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Seaweed Distribution along a Rocky Shore.

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Seaweed Distribution along a Rocky Shore. Prediction:- Seaweed species living higher up on the shore should not decrease in mass as much as seaweeds living lower down the shore. Aim:- Different species from different zones of the rocky shore were dried over the same period of time, weight loss was recorded and % weight loss compared. Method: - * Firstly two ranging poles were placed on the shore (one at the upper end one at the lower end.) The distance was then measured between them, this formed our basis for a belt transact. * The area marked was then divided into 5 meter sections. * A quadrant was then used to measure plant cover, the quadrant was firstly placed beside the ranging pole and the % plant cover measured, it was then moved gradually moved down the beach in 5 metre sections. * The information obtained informed us which plant species lived in various parts of the beach. ...read more.


Seaweeds and animals which live on the upper shore have to be adapt to surviving without water for both long and shorter periods of time, this timescale varies in accordance with the seasons and the gravitational pull of the sun and moon. This causes a tide cycle in which the tide comes in and goes out again this takes 12 hours. This means some plants are underwater all day and some are without water for the majority if not all day. The diagram below approximately shows the tidal cycle and tidal range. As we move further up the beach there is greater exposure in summer this results in desiccation. Seaweeds further up the beach have to adapt to this condition to survive and this has a number of consequences. It makes plants on the upper shore better competitors and they are able to out compete other plants. Some off the upper shore plants develop a thick cuticle so water cannot b lost through transpiration, others have a small surface area e.g.: - Pelvetia, others have small channels to trap and preserve water in e.g.: - Enteromorpha intestinalis. ...read more.


Also for Pelvitia after 3 hours there were 5 weight loses of both 6.2 and 11.8. This variation may have been caused by pieces off seaweed falling off the petri dishes, inaccuracy of reading the balance values other handling errors could also have been the cause. Another problem was small sample sizes this meat that any errors which occurred affected our results enormously. The samples may also have been exposed to different amounts of water before being sampled e.g.:- some may have been in a rock pool while others could have been on the edge of a rock pool and so exposed to very little water. We could have rectified this problem by soaking all the samples for 1 hour before weighing them. By doing this we could have made our results more reliable we could have also made them more reliable by doing more replicates. As a follow up to this experiment we could study all the seaweeds which or red in colour or those brown and green in colour to reveal if colour effects their weight loss. ...read more.

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