Algae: Overview and Importance for Earth’s Atmosphere

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

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.

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

Cyanobacteria and Oxygenic Photosynthesis About 3 Billion Years Ago. Water is the electron donor. CO 2 + H 2 O  CH 2 O + O 2

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 Early Life 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 aerobic respiration, finally leading to the world’s life forms present today.

Ozone in the upper atmosphere (derived from O 2 ) protects against the splitting H 2 O 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. Oxygen also produced the ozone shield which protects water in the upper atmosphere from boiling away as hydrogen

Greenhouse Gasses: Water Vapor Carbon 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 1 st MYA 2 nd – 850 MYA

Plate tectonics provides a resupply of 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 Algae Red Algae Brown algae – brown seaweeds, kelps, diatoms Dinoflagellates Coccolithophores Others

Cyanobacteria Cell Structure

Nostoc filaments with N 2 -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