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Running Head: CRITIQUE OF OCEAN TEMPERATURES IN CORAL REEFS

CRITIQUE OF OCEAN TEMPERATURES IN CORAL REEFS Madison McNeill

Introduction

Coral reef ecosystems are the most diverse marine ecosystem in the world. They provide a home to thousands of species of plants and animals. In the last few decades, global warming has caused increased temperatures, resulting in ocean acidification and increasing surface temperatures of the ocean. This can lead to the bleaching of coral reefs as well as the death of coral reef fishes due to their inability to acclimate to the elevated temperature. These three papers were chosen, because they illustrate the environmental impact higher temperatures have on these coral reefs and the organisms that live within them.

· Dias, M., Ferreira, A., Gouveia, R., Cereja, R., & Vinagre, C. (2018). Mortality, growth and regeneration following fragmentation of reef-forming corals under thermal stress. Journal of Sea Research141, 71-82. doi: 10.1016/j.seares.2018.08.008.

· De'ath, G., Lough, J., & Fabricius, K. (2009). Declining Coral Calcification on the Great Barrier Reef. Science323(5910), 116-119. doi: 10.1126/science.1165283.

· Nilsson, G., Östlund-Nilsson, S., & Munday, P. (2010). Effects of elevated temperature on coral reef fishes: Loss of hypoxia tolerance and inability to acclimate. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology156(4), 389-393. doi: 10.1016/j.cbpa.2010.03.009.

Dias (2018) evaluated how elevated surface temperatures of the ocean affected growth, mortality, and regeneration following the fragmentation of nine coral species in the Indo-Pacific, while De'ath (2009) suggested that the ability of coral in the Great Barrier Reef may have depleted due to a decrease in the saturation state of aragonite and rising temperature stress in this region. The third paper evaluated, Nilsson (2010), examined whether or not an elevated temperature decreased tolerance levels for low-oxygen regions in two species of coral reef fishes. This experiment used adults fishes of two species and tested their ability to acclimate to changes in higher temperatures, which differed from the other two studies in that Dias and De’Ath did not study the fishes in the ecosystems, only the coral there. Dias found that whether or not a coral had previous injury did not impact the mortality, partial mortality, or rate of growth of each fragment. However, the species of coral and the ocean temperature had significant impacts on the results for each fragment. Although the cause for coral calcification of Great Barrier Reef corals was not determined by the De'ath’s study, he did find that it was largely related to increasing temperatures of oceans, which caused more thermal stress in coral populations. This differed from the Nilsson paper, which showed that certain species of coral reef fishes were unable to adjust to higher ocean temperatures, a phenomenon that has occurred due to global warming and ocean acidification.

Analysis

Introduction

When the three articles’ introductions were evaluated, some similarities as well as dissimilarities stood out. For example, the titles of the articles varied in appropriateness. Nilsson's title was too long. The paper had a title that told its audience what the researchers hoped to get out of it, but the title seemed long and bulky. The title, in my opinion, could have been shortened or rephrased to one that grabbed the audience’s attention more quickly, even a change as simple as changing the title to, “Effects of elevated temperature on coral reef fishes.” However, Dias’s title was accurate and concise. “Mortality, growth and regeneration following fragmentation” was a title that accurately explained what was being examined within the confines of this study. De'ath had a title that matched the contents of the paper as well.

The abstract’s statement of purpose of all three articles matched the introductions. For the Dias article, they stressed that the impacts of thermal stress on fragments of regenerating coral species needed to quickly be explored, while De'ath’s abstract was well written, telling readers how many coral colonies were studied and what the results showed. The abstract of Nilsson’s paper plainly stated what occurred within the first two sentences. The abstract’s statement of purpose for this article was to display how two species of coral reef fishes in the Great Barrier Reef are failing to acclimate to higher sea surface temperatures. This was plainly stated in both the abstract and introduction of the article.

The hypotheses of the three articles varied greatly. Dias stated that the change in the global climate has led to rising sea surface temperatures and ocean acidification, which jeopardized coral reef survival. With this sentence, Dias made it clear why his study efforts were so urgent. Nilsson followed a similar pattern when he clearly stated his concerns for the inability of coral reef fishes to acclimate to rising water temperatures. De'ath’s hypothesis was stated in the abstract, which said that his study suggested that the increasing thermal stress may be depleting the ability of Great Barrier Reef corals to deposit calcium carbonate. Thus, the hypotheses of all three articles were given. I also found that Dias, De'ath, and Nilsson all had a nice way of arranging their data, which allowed the information to build to what the experimental design included and what the researchers were hoping to accomplish from this experiment.

Methods

The sample selection among the three articles showed great contrast. The Dias paper used nine reef-forming coral species, while De'ath’s experiment studied 328 colonies of coral from the same genus, Porites, which is a stony coral. Nilsson studied adults of two species of coral reef fishes. For Dias’s paper, the methods were easy to follow and seemed easy to repeat, while De’ath’s methods were harder to follow, for the details did not appear to all be listed. The Methods section of the Nilsson article was both valid and delivered with enough detail that another group could perform most of this study again. Only most of the experiment, because although the article listed when and where the experiment was conducted, the number of each species of adult coral reef fish caught and analyzed was not given in the Methods sections of the paper. This information is crucial, because a small sample size could invalidate the data, while a large sample size could support the data more accurately. Furthermore, if one species of coral reef fishes had a much larger or small number than the other species, the data would also not be well represented in the results found by this study. The number of samples for both of the other articles were given.

While some articles had strong Methods sections, others were missing key components. The experimental design for the three articles chosen all seemed valid. De’ath’s study seemed valid for the experiment being conducted, though I am unsure that this study could be repeated using the paper alone. The experimental design did make sense overall, in that Porites is commonly chosen for sclerochronological analyses because they have annual density bands that are widely distributed. Portites coral also has the capability of growing for hundreds of years, so choosing this genus of coral for a large analysis made sense. Using the three growth parameters De’ath mentioned—skeletal density, calcification rate, and annual extension rate—are good parameters to look at in a genus of coral that has such a long life span. Dias justified every step of his experimental design, making it easy to repeat the process. For instance, Dias utilized contrasting morphologies, because they have different susceptibilities to thermal stress, giving the overall results more credit. These corals were held in captivity for several years, giving the researchers knowledge of the corals’ thermal history. Twenty fragments were cut from each of the nine species, half of which were used as a control. Sources of variations were eliminated in this process by cutting only one coral from each colony. These methods appear valid, and each is given a reason as to why a scientist would conduct the experiment in this way, making the overall flow of the methods logical and easy to follow. This was similar to De’ath’s paper in that De’ath listed the parameters used to test the samples, and he mention that Porites has such a long lifespan, so these types of corals have been proven to record environmental changes within their skeletons. This statement justified why De’ath chose this coral and explained why these particular parameters were chosen. However, he did not specify how to conduct these analyses. Also, although the data was collected within a two-month period for both Dias and Nilsson’s experiments, De’ath’s experiments was a composite collection from the years 1900-2006, containing over sixteen thousand annuals records with corals ranging from ten to 436 years old. Hence, the broad range of years the specimens were collected was overwhelming, not to mention the three growth parameters the paper mentioned but again failed to explain. Lastly, for Nilsson’s experimental design, I found that it was carried out well, using adults of the two species of coral reef fishes and varying temperatures that supported their hypothesis. However, not including the number of each species caught negates the data to a certain degree. Overall, I found that the Methods section of Nilsson’s paper was logical, but it did not contain details that were pertinent to this experiment, whereas Dias included all pertinent information and De’ath failed to include how he performed the parameters that were chosen.

Results

Since the concentration for each study varied, the results were also quite different in composition. Dias et al. (2018) found that injury—whether present or absent—had no impact on the death or growth rate of the coral fragments studied. The researchers determined that the true factors that impacted death and growth rate of the corals analyzed were temperature and the coral species itself. These results were illustrated using tables and figures. Table 1 was difficult to follow, because some of the columns were abbreviated using terms not explained within the content of the article. However, the numbers in the table coincide with the text, showing that injury did not impact the growth or mortality rate of the coral fragments used in this experiment. The results found in De'ath’s paper were easy to follow, but showed that the cause of decline in coral populations in the GBR were still not known. Within the Results section of the articles written by Nilsson and De’ath, I saw that the figures and tables matched the text without repeating the same information to the audience. The figures and tables were accurate with what the text had previously stated, showing P values that were statistically significant, and the data was very easy to understand. The table in Dias’s article could have been better presented if the abbreviations used had some type of key that denote what each header meant. I did not find any discrepancies among the figures and text of the three articles as far as percentages were concerned.

The results found in the three studies did test the hypothesis of the researchers. For Dias’s paper, these results were shown in Figure 1, which illustrated that as temperature increased, the mortality rate of coral species also increased. As Dias mentioned in the Abstract section, there were two coral species that survived this experiment, Turbinaria reniformis and Galaxea fascicularis. However, the results of the Nilsson paper were to test the hypothesis of the researchers in that study, which was that after a given number of days in varying temperatures, the coral reef fishes studied would fail to acclimate to those temperature changes. Again, in the third paper, De’ath’s results tested the hypothesis, including 328 colonies of massive corals form 69 various reefs, which made the results more broad.

Discussion

I found that none of the three articles repeated the same information in both the figures and the text of the article. From the Discussion section of the Dias paper, a reader could tell the main points of the article, which were to show that there was variability in the susceptibility to thermal stress of different coral reef species. These coral reef species had the lowest mortality, partial mortality, and levels of bleaching at 26 degrees Celsius, while their growth rate was at its zenith at this temperature. Dias found that the regeneration rate of corals generally increased as the temperature increased. These results also show that the bleaching resistance capacity of most of the corals analyzed was overcome at 32 degrees Celsius. Because this paper is so new—published in 2018—I could not find its interpretations to be supported by other research. However, the article does list the direction in which the research is headed and lists other studies similar to this one.

The findings of De'ath’s and Dias’s articles were supported by each other, as well as many other articles over coral reef ecology. However, I found very few articles that supported the conclusions drawn by Nilsson (2010) about the effects increasing temperatures had on two species of coral reef fishes, which was a weakness for the paper. In all three journal articles, I found that the interpretation of data was logical.

Conclusion

Summary

The three articles, overall, had both strengths and weaknesses. For instance, all three papers were peer reviewed. Nilsson’s paper had few other articles that backed up its findings, while Dias and De’ath backed up each other’s paper. The article by Dias (2018) was very recent, which made it one of the newest published papers in its field, while the De'ath and Nilsson papers were a few years older. Although the Dias paper had tables and figures that were not entirely straight forward, the content of the article itself was very easy to follow. Each section within the article was set apart, whereas in the article by De’ath, the sections (introduction, methods, etc.) were not separated from each other. The Dias and De’ath papers had appropriate titles, while Nilsson’s title was too long. The abstracts and introductions match for all three articles. The pace for the Dias article is great, leading the audience straight into the hypothesis and objectives for the analysis, while De’ath failed to separate his paper into different sections. Overall, Dias and the other researchers took many steps to ensure accurate results, and the Methods section of this article is explained well enough to be repeated, which differed from Nilsson’s paper in that Nilsson did not include his sample size. When it came to reproducing the experiment, Dias included all pertinent information, but De’ath failed to include how he performed the parameters that were chosen.

De’ath had a concise paper with text that accurately related to the figures mentioned. Overall, the article was concise in its findings, but not as easy to follow as it could have been if the proper sections and subsections had been utilized. The title seemed appropriate, and readers know from the statement of purpose and the introduction that the primary goal of this study was to help determine what is causing the decline in corals’ ability to lay down a calcium carbonate skeleton to more efficiently build coral reef ecosystems. The De'ath paper used a large sample selection, which made the results seem more inclusive as opposed to Dias’s samples size of nine species of corals using twenty fragments of each species. Nilsson’s article had excellent figures that were easy to interpret, in contrast to Dias’s paper that did not explain what some of the abbreviations meant in the tables. The strengths and weaknesses of the three papers varied greatly.

Significance

When evaluating the role these articles play in the world, striking similarities were found. Nilsson’s article showed primary concerns toward two populations of fish species that lived in the Great Barrier Reef, while De’ath and Dias wrote papers over the reactions of different coral species to increasing surface temperatures. De’ath’s article has practical significance similar to the Dias paper, in that major ecosystems are dying as a result of rising ocean surface temperatures, and these researchers tried to find ways to explain these issues. Nilsson’s article examined whether or not increasing temperatures reduced the hypoxia tolerance of coral reef fishes. It has been cited sixty-nine times, cited in papers involving hypoxia tolerance of coral reef fishes, how temperature and hypoxia play a role in respiratory performance of certain tropical fishes, and many other similar studies (Nilsson et al.). De'ath et al. has been cited twenty-four times, which sparked interest for similar research in the Great Barrier Reef in the last decade. The Dias et al. paper was only published in 2018, so not many other researchers have cited this paper yet. This can be seen as a potential problem; however, the article was peer-reviewed by individuals who are well-educated in this particular field. The currency of the Dias article may also be seen as a good attribute, showing that this information was some of the newest in its field of interest. The research among all three articles has significance to today’s society, in that the bleaching of coral reefs has become a growing problem, and without more research to determine what factors are causing this issue, large hypoxic zones in aquatic ecosystems may result.

Overall, all three of these articles illustrated environmental significance. Human survival depends on the biodiversity of plants and animals, and many animals live in these coral reef ecosystems.

Works Cited

De'ath, G., Lough, J., & Fabricius, K. (2009). Declining Coral Calcification on the Great Barrier Reef. Science323(5910), 116-119. doi: 10.1126/science.1165283

Dias, M., Ferreira, A., Gouveia, R., Cereja, R., & Vinagre, C. (2018). Mortality, growth and regeneration following fragmentation of reef-forming corals under thermal stress. Journal of Sea Research141, 71-82. doi: 10.1016/j.seares.2018.08.008

Nilsson, G., Östlund-Nilsson, S., & Munday, P. (2010). Effects of elevated temperature on coral reef fishes: Loss of hypoxia tolerance and inability to acclimate. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology156(4), 389-393. doi: 10.1016/j.cbpa.2010.03.009

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