the stunting effect of increased CO2 in the ocean

The stunting effect of a high CO2 ocean on calcification and development in sea urchin larvae, a synthesis from the tropics to the poles, by Byrne et al., is a scientific paper that examined how 15 species of sea urchin larvae responded to the changes in their ocean environment. Sea urchins have what is called a biphasic life history, which means that part of their life is spent as larvae and the other part is spent as an adult, and these researchers chose to look at the arm lengths of larvae to measure growth. The sea urchin larvae are called echinoplutei and their arms were measured in order to determine the effect changing ocean conditions have on the development of the sea urchins (Figure 1). The ocean changes that the researchers measured included CO2 levels, carbonate mineral saturation levels, and the temperature levels. This research project stemmed from the observed changes in ocean acidity (pH) and temperatures, and the researchers took this information and asked how it is affecting sea urchin growth and development.

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Figure 1: Echinoplutei larvae (Byrne et al. 2013).

The researchers found that increased CO2 levels, or increase acidity of the water decreased arm growth. They also found evidence that increased CO2 levels can compromise the structural integrity of the arm, which means it is both smaller and weaker with an increasing abundance of abnormalities (Figure 2). They also found that it takes the larvae longer to grow and mature, which is more time that the larvae spend in the water unprotected. It is suggested in the paper that these factors may contribute to an increase in larval mortality, and thus a decrease in adults. The affect temperature has on the larvae is almost the opposite of CO2. It was found that increased temperature resulted in faster growth, large arm lengths, and elevated metabolism. Thus, increased temperature may offset the negative impacts that increased ocean acidity has on sea urchins (Figure 3). Current ocean and climate conditions suggest that the ocean will become more acidic and warmer in the near future. This study looked at factor levels of the proposed near future; however, it is still unclear how the combination of increased acidity and temperature will affect sea urchins. It was important in this study that the results were uniform, regardless of where the species is in the world, which suggests that this is an ocean-wide problem. However, not all of the urchins were affected equally, so some urchins may survive better with the changing conditions of the ocean.

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Figure 2: This photo shows the abnormalities and decrease in structural integrity of the arms after being exposed to a lower pH (Byrne et al. 2013).

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Figure 3: This figure shows the offsetting effect temperature has when combined with changes in acidity on arm growth (Byrne et al. 2013).

-by Allie Sifrit

 

Reference:

Byrne M, Lamare M, Winter D, Dworjanyn SA, Uthicke S. 2013 Oct 5. The stunting effect of a high CO2    ocean on calcification and development in sea urchin larvae, a synthesis from the tropics to the           poles. Philosophical Transactions of the Royal Society B-Biological Sciences 386(1627).

 

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