Interesting Projects for Home or School

Water Jars

By Harold Eddleman, Ph.D. President of Indiana Biolab.

If you get some water from a ditch, pond, or puddle, and just let it sit for several weeks or months in a jar, it is likely that one or more species of organism will grow. You should begin with clean jars. The water may evaporate rapidly, but you can reduce evaporation by covering the mouth of the jar loosely with a lid, or bread wrapper or paper held in place by a rubber band or string. If you must replace water lost by evaporation, spring water, well water, or water from the original pond may give best results. Occasionally, nothing will grow. If you start several jars, usually no two jars develop the same organisms, even when the water came from the same pond. Jars started at different times of the year will give different results. Include some sticks or plants from the pond because Hydra and freshwater sponges may grow on them. This simple experiment might easily develop into a very satisfying project lasting many years.

Since many small invertebrates hide in the dead leaves and sediment at the bottom of a pond, you will want to start some jars containing an inch (2.5 cm) of debris from the bottom of the pond, ditch, or marsh. In another jar try an inch of mud from the pond bottom covered with a few inches of water from the same pond. If possible, compare jars prepared from ocean and freshwater (ponds and streams) environments. Jars will be more likely to develop populations of small invertebrates if you are able to hold them near the temperature where they grew in nature.

Another quite different experiment is to pack a long tube or tall jar with mud from any source and mark one side "shade" and let it stand many weeks with the "shade" side always away from the light (lamp or sun). Zones of color should develop in the mud as air vs no air and light vs no light determine which organisms are able to grow. Later I will write much more about the bacteria which develop in mud jars; my favorites are those with red chlorophylls which develop beautiful red color in regions of the jar where light is adequate and oxygen is absent.

Another quite different experiment is to get a fresh dead squid or fish from the ocean and incubate it in a refrigerator at usual refrigerator temperature. Keep it moist (not covered with water) and with plenty of air. After some days, examine the dead animal in the dark. You must wait a long time for your eyes to get used to the darkness. You may find glowing spots on its skin. The glowing spots are colonies of a bacterium which makes light. There are several species of bacteria which produce light. There will be a LINK here to a page devoted to growing and playing with such bacteria. It is said that marine animals obtained inland from fish markets never develop glowing spots, perhaps the surface bacteria are killed by some sort of dip. Dead fish found on the seashore may be tested, but animals direct from the sea give best results. Some luminescent bacteria can be pathogens.

Some organisms have evolved in extreme water cycles. They grow in the rain puddles of spring and produce eggs or cysts which are able to survive in the dry dust of summer. These hatch when the next suitable spring rains arrive. Try collecting dried soil from the puddles of spring and see if you can obtain life from the dry soil several months later. Experimenting with correct temperatures may improve results--try to mimic nature. Examples are fairy shrimp (common in early spring ditches), brine shrimp (common in dried desert pools), water fleas, copepods, seed shrimp. Certain dryland rotifers which have survived 27 years in dry moss in dried moss herbarium collections.

Water jars really get interesting when you try variations, especially if you can examine the water under a microscope. Try getting water from one location, but treating jars of it differently. Put some in a north window away from the hot sun and place others in a south window where the bright sun will favor different organisms. Avoid freezing locations because your jars may freeze and burst causing damage to property and losing your interesting results. You should not screw the lids on tightly because the resulting anaerobic (without air) conditions will prevent the growth of animals large enough to see without a microscope because all animals require oxygen.

If, as an experiment, you decide to screw the lids on for an air tight seal you may find foul odors develop--especially if the water contains carbohydrates and proteins. Such jars will usually be darker in color or even black. In the absence of oxygen, the only organisms able to grow are those able to steal oxygen (reduction) from the food by forming reduced organic compounds which often have foul odors. Similar anaerobic bacteria live in our large intestine and there they generate the reduced substances which cause human feces to have strong odors. Anaerobic jars are often darker color because sulfur may be used as electron accepter producing H2S instead of H2O. The H2S reacting with metals commonly produces black pigments (see qualitative analysis NOT READY). The sulfur comes from sulfur containing amino acids in proteins (cystine and methionine).

Try to think of many different ways to treat different jars. Try keeping some in a dark place and some in light. Add a tiny piece of food (hay, grain of rice) to some jars. Often adding food will yield an ugly, smelly, or moldy mess. If molds grow, be very careful not to sniff, or inhale any of the dusty spores. The safest plan is to dispose of any moldy jars immediately. See safety warning below.

When you add food to your water jars, you are adding starch, sugars, proteins and other biochemicals which are easily digested by numerous species of bacteria. The water will become cloudy with millions of bacteria. A water culture of bacteria which is just barely cloudy contains one hundred million cells per milliliter. There are about 20 drops per milliliter. Thus, one drop will contain about 5 million bacteria! Someday this page will contain a LINK to another page showing how you can count the bacteria in a culture. In unpolluted freshwater, bacterial populations are fairly low, but bacteria populations are high in the slimes on rocks of aquatic habitats.

The bacteria provide food for larger organisms such as protozoa. Someday a L I N K here will take you to pages that will help you grow and study protozoa. Most protozoa have cilia (tiny whiskers) around their mouths which they use to generate a tiny whirlpool sweeping the bacteria and other bits of food into their mouths. Copepods and other tiny multicelled animals eat protozoa. Many of these small invertebrates are large enough to be observed without a microscope. Our web site will have pages devoted to the study of these invertebrates. Send me an e-mail with your questions or comments.

Safety Precautions

If you inhale mold spores, there is a chance they could grow in your lungs and cause death. However, normal outdoor and indoor air is full of mold spores and they seldom cause problems. The main problem with a moldy jar is that huge numbers of spores are present and you could inhale thousands or millions of them and the heavy dose of spores could create a health problem. For example, constant exposure to a foreign material can cause your body to make antibodies which is one step in development of allergies. Avoid dusty, moldy piles of wood chips and grass clippings unless you wear a suitable respirator.

If a jar becomes moldy dispose of it in the trash. If you break a moldy jar, leave the room for an hour so the spores can settle, and then carefully remove the broken glass. Clean up the mess slowly and carefully to avoid getting cut on the contaminated glass or inhaling the mold spores. If you get cut, clean the cut with a soft, clean toothbrush and soap and water. Then flood the wound with alcohol. It may hurt, but that is better than an infection.

If the wound is deep, there is risk of lockjaw, especially if soil or manure is present. See dung jars at our site for some info on lockjaw and consult your physician.

This web site has a page devoted to safety precautions which you should observe. Study safety manuals at your library and ask your teacher and parents to review your research plans.