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The Ocean Ecosystem Chapter 2: 77-98

The Ocean Ecosystem Chapter 2: 77-98. Copepods run the show (…in the classical marine food web…). 70 – 90 % zooplankton biomass is copepods major grazer of phytoplankton; can control phytoplankton biomass strong dominance by few (1 - 3) species

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The Ocean Ecosystem Chapter 2: 77-98

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  1. The Ocean EcosystemChapter 2: 77-98

  2. Copepods run the show(…in the classical marine food web…) • 70 – 90 % zooplankton biomass is copepods • major grazer of phytoplankton; can control phytoplankton biomass • strong dominance by few (1 - 3) species • careful: estimating standing crop vs. primary production can be tricky!! • production may be found in copepod bodies, not in phytoplankton biomass • similar to the situation in tropical rain forests (there, with nutrients bound up in plants; soils are nutrient-poor)

  3. Copepod life cycle

  4. Group activity • Take what you know about seasonal thermal stratification in temperate waters, and now add plankton • Draw a graph of plankton production over a year. Plot phytoplankton and zooplankton as separate lines

  5. Copepod production and life cycles Figure 2.42, p. 81

  6. Vertical migrations • Diel (daily) or seasonal • Here: focus on DVMs (diel vertical migrations) • Cue: light • Surface at night; at depth during day • (some do the reverse) • Follow light intensity to depth / surface

  7. Diel vertical migrations (DVMs)

  8. Why vertically migrate? • Can you come up with reasons? • What are the disadvantages to vertical migrations?

  9. Nanoplankton and picoplankton • Used to think the diatom - dinoflagellate - copepod (“net plankton”) story described ocean production • New methods to measure nanoplankton and picoplankton have been developed • Phytoplankton in these size classes are responsible for most production • Microzooplankton are therefore consuming most of the oceanic primary production

  10. Dissolved organic matter (DOM) • Previously underestimated • Dissolved organic carbon (DOC) • Leaks out of phytoplankton cells • Taken up by bacteria, microzooplankton • May account for a significant proportion of ocean production • Bacteria may play a greater role in production than previously thought…

  11. The microbial loop Figure 2.46, p. 92

  12. Plankton are patchy Many causes for patchy distribution • Stratification / nutrient availability • Advection (movement of water masses) • Oceanic gyres (large-scale) • Eddies & rings (small-scale) • Coastal fronts

  13. The Gulf Stream and core rings

  14. Marine snow • Comprised of the remains of many organisms • Mucous nets from larvaceans, pteropods • Gelatinous zooplankton bodies • Fecal pellets • Algae • Microorganisms • These particles sink to depths • Bacteria colonize the particles, smaller particles stick to them • Major “subsidy” of organic material to deep pelagic and benthic environments

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