Experiment With Sea Urchins In Water Cut from pH 8.1 To 7.7 Shows 25% Drop In Reproduction - ENN

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A new study by scientists into the future effects of acidic sea water shows that the reduced pH value of the oceans’ surface waters will have drastic results in around 100 years’ time. The scientists, from Sweden and Australia, carried out the world’s first research into how a lowered pH of the sea’s surface water affects marine animal life.

In their project, they allowed sea urchins of the species Heliocidaris Erythrogramma to fertilize themselves in water where the pH has been lowered from its normal 8.1 to a pH value of 7.7. This means an environment three times as acidic, and corresponds to the change expected by the year 2100.

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University of Gothenburg researchers, Jon Havenhand and Michael Thorndyke, say that this acidification process of the oceans affects the sea urchin profoundly. Like most invertebrates, the sea urchin multiplies by releasing its eggs to be fertilized in the open water. However, in a more acidic marine environment, the sea urchin’s ability to multiply goes down by 25 percent, as its sperm swim more slowly and move less effectively. If fertilization is successful, their larval development is disturbed to the extent where only 75 percent of the eggs develop into healthy larvae. “A 25 percent drop in fertility is the equivalent of a 25 percent drop in the reproductive population. It remains to be seen whether other species exhibit the same effect, but, translated to commercially and ecologically important species such as lobsters, crabs, mussels and fish, acidification would have far reaching consequences,”� says Jon Havenhand, a researcher from the Department of Marine Ecology working at the Sven Lovén Centre for Marine Sciences in Tjärnö. The researchers wrote their findings up in an article published in Current Biology and entitled it Near future levels of ocean acidification reduce fertilization success in a sea urchin.

The sea urchin lives off the south coast of Australia. From a research point of view, the species is interesting as its shell is made out of limestone, which is broken down in more acidic environments. “Species with limestone skeletons or shells are hit particularly hard when the pH drops, through a drop in ability to grow and a rise in mortality. But, and it’s a big but, we don’t yet know enough about the effects of acidification in the sea, and I hope I’m wrong about the wider consequences of our results,”� says John Havenhand, one of the researchers. He added that the need for more research on a global level is acute.

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http://www.enn.com/ecosystems/article/37799

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1. Evolutionary pressure

A 25% drop in reproduction is an environmental pressure to select for those individuals who have genes that will confer an advantage to them at lower pH. It will be interesting to see what this does to H. Erythrogramma and what the survivors will look like.