Summary
In the article “Ocean Acidification Impairs Olfactory Discrimination and Homing Ability of a Marine Fish,” Munday et al. sought to analyze what might be the impact of the growing CO2 emissions on the oceanic inhabitants. In order to achieve that, the scholars examined how the clownfish larvae’s preference towards various olfactory clues changed in the seawater of different acidity levels. As such, the latter is believed to reduce greatly by the end of the current century from pH 8.15 to pH 7.6, assuming that there will be no significant changes in the way businesses operate. Therefore, the experiment was conducted by rearing the three groups of clownfish in the water with varying acidity levels.
The first group served as a control group and was reared in the normal seawater with a pH level equal to 8.15. The other two groups were taken as testing groups, where one was reared in the water with a pH of 7.8 and the other – with a pH level equal to 7.6.
Next, to analyze how the olfactory preferences change for clownfish within different groups, the researchers chose to compare such olfactory clues as xanthostemon chrysanthus, melaleuca nervosa, megathyrsus maximus, anemone, and those of conspecific adults. In this regard, it is known that under normal conditions, clownfish larvae are attracted by xanthostemon, anemone, and non-parent olfactory clues to choose the best suitable settlement sites. On the other hand, melaleuca, megathyrsus, and parent olfactory clues are generally avoided. Finally, the Atema flume chamber – which allows providing two water streams of different origins – was used to examine the reaction of three group members to the olfactory clues mentioned above.
The results indicate a significant difference in the ability of larval clownfish to discriminate between different olfactory clues depending on the water acidity. As was predicted prior to the experiment, the clownfish from the control group spent significantly more time in the stream of the water that contained xanthostemon, anemone, and non-parent olfactory clues. Additionally, it was found that the group members avoided melaleuca, megathyrsus, and parent olfactory clues. In a similar vein, larvae that were reared in the pH 7.8 water were attracted to xanthostemon and anemone, but the reaction to the stimuli was notably weaker. Moreover, larvae started exhibiting an increased preference towards melaleuca and megathyrsus. Furthermore, clownfish stopped discriminating between non-parent and parent olfactory clues.
The last group of larvae that were reared in the pH 7.6 exhibited the most outstanding results as it was found that clownfish just become passive and do not react to any olfactory clues. Interestingly, such absence of reaction persisted even after the larvae were placed in the seawater with the normal acidity level. Therefore, it was concluded that continued high levels of CO2 emissions and the associated increase in seawater acidity could significantly disrupt the life of the ocean inhabitants.
Article Critique
Even though Munday et al. found evidence that the increased acidity level of the seawater can negatively impact the behavior of clownfish larvae, such results are not generalizable to the other ocean species. However, the experiment clearly indicates that more research in this sphere is needed. Nevertheless, it can be argued that a change in the behavior of even one underwater inhabitant can have far-reaching and unpredictable consequences for the whole aquatic ecosystem. Considering that, it is fair to claim that the conducted research is of high significance for the scientific community, political decision-makers, and the general population.
From the methodological standpoint, there are almost no shortcomings that would make the results unreliable. Indeed, except for the pH level differences, all the other rearing conditions were kept equal, which ensured adequate comparison. Besides, all the experiment ‘participants’ were tested for potential morphological differences and had at least three different parents. Yet, probably, the only limitation that can be mentioned is that the studied population varied only from 20-50 larvae, which may not be enough for generalization.
Work Cited
Munday, Philip L., et al. “Ocean Acidification Impairs Olfactory Discrimination and Homing Ability of a Marine Fish.” Proceedings of the National Academy of Sciences, vol. 106, no. 6, 2009, pp. 1848-1852.