Sample Essay: Distribution vs. Density of Mytilus in Southern California

Abstract

Mussels are sea animals that are often found attached to substrata inside the sea.  They belong to a family of mollucs called the bivalves. They were given these names due to fact that they posses two shell like plates containing one valve for allowing water to flow between the shells and the other one allowing water out. These valves are used during feeding because bivalves are filter feeders. They often feed on phytoplankton found suspended in water. Mussels are found in both salty water and fresh water. Mussels come in a variety depending on the species and the habitat it occupies. However they can be easily identified by their characteristic two plates of shells and the ability of these plates and shells to open and close. Mussels are mainly harvested by man and used as a source of food. Mussels are also eaten by sea animals such as the star fish. Their economic importance is derived from the above characteristics. Generally mussels are sedentary animals and collecting them is relatively easy.

Purpose of the research

The purpose of this research is to study the distribution of various species of mussels in the shoreline of South Carolina and to determine the population of the respective species in particular areas depending on the characteristics of the habitats. Distribution of Mussels can provide information of other essential factors especially the ones that provide the optimum condition for the growth of Mussels. For instance Mussels of different species may require different temperatures for growth or may prefer a particular species of planktons for food. This kind of information is very important to marine biologists when studying the factors that determine the distribution of Mussels and the optimum habitat for growth of the various species. Mussels form an important part of an ecosystem and their population and distribution is very important since they regulate the number of planktons in the ocean and in turn their population is regulated by the animals that predate on them. It is important that this balance is always maintained and reflected in all areas because diversions may result to serious environmental problems. Such a research can also provide insight on how much marine pollution has affected the distribution of mussels; mussels have also been used in some instances as bio-indicators to measure degree of ocean pollution.

Research Methodology

The most crucial thing to consider when doing any research work is to come up with a relevant hypothesis and to devise a most efficient research methodology to test this hypothesis and draw conclusions that are scientific.  The most applicable hypothesis in this case is the alternative hypothesis of whether the intertidal Californian Mussel shows intertidal zonation with respect to density. Therefore the research will seek to determine if this statement is true or false. The hypothesis is a theoretical statement made with a degree of bias with the intention of drawing specific conclusions after the research. The hypothesis provides a guide on the best research method.

Since the purpose of this research seeks to analyze the distribution of different species of Mussels and compare this against the density, it is important to use a research methodology that allows inferences to be made concerning the population represented by the sample, which in this case are the species and their respective distribution densities. The most efficient sampling method is the stratified random quadrant sampling, which will enable one to obtain the variations in different species of mollusks just as it occurs in the entire population of the sampled area. Using this method, locations were randomly chosen that would act as representatives of a particular area. At first a series of transect lines were laid down oriented up and down the shore making sure that they were perpendicular to the shoreline. These lines were laid with respect to the topography of the shoreline. Samples were then collected from the high shore towards the low shore along the shore transect after every 2 meters. Bias associated with the transect location by marking out the exact locations of the samples at 2 meters interval determined by selecting a random number to displace the placement of the quadrant left and right of the transect line. The random number will then be used to represent the displacement in centimeters from the transect line. The sample was then taken using a quadrant of 50 x 50 cm which is the one normally used for intertidal mollusks. The quadrants were then placed on the surface with respect to the transect line as specified by the random number. The number of species in each quadrant was then identified, counted and recorded.

Results

The results clearly show that the number of Mussels increase as one moves towards the sea, therefore the density of Mussels also increase as one moves from the shore towards the sea. From the hypothesis chosen the results have proven that the density of mussels increase as one goes towards the ocean.

The type of species that was found was the Californian Mussel known as Mytilus californianus. Its characteristics is that it was large than most of the other species of Mussel and it belonged to the family Mytilidae. Its shells were thick and like most other members of the family they were mostly found attached on rocky surfaces. From research we were able to find that true to our findings, it is the most common Mussel species in all the west coast of North America, found in the area stretching from North of Mexico to the Alaskan Islands of Aleutian. This species of Mussels are always found clustered together mostly on rocks in the upper section of the intertidal zone. The number of mussels found within the 50 x 50 cm quadrants greatly varied from the shore and as one moved towards the sea and because the area of the quadrant was held constant the density also varied with the same degree.

The results were as follows:

Discussion

The experiment was successful in that the trends observed were tallying with the trends available from previous research as recorded in books and other scientific journals. However there were a few problems encountered in the course of the research. It was risky to venture too much towards the sea because of various threats from harmful sea animals. It was also difficult to locate mussels that were submerged underwater. Another problem was that the process of sampling disturbed these sea animals which are always sedentary.

These results clearly show that there are some factors affecting the distribution of Mussels and these factors vary as one move from the shore towards the sea. One inference that can be drawn is that the harvesting of Mussels is the most probable cause for this distribution because harvesting will most likely take place from the shore towards the sea because it is easy to harvest the ones near the shore. Another inference that can be drawn from the results is that the planktons and other tiny sea animals that Mussels feed on are found in higher population as one move towards the sea therefore a greater population of mussels is found in places where their source of food is also abundant. Temperature could be the other reason for this kind of distribution because temperature of the ocean reduces as one move towards the ocean and therefore it can be said that mussels prefer cooler temperature.

Conclusion

The distribution of the Californian Mussel provided greater insight how ecological and climatic factors affect the distribution of sea animals. This information can be of great relevance when looking into ways of protecting the sea as an environment for thousands of species of animals. Comparison of the data obtained in this case with some data providing the distribution density of mussels in fresh water can give an idea of whether mussels originally preferred sea water and moved to fresh water or the other way round and the reasons for such an observation.

References

Hiroshi, T. Applicability of Mussel as Bio-indicator for pollution in Sea water. Retrieved on 23^rd April, 2009 from www.sciencelinks.jp/j-east/article.org

Moran, D. Species Profiles: Life Histories and Requirements of Coastal Fishes and Invertebrates, Californian Mussel. Retrieved on 23^rd April from www.fwie.fw.vt.edu

Smith, L. Deep-Sea Hydrothermal Vent Mussels: Nutritional State and Distribution. Vol. 66. Retrieved on 23^rd of April, 2009 from www.esajournals.org/doi/abs.