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Stable Isotope Signatures of Middle Palaeozoic Ahermatypic Rugose Corals - Deciphering Secondary Alteration, Vital Fractionation Effects, and Palaeoecological Implications.

Jakubowicz M, Berkowski B, López Correa M, Jarochowska E, Joachimski M, Belka Z - PLoS ONE (2015)

Bottom Line: The results of the present study add to growing evidence for significant differences between Scleractinia and Rugosa, and agree with recent studies indicating that calcification mechanisms developed independently in these two groups of cnidarians.Consequently, particular caution is needed in using scleractinians as analogues in isotopic studies of extinct coral lineages.Answering some of the pertinent palaeoecological questions, such as that of the possibility of photosymbiosis in Palaeozoic corals, may not be possible based on stable isotope data.

View Article: PubMed Central - PubMed

Affiliation: Institute of Geoecology and Geoinformation, Adam Mickiewicz University, Poznań, Poland.

ABSTRACT
This study investigates stable isotope signatures of five species of Silurian and Devonian deep-water, ahermatypic rugose corals, providing new insights into isotopic fractionation effects exhibited by Palaeozoic rugosans, and possible role of diagenetic processes in modifying their original isotopic signals. To minimize the influence of intraskeletal cements on the observed signatures, the analysed specimens included unusual species either devoid of large intraskeletal open spaces ('button corals': Microcyclus, Palaeocyclus), or typified by particularly thick corallite walls (Calceola). The corals were collected at four localities in the Holy Cross Mountains (Poland), Mader Basin (Morocco) and on Gotland (Sweden), representing distinct diagenetic histories and different styles of diagenetic alteration. To evaluate the resistance of the corallites to diagenesis, we applied various microscopic and trace element preservation tests. Distinct differences between isotopic compositions of the least-altered and most-altered skeleton portions emphasise a critical role of material selection for geochemical studies of Palaeozoic corals. The least-altered parts of the specimens show marine or near-marine stable isotope signals and lack positive correlation between δ13C and δ18O. In terms of isotopic fractionation mechanisms, Palaeozoic rugosans must have differed considerably from modern deep-water scleractinians, typified by significant depletion in both 18O and 13C, and pronounced δ13C-δ18O co-variance. The fractionation effects exhibited by rugosans seem similar rather to the minor isotopic effects typical of modern non-scleractinian corals (octocorals and hydrocorals). The results of the present study add to growing evidence for significant differences between Scleractinia and Rugosa, and agree with recent studies indicating that calcification mechanisms developed independently in these two groups of cnidarians. Consequently, particular caution is needed in using scleractinians as analogues in isotopic studies of extinct coral lineages. Answering some of the pertinent palaeoecological questions, such as that of the possibility of photosymbiosis in Palaeozoic corals, may not be possible based on stable isotope data.

No MeSH data available.


Related in: MedlinePlus

Distribution of sampling tracks, and the δ13C and δ18O values found in the individual tracks within the studied coral specimen.Tracks forming continuous isotopic transects are connected with continuous lines. Note the relationship between the occurrence of anomalous isotopic values and distinct luminescence patterns of the sampled carbonates. A-C: Microcyclus praecox, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/20; D-F: Microcyclus roberti, lower Givetian, Madène el Mrakib (Morocco), UAM Tc/B/MM/01; G-I: Microcyclus tortuosus, lower Givetian, Aferdou el Mrakib (Morocco), UAM Tc/B/AM/01; J-L: Calceola sandalina, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/50; M-N: Palaeocyclus porpitus, Telychian, Gotland (Sweden), UAM Tc/B/GO/01. Abbreviations as in Fig 5.
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pone.0136289.g006: Distribution of sampling tracks, and the δ13C and δ18O values found in the individual tracks within the studied coral specimen.Tracks forming continuous isotopic transects are connected with continuous lines. Note the relationship between the occurrence of anomalous isotopic values and distinct luminescence patterns of the sampled carbonates. A-C: Microcyclus praecox, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/20; D-F: Microcyclus roberti, lower Givetian, Madène el Mrakib (Morocco), UAM Tc/B/MM/01; G-I: Microcyclus tortuosus, lower Givetian, Aferdou el Mrakib (Morocco), UAM Tc/B/AM/01; J-L: Calceola sandalina, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/50; M-N: Palaeocyclus porpitus, Telychian, Gotland (Sweden), UAM Tc/B/GO/01. Abbreviations as in Fig 5.

Mentions: Each of the analysed coral specimens shows somewhat different ranges in δ13C and/or δ18O (Table 3), which results in clustering of the values in five non-overlapping fields (Fig 5). No obvious trends in changes of the stable isotope composition occur along the analysed transects (Fig 6), and there is little co-variance between δ13C and δ18O values except for the single specimen of M. praecox from the Holy Cross Mountains, in which some negative correlation (r = −0.70, p = 0.004) can be noticed. In each case, strongly altered portions of corals display δ13C and/or δ18O signals distinct from those of the least-altered parts of the skeletons, and thus fall conspicuously outside the clusters defined by them.


Stable Isotope Signatures of Middle Palaeozoic Ahermatypic Rugose Corals - Deciphering Secondary Alteration, Vital Fractionation Effects, and Palaeoecological Implications.

Jakubowicz M, Berkowski B, López Correa M, Jarochowska E, Joachimski M, Belka Z - PLoS ONE (2015)

Distribution of sampling tracks, and the δ13C and δ18O values found in the individual tracks within the studied coral specimen.Tracks forming continuous isotopic transects are connected with continuous lines. Note the relationship between the occurrence of anomalous isotopic values and distinct luminescence patterns of the sampled carbonates. A-C: Microcyclus praecox, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/20; D-F: Microcyclus roberti, lower Givetian, Madène el Mrakib (Morocco), UAM Tc/B/MM/01; G-I: Microcyclus tortuosus, lower Givetian, Aferdou el Mrakib (Morocco), UAM Tc/B/AM/01; J-L: Calceola sandalina, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/50; M-N: Palaeocyclus porpitus, Telychian, Gotland (Sweden), UAM Tc/B/GO/01. Abbreviations as in Fig 5.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4559396&req=5

pone.0136289.g006: Distribution of sampling tracks, and the δ13C and δ18O values found in the individual tracks within the studied coral specimen.Tracks forming continuous isotopic transects are connected with continuous lines. Note the relationship between the occurrence of anomalous isotopic values and distinct luminescence patterns of the sampled carbonates. A-C: Microcyclus praecox, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/20; D-F: Microcyclus roberti, lower Givetian, Madène el Mrakib (Morocco), UAM Tc/B/MM/01; G-I: Microcyclus tortuosus, lower Givetian, Aferdou el Mrakib (Morocco), UAM Tc/B/AM/01; J-L: Calceola sandalina, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/50; M-N: Palaeocyclus porpitus, Telychian, Gotland (Sweden), UAM Tc/B/GO/01. Abbreviations as in Fig 5.
Mentions: Each of the analysed coral specimens shows somewhat different ranges in δ13C and/or δ18O (Table 3), which results in clustering of the values in five non-overlapping fields (Fig 5). No obvious trends in changes of the stable isotope composition occur along the analysed transects (Fig 6), and there is little co-variance between δ13C and δ18O values except for the single specimen of M. praecox from the Holy Cross Mountains, in which some negative correlation (r = −0.70, p = 0.004) can be noticed. In each case, strongly altered portions of corals display δ13C and/or δ18O signals distinct from those of the least-altered parts of the skeletons, and thus fall conspicuously outside the clusters defined by them.

Bottom Line: The results of the present study add to growing evidence for significant differences between Scleractinia and Rugosa, and agree with recent studies indicating that calcification mechanisms developed independently in these two groups of cnidarians.Consequently, particular caution is needed in using scleractinians as analogues in isotopic studies of extinct coral lineages.Answering some of the pertinent palaeoecological questions, such as that of the possibility of photosymbiosis in Palaeozoic corals, may not be possible based on stable isotope data.

View Article: PubMed Central - PubMed

Affiliation: Institute of Geoecology and Geoinformation, Adam Mickiewicz University, Poznań, Poland.

ABSTRACT
This study investigates stable isotope signatures of five species of Silurian and Devonian deep-water, ahermatypic rugose corals, providing new insights into isotopic fractionation effects exhibited by Palaeozoic rugosans, and possible role of diagenetic processes in modifying their original isotopic signals. To minimize the influence of intraskeletal cements on the observed signatures, the analysed specimens included unusual species either devoid of large intraskeletal open spaces ('button corals': Microcyclus, Palaeocyclus), or typified by particularly thick corallite walls (Calceola). The corals were collected at four localities in the Holy Cross Mountains (Poland), Mader Basin (Morocco) and on Gotland (Sweden), representing distinct diagenetic histories and different styles of diagenetic alteration. To evaluate the resistance of the corallites to diagenesis, we applied various microscopic and trace element preservation tests. Distinct differences between isotopic compositions of the least-altered and most-altered skeleton portions emphasise a critical role of material selection for geochemical studies of Palaeozoic corals. The least-altered parts of the specimens show marine or near-marine stable isotope signals and lack positive correlation between δ13C and δ18O. In terms of isotopic fractionation mechanisms, Palaeozoic rugosans must have differed considerably from modern deep-water scleractinians, typified by significant depletion in both 18O and 13C, and pronounced δ13C-δ18O co-variance. The fractionation effects exhibited by rugosans seem similar rather to the minor isotopic effects typical of modern non-scleractinian corals (octocorals and hydrocorals). The results of the present study add to growing evidence for significant differences between Scleractinia and Rugosa, and agree with recent studies indicating that calcification mechanisms developed independently in these two groups of cnidarians. Consequently, particular caution is needed in using scleractinians as analogues in isotopic studies of extinct coral lineages. Answering some of the pertinent palaeoecological questions, such as that of the possibility of photosymbiosis in Palaeozoic corals, may not be possible based on stable isotope data.

No MeSH data available.


Related in: MedlinePlus