A comparison of marine organisms on shale & limestone coasts. Doolin, Ireland.

Methodology

Doolin is relatively unique in terms of its coastal geomorphology as it has two wave-cut platforms of differing geology; limestone and shale. This site is therefore ideal for comparing marine life in two different environments. The only problem that could be encountered while working at Doolin would be the tide. It was vital that data was collected as the tide was going out as this would give the most up to date information as to what was in the rockpools. Two transects were set out in both sites, each transect going from the shoreline inland until the rockpools stop. All of the rock pools were selected within one metre of transect line for further observation. Each pool was then studied to identify and list marine pool flora and fauna, this was done with the help of a coastal organisms book (Hayward, 2002). The flora/fauna was then classified into categories; hard shelled, soft, free-moving, fixed etc.

Both transects was measured out and levelled using a compass clinometer. This was a very quick and basic method which combines vertical angle measurements with distance measurements. The results then need to be converted by using trigonometry.

-Fig 02-

Limestone Transect, Doolin.

The results could then be analysed and converted using trigonometry.

The rock pools characteristics were then measured, this included the distance from shoreline at high and low tide, the width, depth and length of rock-pool and the pH of water in each rock-pool. All of this data was recorded in tables using 'Microsoft Excel'.

Results

The data received from the compass clinometer levelling were carefully converted using trigonometry and are shown in the two profiles below (Fig 3 & 4). The values measured were generally negative values from the starting point. These were adjusted to show the slope profile easier. For example, the starting point was referred to as "0" and sea level appears at -59 meters, this was converted to represent sea level as "0" and the actual starting point as an elevation of 7 metres and a distance of 59.03 meters from the water line.

-Fig 03- Limestone Transect Profile

The profile below (Fig 4) has been created identically to the limestone profile above. It is quite noticeable that the shale profile was considerably shorter than the limestone profile; this was due to the tide not going out as far on the shale side of the coast.

Results - Shale Transect

-Fig 04- Shale Transect Profile

Other results and tables have been shown in the appendices at the end of the report to avoid clutter in this

Discussion & Evaluation

After analysing the results of both the shale and limestone transects it is clear that both profiles are stepped; which of course is expected from a coastal profile. It is also quite apparent how species diversity increases as the pools go closer to the sea. Fig 05 (appendices) shows 'rock pool 1' on the limestone having three different species of fauna but no flora, in contrast 'rock pool 7' had seven different species of fauna and six species of flora. The shale transect also emerges with similar results in that biodiversity appears to increase as the pools get closer to the shoreline.

Both transects have flora and fauna biodiversity; however 'fig 5' and 'fig 8' show that greater diversity would appear to be on the limestone wave-cut platform. On the basis of this limited data the shale coast supported four species of fauna and just one species of flora. In contrast, the limestone transect appeared to support seven different species of fauna and six species of flora. Initially the conclusion that limestone coasts sustain more diverse organisms appears to be justified, but further investigations would be required to add evidence to this preliminary statement.

Pool size generally appeared to increase in size and depth as they got closer to the sea in both the limestone and the shale coasts, this evidence can be seen from 'fig 6 & 9'.

Conclusion

The evidence from the data collected would suggest rock pools greater to the shoreline can hold a greater biodiversity than those further away.

In comparison between the limestone wave cut platform and the shale it was predicted that the shale would have greater biodiversity. This hypothesis was created from previous work done Nybakken (2001), who suggested the sediment in the shale rockpools created and sustained a more diverse biodiversity. This appeared to be incorrect and there was a greater biodiversity of organisms in the limestone pools. This contrast of results could have been from a number of reasons. Firstly it was quite obvious that the limestone coast was more sheltered than the shale coast, therefore the quality of habitat was higher in the limestone. There was also a large amount of bio erosion on the limestone coast which created larger, deeper and a larger quantity of rock pools.

It would appear that bio-diversity of marine organisms was higher with decreasing distance from the shoreline. The shoreline appeared a controlling factor in biodiversity, however this was expected. It is quite logical to think that a higher biodiversity would be sustained closer to the sea as that is where they originate. The results also determine that species diversity generally increases with increasing pool size. As predicted previously, larger pool sizes would have more space for different more diverse species to inhabit.

In a final conclusive summary, the results taken from both transects would suggest that limestone environments can maintain a more diverse biodiversity of marine organisms. However, other factors such as the distance of pool from the shoreline, the size and depth of the pool and its exposure to the wind and the sea are also influential.

References:

> Nybakken, J. W. (2001). Marine biology: An ecological approach. San Francisco: Benjamin Cummings.

> Hayward, P. (2002) Seashore. London: Collins New Naturalist.

> Kamphuis J. W. (1991) Physical Modelling - Handbook of Coastal & Ocean Engineering, Gulf Publishing Company, Houston, Texas.

> Ovesen, N. K. & Schuldt, J. C. (1992). Beach Management System. Danish Geotechnical Institute, Lyngby.

Appendices

Results - Limestone Transect

-Fig 05- Rock Pool Biodiversity - Transect 1 (Limestone)

Category

Pool 1

Pool 2

Pool 3

Pool 4

Pool 5

Pool 6

Pool 7

FAUNA

Limpets

*

*

*

*

*

*

*

Aurelia Aurita

*

*

*

*

*

Snails

*

*

*

*

*

*

*

Muscles

*

*

*

*

*

*

*

Hermet Crabs

*

*

*

*

Shrimps

*

*

Fish

*

FLORA

Sea Lettace

*

*

*

*

Sea Enenemies

*

*

*

*

*

White Weed

*

*

*

Dumontia Contorta

*

*

Palmaria Palmata

*

Obelia Dichotoma

*

*

*

*

*

-Fig 06- Rock Pool Specifications - Transect 1 (Limestone)

Category

Pool 1

Pool 2

Pool 3

Pool 4

Pool 5

Pool 6

Pool 7

Width - Avg (m)

.22

.40

7.00

.70

5.50

0.3

2.4

Length - Avg (m)

3.00

2.10

.92

5.20

.60

0.84

4.5

Depth - Avg (m)

0.14

0.15

0.15

0.14

0.12

0.19

0.2

Surface Area (m)

3.66

2.94

3.44

8.84

8.80

0.25

0.8

pH

7.9

7.8

8

7.9

7.7

7.7

7.5

Results - Shale Transect

Biodiversity:

-Fig 08- Rock Pool Biodiversity - Transect 2 (Shale)

Category

Pool 1

Pool 2

Pool 3

Pool 4

Pool 5

FAUNA

Shrimps

*

*

Fish

*

Worms

*

Fish (Dead)

*

*

FLORA

White Weed

*

Rock Pool Specifications:

-Fig 09- Rock Pool Specifications - Transect 2 (Shale)

Category

Pool 1

Pool 2

Pool 3

Pool 4

Pool 5

Width - Avg (m)

.00

.70

.20

2.50

5.00

Length - Avg (m)

.40

2.10

2.60

8.00

5.00

Depth - Avg (m)

0.03

0.05

0.06

0.09

0.20

Surface Area (m)

.40

3.57

3.12

20.00

75.00

pH

N/A

N/A

N/A

N/A

N/A

Rob Anders Post Ireland Assignment April/May 2004