Tides are caused by rising and falling of ocean surfaces owing to the moon’s tidal force. This tides results in changes in the water level. The intertidal zone is exposed at low tide and submerged at high tide. The spray zone which is never submerged, receives ocean water due to the crashing waves. The high tide zones are only submerged briefly when there is a highest tide. The middle is regularly exposed and submerged by the tide. The low tide zone is regularly submerged and it is exposed to the air during the lowest tides. The distribution of diverse rocky intertidal organisms is usually dictated by zonation because they are the only organism that that are adapted to live in each zone. The organisms that are involved include Crustaceans, mollusks and enchinoderms.
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The aim of the experiment was to learn about the influence of major environmental and biological processes on the pattern of distribution of rocky shores communities as well as learn how classical and recent experiments have been done in order to understand the causes of these patter to look for evidence that environmental gradients and/or inter-specific competition influence species zonation. Lastly, it will enable one to gain experience in the scientific processes of formulating a hypothesis, testing it empirically and writing up the findings in a scientific report. These objectives will be useful in realizing the hypothesis which proposes that productivity increases from high to low shore because conditions become more benign. Algal competitive ability increases from high to low on the shore. Tall plants are assumed to be stronger competitors than short plants and that environmental conditions are harsher on the high than the low shore, reducing diversity of species and finally, the numbers of species of seaweeds and animals increase down the shore
Causes of zonation
Both physical and biological factors are very crucial in generating as well as maintaining the zonation pattern. Intertidal species are controlled by physical factors at their upper limit of distribution as they tend to be controlled by sets of biological factors at their lower level. For instance, the distribution of the barnacle Chthamalus stellats has the upper limit set by tolerance of desiccation while the lower limit is set by competition with semibalamus balonoides as well as predation by whelk Nucella lapillus. The alga pelvetia canaliculata is limited from living higher on the shore by desiccation. It is however prevented from colonizing the lower levels by completion from fucoids which have higher capacity to withstand physical conditions higher on the shore when other species are removed. The final zones are narrow and well defined because they are determined by inter-specific competition.
The communities are not static and these fluctuations are as a result of irregular phases of predation by Nucella lapillus and the starfish Asterias rubens .Predation by Nucella and Asterias was limited in up-shore extent by the relationship between desiccation tolerance and the temperature.
Physical causes of Zonation
The spray zone is the highest reaches of the shore and the waves are only able to splash the time when there is the strongest winter storm at high tides. It is therefore, influenced greatly by heat, light, wind, and fresh water. On the case of high tide zone, the shoreline is below the spray zone and it is covered with seawater during high tides only. It is said to be influenced by temperature, light, wind as water cover and salt content whereas middle tide zone has the part of the seashore that is covered by the semidiurnal tides twice a day where seaweeds and animals get covered and uncovered by seawater, allowing periodic exposure to air. In the low tide zone organisms are covered with seawater and exposed to air at the lowest of tides only. This zone is stable due to constant temperature and salinity of the water as well as variable physical conditions of air.
Rock quality designation is considered in the process of designing the of the underground and open spaces evaluation of leaching potential of metallic ore aamong other similar cases. This designing is affected by the number as well as geometry of the discontinuity in the rock masses
The horizontal banding of the intertidal zone is caused by dominance of different organisms basically at different heights on the shore. The organisms involved are encrusting lichens and sedimentary animals such as barnacles and mussels. The ecological irrelevance of many of the experiments has led to the conclusion that the causes of zonal discontinuities has been fruitless mainly because ecological zonation is largely dependent on the competitive relations of species and therefore physiological tolerance limits play no part in this explanation. This has caused a revival of interests in the problem as well as a greater concern for the ecological realism of experiments treatments. This experiment is therefore set to bridge this gap that has remained unexplained for a long time
Ascophyllum is the dominant species in this zone and so can only live lower down the shore. It also contains a number of turf species (filamentous red algae) and it is found between Fucusvesiculosus and fucusserratus. It merges with the two and so, Fucusvesiculosus and serratusare also found in this zone. It is shown in figure 6 that the dominant species is Fucusspiralis butspecies such as Ascophyllumnondosom and Pelvetiacanaliculata are also found in the zone. In the Pelvetia zone, Pelvetiacanaliculata dominates the zone, and unlike the other zones, there are very few other species of algae living there as conditions are the harshest.
Ascophyllum is the dominant species in this zone and so can only live lower down the shore and contains a number of turf species. Both physical and biological factors are very crucial in generating as well as maintaining the zonation pattern. The zonation is physically influenced greatly by heat, light, wind, nature water as well as temperature.