Running Head: CRITIQUE OF OCEAN TEMPERATURES IN CORAL REEFS
CRITIQUE OF OCEAN TEMPERATURES IN CORAL REEFS Madison McNeill
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 elevated temperatures. 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 Research, 141, 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. Science, 323(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 Physiology, 156(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.
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.
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.