MEPS 561:1-16 (2016)  -  DOI: https://doi.org/10.3354/meps11908

FEATURE ARTICLE
Risk and resilience: variations in magnesium in echinoid skeletal calcite

Abigail M. Smith1,*, Dana E. Clark1,4, Miles D. Lamare1, David J. Winter2,5, Maria Byrne

1Department of Marine Science, University of Otago, PO Box 56, Dunedin 9054, New Zealand
2Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
3University of Sydney, New South Wales 2006, Australia
4Present address: Cawthron Institute, Private Bag 2, Nelson 7042, New Zealand
5Present address: Institute of Fundamental Sciences, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand
*Corresponding author:

ABSTRACT: Echinoids have high-magnesium (Mg) calcite endoskeletons that may be vulnerable to CO2-driven ocean acidification. Amalgamated data for echinoid species from a range of environments and life-history stages allowed characterization of the factors controlling Mg content in their skeletons. Published measurements of Mg in calcite (N = 261), supplemented by new X-ray diffractometry data (N = 382), produced a database including 8 orders, 23 families and 73 species (~7% of the ~1000 known extant species), spanning latitudes 77°S to 72°N, and including 9 skeletal elements or life stages. Mean (± SD) skeletal carbonate mineralogy in the Echinoidea is 7.5 ± 3.23 wt% MgCO3 in calcite (range: 1.5-16.4 wt%, N = 643). Variation in Mg within individuals was small (SD = 0.4-0.9 wt% MgCO3). We found significant differences among skeletal elements: jaw demi-pyramids were the highest in Mg, whereas tests, teeth and spines were intermediate in Mg, but generally higher than larvae. Higher taxa have consistent mineralogical patterns, with orders in particular showing Mg related to first appearance in the fossil record. Latitude was a good proxy for sea-surface temperature (SST), although incorporating SST where available produced a slightly better model. Mg content varied with latitude; higher Mg content in warmer waters may reflect increased metabolic and growth rates. Although the skeletons of some adult urchins may be partially resistant to ocean acidification, larvae and some species may prove to be vulnerable to lowered pH, resulting in ecosystem changes in coastal marine environments.


KEY WORDS: Carbonate mineralogy · Echinoidea · Larvae · Skeletal morphology · Urchins · Ocean acidification


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Cite this article as: Smith AM, Clark DE, Lamare MD, Winter DJ, Byrne M (2016) Risk and resilience: variations in magnesium in echinoid skeletal calcite. Mar Ecol Prog Ser 561:1-16. https://doi.org/10.3354/meps11908

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