14. Plankton
Plankton are small, often microscopic, buoyant floating organisms found in fresh and salt water. While not all plankton are photosynthetic, planktonic life is centered on photosynthetic microorganisms that are both dependant upon, and limited by solar radiation, light. What has always fascinated me, in my career as a microbiologist and oceanographer, is the incredible variation in structure vs. function that one finds when one examines plankton. The following are some of the plankton that I have photographed that illustrate their beauty and complexity.
These are diatoms! They are literally glass houses as they are made up of silica (or glass) with a little pectin. Imagine what it would be like to live in a glass house!
These are coccolithophorids; the cells have an outer layer of plates, or coccoliths, made of calcium carbonate. The shape of the coccolith can vary dramatically as the micrographs to follow illustrate. Most coccolithophorids are smaller than 10 microns. Coccolithophorids are found only in the oceans. There are 200 or more species of coccolithophorids and they are second only to diatoms in population.
Other plankton include small animals called Radiolaria and Acantharia. Radiolaria are amoeba that have silica spicules which are readily seen when cells are examined in the electron microscope. Acantharia, more amoeba-like organisms, also have spicules, but these are made of strontium sulfate and dissolve rapidly once the animal dies leaving no trace. Thus, they are difficult to identify. Other plankton include the Foraminifera. These are also amoeba but have shells and can be large enough to be seen without a microscope. Most are marine, but there are a few freshwater species as well. Finally, plankton also include bacteria, and a variety of protozoa including paramecium and ciliates of one sort or another. The following micrographs are not identified but do represent the variety of plankton that are found in the environment.
In the oceans, as well as in large lakes and rivers around the world, the plankton act as the water equivalent of forests. Together with the forests, they are the lungs of our planet. They take up the carbon dioxide from burning fossil fuels and the respiratory release from all forms of animals, and convert it into oxygen and water. Without their activity the planet is doomed.
To me personally, what is most amazing is the incredible diversity of structure. Look at diatoms. They all perform the same function in life... photosynthesis. Why are there so many different forms of diatoms, so many structural variations? I have always been intriqued with the issue of structure and function.
These are diatoms! They are literally glass houses as they are made up of silica (or glass) with a little pectin. Imagine what it would be like to live in a glass house!
These are coccolithophorids; the cells have an outer layer of plates, or coccoliths, made of calcium carbonate. The shape of the coccolith can vary dramatically as the micrographs to follow illustrate. Most coccolithophorids are smaller than 10 microns. Coccolithophorids are found only in the oceans. There are 200 or more species of coccolithophorids and they are second only to diatoms in population.
Other plankton include small animals called Radiolaria and Acantharia. Radiolaria are amoeba that have silica spicules which are readily seen when cells are examined in the electron microscope. Acantharia, more amoeba-like organisms, also have spicules, but these are made of strontium sulfate and dissolve rapidly once the animal dies leaving no trace. Thus, they are difficult to identify. Other plankton include the Foraminifera. These are also amoeba but have shells and can be large enough to be seen without a microscope. Most are marine, but there are a few freshwater species as well. Finally, plankton also include bacteria, and a variety of protozoa including paramecium and ciliates of one sort or another. The following micrographs are not identified but do represent the variety of plankton that are found in the environment.
In the oceans, as well as in large lakes and rivers around the world, the plankton act as the water equivalent of forests. Together with the forests, they are the lungs of our planet. They take up the carbon dioxide from burning fossil fuels and the respiratory release from all forms of animals, and convert it into oxygen and water. Without their activity the planet is doomed.
To me personally, what is most amazing is the incredible diversity of structure. Look at diatoms. They all perform the same function in life... photosynthesis. Why are there so many different forms of diatoms, so many structural variations? I have always been intriqued with the issue of structure and function.
posted by tony at 1:37 PM
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