12 June, 2000
What's that brown stuff?
As the Healy began to enter the ice flows, I started to notice a brown sludge on the bottom layer of the chunks of ice that popped up from below the sides of the ship. Being from Nome, I had an idea of what that "stuff" was, since the Bering Sea also freezes over during the wintertime. Luckily my Principal Investigator Lisa Clough, a.k.a. "The Mud Lady", was able to help me with some basic knowledge of this "Ice Algae." Now that I have said I have some basic knowledge, I will tell you that ice algae has not been studied by scientists to any great extent, so many of the ideas I will present are just that, ideas.
Where in the world did this stuff come from?
Some scientists speculate that diatoms may envelop themselves in cysts (develop a hard outer covering) to "winter over", as a means of survival. Other scientists believe that they may survive on organic matter and may also store lipids (fats) for food during the cold winter months. Regardless, as the sea ice begins to thin, and probably more import the layer of snow on top of the ice is reduced, more photosynthetic light can reach the bottom layers of the ice. Ice algae usually begins to appear on the bottom of sea ice around the month of March. Since ice algae is made up of single celled organisms known as diatoms, it is dependent on light for the process of photosynthesis to produce food. The diatoms then can begin to produce food efficiently and begin to reproduce, forming net-like layers under the ice.
Why are they so abundant?
. As more light reaches the bottom layer, the algae begins to reproduce rapidly, causing an algal bloom. Diatoms require red and blue wavelengths of light energy for the process of photosynthesis, as well as nitrogen, phosphorus, and silica. They reflect the green wavelengths; therefore we see them as green in color. As these algal blooms develop, more and more carbon dioxide is taken in to produce sugars and oxygen. The water tends to be already saturated with oxygen, therefore the oxygen given off forms bubbles that rise to the bottom layer of the ice. As these bubbles of oxygen move around, it is thought that they may scrap the layers of algae off of the ice, making the algae form long communal strands. In the Chukchi Sea north of Alaska, these strand have been observed by submersible ROV's to be 20 to 30 feet in length. They have been described as an upside down kelp forest. Amazingly, these colonies may easily contain over 200 species of diatoms.
How do these long strands hold together?
The diatoms form a mucous that seem to be the "glue" that holds them together. Again, there are many ideas of what the main purpose of this mucous is. Diatoms benefit from this mucous; because it gives the colonies buoyancy and helps them stay together. The drawbacks to the formation of this mucous is the fact that it tends to block out needed carbon dioxide and it may also block the elimination of wastes produced during photosynthesis. Mucous also is rich in nitrogen, meaning it requires are large supply of nitrogen to form. If you ever have the opportunity to touch ice algae, you will see that is does in fact feel like secretion from a runny nose.
By this time you might be saying, "So what's the big deal?"
Well, ice algae is the beginning of the Arctic food chain. Ice algae are eaten by zooplankton, which are in turn eaten by krill and small crustaceans. They are, in turn eaten by small fish such as the Polar Cod, which are then eaten by birds and seals. And at the top of food chain is the Polar Bear. With little research being done, scientists are unsure of just how important ice algae is to the overall arctic ecosystem. Some studies suggest that the ice algae are responsible for only 10% of the total primary production of sugars from carbon dioxide (carbon cycling), while others have put the value at 80%.
There are many unanswered question about how this algae functions in the arctic environment and what role it plays in the overall health of the ecosystem. With so many questions remaining, you can be sure that more intensive and extensive research will be done in the future.
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