Discussion
Throughout the excursion, the observation of the variable abiotic factors and biotic factors within the ecosystem allows us to broaden our understanding of the relationships and connection between them. This is evident through the results of the abiotic features which indicate their unique characteristics in which the species within the ecosystem must adapt to for survival. The variable aspects of the air, soil and water of the Homebush Bay mangroves, can be seen in figures 1.2.4, 1.2.5 and 1.2.6, as these show the measurements the variables of each abiotic features recoded on the day along with the ranges in which they should be in for the ecosystem to be functioning normally. In figure 1.2.4, the state of the variables in the air are presented, this shows variation in temperature, wind speed, humidity and light intensity. Outlined in figure 1.2.5 is the temperature, content, moisture and pH of the soil, the results show that the state of the soil matches that of the range in which the soil must stay for the normal functioning of the ecosystem. Presented in figure 1.2.6, is the temperature, pH, turbidity and salinity of the water, the fact that the results taken are within range indicates that the species that make use of the water for survival are able to function normally and are not under any unnecessary stress to adapt to a change in water that they have not adapted to. Therefore the state of the mangroves on the day of the excursion were suitable for the ecosystem to function normally, as the results collected are within range.
The effect of the abiotic features on the species that are able to thrive is particularly evident within the transect in the figure 1.3.1 and the recordings taken from the sampling technique of quadrats in figures 1.3.2, 1.3.3 and 1.3.4. The transect and quadrats results show the adaptations acquired by the different plant species in order to thrive within the conditions of this ecosystem. The quadrats allow us to estimate the abundance of the species being observed in the sample area. In this case, in theory there would be approximately, 4,104,000 seedlings and 836,000 crabs in the 380,000 square meters sampled.
As a result of the varying abiotic feature of this ecosystem, organisms must possess different adaptations in order to survive within this environment. She Grey Mangrove (Avicennia Marina) has adaptations of pneumatophores and halophyte nature this allows them to grow and develop in salt water, hence their location within the creek in the salt water. The pneumatophores on the plants allow them to be able to exchange gas for photosynthesis whilst their halophyte characteristics enable them to balance the salinity of the water they use; this is done through accumulation, excretion and exclusion. The growth of the Coastal Salt Marsh (Sarcocornia quinqueflora) and the Casuarina after the Grey Mangroves, further form the water, indicates that they do not possess the adaptations to be able to cope with the saline conditions of the water in the creek, but they are still adapted to the conditions within the rest of the ecosystem as estuaries have varying conditions. This also indicates that they are xerophytes and are abel to cope in dry conditions, which is evident through their appearance, as they have leaves with a small surface area in order to preserve water and possess characteristics to grow in dry conditions and in various soil types. Therefore it is apparent that the abiotic features of the ecosystem determine the types of organisms present, their health and location within the environment.
However, if there had been a variation the air that was out of range, the state of the environment would have been completely different, this is because the species that exist within this environment have specifically adapted to the ranges and can only survive in condition within those ranges. Due to the abiotic features determining the species that survive in the ecosystem, if the state of each of the abiotic feature went out of range permanently. This would cause the species that cannot adapt to the changing conditions to succumb to the natural selection process and cease to exist whilst species that are able to withstand these conditions will survive and pass on their adaptations to their next generation.
The diagrams of food chains, web and pyramid highlight the interaction between the biotic factors of the ecosystem. The these diagrams show the different food groups in which the different fauna of the environment belong to whilst also showing the complex feeding patterns between the various animal species in the Homebush Bay mangrove environment. The feeding patterns of the different animal species within this ecosystem are depicted within figures; 1.3.5, 1.3.6, 1.3.7, 1.3.8, 1.3.9 and 1.3.10, the food relationships outlined within the diagrams present the trophic interactions between the fauna within the Homebush Bay. With figures 1.3.8 and 1.3.9 these relationships are evident as the feeding patterns of each organism are outline, from the autotrophic plants which are the producers that the ecosystem relies on for it to function. The consumer are grouped into; primary, secondary and tertiary, which is the highest level of animals that feed on other organisms, these are usually the carnivores, in the this case it is the Sacred Ibis.
The relationships between the organisms within this ecosystem can be distinguished into the groups; allelopathy, commensalism, mutualism and parasitism. An allelopathy relationship between the organisms in this ecosystem is that of the casuarina, which eliminates competing plant species by releasing toxins in it’s foliage and saplings, allowing it to thrive without the interference of other plants. A commensalism relationship is that between algae and pneumatophores, as algae is able to use the pneumatophores as a food source without harming or benefiting it. Additionally, mutualism is the relationship between algae and funding as they utilise each other as a form of food source, therefore they both benefit. On the other hand use these organisms as a food source and harm them in the process of extracting their food.
Humans have significantly contributed to the various dangers of endangerment facing the Homebush Bay mangroves ecosystems. The dangers imposed on the environment range from the immense pollution the environment has bee subjected to, to the destruction of the ecosystem to allow room for urban development. From the Indigenous Australians, who used the land as needed, but did not subject the environment to much danger due their small numbers. However this was changed as a result of European settlement in the in the eighteenth century which resulted in alterations to the estuarine environments. With the growth in population along Australia’s coastline a corresponding increase in usage and development has been the outcome resulting in the increase risk towards the mangroves. Degradation of mangrove habitat by the direct loss or alteration changes the abiotic variable of the ecosystem reducing its capacity to function effectively as a viable ecosystem. Thus, endangering the species that depend upon the healthy mangrove ecosystems. The deposition of chemicals into the waterways of the ecosystem due to the industrial factors and agricultural runoff, has compromised the health of the Homebush Bay mangroves ecosystem. These chemicals that became part of the ecosystem are dioxins that cannot be broken down easily, thus flowing into all aspects of the food chains, webs and pyramids of the ecosystem. The presence of these dioxins within the ecosystem is the reason behind the restriction on fishing in the Parramatta River as these chemicals are extremely harmful to humans, therefore not suitable for consumption by humans.