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An investigation into whether the height of sea wrack changes as the depth of seawater increases down the seashore.

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An investigation into whether the height of sea wrack changes as the depth of seawater increases down the seashore. Introduction (1)The wrack family has the most common type of brown seaweed found on the British shore. (1)"Wracks are still widely used as manure" and farmers cut the wrack form shores. My investigation explores how the average height of the wrack family combined changes as I descend the seashore, presuming that the depth of water is proportional to the distance moved down. In the experiment a transect line is run down the shore measuring from 0 metres. At similar intervals, a 30 metre sample line is drawn across perpendicular to the left of the transect line. (Due to the length of shore, the sample line intervals of 40m stated in the plan were altered to intervals of 20m, with the last 2 results being at 10m intervals.) A random number table is then used to select 30 random points along each sample line so that the results are not bias. At each point the nearest plant perpendicular to the sample line is measured and its species recorded. At each sample line, 3 at 3 randomly selected points the pH and temperature are recorded and an average calculated for each to prevent bias. There are a number of variables in my experiment that cannot be controlled and may affect my obtained results. ...read more.


This shows that the saline requirements of this plant are of a lower salt content. (1)Therefore this plant only flourishes near estuaries or in land-locked bays. (1)Like flat wrack it is a smaller species of 10 to 18 inches long with a narrow midrib and short narrow leafy branches with horned fruiting receptacles. (1)Ascophyllum nodosum- egg wrack differs from fucus as it has no midrib or crptostomata, its fronds are long and every couple of inches a large ellipsoidal bladder occurs. (1)There are notches along each frond and narrow branches, which terminate at a receptacle. Its growth takes longer and it has a longer life span, it also likes to be firmly anchored on rocks, which prevent it from being swept to sea and it occupies the middle region of the shore. (1)Pelvetia canaliculata- channel wrack also differs from fucus having no midrib or crypyostomata, neither does it have bladders. (1)It is small being 2 to 6 inches and forms dense tufts at the up most point of the shore at high water level. (1)It has narrow fronds with fork ended branches and its receptacle fruits are fork-like usually having a double forked end. Diagram of zones SAMPLE LINE(s) --------------------------0m TOP of shore-----------------------------> Channel Wrack Flat wrack ------------------------20m Serrated wrack Bladder wrack (Horned wrack) ----------------------- 40m MIDDLE of shore------------------------> Egg wrack Serrated wrack ------------------------60m Bladder wrack Horned wrack ------------------------70m BOTTOM of shore----------------------> ----------------------- 80m (4)Another factor to take into consideration is water deficit, ...read more.


Evaluating evidence and procedures My observations during the experiment showed that there was quite a lot of new growth, probably due to desiccation or a winter storm. This may account for the confidence limits being higher at the bottom because there was greater variation in height. The pH fell a little towards the bottom too which was a little unexpected. Perhaps the equipment used wasn't accurate enough to +/- 0.01 decimal place. Each result was taken from a completely random point along the sample line to avoid bias. Perhaps the ruler wasn't accurate enough. It was not possible to get the tape ruler completely strait due to physical features like contours and rocks. The shore was on a gentle slope with a slight ridge in the middle, which may be a significant affecting factor. (1)Wracks generally fruit during the winter, would this stop growth. The main sources of error in my experiment came from the accuracy of the tape measures and the site chosen to investigate which I had no control over. There would have been little , if any human error due to the random number table, averages made and quantity of results recorded. The limitations in my results were not being able to conduct another experiment in another area to compare results. Also, my experiment would have been more successful if I'd been able to go and record results at a greater distance down the shore, which I also think caused error because of new growth present at 60 to 80 metres. ...read more.

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