Introduction

     Cyanobacteria, also known as blue-green algae, are prokaryotes that live in both freshwater and salt water environments.  By performing the process of photosynthesis, cyanobacteria remove carbon dioxide and bicarbonate ions from the environment and release oxygen.  The cyanobacteria are important to our past because they are thought to have been among the first photosynthetic organisms on Earth beginning approximately 3.5 billion years ago.  It is also believed that cyanobacteria helped increase the amount of oxygen in the atmosphere to its present 21% and reduced the amount of carbon dioxide to its low level of 0.035%.

     Carbon dioxide is known as a greenhouse gas because it traps energy that is being radiated from the Earth's surface, which increases the temperatures of the atmosphere and the Earth.  It is believed that the rising carbon dioxide level caused by increasing fossil fuel combustion is causing a warming trend of our atmosphere.  In order to understand what this rise in carbon dioxide means for the future, we must study how the increase of carbon dioxide will affect organisms; especially those organisms that fix carbon dioxide and make them into organic molecules.  An example of one of these organisms is cyanobacteria.

     As cyanobacteria undergo the process of photosynthesis, they take up carbon dioxide, either as dissolved carbon dioxide in the water or as bicarbonate ions.  Oxygen is produced as a waste product and carbon dioxide is turned into sugars, proteins, nucleic acids, lipids, and other organic molecules.  In order to perform this process, the cyanobacteria need a rich supply of energy.  This energy is collected from the sun by accessory pigments known as phycobilins.  The phycobilins transfer energy to chlorophyll a which passes an excited electron through an electron transport chain to produce ATP (energy) and reduce NADPH⁺.
 

Purpose

The purpose of this investigation is to take three strains of cyanobacteria and expose them to three different atmospheric conditions varying in concentration of carbon dioxide. By taking samples of each strain of cyanobacteria, we will be able to examine their pigment production and growth rates.  We will look for relationships between the carbon dioxide concentrations and the collected data.
 

Hypothesis

We also predict that the growth rates of both the 750 ppm and 100 ppm cyanobacteria will decrease as a result of being exposed to carbon dioxide concentrations outside of the optimum range.  Therefore, we predict that the growth rate of the cyanobacteria in the atmospheric conditions will increase.
 
 

Q:  Is water vapor a greenhouse gas?

A:  Yes.  Carbon dioxide, methane, nitrous oxide, and water vapor are greenhouse gases.  Water vapor is the most abundant and important of these naturally occurring greenhouse gases.