An Investigation to find the Effect of Distance from the Sea on the Number of Species

A preliminary study was carried out at Meadfoot beach, however, studies carried out at Dawlish Warren, the River Lemon and in the woodlands, enabled me to become familiar with skills I would need to carry out my investigation.

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At different sites, different sampling methods where learnt to enable me to chose the most suitable sampling method and statistical analysis for my chosen investigation. Sampling methods learnt included capture, mark, recapture, and random sampling. Finally experiments, where conducted at the River Lemon for me to become familiar with equipment’s what they measure and their uses i.e. pH, velocity of water…

My preliminary study which was carried out at Meadfoot beach enabled me to become familiar with beach profiling and some of the animal and plant species that I should be expected to find on the rocky shore when carrying out my chosen investigation.

We carried out a transect line from the shore (supra-littoral zone) towards the sea (sublittoral zone) and placed a quadrat (50cm by 50cm) every metre to identify the species present in that qaudrat[Appendix 9]. The aim of the transect line (beach profiling) is to help describe the pattern of distribution of organisms according to the height above sea level, depending upon their ability to perform under various physiographic, physical, chemical and biological stresses imposed upon them. Beach profiling is also carried out to determine the depth of sea level at different parts of the beach as this abiotic factor play an very important role in the adaptation and survival of species [Appendix 7 +8].

The result of the transect illustrates the topography of the rocky shore and this data could be also be used alongside with the data of the species present to find the effect of distance and land slope on the species occupying that particular zone.

A rocky shore is defined as ‘the regions with strong waves, all the time which erode the rocks surface and thus leave the rocks exposed.’ (1)

As my investigation had to be carried out at Meadfoot beach, before deciding on my chosen topic I observed and thought about physical (abiotic) and biological (biotic) factors dominating regions of the rocky shore and how these factors influenced the species found.

The seashore is the interface between the marine and terrestrial environment. This transition stage has occurred as a rocky shore. A rocky shore is divided into three main zones, supra littoral, littoral zone which is divided up into a further three zones upper middle and lower littoral and sub littoral. Within each of these areas zonation occurs vertically upon the strata as well as horizontally.

Different species survive in different zones on the rocky shore depending on their ability to cope with varying conditions at each zone. The ability to survive physical factors (abiotic) such as light intensity, air exposure…. And biological factors (biotic) such as competition for food… all interacts in the ability of a specie to survive in a particular zone. The zones can be defined as: –

1. The supra-tidal zone – above high tide

2. The inter-tidal zone – This zone is spilt into 3 further zone.

The splash zone – This zone is found above the highest tide level reached, this zone is likely to be wet by ocean spray and rainwater. The greatest danger for animal and plant species that live on the shore is the risk of being dried up by the sun.

The high inter-tidal zone – This zone is only covered with water only when it is high tides. This zone experiences wave motion (wave action), therefore, species living in this zone must have special adaptations as they must attach themselves securely to the rocks.

The mid- inter-tidal zone – Species present in this zone need to be able to withstand wave action as this zone is rarely exposed to air – they are only exposed for brief periods once or twice a day. Species therefore, living in this zone must be able to adapt (tolerate) to temperature changes.

The lower inter-tidal zone – Species in this zone can only survive short periods without water, the only time species are exposed in the lower inter-tidal zone is during the lowest tide.

3. The infra-tidal zone – This zone is always under water.

While conducting the pilot survey it became obvious to me that the number of different species increased as the distance along the transect line also progressed. I realised that there most be abiotic and biotic factors affecting the survival of species in particular zones. These factors most play a role in why particular species are found in larger quantities in different zones as they must be adapted to be able to cope with the conditions they are exposed to in that region.

These abiotic factors include depth of seawater, light intensity, temperature, pH, and weather conditions. While the biotic factors include, competition, food chain and human impact.

All animal species that live on a rocky shore need food to survive. When food is limited animal species will compete and the fittest will survive. In an intertidal zone food may not be available to all the organisms. Most organisms in the intertidal zone can only feed when the tide is in, for this reason animal species are more likely to be found in the lower intertidal zones rather than the middle or high as they are submerged for longer period of time.

Food Chain

Secondary consumer: eats primary consumers

* May be shell borers – where the predators bore holes either chemically or mechanically into the shells of other organisms and suck out their flesh.

* May paralyze their prey

Primary consumers: eat producers

* Feed directly on algae fronds but most feed on micro-algae, algae spores and small plants in rock pool

The Producers

* The producers of the rocky shore ecosystem are the algae. They absorb sunlight by photosynthesis and convert solar energy into chemical energy, which is used for growth or storage. Algae are grouped according to their colour into phylum chlorophyta (green), phylum phaeophyta (brown) and phylum Phodophyta (red).

* Cells produced by large algae plants are eroded away from the plant as a result of wave action and some of this filtered and consumed by animals.

Detritus Feeders

* The thin coating of sand and mud after the tide has gone out is a nutritious food composed of bacteria, chopped up algae and decaying animals. The organisms that consume this are called detritivores. (8,12)

The first stage involves the trapping of solar energy by a plant in photosynthesis. Some of the energy from the Sun is converted into chemical energy within the structure of the plant cells and for this reason plants are known as producers. This energy is then passed on from the plant to herbivore (known as a primary consumer) which eats it. The energy within the herbivore is passed onto the carnivore (a secondary consumer) which eats the plant eater, and this continues along the chain.

The undigested food (egesta) and the excreta of the animal and respiration are all ways that energy is lost and any remaining energy is consequently used to carry out functions that are necessary to sustain life and to maintain homeostasis. Homeostasis is important because living organisms will only function properly in the correct conditions. Homeostasis involves mechanisms, which keep conditions inside an organism within narrow limits and thus allow independence from fluctuating external conditions.(7)

* Biochemical reactions are controlled by enzymes. Changes in pH and temperature affect the rate of enzyme-controlled reactions. Extreme temperatures and pHs can lead to denaturing of enzymes and other protein.

* Water moves in and out of cells by osmosis. By maintaining a constant water potential in the fluid surrounding the cells, osmotic problems, which could lead to cellular disruption, are avoided.(7)

Energy is lost at each trophic level of the food chain. Most of the energy is lost at the 1st trophic level (producer stage). As energy is lost at each level, the number of trophic levels are limited. (6)

The energy lost from excreta and egesta is transferred to the decomposers and detritivores. Dead organisms will also contribute to detritus and decomposer food chains.

Depth of Sea Water

The depth of the seawater plays a major part in the survival of species, both animal and aquatic plants. Animal and plant species have special adaptations to survive in different zonation zones i.e. littoral zone. If sea levels have increased or decreased in comparison to the level it usually is (standard level the level it is during most of the day) and stayed increased or decreased for a long period of time some species may not be able to survive. As a result of the change in the sea level same species may not be adapted, which to survive in these harsh conditions.

The most important effect the level of seawater has on species in particular aquatic plants (seaweed) is that if the sea level increased secondary effect occurs by which the penetration of light is reduced and hence the degree of colonisation by plants (reduces the rate of photosynthesis). All seaweed must be immersed in the water for photosynthesis to occur. Water filters off some of the wavelengths of light and reduced the intensity that reaches the seaweed. If the sea level has decreased, then light can penetrate more easily, therefore, increases the rate of photosynthesis as long as other factors i.e. carbon dioxide and water are in excess and are not limiting. The turbidity of cloudiness of seawater (due to plankton, sewage and other detritus) can affect the intensity of light reaching submerged seaweed.

Light is needed for some, but not all, of the reactions of photosynthesis. There is a light-dependent stage of photosynthesis, and a light-independent stage in which the reaction occurs in the absence of light. If plants are deprived of light for any long period of time they will die. The plant will die because once the stores of starch have been used up they are not replaced, therefore, there is no energy available for the metabolic reaction of the cells. [Appendix 11]

The following stages would not be able to occur if light was not available i.e. sea level was to high and light was not able to penetrate through. Below is a description of the process of light-dependent reaction.

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