On Friday, Sep. 20 there is NO class/recitation. INSTEAD, consider attending

1. On Friday, Sep. 20 there is NO class/recitation. INSTEAD, consider attending Global Climate Strike rally at 2:30pm on Voorhees Mall. A peaceful protest to demand that: 1. Rutgers go carbon-neutral by 2050 2. Rep. Pallone hold hearings on Green New Deal Extra credit: Turn in one positive comment, one negative comment, and three questions or issues you had about the rally. Due 9/23.

2. Review • Critical depth • Seasonal cycle • Geographic variation • Food web and microbial loop • Eutrophic vs. Oligotrophic food webs • Biological pump

3. Compensation & Critical Depth

4. Annual cycle in N. Atlantic Phytoplankton biomass Zooplankton biomass Spring bloom Fall mini- bloom Nutrients LightTemperature Mixing Mixing Stratified Relative increase

5. Latitudinal variation in seasonal cycles driven by variation in irradiance [Also Irradiance] 90oN = N. Pole 60oN ~Anchorage,AK 30oN ~N. Florida 0oN = Equator

6. Mixed layer is deeper in Atlantic than in Pacific Atlantic Ocean Depth (m) South pole Equator North Pole Pacific Ocean Depth (m) South pole Equator North Pole Temperature

7. Annual cycles in other regions Phytoplankton biomass Zooplankton biomass Try this on your own: Draw the vertical profiles of temperature and light and the critical depth for each region as we did in class for the North Atlantic.

8. Physical mixing processes Phytoplankton Nutrients Zooplankton Sinking & Senescence Higher Trophic Levels Particle Dynamics Particle Flux (Carbon flux) Irradiance

9. Biological Pump Photosynthesis Respiration Sinking Remineralization Chisholm, 2000

10. What’s in a liter of seawater? 1 Liter of seawater contains: • 1-10 trillion viruses • 1-10 billion bacteria • ~0.5-1 million phytoplankton • ~1,000 zooplankton • ~1-10 small fish or jellyfish • Maybe some shark, sea lion, otter, or whale poop This basking shark can filter ~25,000 L seawater per day! *The bigger you are, the fewer you are

11. Size spectrum indicates ecosystem structure Typical slope = -1 Log-scale abundance or biomass Log-scale organism size

12. Predators average ~10x bigger than prey 10:1 ESD = Equivalent Spherical Diameter Hansen et al. 1994

13. Basic assumption: trophic transfer efficiency is ~10% Biomass 10 100 1000 Efficiency 0.1 0.1 fish zooplankton phytoplankton Trophic transfer efficiency = fraction of biomass consumed that is converted into new biomass of the consumer

14. Small things are eaten by (~10x) bigger things. Heterotrophs Autotrophs Fish Zoo- and Phyto- Plankton Protists Bacteria Size (μm)

15. Bacteria absorb organic molecules leaked by microbes and phytoplankton. This creates a microbial “loop.” Heterotrophs Autotrophs Fish Zoo- and Phyto- Plankton Protists Bacteria Microbial Loop Size (μm) Dissolved organic matter

16. Zoom in on food web Photosynthesis respiration Chisholm, 2000

17. Plankton size structure is important indicator of nutrient conditions Diatoms, dinoflagellates Coccolithophores, cyanobacteria Copepods, Krill Protists

18. Importance of microbial loop depends on environmental conditions. Microbial loop

19. Definitions • Eutrophic environments have high nutrient concentrations and high productivity. Coastal upwelling regions and estuaries are Eutrophic. • Oligotrophic environments have low nutrients and low productivity. Subtropical gyres (open ocean) are Oligotrophic. • It takes a lot of mixing or a big nutrient influx to make an environment eutrophic. Stratified systems eventually become oligotrophic.

20. Eutrophic -coastal -estuaries -upwelling -high latitudes Oligotrophic -open ocean -central gyres Clear water over Great Barrier Reef Phytoplankton bloom in Barents Sea

21. Temp. Depth In oligotrophic systems, small phytoplankton (e.g. cyanobacteria) dominate and biomass goes through more levels of plankton to get to fish. Dcr Microbial loop is key

22. In eutrophic systems, large phytoplankton (diatoms) dominate and more biomass goes directly to large plankton and fish. Temp. Depth Dcr Microbial loop is less important

23. Oligotrophic Eutrophic Open Ocean Tuna Carniv. Fish Carniv. Plankton Herbiv. Plankton Phytoplankton 5 Levels 10% Efficiency (between levels) Coastal Ocean Carniv. Fish Carniv. Plankton Herbiv. Plankton Phytoplankton 4 Levels 15% Efficiency (between levels) Upwelling Zone Anchovies Phytoplankton 2 Levels 20% Efficiency (between levels)

24. Draw size spectrum here

26. =109 metric tons C per year =106 metric tons fish per year Open ocean (90% of area) Coastal ocean (9.9% of area) Upwelling zones (0.1% of area) 5 Trophic levels 10% Efficiency 4 Trophic levels 15% Efficiency 2 Trophic levels 20% Efficiency

27. Food-web structure affects the export of carbon to deep ocean Photosynthesis respiration Chisholm, 2000

28. How does organic matter get to the bottom of the ocean? • Dead cells and fecal pellets (plankton poop) sink. Big ones sink faster. • Dissolved organic matter, pieces of gelatinous animals etc. stick together and form bigger “marine snow” that sinks. Organic debris is collectively known as Detritus.

29. Bigger plankton sink faster. They also have bigger, faster-sinking fecal pellets. Large plankton and their fecal pellets Marine snow Small plankton and their fecal pellets

30. Temp. Depth In oligotrophic conditions, there are fewer, smaller particles that sink slowly. More time for bacterial remineralization. Dcr small fecal pellets

31. In eutrophic conditions, there are more, larger particles that sink rapidly, maybe to deep ocean. Temp. Depth Dcr Large fecal pellets Large Marine snow

32. Eutrophic vs. Oligotrophic worksheet