What Are Diatoms?

Diatoms are a protist (single cell organism) which is part of the family of eucaryotic (Cells that have nuclei) algae. There are two types of diatoms, pennales (pennate shaped), and centrales (circular shaped). Diatoms like all plant cells are photosynthetic, meaning they make their own sucrose (sugar) from light, water, and nutrients. Diatoms use oils to store sugar. The oil also keeps the diatoms afloat. Diatoms, as well, have a glass shell that surrounds the entire cell. A diatom will make their shells from silica, which is found in sand. Diatoms, like most of our cells in a human body, reproduce by dividing into two identical halves. After dividing, the two new diatom cells will have to find a silica source to create a glass shell, which is needed for their survival.

Where Can Diatoms Be Found?

Diatoms can be found in all of the world’s waters both fresh and salt, and there are currently over 16,000 species of diatoms. Diatoms can live in open, running, deep, or shallow waters, as long as they have the nutrients, light, and a silica source. When there is no other nutritional source around a diatom, they will use the the nutrients in dead organisms to go under photosynthesis. I found this out when I saw diatoms inside a dead transparent protozoas. Diatoms are commonly found in algae mats, but can be also live in sediment, on rocks, or just about anywhere as long as there is sand to make their glass shell, and nutrients and light to make their food. Diatoms can live under a variety of water conditions, which can be running, calm, shallow, and deep waters, as long as they have the resources to make their food.

Procedure For Culturing Diatoms

What I am trying to accomplish is to see if diatoms can survive and grow in hot water baths. Currently, evidence shows that diatoms cannot grow in hot water. However, my advanced biology class had recently found glass shells in Vulcan hot springs, that are look to be from diatoms. With evidence that was discovered, I developed an experiment hoping to grow my own diatom cultures, and placing them in hot water baths. If the diatoms grow, this will provide new evidence that diatoms can grow in hot water. To grow diatoms, I go to the south fork of the Salmon river to collect rocks, sand, and sediment to provide the diatoms for the cultures as well as an environment. Before I create the culture, I make up around 1040 ml of media that will provide additional nutrients for the diatoms. The media has to have a pH reading of 7.8, and if it is too low, I add 1 gram of calcium carbonate (CaCO3), and more if the pH is still too low. If the pH is too high, I add a drop of hydrochloric acid (HCl), I add more drops as needed to rise the pH to 7.8. After the media is made, I then add the sand, and sediment to chlorine evaporated water to flasks. After the sand, and sediment have settled, I add media to the flask. The media consists of 1000 ml (milliliters) of distilled water, 20 ml (milliliters) of Carolina’s media solution, and 20 ml (milliliters) of Carolina’s sterilized soil water. I autoclave the media for 25 minutes, and then let the media cool for at least 4 hours. The media will then be entirely sterilized. For an additional silica source for the diatoms, I add 3-4 drops of sodium silicate (NaSi). For the 10 gallon aquarium I add 10 ml (milliliters) of sodium silicate. If a culture can reach a high diatom population, I will prepare a hot water bath.

Hot Water Bath Materials

10 gallon aquarium
10 inch heater
Growth Light
Bricks (to raise water level)
Growth Light

Procedure For Hot Water Bath

First I set the hot water bath temperature at a low temperature of 35 degrees Celsius. Then I estimate the current diatom population, and to see if they are growing. I will make this check three times a week. If the diatoms begin to grow and the population increases, I will increase the temperature by 3-5 degrees Celsius. If the diatoms are not growing under a certain temperature I will decrease the temperature by 2-3 degrees Celsius. The temperature has to be increased a little at a time because a too hot temperature could kill the diatoms. The cultures would be kept inside the flask when in the hot water bath, because the media will dilute under the large amount of water, as well as the sand and sediment. The water level must be low enough so it doesn’t completely submerge the entire culture, but it has to be high enough for the aquarium heater to heat the water. I add the bricks to the aquarium, and set the cultures on top of them. Then the water level will be low enough so it won’t completely submerge the culture, but high enough for the aquarium heater to heat the water.