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 Populations in freshwater Ecosystems Paper

Aim: To compare two or more fresh water ecosysterms at the wetlands center.

In this study I will want to compare two ecosystems. I predict that pollution in the water will be quite minimal because the freshwater habitats are under conservation . Also the other reason being that the people working on the habitats will try to keep it a healthy habitat with a good balance at each trophic level so that the animals will live. Ipredict that the nitrate levels to be quite high in a habitat with other animals such as ducks. The reason being that the excrement will cause the process of eurification and make the levels higher. I also predict that the Oxygen levels will be quite high (about 8 parts per million), because the conservationists may clean out the excrement .For a healthy habitat the abiotic factors are:

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* The light level must be good so that- plants can photosynthesize and don’t decompose and cause the microbes to use the oxygen.

* Temperature is important so that- if the water is too cold the anmals will die and decay and the same if it is too warm.

* Flow rate of the water is important so that- the habitat isn’t destroyed by the fast water flow.

* Nitrate level is essencial- Too much nitrogen is a problem caused by the polluton of algae which restricts the light, this kills the organisms underneeth causing defecation and making organic remains. Then the nitrifying bacteria make nitrates out of the ammonium compuonds.

* Oxygen levels- could be a problem if there is the pollution of algae (see nitrate levels), or if there ifs something decomposing then microbes will use up the oxygen.

For my investigation I will find the nitrate level by using testing strips and oxyen level by winkler’s method find the parts per million (ppm).

The biotic factors are:

* Types of plans- blanket weed and duck weed are both indications of a habitat with low ligh or in the danger of losing light. Mill foil is a good plants as it oxygenates the water.

* Features and adaptations of animals- this is something that I will show later on in my investigation.

* The number and types of animals- This table shows what species are in high, low or intermediate pollution.(next page)

I will look at all three of these biotic factors in my investigation. I predict the more animals there are the less polluted it is because there Is enough oxygen, light, for the organisms to live. I will use various techniqus to examin the different organisms. I will take a sample fron the top, middle and bottom layer of the habitat to get a clearer view.

Farmyard freshwater habitat

This habitat was shared with some gese aswell as all the animals in the water. This ment that there was a lot of excrement. I was surprised to find out that eventhough there was a lot of excrement, the nitrate level was 0 and the phosphate level was high. The reason being that the water was filterd and removed the nitrates. The oxygen level was also high 9.1 parts per million, due to the water being filtered. The animals that I found ment that habitat was ok, although there was a leech there were not enough to indicate that the habitat was very polluted. The duck weed and algae also indicated the same thing.

In the habitat I found:

Plants- duck weed and algae

Animals- Daphnia, cyclops, leeches and spring tails.


What depth found in

Number pr sample (A4 paper size tray) estimate


Top(T), middle(M) and Bottom(B)

T= 3500 M= 7000

B= 3000



T= 100 M= 80

B= 40

Spring tails


M= 2



B= 1

Small freshwater habitat

This habitat was smaller but deeper thatn the other habitat. It also did not share the habitat with any other animals. This ment that the water would be cleaner thatn the other habitat. This showed in the type of animals and the oxygen level being 9.2ppm. The nitrogen level was 0 again due to the water being filtered. He indications of this habitat being clean was the growth of mill foil and water mites.

Plants- mill foil and algae

Animals- flat worm, water mite, cyclops, water snail and water flea.


What depth found in

Number pr sample (A4 paper size tray) estimate

Flat worm



Water mite





T= 50 B=40

Water snail


M= 1

Water flea


M= 20 B= 10

Here is a food web for fresh water habitats:


flat worm

Planarians have extraordinary powers of regeneration and they normally reproduce by pulling in two. The fragments then regenerate their missing parts.

water mite

Water Mites have a globular, sack-like body and are related to spiders. They have eight legs and a line that separates their thorax from their abdomen. Some water mites are parasitic and suck off the gills of fresh water clams and mussels. Some water mites have special hairs on their legs that help them swim.

Cyclops is a genus of copepods named for the animal’s single eyespot, reminiscent of the one-eyed monster in Greek mythology. Although most species of Cyclops are marine, many are commonly found in quiet freshwater habitats.

Common Name:

Fresh Water Snail or Planorbis

Scientific Name:

Planorbis leavis


Animalia Mollusca Gastropoda Pulmonata aquatica Planorbidae

Physical Description:

This snail appears like a smaller and darker colored version of the

garden snail. They have a spiral shell that is almost spherical and

a body that is the same color as raw liver. Their shells are a lighter

dark brown than the bodies.


This snail spends it’s life under the water in calm pools. They stick

to rocks and feed on the algae and bacteria that grow on them.

Breeding takes place in the spring, and the snails are often

hermaphroditic, but still require another mate for fertilization.

Prey and Predators:

Crayfish, skunks, opossums, and amphibians will eat these

small gastropods. The planorbis is hardly an aggressive predator,

but they eat the microscopic organisms with less intelligence than


Signs of Existence:

These snails can be found on any hard surfaces in the calm parts

of the water. They share the same pools as many crayfish, but

are more easily spotted because of their large numbers.

water flea

Water fleas belong to the Crustacea, a large group of ‘jointed limbed’ animals, most of which live in water. Water fleas are placed in the order Cladocera and are probably called ‘fleas’ because they move through the water by a sort of hopping. Water fleas are very common in fresh water, in Britain you can find about 80 different species, in The Netherlands about a 100 species. Many of them are rare.

The chief characteristic of the water fleas is that the main part of the body is enclosed in a kind of shell, with the appearance of two lids, but made of one piece. Because you can see through them, you can study for instance the beating of the heart and follow the course of the blood cells round part of the body. Their sizes differ from several hundred microns to more than five millimeter for the larger species.

The common water flea, Daphnia pulex can be found in almost all sorts of eutrophic (rich in nutrients) waters. They reproduce in summer mostly parthenogenetic, that is, the eggs develop without undergoing fertilization.

At the end of the summer, some of the eggs develop into the smaller males, capable of fertilizing the eggs in females, which then develop into the so called ‘winter eggs’; mostly only one or two are present in the females. These eggs can also be found in populations under stress, such as during the drying up of a pond.


Leeches are classified as annelids, or segmented worms. They are related to earthworms and share many traits. They are found in shallow ponds, lakes, and marshes. Some leeches have even been found to live in small desert water holes as well as in antarctic waters. Most leeches live in water; however, some leeches are amphibious. Other leeches are called land leeches and live in moist regions around the world.

Leeches can be found nearly every place there is water. Shallow ponds, lakes, and marshes are popular leech collecting sites. The best time for leech collecting is during the spring and summer. Most leeches are nocturnal and avoid light. Leeches can often be found in shady areas of ponds or in dark places under rocks, logs, and debris of the bottom of lakes.

spring tails

Springtails sometimes cause alarm to homeowners when seen outdoors in enormous numbers, appearing as “piles of soot” in driveways, backyards, on mud puddle surfaces, etc. Occasionally, they enter the home where dampness occurs such as in basements, cellars, bathrooms, and kitchens, especially near drains, leaking water pipes, sinks, and in the soil of over-watered house plants. They usually appear in the spring and early summer but can be found all year round. Some are known as “snow fleas,” appearing on the top of snow during late winter and early spring. These very small, leaping insects do not bite humans, spread disease, nor damage household furnishings. They are usually a nuisance by their presence.

Springtails are minute, wingless insects about 1/16 to 1/8 inch (1 to 2 mm) long. Colors vary from white, gray, yellow, orange, metallic green, lavender to red with some being patterned or mottled. They get their name from the ability to catapult themselves (leap) through the air three to four inches by means of a taillike mechanism (furcula) tucked under the abdomen. When disturbed, this appendage functions as a spring, propelling them into the air away from the danger source. Young resemble adults except for size and color. Eggs are spherical.

Because both habitats are in conservaton and filtered the nitrate level is 0. The health of the pond is not normally that good in the city due to the pollution given off by cars and so on. For more accurate readings of the animals I could have calculated the sizes more accuraltely. This could have an effect on my results.

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 Populations in freshwater Ecosystems. (2018, Dec 14). Retrieved from https://paperap.com/paper-on-populations-in-freshwater-ecosystems/

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