Lecture 7: Phytoplankton diversity Diatoms Dinoflagellates Coccolithophorids Cyanobacteria Trichodesmium Prochlorococcu

1. Lecture 7: Phytoplankton diversity Diatoms Dinoflagellates Coccolithophorids Cyanobacteria Trichodesmium Prochlorococcus Relevance to ecology and elemental cycles

2. Light distribution within the ocean

4. Definitions Phytoplankton: Photosynthetic plankton. Phycology: The branch of biology concerned with phytoplankton and other algae. Autotrophy: The formation of organic material (carbohydrates, lipids etc) from inorganic substrates (CO2, H2O). Heterotrophy: The derivation of nutritional requirements from consumption of �fixed� carbon (carbohydrates etc). Mixotrophy: Autotrophy and heterotrophy in the same organism.

5. Plankton Size Classes Macroplankton: 2-20 cm, krill etc (not phytoplankton) Mesoplankton: 0.2 mm-2 cm, large zooplankton Microplankton: 20-200 �m, small zooplankton Nanoplankton: 2-20 �m, includes diatoms, dinoflagellates Picoplankton: 0.2-2 �m, mostly bacteria, includes prochlorococcus and synechococcus - dominant in the gyres. Femtoplankton: < 0.2 �m, mostly marine viruses

6. Three Empires (or domains) Archaea (archaebacteria) halo- & theromophiles methanogens Bacteria includes cyanobacteria Eukaryotes animals protists fungi plants

7. Taxonomic Diversity Empire: Eubacteria Kingdom: Bacteria (cyanobacteria and prochlorophyceae) Empire: Eukaryota Kingdom: Protozoa (dinoflagellates) Kingdom: Plantae (microflagellates) Kingdom: Chromista (diatoms & some microflagellates)

8. Number of Marine Species Cyanobacteria 150 Prochlorophyceae 2 Dinoflagellates 1,800 Microflagellates 200 Diatoms 5,000

9. The Diatoms Intensely studied because of their importance to ecology and elemental cycles Often dominant in temperate & high latitudes at the coast and in blooms Single-celled (2 to 1000 um), but can form chains External glass skeleton, comprises 4-50% of the cell weight ? dense cells, large contribution to export Not capable of independent movement use spines & density regulation (ions, oils) to maintain position in the water column

10. Pennate diatoms

11. Diatom chains

12. Centric diatoms

17. Toxic Diatoms Major contributor to harmful algal blooms (HABs) Most common example: Pseudonitzschia genus ~ produces domoic acid, leads to amnesic shellfish poisoning (seizures, death). Common off Oregon. Large event in 1998 - significant sea lion mortality off California.

18. The Dinoflagellates Also very abundant and ecologically important Single-celled, rarely form chains (cf diatoms) No glass skeleton Have two flagella for movement Only some are strictly autotrophic About 50% of dinoflagellate species are strict heterotrophs, can not carry out photosynthesis, therefore considered protozoa Some are mixotrophic - both photosynthesize and consume other plankton

19. Dinoflagellates

21. Dinoflagellates

23. Toxic Dinoflagellates Major contributor to harmful algal blooms (HABs) Examples: Karenia brevis ~ produces brevetoxins which can become airborne and cause respiratory irritation. Common HAB-forming species off western Florida Alexandrium genus ~ produces saxitoxin, leads to paralytic shellfish poisoning (paralysis, respiratory failure, death). Common off Oregon.

25. The Coccolithophorids About 150 species < 20 um in size, usually spherical External calcareous shell of plates called coccoliths Like diatoms, this makes them efficient �exporters� Also leads to unique reflective properties Large blooms easily visible from satellites Essentially global distribution - blooms common in the Bering Sea

26. Coccolithophorids: Emiliania huxleyi

27. Cyanobacteria: Trichodesmium

28. Cyanobacteria: Trichodesmium

29. Long term trends in N2 fixation: North Pacific

30. Long term trends in N2 fixation: North Pacific

31. Cyanobacteria: Prochlorococcus

35. Summary