Fresh Water Ecology.

I, also, think that the Swale will be fairly oxygenated as there are lots of rocks and stones in it, obstructing the natural flow of the river, so the river is colliding with the rocks at quite a speed which aerates the water as air is getting into it, thus, oxygenating it. I predict that the flow is reasonably fast from my own knowledge but I'm not quite sure how fast.

Apparatus

x White Tray

x Small Sieve

x Magnifying Glass

x Clipboard

x Identification Sheet (pictures of various organisms)

Diagram

Method

I will work in a group of two and we're going down to the River Swale with the equipment. We are going to use the sieve/net to test various parts of the River to see which organisms are living there. We'll take some samples from disturbing stones and some samples from the middle of the River where the current is fairly fast and where it seems more oxygenated.

Before we begin collecting any organisms, we'll fill the white tray up with some water so as not to kill the organisms when we put them into the tray to investigate them. Then we'll go into the River and put the sieve under the water. Where we will be searching under rocks etc. we'll have to rummage around and but where the river is fast-flowing we'll put the sieve/net in the water and let the current flow into it bringing various organisms with it.

Once we've got some organisms in the sieve/net, we'll put them into the white tray and try to identify what they are. Once we've identified them, we'll record the data and release them back into the water. We're going to do this five times to get some varied data. Twice, the data will be from a slow, settled part of the river and the other three repetitions will be from the fast-flowing part of the river.

We will also measure the speed of flow of the River Swale. About three people will do this by measuring out 10 metres and 1 person will stand at the beginning and one at the end of the 10-metre span. The first person will put a little plastic container on the surface of the water, and as soon as that's done, the third person will begin timing. We will then record the time of how long it takes for the little plastic container to travel 10 metres. We're going to do this in slow-moving and fast-moving water.

Evidence

From the River Swale

Repeats

Organism

-Slow-Flowing

2-Slow-Flowing

3-Fast-Flowing

4-Fast-Flowing

5-Fast-Flowing

Stonefly Nymphs

2

(Leuctra)

9

Mayfly-Baetis

Ecdyonulus

(big one!)

Chironomid Larva

Fresh Water Shrimp

Fresh Water Beetle

Ephemera

The river was flowing at about 32 seconds/10 metres in the shallow/more settled area and it was flowing at about 24 seconds/10 metres in the deep/faster waters.

From the data provided

Species

Tally

Asellus (water hog louse)

0

Gammerus (f.w. shrimp)

3

Chironomous Larvae

3

Flat Worm

3

Ram's Horn Snail

7

Tubifex

7

Trent River Biotic Index

The Trent River Biotic Index tells us how clean/polluted the river is. The Biotic Index calculates from 1-15, 1 being heavily polluted and 15 being very clean.

Using the table, we were given at the beginning of the experiment, I worked out that the Trent River Biotic Index for the River Swale was 8 and the Trent River Biotic Index for the data we were given was 5.

Diversity Index

I'm going to calculate the Diversity Index from my data collected.

N(N-1)

_____

Diversity Index ?n(n-1)

N = total number of individuals

n = number of individuals in each species

? = sum of

N

n(n-1)

N

n(n-1)

8(18-1)

2(2-1)

306

2

8(18-1)

9(9-1)

306

72

8(18-1)

(1-1)

306

0

8(18-1)

2(2-1)

306

2

8(18-1)

(1-1)

306

0

8(18-1)

(1-1)

306

0

8(18-1)

(1-1)

306

0

8(18-1)

(1-1)

306

0

Total

76

Therefore, the Diversity Index for the River Swale is

306

____ = 4.25

76

N

n(n-1)

N

n(n-1)

43(43-1)

0(10-1)

806

90

43(43-1)

3(3-1)

806

6

43(43-1)

3(13-1)

806

56

43(43-1)

3(3-1)

806

6

43(43-1)

7(7-1)

806

42

43(43-1)

7(7-1)

806

42

Total

342

Therefore the Diversity Index for the data provided is

1806

_____ = 5.28

342

Biochemical Oxygen Demand

The Biochemical Oxygen Demand is a measure of the oxygen used up by micro-organisms in the water.

We filled a labelled 250cm³ bottle with river water with as little disturbance as possible. We used a syringe to put 1cm of 0.1% methylene blue into the water. We then made the bottle airtight by screwing the lid on. We incubated the bottle at 20ºC for 5 days in the dark. We examined it to see if the blue colour had disappeared. As long as there is oxygen in the water, it will stay blue. Once it is used up the colour disappears.

Comparison

With the data that I have collected from the River Swale and the data that I have been given, I have worked out the Trent River Biotic Index and the Diversity Index. From these results I can draw up a comparison. The Biotic Index calculates from 1-15. The River Swale was 8 that means that it is quite fresh and oxygenated water whereas the river data that I have been given had a Biotic Index of 5 meaning that it is less oxygenated therefore the creatures that are found in it tend to be creatures that don't need that much oxygen.

The Diversity Index for the River Swale was 4.25 and the Diversity Index for the other river was 5.28. The higher the diversity index, the more variety of species there are in that specific river. So this specific data shows that there is more variety of species in the other river to the River Swale.

Evaluation

I enjoyed this experiment because it was different, however, the data we collected from the River Swale isn't really reliable because we didn't collect enough species. We didn't have the time to take more samples therefore the Trent River Biotic Index and the Diversity Index aren't very reliable. If we had joined all the class's results together and each used those results, we would have got a much more accurate and reliable outcome. We should also have tested different parts of the River (not necessarily length ways but width ways).

My prediction cannot be proved or disproved because of the number of species we collected. We did manage to account for all the species and name them all, and they all came towards the top of the Biotic Index group suggesting the river is high in oxygen. The smallest creatures were obviously the hardest to identify.

Overall, I've gained knowledge on how to calculate various things to do with rivers and can now identify a few different river organisms.

By

Emma Ward

2 TLW