Zigzag microstructure in rugose corals: A possible indicator of relative seawater Mg/Ca ratios

Webb, Gregory E.; Sorauf, James E.

doi:10.1130/0091-7613(2002)030<0415:zmirca>2.0.co;2

Cited by 28 publications

(29 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hardie's oceanic Mg/Ca model is further supported by synchronized transitions between MgSO 4 and KCl evaporites (Hardie, 1996), fluid inclusion data (Lowenstein et al, J. B. Ries: Effects of secular variation in seawater Mg/Ca on marine biocalcification 2837 , 2005Brennan and Lowenstein, 2002;Brennan, 2002;Horita et al, 2002;Brennan et al, 2004;Timofeeff et al, 2006), secular variation in the skeletal Mg/Ca ratio of rugose corals (Webb and Sorauf, 2002), echinoderms (Dickson, 2002(Dickson, , 2004Hasiuk and Lohmann, 2008), and abiogenic carbonates (Hasiuk and Lohmann, 2008); secular variation in the ratio of aragonite-to-calcite within bi-mineralic calcareous serpulid worm tubes (Railsback, 1993); secular variation in the Sr/Mg ratio of abiogenic marine carbonates (Cicero and Lohmann, 2001); the occurrence of higher seawater Sr/Ca ratios during predicted calcite sea intervals than during predicted aragonite sea intervals (Sr would be depleted in seawater during aragonite sea intervals because Sr is more readily incorporated in aragonite than in calcite; Steuber and Veizer, 2002); and secular variation in the Br concentration of marine halite (Siemann, 2003).…”

Section: Insight Into the Composition Of Organisms' Calcifying Fluidsmentioning

confidence: 94%

“…However, experiments conducted by Mucci and Morse (1983), Burton and Walter (1991), Hartley and Mucci (1996), De ChoudensSanchez and Gonzalez (2009), and Lee and Morse (2010) revealed that atmospheric pCO 2 and solution saturation state had no statistically significant effect on the Mg-content of calcite that precipitated from experimental seawater solutions. Although variations in temperature, and salinity across latitude and depth are thought to cause regional differences in the Mg-content of marine calcite (Morse and Bender, 1990), global secular variation in these seawater parameters (T =20-30 • C; salinity = 30-40) would not have been sufficient to explain the observed global secular trends in the Mg-content of biogenic marine calcite (e.g., Dickson, 2002Dickson, , 2004Webb and Sorauf, 2002;Steuber and Rauch, 2005;Hasiuk and Lohmann, 2008) throughout Phanerozoic time.…”

Section: Seawater Mg/camentioning

confidence: 99%

See 1 more Smart Citation

Review: geological and experimental evidence for secular variation in seawater Mg/Ca (calcite-aragonite seas) and its effects on marine biological calcification

Ries¹

2010

Biogeosciences

224

170

View full text Add to dashboard Cite

Abstract. Synchronized transitions in the polymorph mineralogy of the major reef-building and sediment-producing calcareous marine organisms and abiotic CaCO 3 precipitates (ooids, marine cements) throughout Phanerozoic time are believed to have been caused by tectonically induced variations in the Mg/Ca ratio of seawater (molar Mg/Ca>2="aragonite seas", <2="calcite seas"). Here, I assess the geological evidence in support of secular variation in seawater Mg/Ca and its effects on marine calcifiers, and review a series of recent experiments that investigate the effects of seawater Mg/Ca (1.0-5.2) on extant representatives of calcifying taxa that have experienced variations in this ionic ratio of seawater throughout the geologic past.Secular variation in seawater Mg/Ca is supported by synchronized secular variations in (1) the ionic composition of fluid inclusions in primary marine halite, (2) the mineralogies of late stage marine evaporites, abiogenic carbonates, and reef-and sediment-forming marine calcifiers, (3) the Mg/Ca ratios of fossil echinoderms, molluscs, rugose corals, and abiogenic carbonates, (4) global rates of tectonism that drive the exchange of Mg 2+ and Ca 2+ along zones of ocean crust production, and (5) additional proxies of seawater Mg/Ca including Sr/Mg ratios of abiogenic carbonates, Sr/Ca ratios of biogenic carbonates, and Br concentrations in marine halite.Laboratory experiments have revealed that aragonitesecreting bryopsidalean algae and scleractinian corals and calcite-secreting coccolithophores exhibit higher rates of calcification and growth in experimental seawaters formulated with seawater Mg/Ca ratios that favor their skeletal mineral. These results support the assertion that seawater Mg/CaCorrespondence to: J. B. Ries (jries@unc.edu) played an important role in determining which hypercalcifying marine organisms were the major reef-builders and sediment-producers throughout Earth history. The observation that primary production increased along with calcification within the bryopsidalean and coccolithophorid algae in mineralogically favorable seawater is consistent with the hypothesis that calcification promotes photosynthesis within some species of these algae through the liberation of CO 2 .The experiments also revealed that aragonite-secreting bryopsidalean algae and scleractinian corals, and bacterial biofilms that secrete a mixture of aragonite and high Mg calcite, began secreting an increased proportion of their calcium carbonate as the calcite polymorph in the lower-Mg/Ca experimental seawaters. Furthermore, the Mg/Ca ratio of calcite secreted by the coccolithophores, coralline red algae, reef-dwelling animals (crustacea, urchins, calcareous tube worms), bacterial biofilms, scleractinian corals, and bryopsidalean algae declined with reductions in seawater Mg/Ca. Notably, Mg fractionation in autotrophic organisms was more strongly influenced by changes in seawater Mg/Ca than in heterotrophic organisms, a probable consequence of autotrophic organisms inducing a less controlled ...

show abstract

Section: Insight Into the Composition Of Organisms' Calcifying Fluidsmentioning

confidence: 94%

Section: Seawater Mg/camentioning

confidence: 99%

Review: geological and experimental evidence for secular variation in seawater Mg/Ca (calcite-aragonite seas) and its effects on marine biological calcification

Ries¹

2010

Biogeosciences

224

170

View full text Add to dashboard Cite

show abstract

“…period during which the ocean Mg/Ca ratio is inferred to have changed dramatically (from <1 to 5.2 mol/mol), provides a great opportunity to test the impact of seawater chemistry on coral calcification. In general, the evolution of corals, both Rugosa (Webb and Sorauf, 2002) and Scleractinia, indicates that variations in the Mg/Ca ratio might have influenced their skeletal composition (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Aragonitic scleractinian corals in the Cretaceous calcitic sea

Janiszewska

Mazur

Escrig

et al. 2017

Geology

View full text Add to dashboard Cite

Changes in seawater chemistry have affected the evolution of calcifying marine organisms, including their skeletal polymorph (calcite versus aragonite), which is believed to have been strongly influenced by the Mg/Ca ratio at the time these animals first emerged. However, we show that micrabaciids, a scleractinian coral clade that first appeared in the fossil record of the Cretaceous, when the ocean Mg/ Ca ratio was near the lowest in the Phanerozoic (thus a priori favoring calcitic mineralogy), formed skeletons composed exclusively of aragonite. Exceptionally preserved aragonitic coralla of Micrabacia from the Late Cretaceous Ripley Formation (southeastern USA) have skeletal microstructures identical to their modern representatives. In addition, skeletons of Micrabacia from Cretaceous chalk deposits of eastern Poland are clearly diagenetically altered in a manner consistent with originally aragonitic mineralogy. These deposits have also preserved fossils of the scleractinian Coelosmilia, the skeleton of which is interpreted as originally calcitic. These findings show that if changes in seawater Mg/Ca ratio influenced the mineralogy of scleractinian corals, the outcome was taxon specific. The aragonitic mineralogy, unique skeletal microstructures and ultrastructures, and low Mg/Ca ratios in both fossil and living micrabaciids indicate that their biomineralization process is strongly controlled and has withstood major fluctuations in seawater chemistry during the past 70 m.y. INTRODUCTIONVariation in seawater chemistry is thought to have played an important role in the evolution of skeleton-forming marine organisms and in the composition of their skeletons. The Mg/Ca ratio of seawater in particular has varied dramatically throughout the Phanerozoic (Stanley and Hardie, 1998;Porter, 2010). Abiotic precipitation experiments with seawater analogs have shown that precipitation of different CaCO 3 polymorphs is mainly controlled by the Mg/Ca ratio and temperature (Morse et al., 1997). At ~25 °C, present-day seawater ionic strength, and atmospheric CO 2 concentrations, the Mg/Ca ratio separates a regime of low-Mg calcite precipitation (Mg/Ca < 2) from a regime of aragonite/high-Mg calcite precipitation (Mg/Ca > 2) (Hardie, 1996). Based on the composition of early diagenetic carbonate cements and oolites (Sandberg, 1983), fluid-inclusion data (e.g., Lowenstein et al., 2001;Horita et al., 2002), and modeling of Mg/ Ca fluctuations linking the chemical composition of the oceans with rates of oceanic crust formation (Hardie, 1996), the Phanerozoic has thus been divided into periods of calcitic and aragonitic seas, respectively (Fig. 1). It was suggested that the carbonate polymorph of hypercalcifying marine organisms was dictated by the seawater Mg/Ca ratio: during periods with high Mg/Ca ratio, aragonite-forming organisms dominated, whereas during periods with low Mg/Ca ratio, calcite-secreting organisms flourished (Stanley and Hardie, 1998). Furthermore, it was proposed that the skeletal mineralogy of newly evolv...

show abstract

“…Although petrographic techniques can indicate original high magnesium content for fossilized skeletal calcite (4,(13)(14)(15), diagenetic loss of magnesium from the lattice of high-Mg calcite has impeded quantitative analysis of the geologic history of this mineral's production by organisms. Faced with this limitation, we undertook experiments on the effect of seawater chemistry on the skeletal mineralogy of three extant species of coralline algae that produce high-Mg calcite in modern seas.…”

mentioning

confidence: 99%

Low-magnesium calcite produced by coralline algae in seawater of Late Cretaceous composition

Stanley

Ries

Hardie

2002

Proc. Natl. Acad. Sci. U.S.A.

137

131

View full text Add to dashboard Cite

Shifts in the Mg͞Ca ratio of seawater driven by changes in midocean ridge spreading rates have produced oscillations in the mineralogy of nonskeletal carbonate precipitates from seawater on time scales of 10 8 years. Since Cambrian time, skeletal mineralogies of anatomically simple organisms functioning as major reef builders or producers of shallow marine limestones have generally corresponded in mineral composition to nonskeletal precipitates. Here we report on experiments showing that the ambient Mg͞Ca ratio actually governs the skeletal mineralogy of some simple organisms. In modern seas, coralline algae produce skeletons of high-Mg calcite (>4 mol % MgCO3). We grew three species of these algae in artificial seawaters having three different Mg͞Ca ratios. All of the species incorporated amounts of Mg into their skeletons in proportion to the ambient Mg͞Ca ratio, mimicking the pattern for nonskeletal precipitation. Thus, the algae calcified as if they were simply inducing precipitation from seawater through their consumption of CO2 for photosynthesis; presumably organic templates specify the calcite crystal structure of their skeletons. In artificial seawater with the low Mg͞Ca ratio of Late Cretaceous seas, the algae in our experiments produced low-Mg calcite (<4 mol % MgCO3), the carbonate mineral formed by nonskeletal precipitation in those ancient seas. Our results suggest that many taxa that produce high-Mg calcite today produced low-Mg calcite in Late Cretaceous seas.S ince the beginning of the Paleozoic Era, there have been two intervals of ''calcite seas,'' in which nonskeletal carbonate precipitates from seawater have consisted of low-Mg calcite and three intervals of ''aragonite seas,'' in which these precipitates have consisted of high-Mg calcite or of aragonite, the orthorhombic polymorph of CaCO 3 (1) (Fig. 1). Fossils reveal the same temporal patterns for the skeletal mineralogies of anatomically simple organisms that have functioned as major producers of carbonate reefs or bioclastic sediments on shallow sea floors; such organisms exert less control than more complex organisms over the chemical milieu in which they build their skeletons (2, 3). Calcareous skeletons of many anatomically simple organisms share two traits with nonskeletal precipitates: first, they consist of needle-shaped crystals, and second, these crystals are commonly arrayed radially to form spherulites (semiround bundles) (4).Laboratory experiments show that the mineralogy of nonskeletal carbonate precipitates varies with the Mg͞Ca ratio of seawater. † ‡ In water at the ionic strength of modern seawater (0.7) and temperatures typical of tropical seas (25-30°C), low-Mg calcite precipitates when the ambient Mg͞Ca mole ratio is below Ϸ1. When the ambient mole ratio is above Ϸ1, high-Mg calcite precipitates and the percentage of magnesium carbonate incorporated into a crystal increases with this ratio, reaching Ϸ6-8 at a ratio of 2, depending on temperature (Fig. 2). At ambient mole ratios between Ϸ2 and slightly above 5, aragonit...

show abstract

Zigzag microstructure in rugose corals: A possible indicator of relative seawater Mg/Ca ratios

Cited by 28 publications

References 13 publications

Review: geological and experimental evidence for secular variation in seawater Mg/Ca (calcite-aragonite seas) and its effects on marine biological calcification

Review: geological and experimental evidence for secular variation in seawater Mg/Ca (calcite-aragonite seas) and its effects on marine biological calcification

Aragonitic scleractinian corals in the Cretaceous calcitic sea

Low-magnesium calcite produced by coralline algae in seawater of Late Cretaceous composition

Contact Info

Product

Resources

About