and thus decrease PPMR when large size prey are sufficient; my field observations based on stable isotope analysis reveal that PPMR is smaller when nutrient supply is higher and supports more large prey. My research combining in situ observations and theoretical modeling point out that prey stoichiometry and size affect zooplankton production and modifies predation, indicating the important role of stoichiometry and allometry in trophic transfer efficiency in nature.|
||1. Hessen DO, Elser JJ, Sterner RW, Urabe J (2013) "Ecological stoichiometry : An elementary approach using basic principles." Limnol Oceanogr 58(6):2219–2236.|
2. Persson J, et al. (2010) "To be or not to be what you eat: Regulation of stoichiometric homeostasis among autotrophs and heterotrophs." Oikos 119(5):741–751.
3. Dickman EM, Vanni MJ, Horgan MJ (2006) "Interactive effects of light and nutrients on phytoplankton stoichiometry." Oecologia 149(4):676–689.
4. Elser JJ, et al. (2000) "Nutritional constraints in terrestrial and freshwater food webs." Nature 408:578–580.
5. Denno RF, Fagan WF (2003) "Might nitrogen limitation promote omnivory among carnivorous arthropods?" Ecology 84(10):2522–2531.
6. Hessen DO (1990) "Carbon, nitrogen and phosphorus status in Daphnia at varying food conditions." J Plankton Res 12(6):1239–1249.
7. Jensen TC, Anderson TR, Daufresne M, Hessen DO (2006) "Does excess carbon affect respiration of the rotifer Brachionus calyciflorus Pallas?" Freshw Biol 51(12):2320–2333.
8. Jensen TC, Hessen DO (2007) "Does excess dietary carbon affect respiration of Daphnia?" Oecologia 152(2):191–200.
9. Darchambeau F, Faerøvig PJ, Hessen DO (2003) "How Daphnia copes with excess carbon in its food." Oecologia 136(3):336–346.
10. Sterner RW, Elser JJ (2002) Ecological stoichiometry : the biology of elements from molecules to the biosphere (Princeton University Press, Princeton, NJ).
11. Zhang C, Jansen M, De Meester L, Stoks R (2016) "Energy storage and fecundity explain deviations from ecological stoichiometry predictions under global warming and size-selective predation." J Anim Ecol 85(6):1431–1441.
12. Vrede T, Dobberfuhl DR, Kooijman SALM, Elser JJ (2004) "Fundamental connections among organism C : N : P Stoichiometetry, macromolecular composition, and growth." Ecology 85(5):1217–1229.
13. Elser JJ, et al. (2003) "Growth rate – stoichiometry couplings in diverse biota." Ecol Lett 6:936–943.
14. Moreno AR, Martiny AC (2018) "Ecological stoichiometry of ocean plankton." Ann Rev Mar Sci 10(1):43–69.
15. Acharya K, Kyle M, Elser JJ (2004) "Biological stoichiometry of Daphnia growth: An ecophysiological test of the growth rate hypothesis." Limnol Oceanogr 49(3):656–665.
16. Main TM, Dobberfuhl DR, Elser JJ (1997) "N : P stoichiometry and ontogeny of crustacean zooplankton: A test of the growth rate hypothesis." Limnol Oceanogr 42(6):1474–1478.
17. Carrillo P, Villar-Argaiz M, Medina-Sánchez JM (2001) "Relationship between N : P ratio and growth rate during the life cycle of calanoid copepods: An in situ measurement." J Plankton Res 23(5):537–547.
18. Cebrian J, et al. (2009) "Producer nutritional quality controls ecosystem trophic structure." PLoS One 4(3):1–5.
19. Longhurst A (1984) "Importance of measuring rates and fluxes in marine ecosystems." Flows of Energy and Materials in Marine Ecosystems: Theory and Practice, ed Fasham MJR (Springer US, Boston, MA), pp 3–22.
20. Katechakis A, Haseneder T, Kling R, Stibor H (2005) "Mixotrophic versus photoautotrophic specialist algae as food for zooplankton: The light: nutrient hypothesis might not hold for mixotrophs." Limnol Oceanogr 50(4):1290–1299.
21. Andersen KH, et al. (2016) "Characteristic sizes of life in the oceans , from bacteria to whales." Ann Rev Mar Sci 8:217–243.
22. Hansen B, Bjørnsen PK, Hansen PJ (1994) "The size ratio between planktonic predators and their prey." Limnol Oceanogr 39(2):395–403.
23. Ward BA, Follows MJ (2016) "Marine mixotrophy increases trophic transfer efficiency, mean organism size, and vertical carbon flux." Proc Natl Acad Sci USA 113(11):2958–2963.
24. Fuchs HL, Franks PJS (2010) "Plankton community properties determined by nutrients and size-selective feeding." Mar Ecol Prog Ser 413:1–15.
25. Ciotti AM, Lewis MR, Cullen JJ (2002) "Assessment of the relationships between dominant cell size in natural phytoplankton communities and the spectral shape of the absorption coefficient." Limnol Oceanogr 47(2):404–417.
26. Poulin FJ, Franks PJ (2010) "Size-structured planktonic ecosystems: constraints, controls and assembly instructions." J Plankton Res 32(8):1121–1130.
27. Moorthi SD, et al. (2016) "Unifying ecological stoichiometry and metabolic theory to predict production and trophic transfer in a marine planktonic food web." Philos Trans R Soc (part B) 371:1–10.
28. Finkel Z V, Irwin AJ, Schofield O (2004) "Resource limitation alters the 3 ⁄ 4 size scaling of metabolic rates in phytoplankton." Mar Ecol Prog Ser 273:269–279.
29. Fenchel T (2014) "Respiration in heterotrophic unicellular eukaryotic organisms." Protist 165(4):485–492.
30. Banse K (1976) "Rates of growth, respiration and photosynthesis of unicellular algae as related to cell size—a review." J Phycol 12(2):135–140.
31. Lewis Jr. WM (1989) "Further evidence for anomalous size scaling of respiration in phytoplankton." J Phycol 397:395–397.
32. Tang EP, Peters RH (1995) "The allometry of algal growth rates." J Plankton Res 17(6):303–315.
33. Glazier DS (2009) "Metabolic level and size scaling of rates of respiration and growth in unicellular organisms." Funct Ecol 23:963–968.
34. West G, Brown JH, Enquist BJ (1997) "A general model for the origin of allometric scaling laws in biology." Science 276:122–126.
35. West GB, West GB, Brown JH, Enquist BJ (1999) "The fourth dimension of life : fractal geometry and allometric scaling of organisms." Science 284:1677–1679.
36. Glazier DS (2010) "A unifying explanation for diverse metabolic scaling in animals and plants." Biol Rev 85(1):111–138.
37. Glazier DS, Hirst AG, Atkinson D (2015) "Shape shifting predicts ontogenetic changes in metabolic scaling in diverse aquatic invertebrates." Proc R Soc B-Biological Sci 282(1802):1–9.
38. Moloney CL (1989) "General allometric equations for rates of nutrient uptake, ingestion, and respiration in plankton organisms." Limnol Oceanogr 34(7):1290–1299.
39. Glazier DS (2006) "The 3/4-power law is not universal: evolution of isometric, ontogenetic metabolic scaling in pelagic animals." Bioscience 56(4):325–332.
40. Jeyasingh PD (2007) "Plasticity in metabolic allometry : the role of dietary stoichiometry." Ecol Lett 10:282–289.
41. Kiørboe T, Hirst AG (2014) "Shifts in mass scaling of respiration, feeding, and growth rates across life-form transitions in marine pelagic organisms." Am Nat 183(4):E118–E130.
42. Fenchel T (1974) "Intrinsic rate of natural increase : the relationship with body size." Oecologia 14:317–326.
43. Hendriks AJ (1999) "Allometric scaling of rate , age and density parameters in ecological models." Oikos 86(2):293–310.
44. Brown JH, Gillooly JF, Allen AP, Savage VM, West GB (2004) "Toward a metabolic theory of ecology." Ecology 85(7):1771–1789.