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Mesoscale Microbial Dynamics in the Ocean: Role of Ecosystem Structure and Elemental Flows

This Agouron-CMORE summer course explores the role of ecosystem structure in elemental flows in the ocean, the issue of scales in ecology, and the separation of physical and biological processes in generating biological gradients. The course also examines mesoscale perturbations in the North Pacific Subtropical Gyre and highlights the importance of understanding the basics of ecosystem structure. Collaborators from various institutions and the Hawaii Ocean Time-Series team contribute to the course's content and discussions.

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Mesoscale Microbial Dynamics in the Ocean: Role of Ecosystem Structure and Elemental Flows

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  1. Agouron-CMORE Summer Course Mesoscale Microbial Dynamics Ricardo M Letelier Oregon State University Collaborators: D. Karl (UH), R. Bidigare (UH), M. Church (UH), R. Lukas (UH) J. Dore (UH), J. Christian (Dept. Fisheries & Oceans Canada), A. White (OSU), Y. Spitz (OSU), M. Abbott (OSU), J. Richman (OSU), C. Sakamoto & K. Johnson (MBARI), S. Emerson (UW),… and the Hawaii Ocean Time-series (HOT) team Letelier Hawaii June 2008

  2. Agouron-CMORE Summer Course OUTLINE 1) Role of ecosystem structure in elemental flows in the ocean. 2) The issue of scales in ecology 3) Can we separate the contribution of physical and biological processes in the generation of biological gradients? 4) Mesoscale perturbations in the NPSG 5) Back to the basics

  3. Agouron-CMORE Summer Course The role of Ecosystem structure in the flow of enery and elements “That swarm of locusts” In 1889 G.T. Garruthers described in Nature a swarm of locusts over the Red Seaand derived a figure of 24 quadrillion locusts equivalent to 43 billion tons. Thirty years later Vladimir Vernadsky worte in his book La Geochimie: “expressed in terms of chemical elements and in metric tons, may be seen as analogical to a rock formation, or more precisely: to a moving rock formation endowed with free energy”

  4. Agouron-CMORE Summer Course Major role of organisms in biogeochemical cycles: • Storage of energy and elements • Mobilization of stored elements, energy, and information in space • Coupling (or uncoupling of elemental cycles) Modified from U.S. JGOFS

  5. Lagrangian studies in pelagic ecology Agouron-CMORE Summer Course • The interaction between different types of organisms at different trophic levels and the environment (ecosystem structure) will influence how bioelements and organic energy are distributed and stored in the biosphere. • In turn, the availability of bioelements and energy, as well as the rate of perturbation of the ecosystem will affect the ecosystem structure. •  Interaction of ecology and physics

  6. Agouron-CMORE Summer Course Probably, the composition and physiological state of the microbial assemblages, as well as the elemental fluxes will vary significantly across the front. From Jim Yoder, 1994

  7. Agouron-CMORE Summer Course MODIS Terra L2 1 km resolution scene (October 3rd 2001) – COAS/OSU Direct Broadcast Sea Surface Temperature Chl a Chl Fluorescence Line Height (°C) (mg m-3) (W m-2mm-1 sr-1) It is too bad we have to deal with a stirred, rather than a well mixed ocean ! But …

  8. Agouron-CMORE Summer Course At different scales physical variability will generate environmental stress: When addressing environmental impacts in ecosystem dynamics we need to consider that a biological unit becomes under stress when the rate of change in the environment is faster than its rate of adaptation. Different biological units with distinct generation times and adaptative rates will respond differently to a given environmental perturbation. Large tree Generation Time ≈ 20-60 years Phytoplankton GT ≈ 1-7 days

  9. Time-space scales of physical processes F Z P B Agouron-CMORE Summer Course From T. Dickey

  10. Agouron-CMORE Summer Course Small spatial scales: mm Schematic diagram of the microhabitat around a marine snow aggregate Physical, chemical and biological processes all operate within this microzone C. Turley, 2002. 0.5 - 20 millimeters

  11. Slightly larger spatial scale: meters chl sigma-t sigma-t vel Profile taken over Oregon shelf in 80m of water N2 phytoplankton vertical gradients linked to small-scale vertical shear, under stable stratification Agouron-CMORE Summer Course T. Cowles unpubl.

  12. Agouron-CMORE Summer Course Studying the response of pelagic assemblages FLH chl

  13. Agouron-CMORE Summer Course • How can we separate the importance of the variability in biological processes from physical effects when studying ecosystem dynamics in pelagic environments ? • We can do it in the lab in order to understand single species mechanisms of adaptation, or • - We can try to map biological and physical variability at similar spatial and temporal scales (Okubo, Powell, Denman, Platt, Abbott) Letelier URI July 2005

  14. Agouron-CMORE Summer Course 60°42’S 60°06’S Using Optical Drifters 60°30’S 61°W 60°W 62°W dw/dz From work with M Abbott and D Karl

  15. Agouron-CMORE Summer Course

  16. Chl absorption = [chl]  a* 0.016 0.016 0.014 0.014 Chl fluorescence 0.012 0.012 0.01 0.01 Lu/Es Lu/Es 0.008 0.008 0.006 0.006 0.004 0.004 0.002 0.002 0 0 400 400 450 450 500 500 550 550 600 600 650 650 700 700 Wavelength, nm Wavelength, nm Agouron-CMORE Summer Course Letelier et al. 1996

  17. Agouron-CMORE Summer Course • Apparent increase in photosynthetic efficiency with upwelling periods • However • We did not have in situ validation of the interpretation • Only a couple of examples to date (ours and John Cullen’s group)

  18. Agouron-CMORE Summer Course - Using numbers to start identifying general patterns Diatom dominated Prokaryote dominated Average ( 1 standard deviation) decorrelation scales for SST, chlorophyll, fluorescence per unit chlorophyll and drifter speed as a function of distance offshore (nearshore < 200 km, 200  transition  400 km, offshore >400 km). From Abbott and Letelier, 1998.

  19. Agouron-CMORE Summer Course Optical Drifters Results • Allow us to study the evolution of phytoplankton assemblages in a water parcel • Hard to separate changes in physiology versus algal assemblage • Assessing spatial/temporal decorrelation scales • Helps identifying the potential role of physics versus biology in phytoplankton patchiness • Provides information to work on possible evolutionary strategies of phytoplankton taxa to cope with a fluctuating environment

  20. (Fe) Parameter (arb. units) light Light Temp Depth Nutrient input (N,P,Si,Fe) Agouron-CMORE Summer Course N, P, Si and Fe are some of the main elements limiting microbial biomass or activity. 106C : 16N : 1P : 0.001 Fe (:16 Si) MODIS image from NASA/GSFC

  21. Agouron-CMORE Summer Course • A long-term record in the NPSG suggests • a significant and persistent increase in • chlorophyll concentrations in the late 1970’s. Depth, m Karl et al. (2001)

  22. Agouron-CMORE Summer Course Pacific Decadal Oscillation warm phase cool phase HOT Karl et al. (2001)

  23. Agouron-CMORE Summer Course A general hypothesis regarding how ocean biology responds to changes in large scale physical forcing. Karl et al. (1999)

  24. Agouron-CMORE Summer Course • Revisiting the ENSO/PDO – SRP hypothesis: • After 16 years of research, do the Hawaii Ocean Time-series observations support the early model of a relationship between inter-annual/decadal climate indices and SRP availability? • 2) Can we confirm some of the physical and biological mechanisms proposed to explain the observed inter-annual and decadal trends?

  25. Agouron-CMORE Summer Course Pacific Decadal Oscillation & P availability • Gyre-wide circulation patterns may also • modulate the availability of specific nutrients • in ways that are not yet well understood. PDO Index

  26. 3 2 1 PDO Index 0 -1 -2 -3 89 90 91 92 93 94 95 96 97 98 99 2000 01 02 03 04 Time, years Ocean Sciences Meeting Pacific Decadal Oscillation & SRP availability • The HOT data suggest that an inverse relationship exists between SRP availability in the upper euphotic zone and PDO Index Cross-correlation analysis of nutrients relative to PDO Index 0.5 0.25 NO3- Correlation coeff. 0 -0.25 SRP -0.5 335 -365 -265 -165 -65 35 135 235 Lag time, days From N. Mantua (U.W)

  27. Agouron-CMORE Summer Course Temporal and vertical distribution of SRP and major taxa supporting diazotrophy Coccoid cyanobacteria Filamentous cyanobacteria Diatom/Richelia

  28. Agouron-CMORE Summer Course Temporal and vertical distribution of SRP and major taxa supporting diazotrophy Coccoid cyanobacteria Filamentous cyanobacteria Diatom/Richelia

  29. Agouron-CMORE Summer Course • Some common characteristics of taxa forming conspicuous blooms in the NPSG • Large cell size • Form assemblages • Capacity to fix N2 • Buoyancy controls 2005 Bloom Diatoms with Richelia 1989 Bloom Trichodesmium spp. From M Church From D Karl From A White

  30. 180 160 140 120 91 01 1988 89 90 92 93 94 95 96 97 98 99 2000 02 03 04 100 Time, years 80 60 0.02 40 20 0.01 0 0 17 19 21 23 25 27 Agouron-CMORE Summer Course Evidence for summer increases in Trichodesmium and diatoms [Chl a] mg m-3 [N03+NO2], mg l-1 Upper watercolumn fluorescence trace “roughness” Upper watercolumn Low Level SRP 0 0.4 0.2 0.6 0.8 0 0.06 0.05 50 0.04 Depth, m 0-45 m mean chl a profile variability, (mg m-3) db-1 0.03 100 150 HOT55 1994 Dore et al. 2008 200 50 Depth, m 100 0-45 m mean Low Level SRP (nmol kg-1) 150 HOT115 2000 200 Temperature, ºC st, ‰ PDO Index

  31. Agouron-CMORE Summer Course

  32. Agouron-CMORE Summer Course Characterization of the biology and chemistry in an anti-cyclonic eddy in the vicinity of Station ALOHA From Fong et al. 2008

  33. A [chl a], mg m-3 B Depth, m Temp, °C 4000 m PC Flux, mg C m-2 d-1 Time, Days since 01/01/1998 Agouron-CMORE Summer Course 1998 Summer cyclonic eddy at Station ALOHA (22º 45’N, 158º W)

  34. Agouron-CMORE Summer Course NODC51001 Buoy Wind Speed and SST Stability in the upper water column during summer months precedes phytoplankton bloom events.  SeaWiFS image of Sea Surface Chlorophyll Karl et al. (1992) These bloom events trigger large fluxes of organic matter into the deep ocean. 

  35. Agouron-CMORE Summer Course From Sakamoto et al. 2004

  36. Agouron-CMORE Summer Course But what do we see when we look at a Long term record? From White et al. 2006

  37. Agouron-CMORE Summer Course • Possible bloom initiation as a result of a nutricline upward shift • Enhanced nutrient diffusion as a result of nutrient entrainment into the base of the euphotic zone (McGuillicuddy et al. 1998) • Luxurious uptake of nutrients by seeding populations at the base of the euphotic zone (Steven and Glombitza 1972). • Buoyancy controlled migrations into the base of the upper nutricline (Karl et al. 1992; White et al. submitted). 0 0 20 20 ML Depth 40 40 60 60 Depth, m 80 80 100 100 120 120 Nutricline 140 140 160 160 Time Time

  38. 200 150 91 01 1988 89 90 92 93 94 95 96 97 98 99 2000 02 03 04 Time, years 100 50 0 -50 -100 -150 -200 Agouron-CMORE Summer Course Assessing the contribution of mesoscale events to the variance in SSH SSH residual, mm SSH residuals Power spectrum density PDO Index 105 104 • Power spectrum analysis of SSH anomaly from TOPEX/Aviso time-series suggests an increase of high frequency contribution to the variance during periods when the PDO index is positive (warm). 103 E(m/s)2 102 101 1.0 100 10-1 10-2 10-3 f(cycles/day)

  39. Agouron-CMORE Summer Course Prymnesiophytes • Does the effect of mesoscale perturbation rates affect other components of the ecosystem? Chrysophytes Diatoms

  40. Agouron-CMORE Summer Course • in order to characterize and understand long term ecosystem trends we need to describe changes in the mean, variance, and frequency of perturbations. • Biologically driven elemental fluxes are the result of an uncoupling between photosynthesis and respiration in space and time, • - This uncoupling is generated by physical and chemical gradients After Dave Ullman

  41. Agouron-CMORE Summer Course Over what scales should we able to predict ecosystem behavior ? Time-space scales of physical processes F Z P B From T. Dickey

  42. Agouron-CMORE Summer Course CONCLUSIONS 1) Even in oceanic environments considered stable, we observe large scales of variability that are, to some extent predictable. 2) Changes of ecosystems in the ocean are the result of combined perturbations with distinct modulations. 3) Gradients generate uncoupling between production and remineralization (unbalanced vs balanced systems). 4) Mean, variance, and frequency, are all important characteristics describing the environmental conditions of an ecosystem. 5) We need to define the question before deciding the resolution scale of our study.

  43. END OF TALK

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