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Gazeau F, Urbini L, Cox TE, Alliouane S, Gattuso JP
Comparison of the alkalinity and calcium anomaly techniques to estimate rates of net calcification
The increasing acidification in the world's oceans necessitates reliable methods for the determination of its impacts on marine organisms. Gazeau and co-workers estimated calcification rates in 4 benthic calcifiers with 2 non-destructive methods: the alkalinity and the calcium anomaly techniques. While rates derived using the 2 approaches did not significantly differ from each other for corals, the alkalinity anomaly technique is preferable for coralline algae, as these precipitate calcite with a significant proportion of magnesium. For mussels and sea urchins, the alkalinity anomaly technique appears valid but requires corrections to take ammonium excretion into account. Finally, as sea urchins precipitate high amounts of magnesian calcite, studies using these organisms should measure magnesium incorporation rates as well.