Algae | Cyanobacteria | Anoxygenic Photosynthetic Bacteria
Heterotrophs | Sulfate Reducers | Methanogens


Ponds contain a rich diversity of microbes. This cross section of a pond shows the different habitats within the pond. The amount of light and oxygen change at different depths, creating different habitats for different microbes.

The green microbes growing closest to the top are green algae and cyanobacteria. This green color comes from chlorophyll, a chemical that turns solar energy into food that the microbes can use. The conversion of light into chemical energy is called photosynthesis. Deeper in the pond are other colorful bacteria that have either purple or green chlorophyll. Still deeper in the pond are sulfate reducers and methanogens which inhabit the dark, lower part of the pond.

Ponds are home to a huge variety of microbes that represent nearly all kingdoms of life.


Plants are well known for their ability to convert sunlight into energy for food. This process is known as photosynthesis. Many other organisms can also convert the sun's energy into food, including many different algae and bacteria.


Algae are photosynthetic eukaryotic organisms. Waters contain a huge variety of algae including golden, yellow, brown, red, green, and yellow-green algae as well as diatoms. Algae can be microscopic or macroscopic, in which case they are known as kelp. At one time, scientists grouped algae together with the plant kingdom, but now algae are considered members of the kingdom Protoctista. The Protoctista is a kingdom of organisms which is neither plant, animal, fungus or bacteria. Like plants, algae are organisms which long ago formed a symbiosis with photosynthetic bacteria.


Photosynthetic Bacteria

Not only are plants and algae photosynthetic, but also some bacteria are photosynthetic. Bacteria contain different types of chlorophyll which give them different colors.


Blue green photosynthetic bacteria are called cyanobacteria. These were formerly thought to be algae, until scientists found that they had no nuclei, like other bacteria. Close relatives of cyanobacteria were probably the ancestors of the photosynthetic organelles (plastids) in modern plants.