Introduction

Rocky seashores show gradual changes in biotic and abiotic factors across a habitat that occurs in a restricted area. This makes them a very useful "natural laboratory" for analyzing interactions among intertidal organisms, their environment and other biological processes. This biologically rich environment shows how communities in tidal areas are affected in very exposed and very sheltered sites. As the water level changes, (brought about from action of the tide) the exposure to the water with a high salinity also varies.

Aberdour rocky seashore was chosen for analysis in this report, which aims to represent the abundance of species and diversity in this ecosystem reliably. It will also show the differences in variation and distribution between species in exposed and sheltered areas of the shoreline – while considering the variation and distribution at varies heights below the water line.

Analysis

Within a sheltered/exposed intertidal habitat, zonation is an extremely common occurrence. Duration of immersion with regards to seawater has a direct effect on the extent of desiccation, temperature and salinity stress an organism experiences (Gilman et al, 2006)[1]. Different species flourish in different levels of protection from the physical environment; wave activity frequently being the most crucial. (Ballantine, 1961)[2]. Therefore it can be assumed that the degree of exposure to wave action can directly affect these environmental factors. The more exposed areas will encounter more frequent immersion and much more constant action from harsh tides, leading to increased dislodgement from the rock surfaces and damaging of organisms, which leads to the absence of the weaker organisms.

The prevailing wind will also have an effect on the degree of exposure to desiccation in exposed areas. In comparison, the more sheltered areas of the shore do not face the open sea or prevailing wind and therefore maintain a more consistent environment to the organisms within it.

The organisms which are furthest from the water level are subject to the greatest degree of desiccation stress (Frankie, Navarrrete & Bozinovic 2007) [3] This results in the variety of organisms present being low compared to those in sites which are closer to the water level.

Results

At Aberdour rocky seashore, the sheltered and exposed sites where compared by the data in kite diagrams (see bellow). A SACFORD scale provides a unified system for recording the abundance of marine organisms in biological surveys. The species abundance is mapped against the vertical height above the chart datum in both kite diagrams. The data gives a reliable representation of the effect of exposure to wave action in an exposed habitat. The biological scale results to be the most appropriated to show both physical tolerance range and biotic interactions among species present.. Collection both data from the exposed and sheltered area on the same day (05.03.2015) makes the comparison much more reliable by reducing variables.

Data was also collected by the use of a quadrat. A 1m2 quadrat was placed randomly at perpendicular point of the shoreline from both the exposed and sheltered sites. The abundance of species absent and present was recorded.

From the data recorded, lichens are shown to be present in both sites – although they are only shown to be present in areas above the water line. Lichens have very low growing points, and grow comparatively slowly; so in more favourable environments (e.g closer to the shore), they would be out- competed by other organisms for sunlight. (Field Studies Cousin, 2008)[4]. Lichens are an association of fungus and algae. The fungal aspect of the lichen makes it efficient at storing water, and the algal proportion produces its own food. (Field Studies Council, 2008)[5]. This makes them well-adapted to the exposed conditions and able to survive in the absence of the supply of nutrition and far away from the seawater.

Barnacles and limpets are highly abundant in both the sheltered and exposed sites. They are also present and a broad range of levels along the shoreline, which suggests they are an all-round, well-adapted species for rocky seashores.

Mytilus edulis is highly abundant in the lower mid-shore areas of the exposed sight but is absent from the sheltered sight. It can be hypothesised that this is because Mytilus edulis can be shown to prefer a constant splash from the waves. (Seed, 169)[6]. Mussels attach themselves to stones or shells with the help of strong threads, known as the mussel's 'beard'. The threads keep the mussel in place so that it isn't affected by movement in the water. (eol.org)[7]. This makes it capable of survival in the prevailing winds and harsh wave actions of the exposed sight.

The Fucus species are shown to have not much difference in their degree of abundance in both sites. However their distribution varies slightly as they appear to be in more of the further from the water line in the sheltered site. They possess mucilage-covered blades which are resistant to dying out and to changes in temperature. (britannica.com)[8]. The Fucus species face interspecific competition with other species such as Ascophyllum nodosum, but the mechanisms of the Fucus species make more adapted to the exposed sites conditions. Ascophyllum nodosum is much more abundant in the sheltered site (showing that it out-competes Fucus species at this site) but is present in both sites at lower in the shoreline. Changes in phlorotannin content […](a chemical deterrent for seaweed)[…] caused by nutrients, levels of phlorotannins are also found to vary plastically as a response to other environmental factors such as salinity, light availability, ultraviolet radiation and the intensity of herbivory (reviewed by Targett and Arnold, 1998; Amsler and Fairhead, 2006; Jormalainen and Honkanen, 2008)[9]. Increased exposure to sunlight has been proven to increase phlorotannin content in Fucus vesiculosus, but have no effect on phorotannin content of Ascophyllum nodosum. (Pavia & Toth, 2000)[10].

Conclusion

Having compared the kite diagrams that show the difference in species variation and abundance in exposed and sheltered sites and analysed the data displayed, it is clear that different species show a preference in one or the other environments. It was hypothesised that this was due to how well adapted the species where to their environment and the species direct competition.

The area that species occupied in the sheltered and exposed site does not have much variation, but the abundance of the species in each showed a notable difference. The species recorded are abundant in a similar area with regards to distance from the shoreline, in relation to the various species positions above the water line. The areas in which they are abundant is only altered when in direct competition with other species.

References

[1] Gilman. S., Harley, C, Strickland, D, Vanderstraeten, O, O’Donnell, M and Helmuth, B (2006). Evolution of effective shore level as a method of characterizing intertidal wave exposure regimes. Limnol. Oceangr. Methods, 4, pp 448-457.

[2] W. J. Ballantine, 1961, A Biologically-defined Exposure Scale for the Comparative Description of Rocky Shores. Zoology Department, Queen Mary College, London.

[3] Finkw, G.G, Navarrete, S. and Bozinovic, F (2007). Tidal regimes of temperate coasts and their influences on aerial exposure for intertidal organisms. Marine Ecology Progress Series, 343, pp. 57-62.

[4] 6. Theseashore.org.uk, (2008). FSC (Field Studies Council) - Bringing Environmental Understanding to All. [Online] Available at: http://www.theseashore.org.uk/theseashore/Sheltered%20rocky%20shore%20splash%20zone.html [Accessed 14 Mar. 2015].

[5] 7. Theseashore.org.uk, (2008). The Sea Shore - FSC (Field Studies Council). [Online] Available at: http://www.theseashore.org.uk/theseashore/Exposed%20rocky%20shore%20upper%20shore.html [Accessed 14 Mar. 2015].

[6] . Seed, R. (1969). The ecology of Mytilus edulis L. (Lamellibranchiata) on exposed rocky shores. Oecologia, 3(3-4), pp.277-316.

[7] Encyclopedia Britannica, (2007). Fucus | algae genus. [Online] Available at: http://www.britannica.com/EBchecked/topic/221333/Fucus [Accessed 15 Mar. 2015].

[8] Encyclopedia Britannica, (2007). Fucus | algae genus. [Online] Available at: http://www.britannica.com/EBchecked/topic/221333/Fucus [Accessed 15 Mar. 2015].

[9] Targett and Arnold, 1998; Amsler and Fairhead, 2006; Jormalainen and Honkanen, 2008

[10] Pavia, H. and Toth, G. (2000). Influence of light and nitrogen on the phlorotannin content of the brown seaweeds Ascophyllum nodosum and Fucus vesiculosus. Island, Ocean and Deep-Sea Biology, 152, pp.2 & 3