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Environmental sciences science fair project:
The Effect of Bleach on the Survival Rate of Daphnia




Science Fair Project Information
Title: The Effect of Bleach on the Survival Rate of Daphnia
Subject: Environmental Sciences
Grade level: Elementary School - Grades 4-6
Academic Level: Ordinary
Project Type: Experimental
Cost: Low
Affiliation: Selah Intermediate School
Year: 2005
Description: Daphnia are placed in Petri dishes filled with different concentration of water / bleach solution. Daphnia is checked every ten minutes with a microscope to see how many are still alive (their heart will stop beating if they die).
Link: http://www.selah.k12.wa.us/SOAR/SciProj2005/LaurenG.html
Short Background

Daphnia

Daphnia magna with eggs
Daphnia magna with eggs

Daphnia are small, planktonic crustaceans, between 0.2 and 5 mm in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because of their saltatory swimming style (although fleas are insects and thus only very distantly related). They live in various aquatic environments ranging from acidic swamps to freshwater lakes, ponds, streams and rivers.

The lifespan of a Daphnia does not exceed one year and is largely temperature dependent. For example, individual organisms can live up to 108 days at 3C while some organisms live for only 29 days at 28C. A clear exception to this trend is during the winter time in which harsh conditions limit the population in which females have been recorded to live for over six months. These females generally grow at slower rate but in the end are larger than ones under normal conditions.

Sometimes Daphnia may be used in certain environments to test the effects of toxins on an ecosystem. This makes Daphnia an indicator species, particularly useful in that area because of its short lifespan and reproductive capabilities. Because they are nearly transparent, their internal organs are easy to study in live specimens (an example might be to study the effect of temperature on the heart rate of these ectothermic organisms). They are often fed to tadpoles or small species of amphibians such as the African Dwarf Frog, Hymenochirus biettgeri. Daphnia are also a popular live food in tropical and marine fish keeping.

Several water flea species are considered threatened. The following are listed as vulnerable by IUCN: Daphnia nivalis, Daphnia coronata, Daphnia occidentalis, and Daphnia jollyi. Some species are halophiles, and can be found in hypersaline lake environments.

Bleach

Common chemical bleaches include household "chlorine bleach", a solution of approximately 36% sodium hypochlorite (NaClO), and "oxygen bleach", which contains hydrogen peroxide or a peroxide-releasing compound.

Bleach is a liquid that is used as a cleaner. It also can cause things to turn white or pale. Bleach can harm people's skin if they do not use it carefully.

Mixing bleach with some things commonly found at home, like vinegar or even fruit juice can produce chemicals like Chlorine that are irritating or even dangerous. Bleach should also not be mixed with ammonia, because a dangerous chemical reaction will occur. This reaction can kill people.

Certain types of bleaches produce toxic waste. Some of them produce dioxins.

In the textile dye and finish industry, sodium hydrochlorite is available in powder form. It is usually used to strip color from dyed polyester fabrics in order to re dye the fabric. I also find it useful in a final dye stage to clear any excess dye from the polyester fabric. Use a final scour at 60C or 140 F. Use 5% active bleach on the weight of the goods. Drop the final scour bath after bleaching and rinse with clean water at 60C or 140 F. The polyester fabric will pass the 2A wash fastness test even on deep shades.

Bleach made from hydrogen peroxide is used to make hair lighter in color, orange, blonde, or even white. It is often used by dark-haired people to make highlights, and most light hair dyes contain it.

Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)

For more information (background, pictures, experiments and references): Daphnia, Bleach

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