Sediments harm clownfish larvae

Many aquatic species can be influenced by anthropogenic activities. Some may be familiar with the impact of rising CO₂ concentrations on ocean acidification and coral reefs. Dam construction and overfishing have also hurt certain aquatic species. As seen by these examples, the physical activity itself or the substances associated with these activities can cause the harm. Within these two categories, there may be a myriad of substances that can impact certain species. Therefore, an important area of research that can add to such knowledge of the harm human beings cause on those living in water can be the study of how specific substances associated with anthropogenic processes influence specific aquatic species.

                                          Clownfish.

                                          Credit: Erika Woolsey

 

An article on Science Daily entitled “Arrested development: Sediment wreaks havoc with fish larvae” discusses the findings of a publication by Wenger, et al. in The Journal of Experimental Biology regarding the impact sediments have on clownfish larvae. The Journal of Experimental Biology publication starts off by stating that research into clownfish larvae has been relatively new and gives a broad overview of factors relating to sediment deposition that may hurt the larvae, including increased water turbidity and the presence of the sediment itself. The publication then discusses its results, which included the observation that a general increase in larvae development time was associated with increased sediment concentrations. Interestingly, another key finding was that the increase in the weight and length of the larvae was particularly pronounced for larvae exposed to low sediment concentrations but not for those exposed to no or higher sediment concentrations. Finally, though differences in sediment concentration affected larvae development, the study notes that varying sediment concentrations alone did not affect the mortality of the fish significantly.     

The Science Daily article provided a simplified yet moderately inaccurate summary of The Journal of Experimental Biology publication. A key point that the Science Daily article brought up was that sediment does increase the time for clownfish larvae development, an idea the publication would agree with. The Science Daily article then goes on to make a case that this will negatively affect clownfish populations because increased time as larvae correlates with increased mortality from predation vulnerability. This idea may logically make sense and is not contrary to the publication’s finding that differing sediment concentration alone had almost no effect on mortality because the study did not expose the larvae to predators, which can reasonably kill the larvae more easily than adult fish. Though the Science Daily article does well in the above, the Science Daily article incorrectly states that the time it took for larvae to develop doubled in “many cases”. This is incorrect because information reported in The Journal of Experimental Biology publication mentions that only two larvae exposed to high sediment concentrations had a doubling of “pelagic larval duration”, or PLD. Furthermore, the publication finding that the median time to metamorphosis for larvae exposed to sediments was 12 days compared to 11 days for the controls does not support the “many cases” argument.    

In addition to mentioning false information, the Science Daily article also has three other flaws: making assumptions, using strong language inappropriately, and excluding key information in the publication. The Science Daily article assumes that sediment comes from “dredging and flood plumes” whereas The Journal of Experimental Biology publication just oftentimes describes sediments as “sediments” or “suspended sediments”. The Science Daily article also uses strong language in its title with words such as “wreaks havoc”. This language is certainly an exaggeration given The Journal of Experimental Biology publication’s finding that sediment concentrations alone have little influence on mortality. Finally, The Journal of Experimental Biology publication devotes considerable attention to the sediment’s implications on larvae length and weight, a topic the Science Daily article does not discuss.

Overall, the Science Daily article brings attention to the important issue that sediment can lead to increases in time for clownfish larvae development. However, the Science Daily article does so in a way with a multitude of flaws, including the providing inaccurate information, the making of assumptions, the use of strong language, and the exclusion of important information. This is why I would give the Science Daily article a score of 5/10.

 

Links:

Science Daily Article:

http://www.sciencedaily.com/releases/2014/10/141023101009.htm

The Journal of Experimental Biology Article: http://jeb.biologists.org/content/early/2013/12/03/jeb.094409.full.pdf+html