Oddities and Non-diatoms
Fossilized Traveler:
The photos to the right are pictures of a diatom found at the bottom of Lake Mendota in Wisconsin- nearly at the center of the North American landmass. However, diatom itself belongs to the genus Actinoptychus, which is only found in the ocean and needs saltwater to live.
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How did it get here? The best guess is that this diatom hasn't been alive for millions of years: it died long ago and settled to the bottom of an ancient ocean along with billions of other marine diatoms. Those diatoms were slowly crushed and packed together until they formed a silica-rich layer of rock which we know today as "diatomaceous earth."
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Because there are so many small spaces between the individual shells that make up diatomaceous earth, it is very porous. This means that it can be used in filters to strain out impurities from water.
It is suspected that the diatom you see here was one of many that were mined out of the ground and manufactured into a pool filter, which was used by someone in the Lake Mendota watershed. When the pool was drained, some small bits of the filter were washed away too. All that water eventually made it into the lake, and this diatom settled to the bottom of the lake, just like it did in the ocean millions of years ago.
Misshapen Diatoms:
Not all diatoms turn out to be perfect copies of the cell they split from. The genus Staurosira (pictured to right) is especially known for having high rates of mutations and deformities. Often, these deformities take the form of abnormal outlines or line patterns.
Deformities are thought to occur when diatoms are reproducing in a stressful environment: maybe the water is too hot, or maybe there are increased levels of heavy meals present.
Sometimes, researchers may mistake a deformed diatom to be a new species. Be on the lookout for abnormalities!
Protective Casings:
The sphere-like objects you see here do not belong to diatoms at all. Rather, they are the products of a related class of algae called chrysophytes, or "golden algae." Chrysophytes, unlike diatoms, often have a whip-like tail known as a flagella which allows them to propel themselves through the open water, while diatoms can only drift or crawl across surfaces.
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One of the other unique characteristics of chrysophytes is that in times of stress, they are able to envelop themselves in a silicon ball like the ones seen at right. This protective casing known as a "statocyst"can house the chrysophyte while it rests in a dormant state. The statocyst usually has a single hole that leads in and out of it. The chrysophyte can live within the statocyst much like a bear does during hibernation, waiting until outside conditions have become more favorable before emerging. This phenomena has been known to occur in locations where ponds and streams periodically dry up, freeze, or change pH.
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Some studies have even shown that humans can cause statocysts to become more common. In areas where humans have settled, we often change the water quality by increasing the amounts of phosphorus present and lowering the water's pH. This change has been shown to correlate with an increase in the number of statocysts that are deposited in the bottoms of lakes. For more information on this phenomenon, the full article can be found here.
Spirogyra:
The photo below is not of a diatom, but it is of a beautiful and noteworthy genus of green algae: Spirogyra. Spirogyra was in fact the very first kind of micro-algae ever observed and described. In 1674, Antione van Leeuwenhoek described it as, "green streaks spirally wound serpent-wise and... about the thickness of a hair on one's head." van Leeuwenhoek went on to also discover single-celled life (bacteria) and red blood cells, and his observations made him a strong opponent of the then-commonly held theory that life was generated out of nothingness. Because of his work with microscopes and algae, he is now known as the Father of Microscopy.
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