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.
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.
These bacteria are jacks of all trades. They can fix their own carbon and their own nitrogen from the atmosphere.
In addition to blue green bacteria there are other types of photosynthetic bacteria. Unlike plants and cyanobacteria, these bacteria do not produce oxygen as a by product of photosynthesis and are therefore known as "anoxygenic."
This purple sulfur bacterium require hydrogen sulfide as an electron and hydrogen donor to make food in the way plants require water as an electron and hydrogen donor.
This green sulfur bacteria requires sulfur to live.
These green, flexible bacteria move by gliding.
Many microbes live in ponds and feed off of other organisms and decaying organic matter (detritus). Since they cannot produce their own food, these organisms are called "heterotrophs" which means "other eating."
Amoeba are famous heterotrophs that surround their food with their bodies to eat.
Animals are generally studied in a branch of science called zoology. Since some animals are too small to be seen without the aid of a microscope, these animals are included in this Microbe Zoo. All animals are heterotrophs.
Hydra with green symbiotic algae
Hydra are tiny animals, most of which are microscopic. Many hydra live together with algae in a symbiosis.
Some microbes breathe sulfate instead of oxygen. These bacteria, called sulfate reducers, thrive in sediments, such as those found at the bottom of a pond. Sulfate reducers are often found in the black colored zone of a pond because they convert sulfates into metal sulfides which are black.
For more information on sulfate reducers see the Redox Mine Shaft.
Living at the bottom of the pond, furthest away from oxygen are the methane producers. These microbes also live in murky swamps, where they produce swamp gas, also known as methane.
For more information on methane producers visit the Cow Rumen.
Ponds are a fantastic source of microbes which are easy to see with the proper magnification. Scoop up some pond water in a jar and examine the water using a magnifying glass and/or a microscope. How many different types of microbes can you see? Compare the types of microbes you find at the top of the pond with those you find near the bottom of the pond. Why are the microbes near the surface different from those at deeper levels?