Flat periwinkle Investigation

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Brown Flat Periwinkles: Raw Data Collected from the Sheltered Shore of Angle Point

Zone

Quadrat number

Abundance

Running Mean

LOWER

0

0.000

LOWER

2

0

0.000

LOWER

3

0

0.000

LOWER

4

0

0.000

LOWER

5

0

0.000

LOWER

6

0

0.000

LOWER

7

0

0.000

LOWER

8

0

0.000

LOWER

9

0

0.000

LOWER

0

0

0.000

LOWER

1

0

0.000

LOWER

2

0

0.000

LOWER

3

0

0.000

LOWER

4

0

0.000

LOWER

5

0

0.000

LOWER

6

0

0.000

LOWER

7

0

0.000

LOWER

8

0

0.000

LOWER

9

0

0.000

LOWER

20

0

0.000

LOWER

21

0

0.000

LOWER

22

0

0.000

LOWER

23

0

0.000

LOWER

24

0

0.000

LOWER

25

0

0.000

LOWER

26

0

0.000

LOWER

27

0

0.000

LOWER

28

0

0.000

LOWER

29

0

0.000

LOWER

30

0

0.000

LOWER

31

0

0.000

LOWER

32

0

0.000

LOWER

33

0

0.000

LOWER

34

0

0.000

LOWER

35

0

0.000

LOWER

36

0

0.000

LOWER

37

0

0.000

LOWER

38

0

0.000

LOWER

39

0

0.000

LOWER

40

0

0.000

LOWER

41

LOWER

42

LOWER

43

LOWER

44

LOWER

45

LOWER

46

LOWER

47

LOWER

48

LOWER

49

LOWER

50

Zone

Quadrat number

Abundance

Running Mean

Introduction: Aims and Hypothesis

The flat periwinkle exists as two distinct species littorina obtusata and littorina mariae, (http:/lineone.net/wildlife/molluscs_flat_periwinlkle.html) both species are common to the sheltered shores of Great Britain and both species can be found in range of different coloured shells (Fish JD and Fish S 1996). The aim of this investigation is to determine if this difference in shell colour will have a significant effect on the distribution of the flat periwinkle on the sheltered shore of Angle point. The distribution and abundance of the flat periwinkle will ultimately be determined by the interactions that the organism experiences between its environment and other organisms. Thus, if changes in shell colour result in the interactions that the flat periwinkle experiences between its biotic and abiotic environment changing, or if different colours of flat periwinkle carry unique genes that effect the species vulnerability to disease or behavioural patterns for example, then differences in shell colour will have a significant effect on the distribution of the flat periwinkle.

The flat periwinkles interactions with the abiotic environment could change as a result of shell colour. As different colours absorb heat at different rates, with darker colours absorbing more heat then lighter colours, there could be a relationship between the internal temperature of a flat periwinkle and its shell colour. This is significant because the internal temperature of an organism determines the efficiency that its enzymes operate at. Therefore, as the flat periwinkle will compete better when working at an optimum metabolic rate, and as different zones along the sheltered shore can be assumed to be at different temperatures (due to aspect, height, and the relative position of the sea); so it would make sense to predict that rather then an even distribution of different colour of flat periwinkle along the sheltered shore, what will be observed will be distinct zones in which one colour of flat periwinkle dominate to the detriment of the others.

Changes in colour could also effect the biotic interactions that the flat periwinkle will experience. Simply put, it was observed from a previous trip to Angle point that different zones along the sheltered shore had a different visual appearance. Therefore it makes sense to assume that different colours of flat periwinkle would experience different degrees of camouflage depending on where they were located on the shore. Therefore, due to the effect of predation it makes sense to assume that what will be observed will be distinct zones in which one colour of flat periwinkle dominates as a result of its colour that enhances its ability to avoid predator attack.

Hypothesis: As a result of what has been discussed above it is possible to predict that following the collection of data from angle point the subsequent chi squared test will disprove the null hypothesis. I.E the results should show that the ratio of different colours of the flat periwinkle will vary with zonation.

Null Hypothesis: The ratio of different colours of flat periwinkles will be independent of zonation.

Site Justification: To test the hypothesis a site had to be chosen in which flat periwinkles would be abundant. Background Reading (Fish JD and Fish S 1996) revealed that flat periwinkles generally preferred sheltered environments, and as the nearest sheltered shore available was at Angle Point. It was decided that data would be collected from this site. Moreover as the investigation relied on a detailed knowledge of the structure of the shoe (with reference to the upper, middle, and lower shore), a shore had to be chosen for which the zonation was known. Simply put for Angle point it was very easy to find the heights at which the different zones ended and began (A Williams Pers Comm).

Method: How Data was Collected From Angle Point

In conjunction with data provided that listed the heights at which each zone (upper, middle, and lower) began and ended at Angle point (A.Willaims Pers Comm) a 60cm cross staff was used to determine the midpoint of 1st the lower shore then middle shore and finally the upper shore. At this point markers were laid down at the midpoints of the three zones (upper, middle and lower). This was not stated in the planed method, but this amendment had to made because the heights at which each zone began and ended was provided relative to the seas position at a certain time, clearly as the day progressed and the sea came in it would be difficult to accurately account for this and thus assessing the midpoint of each of the zones at a later point would not have been practical.

With the midpoint of each zone clearly identified using markers, a horizontal belt transect of the lower shore was then conducted. The 0.25 meter squared quadrat was laid on the shore and then the numbers of flat periwinkles were counted, noting how many fell into each different colour category. Flat periwinkles were identified by their teardrop shaped operculum, flattened spire and rounded almost spherical shape. Each quadrat was thoroughly checked, ensuring that both the top and bottom of each piece of seaweed was thoroughly examined. Background reading (Charles, 1982) just prior to the experiment revealed that flat periwinkles were likely to be found on Fucus spiralis, F. vesiculosus, Ascophyllum nodosum, and F. Serratus so these species of seaweed were checked with even more thoroughness.

Once the total number of each of the different colours of flat periwinkles had been counted, the quadrat was flipped over on its side 180 degrees to the right ensuring that the right edge remained in contact wit the shore and the above method for counting the numbers of yellow, green and brown flat periwinkles was repeated, and the belt transect repeated of the lower shore in this manner until the tide cam in to such a level that work on the lower shore had to be stopped for that day. At this point the experiment proceeded to the middle shore as indicated by the marker, and a belt transect was conducted at this point in exactly the same manner as it had been on the lower shore. Data was collected until the incoming tide made the collection of data no longer possible and then the same method was repeated on the upper shore. Data was collected in this manner on 2 consecutive days: the 15-16 July 2001.
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Method: Amendments made to the Planned Method

Whilst conducting the experiment it was noted that in addition to yellow and brown flat periwinkles, green flat periwinkles existed also, and so the abundance of green flat periwinkles was noted. Whilst counting the numbers of flat periwinkle that were green it was noted that if the surface of some of them was scratched, a green algal covering was removed resulting in a yellow periwinkle being identified instead of a green one. This became apparent after the third quadrat and so results for the first three quadrats of the lower ...

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