Algae: Overview and Importance for Earth’s Atmosphere

Earth’s Atmosphere: Not Much of It

Mass Atmosphere = 5.2 x 1018 kgMass Oceans = 1.4 x 1021 kgMass Earth = 6.0 x 1024 kgLive Biomass = 1 x 1015kgCarbon Dioxide = 3 x 1015 kgTrunover Time for carbon dioxide = 5 years in atmosphere, centuries in oceans

Carbon dioxide cycles between low values in summer andhigher values in winter in the Northern Hemisphere due toseasonal differences in photosynthesis.

Annual input from fossil fuels and deforestation: 3 x 1013 kg carbon dioxide. Half accumulates in the atmosphere, rest isabsorbed in oceans, leading to acidification.

Pre-industrial carbon dioxide level was 280 ppm, now 380 ppm.

Early Earth Atmosphere:

No OxygenLots of Carbon Dioxide,Methane, Water Vapor, Hydrogen

Cyanobacteria and Oxygenic PhotosynthesisAbout 3 Billion Years Ago. Water is the electron donor. CO2 + H2O CH2O + O2

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

Modern Stromatolites Fossil Stromatolite (2.5 Billion Years Old)

Banded Iron Formation

Oxygen Was A Poison to EarlyLife Forms on Earth. Took about 1 billion years before oceans and atmosphere were fully oxygenated

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

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 andMars.

Oxygen also produced the ozone shield which protects water in the upperatmosphere from boiling away as hydrogen

GreenhouseGasses:

Water VaporCarbon Dioxide*Methane*Nitrous Oxide*

*Increasing Due To Human Activity

Evolution of the modern algae orders.

60 Ma

1500 Ma

600 Ma to present – evolution of animal kingdom

SNOWBALL

EARTH

1st - 2200 MYA2nd – 850 MYA

Plate tectonics provides a resupplyof carbon dioxide to the atmosphere

Diatoms Grasses

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

Evolution and impacts of algae on the atmosphere continue today…

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 AlgaeRed AlgaeBrown algae – brown seaweeds, kelps, diatomsDinoflagellatesCoccolithophoresOthers

Cyanobacteria Cell Structure

Nostoc filaments with N2-fixing heterocysts

Nostoc colony

Ceramium – filamentous red seaweed

Porphyridium – Unicellular Bangean Red Algae

Chlamydomonas

Ulva

Enteromorpha

Monostroma

Diatoms

Heterokont in sexual stage

Desmokont Dinokont

Dinoflagellates

 Red-Tide Forming

Prorocentrum Lingulodinium

Red Tides

Coccolithophores Haptophytes w/ two smooth flagella and a coiled hapto- nema

Emiliania huxleyi

Ca + 2HCO3 ---> CaCO3 + H2O + CO2