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Climate Change... What a Pain in the Gut!

Updated: Apr 27

We all know that climate change is a serious threat looming over us. On a global scale, climate change may alter local weather patterns, expand deserts, and cause sea level rise which could engulf coastal communities. However, it is important to keep in mind that, alongside these sweeping changes, climate change will impact every single species on an individual level... often in ways we may not anticipate...

Juvenile brown-banded bamboo shark (Image credit: Tony Shih, Source: www.fishesofaustralia.net.au/)

When we talk about climate change, we are referring to "Greenhouse gases" accumulating in unnaturally high concentrations in the atmosphere, which alter planetary temperature regulation. Greenhouse gases, including carbon dioxide (C02), methane, nitrous oxide and fluorinated gases, are released into the atmosphere by burning "fossil fuels", like coal, oil and natural gas. These gases trap heat which would normally reflect out into space and cause air temperatures to rise. The average air temperature is predicted to rise by as much as 2 - 5°C in less than 100 years (Meehl et al, 2007).


The process of climate change (Image Credit: Michal Bednarski, Source: https://www.nrdc.org)

Whatsmore, these gases can dissolve into the oceans and cause the pH of the water to drop. This is known as "ocean acidification". The pH (a measure of how acidic or alkaline a substance is) of the ocean is predicted to drop by as much 0.14 - 0.5 units of pH by the year 2100 (Meehl et al, 2007).


A recent study assessed how climate change may affect the brown-banded bamboo shark (Chiloscyllium punctatum). Specifically, the researchers analysed how ocean acidification and rising water temperatures will affect how these sharks are able to digest their food. Researchers grew shark eggs under different environmental conditions, to see how rising water temperatures, decreasing pH and a combination of both might affect the juvenile sharks once they hatched. They assessed the effects by measuring the levels of two digestive enzymes in the sharks' gut; trypsin in the pancreas and alkaline phosphatase from the intestine. These enzymes are involved in the digestion of dietary protein and other metabolic functions (Rosa et al, 2016).


Brown-banded bamboo shark embryo in egg (Image credit: Ryan Kempster, Source: http://www.nbcnews.com/)

The researchers found that, compared to normal conditions (column on the left of the graphs), when assessing both acidic and high temperature conditions, both enzymes were increased (column on the right of the graphs) in the bamboo sharks' gut.

How climate change affects bamboo shark digestion (Rosa et al 2016)
  • left column = normal conditions

  • 2nd left = normal temperature with ocean acidification

  • 3rd left = normal pH with increased water temperature

  • right = ocean acidification + water warming


However, what you may have noticed, is the other 2 columns in the centre of the graph, which are drastically different from the normal conditions. The study found that under conditions of ocean acidification without warming (labelled b), the activity of both enzymes were significantly reduced. In contrast, under conditions of increased water temperature (column c) the enzymes were massively increased (Rosa et al, 2016).


These enzymes are associated with overall health and wellbeing in these sharks. Therefore, when they are reduced or increased dramatically, it implies that the shark is not at its best. The authors concluded that at a glance it seems ocean and acidification and ocean warming may counteract each other in how they affect brown-banded bamboo shark digestion. However, they also stated that the alterations in metabolism in these juvenile sharks might affect how well they grow and their ability to reproduce, which could have major population-level implications (Rosa et al, 2016).


The brown-banded bamboo shark (Image Source: www.tropicblue-vn.com)

These findings highlight the major problem with speculating how climate change will affect different animals... it is very difficult to predict! Scientists can do their best to assess how changing conditions may affect individual species, but in reality the effects will wary depending on location and lifestyle, and we do not know for sure exactly how CO2 levels will change over the upcoming decades. The only way to ensure that climate change does not have a detrimental impact on marine life will be to stop greenhouse gas emissions as much as possible. We must all try to reduce our energy uses and move towards being more sustainable as soon as we possibly can.


Is there something you could do in your daily life to reduce your carbon footprint?



References

Meehl GA, Stocker TF & Collins WD, Friedlingstei, P, Gaye T, Gregory JM, Kitoh A, Knutti R, Murphy JM, Noda A, Raper SCB, Watterson IG, Weaver AJ & Zhao ZC (2007). Global climate projections. In: Solomon S, Qin D & Manning M (Eds.). Climate Change 2007: the Physical Science Basis, pp. 686–688. Cambridge, UK: Cambridge University Press.


Rosa R, Pimentel M, Galan JG, Baptista M, Lopes VM, Couto A, Guerreiro M, Sampaio E, Castro J, Santos C, Calado R & Repolho T (2016). Deficit in digestive capabilities of bamboo shark early stages under climate change. Marine Biology, 163:60, doi: 10.1007/s00227-016-2840-z. Access online.


By Sophie A. Maycock for SharkSpeak.

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