Zonation of Nodilittorina Unifasciata and Nodilittorina Pyramidalis

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Unifasciata and Pyramidalis are gastropods found on the intertidal zone along the rock platforms of Fairlight Beach, where they occur in clusters of individuals throughout the littoral to mid-littoral zone. The aim of the experiment was to test hypotheses:

H0: "There is no correlation between the means of Unifasciata and the distance from water"

HA: "There is a correlation between the means of Unifasciata and the distance from water"

H0: "There is no correlation between the means of Pyramidalis and the distance from water"

HA: "There is a correlation between the means of Pyramidalis and the distance from water"

H0: "There is no difference between the means of Pyramidalis and Unifasciata"

HA: "There is a difference between the means of Pyramidalis and Unifasciata"

The results of the experiment support zonation on the Fairlight rock platform, as we rejected the H0 and accepted the HA for all accounts and show a correlation for all variables.

Introduction:

Both species of nodilittorina are marine gastropods that feed on algae and lichen found on the rock surfaces. They are located within the intertidal zone along the rock platforms of Fairlight Beach, where they occur in clusters of individuals throughout the eulittoral zone. However clusters become less and less frequent as you cross the littoral fringe. Both species occur commonly in littoral zone. However a few species of Nodilittorina Pyramidalis were found in the lower area of the supralittoral zone, a zone which receives little to no inundation but relies on strong waves and ocean spray. Our aim of this experiment was to test Hypothesis

H0: "There is no Correlation between the means of Unifasciata and the distance from water"

HA: "There is a Correlation between the means of Unifasciata and the distance from water"

H0: "There is no Correlation between the means of Pyramidalis and the distance from water"

HA: "There is a Correlation between the means of Pyramidalis and the distance from water"

H0: "There is no difference between the means of Pyramidalis and Unifasciata"

HA: "There is a difference between the means of Pyramidalis and Unifasciata"

Figure A ("sessile animals of the sea shore" -Vernon A. Harris page 15"):

Figure A shows the species in order in which they appear from the sublittoral zone to the littoral fringe. The Distribution of the Nodilittorina species does not occur until the littoral zone therefore it is commonly referred to as the periwinkle zone. As you can see, the Nodilittorina Pyramidalis occurs beyond the point of the last unifasciata. In our experiment we should also be able to see the distance in which Pyramidalis continues and Unifasciata ceases.

Methods:

The experiment was performed during low tide so that the rock platform were completely exposed and the population could be accurately counted throughout the transect.

For the experiment a transect of 20m by 20m square was measured out and a origin point (0,0) was designated at the bottom left corner creating a x and y axis.

Split into two sub groups of three, 10 grid references per group were selected at random using the random numbers table.

At each grid reference a 1m by 1m quadrat was placed down and the two species being investigated, Nodilittorina Unifasciata and Nodilittorina Pyramidalis were then counted and recorded.

Any crevices or large rocks were recorded down, as well as percentage cover of water, barnacle and bare rock.

Once the raw data had been recorded, it was then tabulated, graphed and analyzed using a statistical program called SPSS.

Results:

Table A (Raw tabulated data from sub-group 1):

Distance from water (metres)

Y'axis(M)

X'axis(M)

Unifasciata(U)

U2

U3

U4

Total U

Pyramidalis(P)

P2

P3

P4

Total P

16

4

14

0

0

0

0

0

0

0

0

0

0

5

15

9

0

0

0

0

0

0

0

0

0

0

20

0

17

0

0

0

0

0

0

0

0

0

0

19

1

17

0

0

0

0

0

0

0

0

2

2

17

3

13

0

0

4

0

4

0

0

0

0

0

16

4

1

3

0

3

16

22

8

0

0

0

8

12

8

4

0

41

50

21

112

0

0

0

0

0

1

19

18

0

0

0

0

0

0

0

0

0

0

9

11

9

7

3

126

1

137

0

0

0

0

0

10

10

2

69

22

36

72

199

0

0

0

0

0

Other:

Bare rock 100%

Water 70%. Bare Rock 30%

Water 40%. Bare rock 60%

Water 10%. Bare rock 80%. Honeycomb barnacle 10%

Bare rock 80%. Crevasse.

Damp rock 80%. Honeycomb barnacle 10%. Water 10%

Damp rock 80%. Honeycomb barnacle 20%

Oysters 90%. Water 10%

Honeycomb barnacle 80%. Damp rock. Water 20%

Honeycomb barnacle 80%. Damp rock 15%. Water 5%

Table B (Raw tabulated data from sub-group 2):

Distance from water (metres

Y'axis(M)

X'axis(M)

Unifasciata(U)

U2

U3

U4

Total U

Pyramidalis(P)

P2

P3

P4

Total P

5

15

1

32

68

44

41

185

0

0

0

0

0

2

18

8

0

0

0

0

0

0

0

0

0

0

15

5

3

6

42

8

6

62

0

5

0

0

0

16

4

10

0

0

0

0

0

1

0

0

0

0

12

8

6

32

1

1

2

36

7

1

0

0

0

9

11

10

41

1

3

7

52

0

0

0

0

0

7

13

14

0

0

0

0

0

0

0

0

0

0

4

16

3

39

153

31

27

250

0

0

0

0

0

9

1

4

0

0

0

0

0

1

0

0

0

0

10

10

5

8

10

0

0

18

0

0

0

0

0

Other:

Water 68% Bare rock 32%

Water 1% Oyster 88% Bare Rock 11%

Water 3% bare rock 97%

Water 1% bare rock 99%

Water 25% Crevice

Water 40% Crevice

Neptunes necklace 65% Oyster 8% Bare rock 27%

Oyster 20% Crevice

Water 75% Bare Rock 25%

Water 25% Bare Rock 75%

Figure B (correlation of Unifasciata and Distance from water):

Correlations

Distance from water

Unifasciata

Distance from water

Pearson Correlation

1

-.308

Sig. (2-tailed)

.187

N

20

20

Unifasciata

Pearson Correlation

-.308

1

Sig. (2-tailed)

.187

N

20

20

Figure C (Correlation of Pyramidalis and Distance from water):

Correlations

Distance from water

Pyramidalis

Distance from water

Pearson Correlation

1

.340

Sig. (2-tailed)

.142

N

20

20

Pyramidalis

Pearson Correlation

.340

1

Sig. (2-tailed)

.142

N

20

20

Figure D (T-Test of Unifasciata and Pyramidalis)

One-Sample Statistics

N

Mean

Std. Deviation

Std. Error Mean

Unifasciata

20

53.85

78.911

17.645

Pyramidalis

20

1.25

2.593

.580

One-Sample Test

Test Value = 0

95% Confidence Interval of the Difference

t

df

Sig. (2-tailed)

Mean Difference

Lower

Upper

Unifasciata

3.052

19

.007

53.850

16.92

90.78

Pyramidalis

2.156

19

.044

1.250

.04

2.46

Figures E & F (Species vs Distance from water):

Results:

The raw results recorded are shown tabulated in Tables A and B, which shows distance from water, the x and y coordinates for the quadrate within the transect area. The counts for Unifasciata and Pyramidalis are also shown per quadrate as quarterly and a total count. The "Other" column shows the percentage cover of other observed interests such as water, bare rock, barnacle and crevasses. The reason the data is split into two Tables is because the raw data was recorded by two different groups and then tabulated separately.

Figures B, C shows the output from a correlation analysis performed on SPSS using the combined raw data recorded. Figure B shows a qualitative analysis of the data found, and shows that between Unifasciata and distance from water there is a weak, negative correlation. Figure C shows that the analysis found that there is a weak correlation between Pyramidalis and the distance from water.

Figure D shows the output of a t-test analysis performed on SPSS the significance of Unifasciata is 0.007 and the significance level of Pyramidalis is 0.044.

Figures E and F shows the data plotted on a graph this shows the distribution of both species based on their distance away from the water. In Figure F it shows the Unifasciata has its highest counts at around 5m from the sea, with the highest count at 250 at 4m from 0m to 4m there is 0 counts. The counts start to decrease as you move further away from the water until finally you have zero counts at 19m and 20m. Figure G shows Pyramidalis present at 9m with a count of 1and the highest count of 8 at 12m and 16m and the furthest count at 19m away from sea level.

Discussion:

The results shown in Figures E and F show that the Unifasciata species occur closer to the water than Pyramidalis as they occur at 4m and Pyramidalis occur at 9m. It also shows that Pyramidalis occurs the furthest away from the water, as its presences reaches 19m and Unifasciata species only reaches 17m. This agrees with known behavioral patterns of the species shown in the distribution chart Figure A.

The correlation analysis performed on SPSS gave us qualitative results, showing that there was weak correlations with both species and distances to water, however Unifasciata showed a weak negative correlation of -0.308 which means as the distance away from the water increase the number of Unifasciata decreased opposed to the Pyramidalis having a weak positive correlation of 0.340 which means as the distance away from the water increases so does the number of Pyramidalis individuals. The output from the correlation analysis shows a correlation for both Unifasciata and Pyramidalis and distance from water so we reject the H0: "There is no Correlation between the means of Unifasciata and the distance from water" and H0: "There is no Correlation between the means of Pyramidalis and the distance from water" and accept the HA: "There is a Correlation between the means of Unifasciata and the distance from water" and HA: "There is a Correlation between the means of Pyramidalis and the distance from water". The rejection of the null hypothesis was to be expected, as we know from previous research and knowledge that the distance from water has a direct affect on the presence of Pyramidalis and Unifasciata. (Vernon A. Harris, Springer, 1990 "Sessile animals of the sea shore")

The t-test shows us that the significance for both Unifasciata and Pyramidalis was both less than 0.05 significance, which shows us that we reject the H0: "There is no difference between the means of Pyramidalis and Unifasciata" and accept the HA: "There is a difference between the means of Pyramidalis and Unifasciata" as there was a slight difference between the two means.

The experiment performed reinforces known knowledge on the behavioral patterns of both species and the schematic zonation of the intertidal ecology of eastern Australia. However the results from the experiment don't properly show the distinct nature of the zonation as there were gaps between each sample distance from the water. The research could be better used if sample had been done every metre till then end of the mid-littoral zone to properly show the zonation and pattern of both species. The sample are should also have been performed at several locations for a more accurate experiment.

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