1. Plankton
Marine life is classified into three groups: Plankton, Nekton, and Benthos
Plankton
Nekton
Benthos

2. Plankton
Plankton refers to the drifting organisms within the pelagic zone
Phytoplankton are autotrophic, photosynthetic algae, which form the base of the marine food web
Zooplankton are heterotrophic; the primary (and in some cases secondary and tertiary) consumers of the marine food web

3. Plankton form the base of the marine food web

4. ‘Bottom’ of the Food Chain

5. How are plankton classified?
By Metabolism (autotrophic vs. heterotrophic)
By Life History (meroplankton vs. holoplankton)
By Taxonomy (Crustaceous vs. Gelatinous zooplankton, for example)

6. Phytoplankton
Phytoplankton are responsible for 40% of all the world’s photosynthetic food on Earth (and 95% of all the ocean’s!)
Provide ~one half of all the oxygen we breathe!
Collectively, the production of organic compounds from CO2 is referred to as primary productivity

7. Phytoplankton
Phytoplankton require nutrients, especially nitrogen and phosphorus (macronutrients) but also iron (micronutrients)
For this reason, phytoplankton appear in abundance (“blooms”) in regions of upwelling, where cold, nutrient-rich water reaches the photic zone

9. Global Primary Productivity

10. Localized Primary Productivity
In tropical regions, there is plenty of sunlight but productivity is limited by nutrients trapped beneath the thermocline
In polar regions, there are plenty of nutrients, but sunlight (and sinking out of the photic zone via mixing) limits productivity
In temperate regions, the combination of sunlight and nutrients is just right, but only seasonally!

11. Tropical Productivity Profile

12. Primary Productivity in Temperate Regions
Localized primary productivity occurs seasonally, accompanied by physical changes to the water column
In temperate regions, primary productivity is limited by light (winter) and by nutrients (summer)
Peak productivity occurs during spring, in an abundance of phytoplankton known as a “spring bloom”

14. Primary Productivity in Temperate Regions
During winter, nutrients are at their highest, but light is at its lowest
In spring, solar energy reaching the photic zone increases and nutrients are still abundant
In summer, strong warming of the water creates a seasonal thermocline which restricts nutrients from reaching the photic zone
In fall, storms enhance mixing, and a second seasonal bloom results

16. Compensation Depth
Net primary productivity is the amount of carbon dioxide removed via photosynthesis minus the amount of carbon dioxide released by respiration
Compensation depth refers to the depth in the water column at which the rate of photosynthesis equals the rate of respiration
Above this depth, phytoplankton survive
Below this depth, phytoplankton die

18. Phytoplankton
Phytoplankton are mostly single-celled algae (Kingdom Protista)
There are 8 major types of phytoplankton, 2 of which are most prominent:
Diatoms
Dinoflagellates

19. Diatoms √ Dominant (>5,600 species) Composed of silica shells
Important source of nutrition for zooplankton √

20. Dinoflagellates Can be autotrophic or heterotrophic!
Most are planktonic, but others form symbiotic relationships with coral (zooxanthellae) and giant clams
Flagella for movement
Responsible for red tides (harmful algal blooms)

21. Red Tide caused by Dinoflagellate

22. Harmful Algae Blooms (HAB’s)
Caused by dinoflagellates and other small flagellates

23. Zooplankton
Zooplankton are the most numerous primary consumers in the ocean
The most important source of protein in the oceans!
Zooplankton eat bacteria, phytoplankton, and other zooplankton!
Nearly every major animal group is represented in the zooplankton

24. Zooplankton Zooplankton are classified as either:
Holoplankton
Meroplankton
Holoplankton are always plankton – they live and die in the water column
Meroplankton are only plankton for part of their lives; many marine organisms begin their lives as small planktonic organisms, but gain the ability to swim or metamorphose into a benthic organism

25. Once a copepod, always a copepod…
Holoplankton
Once a copepod, always a copepod…

26. Meroplankton
Includes larval (very young) fish, crabs, clams, squid, lobsters, starfish, etc.

28. Types of Zooplankton: Copepods
Copepods are the most abundant of all the zooplankton (70%)
Holoplanktonic
Crustaceous
Herbivorous, Omnivorous, Carnivorous, and Parasitic
Marine and freshwater

29. Copepods 14,000 species globally
You, too, can become a copepodologist!
Important source of protein for secondary consumers!

30. Types of Zooplankton: Pteropods
Composed of calcium carbonate, CaCO3

31. Jellyfish and ctenophores are gelatinous zooplankton!

32. Avoiding Predation Translucence and Transparency
Outward spines for protection
Swimming behavior and migration

33. The Greatest Migration on Earth
Every night at dusk, swarms of zooplankton migrate to the surface, and return to depth again at dawn
Increasing Depth

35. Deep-Scattering Layer

36. How to capture zooplankton

37. Quantitative Zooplankton Tows

38. Think Like Plankton
Life in a pelagic habitat (no solid substrate); 3-D
Properties of water

39. Properties of Water
Water is viscous, ESPECIALLY if you are a very small organisms living in it
Reynolds number:
Re = inertial forces
viscous forces

40. Reynold’s Number For very small organisms, inertia is non-existent
Viscous forces dominate (low Reynolds number) for small organisms, such as plankton!
Inertial forces dominate (high Reynolds number) for larger organisms, such as humans, large fish or whales

41. Reynolds Number