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TBiologywo different shores with different levels of exposure were surveyed

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  • Category: Biology

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Seashores can vary greatly in nature from one another. One of the factors that is most responsible for this diversity is the level of exposure to which the shore and the organisms that make it their home are subjected. In this investigation, two different shores with different levels of exposure were surveyed. Based upon this survey, the level of exposure for each shore was determined using Ballantines exposure scale. This scale uses the presence, absence and level of abundance of particular organisms to rate the level of exposure of the shore ranging from very exposed to very sheltered.

Additionally, the shores were compared and important differences were noted. This comparison indicates which organisms prefer more exposed environments and which prefer more sheltered ones. In addition to the general survey, two specific projects were undertaken to more closely examine a particular aspect of the shores life. The first project, carried out at the more sheltered site (coordinates 22, 10 on the provided map), examined the length of brown algae and its relation to the age of the algae.

Two species of brown algae were measured in this examination, Fucus vesiculosus and Ascophyllum nodosum. The presence of Polysiphonia lanosa on the Ascophyllum was also noted. The second project, conducted at the more exposed shore (coordinates 8, 2 on the provided map), counted the absolute numbers of two organisms, the Patella species of limpets and Actinea equina, in 20 adjoining half meter by half meter quadrats in the Eulittoral range of the shore. Methods: The general survey was conducted according to the instructions provided by Dr. Breen.

All of the counts were started at low tide durring a period of spring tides to allow easy access to the sub-littoral zone. At each shore a number of different censuses were done at different levels f the shore. All of the organisms in a 0. 5 x 0. 5 meter quadrant were counted in each census. The first count was done at the low tide mark. Then counts were done at each 0. 5 vertical meters from the low tide point. This resulted in a total of 8 counts at the sheltered site and 7 counts at the exposed site.

The absolute number of organisms or percent coverage determined in each count was used to rate the frequency with which particular organisms were present as absent, rare, occasional, frequent, common or abundant (see appendix a, the sample data collection sheet for a more detailed description). The first project, the measurement and omparison of the length and age of Fucus vesiculosus and Ascophyllum nodosum. was carried out at the more sheltered site. The age of Fucus vesiculosus was determined by counting the number of bladder pairs and likewise the age of Ascophyllum nodosum. was determined by counting the number of bladders.

For Fucus, the age is the number of bladder pairs and for Ascophyllum it is the number of bladders. The length of each algae was also measured using a ruler. Twenty plants of each species, chosen randomly, were measured. Addtitionally, the presence of Polysiphonia lanosa growing on the Ascophyllum samples was noted as was the ge of the Ascophyllum when the Polysiphonia first appeared. The second project was completed on the more exposed site. Counts for the number of individuals of the Patella species of limpets and Actinea equina individuals were conducted for twenty adjoining 0. 5 x 0. meter quadrats in a straight line.

The counts were done in the Eulittoral portion of the shore. The measurments were taken starting higher up on the shore and working in a line straight down the shore to a lower area. Results and Discussion: Many differences were found between the two different sites (for actual frequency data see appendix b). In comparing the two sites there were a few species that were found exclusively or nearly exclusively on shore or the other. The lower zones of the sheltered site were heavily inhabited, even dominated by brown algae and in particular by Fucus serratus.

This contrasted sharply with the more exposed site where no brown algae of any species was found. Additionally, The sheltered site had sponges and hydroids, both of which were absent at the more exposed site. On the other hand, the exposed shore had abundantChthalamus species of barnicles and frequent Himanthalia elongata, a brown algae, which were not found on the sheltered shore. Top shells, particularly Gibbula umbilicalis, and Littorina neritoides were abundant on the exposed shore but were not present on the sheltered shore.

Also on the exposed shore Mytilus edulis , the mussels, and Paracentrotus lividus, the purple sea urchins, were abundant, and Actinea equina, the red sea anemones, were occasional while none of these species were found on the sheltered shore site. This being said however, there were similarities between the sites as well, for example neither site had more than a few individuals of Laminaria species or the other kelps other than Himanthalia elongata. Also Littorina saxatilis was absent on oth shores and both shores had many Balanus species barnicles and Patella species limpets. Ballantine’s exposure scale was then applied to both shores.

Based on the presence and absence of the particluar species used by Ballantine to classify the shores, the more sheltered site can be classified as a fairly sheltered shore, although within this classification it leans toward the more sheltered side. This is because it did exhibit some characteristics of a sheltered shore even though in the end more characteristics pointed to the fairly sheltered classification. Using the same technique, the more exposed site can be classified as an exposed hore but like above it leans within this category, this time toward the very exposed side.

Again this is is because even though there were more characteristics pointing to the classification of exposed shore, there were some characteristics of a very exposed shore present. This is also a testiment to the fact that these categories do not have clearly defined boundaries and they merge into one another. The resluts of the first project, the measurement of the size and age of Fucus vesiculosus and Ascophyllum nodosum. were only were analyzed in a number of ways (see appendix c for the data for Fucus vesiculosus and Ascophyllum nodosum).

First, the length of the sampled individuals of Fucus vesiculosus was plotted against the age of each individual and a regression line was calculated. It turned out that for Fucus vesiculosus, there was almost no correlation between length and age as was indicated by the very low correlation coefficient generated from the calculation of the best fit line, the correlation coefficient, R, was R = 0. 109 when a perfect correlation is R = 1. 000. Following this analysis the average, max, min and median age and length were calculated for Fucus Vesiculosus (Table 1).

Then the length and age were plotted gainst each other for Ascophyllum nodosum. The correlation to the regression line was much higher (R = 0. 845) for Ascophyllum nodosum than for Fucus vesiculosus, suggesting a correlation between length and age. Then the average, max, min and median age and length were calculated(Table 1). The presence of Polysiphonia langosa was also analyzed. It was found that the average age of the Ascophyllum nodosum at which the Poysiphonia langosa begin growing on it was 2. 2 years. Additionally, it was found that 65 % of the Ascophyllum nodosum individuals sampled had Polysiphonia langosa growing on them.

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