1. Algae: Overview and Importance for Earth’s Atmosphere

2. Earth’s Atmosphere: Not Much of It
Mass Atmosphere = 5.2 x 1018 kg
Mass Oceans = 1.4 x 1021 kg
Mass Earth = 6.0 x 1024 kg
Live Biomass = 1 x 1015kg
Carbon Dioxide = 3 x 1015 kg
Trunover Time for carbon dioxide =
5 years in atmosphere, centuries
in oceans

3. Carbon dioxide cycles between low values in summer and
higher values in winter in the Northern Hemisphere due to
seasonal differences in photosynthesis.
Annual input from fossil fuels and deforestation: 3 x 1013 kg
carbon dioxide. Half accumulates in the atmosphere, rest is
absorbed in oceans, leading to acidification.
Pre-industrial carbon dioxide level was 280 ppm, now 380 ppm.

4. Early Earth Atmosphere:
No Oxygen
Lots of Carbon Dioxide,
Methane, Water Vapor, Hydrogen

5. Cyanobacteria and Oxygenic Photosynthesis
About 3 Billion Years Ago. Water is the electron donor CO2 + H2O  CH2O + O2

6. Oxygenic photosynthesis is complicated
Oxygenic photosynthesis is complicated. It requires two photosystems and is thought to have arisen only once in the course of evolution.

7. Oxygen Was A Poison to Early Life Forms on Earth. Took about 1
Modern Stromatolites Fossil Stromatolite (2.5
Billion Years Old)
Banded Iron Formation
Oxygen Was A Poison to Early
Life Forms on Earth. Took about 1
billion years before oceans and
atmosphere were fully oxygenated

8. Oxygen in the air allowed the evolution of eucaryotes and aerobic
respiration, finally leading to the world’s life forms present today.

9. Oxygen also produced the ozone shield which protects water in the upper
atmosphere from boiling away as hydrogen
Ozone in the upper atmosphere (derived from O2) protects against the splitting
H2O to H and OH, with H escaping to space.
Earth has lost about 25% of its water while water is nearly all gone on Venus and
Mars.

10. Greenhouse
Gasses:
Water Vapor
Carbon Dioxide*
Methane*
Nitrous Oxide*
*Increasing Due
To Human
Activity

11. 1500 Ma
60 Ma
Evolution of the modern algae orders.

12. 600 Ma to present – evolution of animal kingdom

13. SNOWBALL EARTH
1st MYA
2nd – 850 MYA

14. Plate tectonics provides a resupply
of carbon dioxide to the atmosphere

15. 50 MYA Diatoms and Grasses Reduce Carbon Dioxide to Very Low Levels
Diatoms Grasses

16. Evolution and impacts of algae on the atmosphere continue today…

17. In this course we emphasize the ecology and biology of the algae rather than the taxonomy. Main groups we will cover:
Cyanobacteria (blue-green algae)
Green Algae
Red Algae
Brown algae – brown seaweeds, kelps, diatoms
Dinoflagellates
Coccolithophores
Others

18. Cyanobacteria Cell Structure

19. Nostoc colony
Nostoc filaments with N2-fixing heterocysts

20. Ceramium – filamentous red seaweed

21. Porphyridium – Unicellular Bangean Red Algae

22. Chlamydomonas

23. Enteromorpha
Monostroma
Ulva

24. Diatoms
Heterokont in sexual stage

26. Prorocentrum Lingulodinium
Red-Tide Forming
Dinoflagellates
Desmokont Dinokont
Prorocentrum Lingulodinium

27. Red Tides

28. Coccolithophores
Haptophytes
w/ two smooth
flagella and
a coiled hapto-
nema
Emiliania huxleyi
Ca + 2HCO3 ---> CaCO3 + H2O + CO2