Marine Ecosystems and Food Webs

1. Marine Ecosystems and Food Webs

2. Carbon Cycle Marine Biota Export Production

3. Export Production of Organic Carbon

4. Ocean Ecosystem Structure Trophic levels and dynamics

5. Ocean Ecosystem Structure Trophic levels and dynamics

6. Ocean Ecosystem Structure Trophic levels and dynamics

7. Ocean Ecosystem Structure Trophic levels and dynamics

8. Ocean Ecosystem Structure Example of a more complex Food Web

9. Ocean Ecosystem Structure Energy Transfer between Trophic Levels is not efficient

10. Trophic levels and dynamics Food Web Energy

11. ENERGY

13. How about Mass Transfer?

18. How do we measure Biomass? Mass transfers are more easy to keep track than energy transfers

19. Alaska

20. Large scale Eddies 200 km

22. Color sensor satellites: MODIS, SeaWiFS, MERIS, OCTS, and CZCS http://oceancolor.gsfc.nasa.gov/SeaWiFS

23. A simplified diagram of an ecosystem

24. A useful way to keep track of biomass in the lower trophic levels is to follow the path of MACRONUTRIENTS Carbon C Nitrogen N Phosphorus P

25. Redfield Ratio C : N : P Atlantis in 1934 and today 106 : 16 : 1 Redfield A.C.,On the proportions of organic derivations in seawater and their relation to the composition of plankton. In James Johnson Memorial Volume. (ed. R.J. Daniel). University Press of Liverpool, pp. 177-192, 1934. This works stems from his participation as a physiologist in the voyages of WHOI's first research vessel Atlantis.

26. C : N : P source 1) atmosphere source 1) from N2 atmosphere gas2) ocean subsurface3) remineralization of dead organic matter 4) biological (e.g. excretions) source 1) not biological, not atmospheric2) fluvial At large Nitrogen appears to be the limiting factorin ocean productivity in today’s oceans

27. What is the explanation for the Redfield ratio? • Redfield (1958) “biological control of chemical factors" in the ocean: living organisms in the ocean evolved to have a N:P ratios of about 16 → when N is not limiting then N and P but also C and O interact to produce this relation. • Very stable in deep ocean • Not so stable between phytoplankton species. • Perhaps only general average?

28. N=nitrogen P=phytoplank. Z=zooplank. D=detritus Simple Nitrogen Model Net Primary Production (NPP) ~45 Pg C/yr hn NPP P ~1 Pg C (0.2 % of photosynthetic biomass) N S(No-N) D Z Phytoplankton biomass turns over in about a week!

29. Description of the oceanic ecosystem based on Nitrogen exchanges Fixation N2 Nitrification Mineralization NH4 NO3 Uptake Phytoplankton Grazing Mix Layer depth Chlorophyll Zooplankton Mortality Large detritus Water column Susp. particles Nitrification N2 NH4 NO3 Denitrification Aerobic mineralization Organic matter Sediment

30. Carbon Cycle Marine Biota 45 GIC/yr Export Production

31. What are the controls on Primary Production? • Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients • Ocean nutrient inventory • Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions) • Changes in Redfield Ratio

32. Export Production of Organic Carbon

33. What are the controls on Primary Production? • Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients • Ocean nutrient inventory • Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions) • Changes in Redfield Ratio

34. What are the controls on Primary Production? Nutrient Sources for Primary Production The flux of organic carbon must be sustained by an adequate flux of macronutrients If macronutrients are unavailable then primary production is reduced!

35. Surface CHL-A 1) Central Gyres 2) Upwelling Regions

36. Phytoplankton Blooms and Physical Environment Bands of the dionflagellate Lingulodinium polyedrum moving onshore over the troughs of a series of internal waves

37. Nonlinear Internal Waves and Phytoplankton Isopycnals

38. What are the controls on Primary Production? • Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients • Ocean nutrient inventory • Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions) • Changes in Redfield Ratio

39. What are the controls on Primary Production? Nitrogen appears to be the limiting factor for growth in modern time. • Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients • Ocean nutrient inventory C : N : P 106 : 16 : 1

40. Modern TIME N2 fixation Denitrification N = 25790 N* = N – 16 P (Gruber & Sarmiento 1997)

41. What are the controls on Primary Production? • Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients • Ocean nutrient inventory • Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions) • Changes in Redfield Ratio

43. Southern Ocean HNLC Map of annual average nitrate concentrations in the surface waters of the oceans. Data from Levitus, World Ocean Atlas, 1994.

44. What are the controls on Primary Production? • Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients • Ocean nutrient inventory • Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions) • Changes in Redfield Ratio

45. What are the controls on Primary Production? • Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients • Ocean nutrient inventory • Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions) • Changes in Redfield Ratio Climate Variability and Change