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Succession in a water column An adapting ecosystem maneuvering between autotrophy and heterotrophy

Explore the adaptable nature of ecosystem species, shifting between autotrophy and heterotrophy. Study the complex patterns and dynamics influencing biomass, biodiversity, and nutrient fluxes. Discuss the traits defining species strategies over time and space, driven by environmental changes and niche presence. Analyze trait distributions using quantitative genetics and adaptation theories. Delve into the role of phytoplankton and bacteria in ecosystem dynamics, with implications for community structure and evolution.

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Succession in a water column An adapting ecosystem maneuvering between autotrophy and heterotrophy

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  1. Succession in a water columnAn adapting ecosystem maneuvering between autotrophy and heterotrophy Jorn Bruggeman Theoretical biology Vrije Universiteit Amsterdam

  2. NO3- NH4+ DON labile stable Ecosystem building blocks: species nitrogen phytoplankton zooplankton detritus • Differential changes in abundance produce patterns of interest • total biomass: chlorophyll concentrations, prey fields, fish stocks • mass fluxes: carbon exports • individual abundances: harmful algae • total number of species: biodiversity indices Forever incomplete , severely underdetermined , no initial state available

  3. 1. Omnipotent population • Standardization: one model for all species • Dynamic Energy Budget theory (Kooijman 2000) • Species differ in allocation to strategies • Allocation parameters: traits generic species defense predation heterotrophy autotrophy size

  4. 2a. Continuity in traits: distributions Phototrophs and heterotrophs: a section through diversity bact 1 heterotrophy bact 2 bact 3 ? ? ? mix 1 mix 2 mix 3 ? phyt 1 mix 4 ? phyt 2 ? phyt 2 phyt 3 phototrophy

  5. 2b. Species projection in trait space Discrete distribution Continuous approximation

  6. 3. Succession & persistence of species • The environment changes • External forcing (light, mixing) • Ecosystem dynamics (e.g. depletion of nutrients) • Changing environment drives succession • Best strategy will be time- and space-dependent • Trait value combinations define species & strategy • Trait distribution will change in space and time • “Everything is everywhere; the environment selects” • Assumption: background concentrations of all possible species • Actual invasion will depend on niche presence

  7. Dynamics of the trait distribution Trait distribution approximated by a normal distribution: trait specific growth rate total biomass trait mean trait variance total biomass mean Lande (1976) – quantitative genetics Abrams at al. (1993) – adaptation Wirtz & Eckhardt (1996) – ecosystem dynamics Dieckmann & Law (1996) – evolution Norberg et al. (2001) – ecosystem dynamics variance • Extensions • log-normal distribution • multiple (potentially correlated) traits • diffusion and advection of moments

  8. Trait 1: investment in autotrophy Trait 2: investment in heterotrophy Phytoplankton and bacteriaautotrophy & heterotrophy maintenance + light harvesting nutrient + structural biomass + organic matter harvesting organic matter death +

  9. Model characteristics • Ecosystem state variables • nutrient, organic matter, structural biomass • mean autotrophy • mean heterotrophy • variance of autotrophy • variance of heterotrophy • covariance autotrophy-heterotrophy • Parameters • maximum autotrophic and heterotrophic production • half-saturation constants for light, nutrient, organic matter • maintenance rate, death rate

  10. Setting: plankton in a water column immigration vertical diffusion biological activity

  11. Resultsnutrient, biomass, organic matter

  12. Resultsautotrophic and heterotrophic biomass

  13. Resultsautotrophy & heterotrophy ratio and correlation

  14. Discussion • Phytoplankton-bacteria ecosystem • time: seasonal shift from pure autotrophy to mixotrophy • depth: deep chlorophyll maximum • depth: mixotrophy near surface, pure heterotrophs in deep water • Information in trait distribution moments • traits means give an impression of the ecosystem strategy • correlation coefficient gives insight in underlying community structure • cf. Adaptive Dynamics • no separation of ecological and adaptation (evolutionary) time scales • source of diversity = immigration, not mutation

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