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Abstract
Bitoujou is one of the few widely known coral communities in northern Taiwan, and as more and more coral reefs are endangered, it has become increasingly important to monitor the conditions of the coral community. The study included visiting the site, and performing water tests, shore counts, and fish counts in order to determine the healthiness of the coral community through relationships between coral and water quality, along with relationships between coral and reef fish. Specific data were collected on the number of species of coral present, and also on the number of various different species of coralivorous butterfly fishes spotted. The results will be extremely helpful in later studies and monitoring of the Bitoujou area.
Introduction
Bitoujou is one of the few coral communities in Taiwan. Located along the northern coast of Taiwan, it is a closed in area from the western Pacific Ocean. The shore is rocky with many large stones, and right beyond are high mountains. The water in Bitoujou is quite shallow. The area is open to tourism, with shops nearby, steps leading into the water, and boats passing by. However, there are no records to monitor the conditions of this coral community, which can possibly be affected seriously by this human activity and other factors. Since coral reef communities, which contain wide species diversity and sustain many fish, are currently disappearing worldwide, understanding the conditions of this coral community is important for preserving it. This study should hopefully answer whether the condition of the coral reef is changing and set a baseline for further studies in the future. The study observed the species of coral in the reef, looking at species such as catspaw coral, the Porites compressa finger coral, and Leptastrea purpurea (1) brain coral. To determine the quality of the water, our study took many water tests on phosphate concentration and other such. Observers noted the organisms on the shore. Transect lines were set, and researchers swam along the lines to count numbers of butterfly fishes. This is a method of evaluating the health of the corals according to the Species Indicator concept also used in the paper Coevolution of corals and coral feeding fishes of the family Chaetodontidae by Reese, E.S., 1977 (2), and also in his works of 1981(3). Since certain species of butterfly fish, such as the Chaetodon ocellicaudus, otherwise known as the spot-tailed, and Chaetodon octofasciatus (4), known as the eight-banded, are entirely corallivorous, they are fit to be investigated. According to the species indicator concept, when the coral start dying and decrease in numbers, these corallivorous butterfly fishes will have no alternative to eat, and therefore will also decrease in number from migration to other areas. Even before the coral dies out, when it is just less healthy, the butterfly fish that eat it will realize that it is less nutritious than healthy coral (5), containing less glycogen and lipids, and will move away as it slowly declines in health. At this stage, it is perhaps not quite evident to us if we only count the number of coral we see that the coral is declining. However, by observing these fish, it can be detected. Also, since butterfly fish are territorial, the tiny changes in the coral conditions will cause them to react quickly and become more aggressive in order to protect the tiny bit of food source they have (6). Butterfly fish also have other qualities that make them easier for humans to observe. They do not fly at the sight of humans and are diurnally active, therefore observers have a better chance of seeing them. Also, butterfly fish are monogamous and territorial, so they always appear in pairs over a certain area. Since they live from 10 to 12 years and rarely change their territory (7), once a pair is followed, their territory can be determined, and that makes it possible to find out how aggressive they are. These qualities of butterfly fish make them easy to investigate and suitable for our study. This made up an important part of our study.
Conclusion
To improve the fish census counts for this study, specific regions could have been marked and observed to see how big the territories of the butterfly fish were and how fiercely they defended their areas. This would prevent recounting of the same fish, show how they interacted, and help identify the spot for later studies. Observing the ferocity with which the butterfly fish defended their territories is also an indicator of the health of the corals. This would provide the study with more accurate data. The butterfly fish census alone could have many mistakes, for instance, the fish could be accidentally counted twice, and the numbers change from time to time. However, in the results, the number of mirror butterfly fish appeared to be 11 the first time, 22 the second, and 27 the third time. The Chaetodon ocellicaudus (4), spot-tailed, which was around 8 most times, was recorded as 15 once. The results for the Chaetodon octofasciatus (4) eight-banded butterfly fish showed 11 on one, whereas it was 2 on another. This shows that there probably was some mistake with the counts. Also, since the site hasn't been investigated previously, our study was unable to determine all the species present there, causing some corallivorous species of fish which could be used for our study to be left out. Some of these would include the Asian butterfly fish and Oriented butterfly fish. However, because there isn’t any previous data to compare with, we can't tell just yet whether the condition of the community is declining, unless there are absolutely no fish, which was not the case. In the coral counts, the species most abundant was the catspaw coral. It covered approximately 23% of the bottom of the ocean bottom. But the accuracy of this data can be questioned, since none of the researchers in this study were experienced in this area, and have totally no preparation beforehand or skill at this. More accurate data would have to come from swimming down to the coral and use quadrates to measure their coverage (13). For the shore count taken in this study, species such as Portunus pelagicus (11), the red-spotted crab Portunus sanguinolentus, and blue damsel fish Pomacentrus caeruleus (11) were identified. The most abundant species were blue swimming crabs, Portunus pelagicus, which were blue mostly. The interesting thing found was that many species were lacking eyes or handicapped, providing a possibility that there was some poison in the water. However, the shore counts have only been done once, so it is unclear whether this is a serious problem. It could be that these animals have just happened to be around for a moment.
The water sampling methods were very important in determining the health of the coral community. They provide us with data about the water quality, which has a great effect on the coral. The different water tests would give different results, because of different components used to measure the quality. It is important to be consistent in what methods we use to ensure the results are in the same units and apply to the same conditions. Otherwise it wouldn't be possible to compare results. The water quality is what would most likely change first if there really were effects caused by
humans.
The pollution of water could be otherwise detected through flatworms, which are sensitive to this because of their absorbing skin. However, we were unable to identify any, as they tend to hide in cracks. Also, foraminifera could also have been a good indicator species. "These shelled protists are ideal indicator organisms because: Foraminifers are widely used as environmental and paleoenvironmental indicators in many contexts." (13) In recent researches from other places, these have been very helpful in assessment of coral reef conditions. However, it is not quite easy to test these, and our study did not have knowledge of the ways to access the needed materials and preparations. Also, as mentioned in the review of paper two on coral ecology, the method of observing population numbers of large to small herbivores, carnivores, and sea grasses is also a future option for studying.
In an overall, the results do not lead to a clear conclusion on the condition of the coral community. However, it seems most likely that the coral community is under some danger. To make a clearer and more certain conclusion on the community's condition, future and further studies would need to be conducted.
Through the low coral coverage at the ocean bottom, the few numbers of corallivorous butterfly fishes viewed compared with non-corallivorous ones, and the seemingly high number of handicapped or mutilated crabs and shore fish, it does not seem like the coral community is in a good condition. Future studies would include finding out the health of the coral and which specific factors are affecting the coral community's condition, such as disease, tourism, pollution, or boats. Yearly continuous study of the area's water quality, coral coverage, butterfly fish numbers, and species diversity would help in determination of the community's true condition, since this study would provide a baseline to be compared with.
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