Sea urchins threatened by ocean acidification

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Ocean acidification will reduce sea urchin populations, according to a study published in a recent issue of the journal Current Biology.

A group of Swedish and Australian scientists led by Jon Havenhand have found the reproductive success of sea urchins to significantly decrease if the pH of the world's oceans drop to predicted levels by 2100.

Because sea urchins release their gametes freely into the water where they are fertilized and develop as larvae, the chemical nature of the seawater into which gametes are released plays a key role in fertilization and larval development.

Studying the urchin Heliocidaris erythrogramma, a species commonly found in southern Australia, the authors found that dropping the pH levels of seaweater from 8.1 (its current value) to 7.7 (predicted value for 2100) reduced the reproductive success of the sea urchin in several ways, lowering the swimming speed of the sea urchin sperm by 12%, lowering sperm motility by 16% and lowering the success of fertilized eggs to develop into cleaving embryos and swimming larvae by 20% and 26% respectively.

Increased acidity of the world's oceans has been shown to adversely effect other marine invertebrates (see Global warming and acidification threaten coral survival and Coralline algae will suffer as oceans acidify).

For more information, see the paper: Havenhand, JN, F-R Buttler, MC Thorndyke and JE Williamson (2008) Near-future levels of ocean acidification reduce fertilization success in a sea urchin. Current Biology 18, pp. R651"R652.