Rocky shore

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Anjajavy Forest on Tsingy rocks jutting into the Indian Ocean

A rocky shore is an intertidal area of seacoasts where solid rock predominates. Rocky shores are biologically rich environments, and make the ideal natural laboratory for studying intertidal ecology and other biological processes. Because they are so accessible, they have been studied for a long time and their species are well known.^[1][2]

[edit] Factors favoring marine life

There are a large number of factors that favor the survival of life on rocky shores. Temperate coastal waters are mixed by waves and convection maintaining adequate availability of nutrients. Also, with the effect of the tides, the sea brings plankton and broken organic matter in with each tide. The high availability of light and nutrient levels means that primary productivity of seaweeds and algae can be very high. Interestingly, rocky shores can benefit from the result of human actions through the phenomenon known as nutrient run-off.

[edit] Factors affecting the distribution and abundance of marine life on rocky shores

Regardless of the factors that favour life on rocky shores, there are a number of challenges that marine organisms which use them as their habitat must face. Generally, the distribution of its benthic species is limited by salinity, wave exposure, temperature, desiccation and general stress.The constant threat of desiccation during exposure at low tide can result in dehydration which many creatures have developed strong adaptations to prevent such as production of mucous layers and shells. Many species use shells and holdfasts to provide stability against strong wave actions. There are also a variety of other issues such as varying temperature fluctuations due tidal flow, changes in salinity and various ranges of illumination which can make life very difficult for rocky shore organisms. This can be coupled with predation from birds and from other marine creatures and also the vast effects of pollution.

[edit] Examples of rocky shores

An interesting example of a rocky shore is the tsingy outcrops on the west coast of Madagascar, where the rock formation is dramatic and often consists of one gigantic piece of rock. This formation occurs where the Madagascar dry deciduous forests meet the ocean. Rocky shores are areas of bedrock exposed between the extreme high and extreme low tide levels on the seashore.

The rocky shores around the Mediterranean Sea are also very rich with life.

A rocky beach in Croatia overlaid with cement and attached ladder. This is done for comfortability and access to the waters.

New Zealand's rocky shores around the Auckland area are also very interesting. Many rock pools were created during the violent eruptions that formed the shore eons ago. A variety of species are found in the area, including:

• Cushion star,
• Hermit crab,
• Rock crab,
• Cat's eye snail,
• Red beadlet anemone,
• Black nerita snail,
• Brown rock whelk,
• Kina (sea urchin),
• Eleven-armed sea star

[edit] Rocky shores of the North Atlantic

On the rocky shores of the North Atlantic the distribution of benthic algae often show distinct patterns along a horizontal wave exposure gradient and along a depth gradient.^[3].^[4] Typically, algae such as Fucus vesiculosus and Ascophyllum nodosum will occupy the upper strata on the medium exposed shores, whereas Gigartina stellata, Alaria esculenta and Laminaria digitata will occupy the lower strata on exposed shores. By combining algal attributes with observed physical and chemical forcings it appears that at least parts of the distribution patterns can be explained. ^[5]. The counter clock-wise cyclic pattern in phase space between a predator (y-axis) and its prey (x-axis) that are observed for some terrestrial organisms, like hare and lynx,^[6] has also been observed for rocky shore grazer- food systems.^[7]

[edit] Rocky shore pollution

Rocky shores are exposed to many forms of pollution, in particular pollution related to oil spills. Prominent spills are the Torrey Canyon spill,.^[7] The Amoco Cadiz spill outside the Brittany coast in France^[8] and the Exxon Valdez spill outside alsaka, USA.

[edit] References

1. ^ J H Connell, Community Interactions on Marine Rocky Intertidal Shores. 1972. Annual Review of Ecology and Systematic Vol. 3: 169-192
2. ^ J. R. Lewis (1964). The Ecology of Rocky Shores. English Universities Press, London. 
3. ^ Jones , WE and Demetropoulos, A. 1968. Exposure to wave action: measurements of an important ecological parameter on rocky shores on Anglesey. J.exp. mar. biol. ecol. 2:46-63
4. ^ Seip,K.L.1980. A mathemaical model of competition and colonization in a community of marine benthic algae. Ecological modelling 10:77-104
5. ^ Seip, K.L. Mathematical models of rocky shore ecosystems. In Jørgensen, SE and Mitch, WJ (Eds) Application of ecological modelling in environmental management, Part B, Chap 13, pp 341-433
6. ^ E. R. Leigh (1968) The ecological role of Volterra's equations, in Some Mathematical Problems in Biology – a modern discussion using Hudson's Bay Company data on lynx and hares in Canada from 1847 to 1903
7. ^ ^{a b} Southward, AJ and Southward, EC. 1978. Recolonization of Rocky shores after the use of toxic dispersants to clean up the Torrey Canyon spill. J. Fish. Res. Board. Can 35:682-706.
8. ^ Seip,KL. 1984. The Amoco Cadiz Oil spill- at a glance. Mar. Poll. Bull. 15 (6) 218-220