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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

Micro- and ultrastructure of the studied coral specimens.A-C: Microcyclus tortuosus, lower Givetian, Aferdou el Mrakib (Morocco), UAM Tc/B/AM/01. A. Transmitted-light view; the corallite has been mostly recrystallised to a uniform, fine calcite crystal mosaic (MS) with rare ghosts of the original fibrous texture (FB). Note the presence of a cement-filled boring (arrow). B. CL pattern showing the dark blue-luminescent (BL) centre of the corallite and its red-luminescent outer parts (RL). Note also a contrasting luminescence pattern of a boring (arrow; see A for a transmitted-light view). C. SEM view showing invariably small (microspar to small spar), irregular calcite crystals indicative of strong recrystallisation of the skeleton. D-F: Palaeocyclus porpitus, Telychian, Gotland (Sweden), UAM Tc/B/GO/01. D. Transmitted-light photomicrograph; note recrystallisation of the original skeletal material to small sparry calcite crystals (SP) and the entire lack of visible original microstructural features. The interseptal spaces were partially occluded by early diagenetic cements (arrows). E. CL view; the specimen shows uniform red luminescence (RL) with only interseptal spaces filled by yellow to orange-luminescent cements (YL, arrows—see D for a transmitted-light view). F. SEM photomicrograph illustrating complete transformation of the original corallite microstructure into a uniform, fine calcite crystal mosaic. G-L: Calceola sandalina, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/50. G-H. Transmitted-light views showing well-defined original growth increments in the inner part (IN) of the corallite walls, and more advanced recrystallisation of the outer (OUT) skeleton portions. I. CL view of a corallite portion shown in H; note distinct contrast between laminated, dull to faintly-red luminescent (DL), inner part of the wall and homogenously red-luminescent (RL) outer portion of the corallite. J-L. SEM photomicrographs showing well-defined lamellar ultrastructure of the corallite wall.
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pone.0136289.g004: Micro- and ultrastructure of the studied coral specimens.A-C: Microcyclus tortuosus, lower Givetian, Aferdou el Mrakib (Morocco), UAM Tc/B/AM/01. A. Transmitted-light view; the corallite has been mostly recrystallised to a uniform, fine calcite crystal mosaic (MS) with rare ghosts of the original fibrous texture (FB). Note the presence of a cement-filled boring (arrow). B. CL pattern showing the dark blue-luminescent (BL) centre of the corallite and its red-luminescent outer parts (RL). Note also a contrasting luminescence pattern of a boring (arrow; see A for a transmitted-light view). C. SEM view showing invariably small (microspar to small spar), irregular calcite crystals indicative of strong recrystallisation of the skeleton. D-F: Palaeocyclus porpitus, Telychian, Gotland (Sweden), UAM Tc/B/GO/01. D. Transmitted-light photomicrograph; note recrystallisation of the original skeletal material to small sparry calcite crystals (SP) and the entire lack of visible original microstructural features. The interseptal spaces were partially occluded by early diagenetic cements (arrows). E. CL view; the specimen shows uniform red luminescence (RL) with only interseptal spaces filled by yellow to orange-luminescent cements (YL, arrows—see D for a transmitted-light view). F. SEM photomicrograph illustrating complete transformation of the original corallite microstructure into a uniform, fine calcite crystal mosaic. G-L: Calceola sandalina, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/50. G-H. Transmitted-light views showing well-defined original growth increments in the inner part (IN) of the corallite walls, and more advanced recrystallisation of the outer (OUT) skeleton portions. I. CL view of a corallite portion shown in H; note distinct contrast between laminated, dull to faintly-red luminescent (DL), inner part of the wall and homogenously red-luminescent (RL) outer portion of the corallite. J-L. SEM photomicrographs showing well-defined lamellar ultrastructure of the corallite wall.

Mentions: Of the two Moroccan representatives of Microcyclus, the M. roberti specimen from Madène el Mrakib still shows well-defined traces of original fibrous stereome and centres of calcification, similar to those found in M. praecox. These are mostly preserved as ghosts not coinciding with the current calcite crystal outlines (Fig 3G and 3H). SEM analyses show the presence of microspar to small spar crystal mosaic, but the sites of the original centres of calcification are still well visible (Fig 3K and 3L). The M. roberti corallite shows no luminescence in the central and upper portion of the skeleton, whereas the lower part of the corallite gives red luminescence responses (Fig 3I). A thin layer of calcitic cement rimming the corallite has a distinct red to orange luminescence (Fig 3J). A skeleton of M. tortuosus from the Aferdou el Mrakib locality, in turn, consists mostly of microspar to fine spar cloudy calcite crystals, with few remnants of the original fibrous texture (Fig 4A), no visible centres of calcification, and a very homogenous calcite crystal mosaic visible under SEM (Fig 4C). The corallite shows dark blue luminescence in its central part, and only borings and peripheral portions of the skeleton luminesce red to orange (Fig 4B).


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)

Micro- and ultrastructure of the studied coral specimens.A-C: Microcyclus tortuosus, lower Givetian, Aferdou el Mrakib (Morocco), UAM Tc/B/AM/01. A. Transmitted-light view; the corallite has been mostly recrystallised to a uniform, fine calcite crystal mosaic (MS) with rare ghosts of the original fibrous texture (FB). Note the presence of a cement-filled boring (arrow). B. CL pattern showing the dark blue-luminescent (BL) centre of the corallite and its red-luminescent outer parts (RL). Note also a contrasting luminescence pattern of a boring (arrow; see A for a transmitted-light view). C. SEM view showing invariably small (microspar to small spar), irregular calcite crystals indicative of strong recrystallisation of the skeleton. D-F: Palaeocyclus porpitus, Telychian, Gotland (Sweden), UAM Tc/B/GO/01. D. Transmitted-light photomicrograph; note recrystallisation of the original skeletal material to small sparry calcite crystals (SP) and the entire lack of visible original microstructural features. The interseptal spaces were partially occluded by early diagenetic cements (arrows). E. CL view; the specimen shows uniform red luminescence (RL) with only interseptal spaces filled by yellow to orange-luminescent cements (YL, arrows—see D for a transmitted-light view). F. SEM photomicrograph illustrating complete transformation of the original corallite microstructure into a uniform, fine calcite crystal mosaic. G-L: Calceola sandalina, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/50. G-H. Transmitted-light views showing well-defined original growth increments in the inner part (IN) of the corallite walls, and more advanced recrystallisation of the outer (OUT) skeleton portions. I. CL view of a corallite portion shown in H; note distinct contrast between laminated, dull to faintly-red luminescent (DL), inner part of the wall and homogenously red-luminescent (RL) outer portion of the corallite. J-L. SEM photomicrographs showing well-defined lamellar ultrastructure of the corallite wall.
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Related In: Results  -  Collection

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

pone.0136289.g004: Micro- and ultrastructure of the studied coral specimens.A-C: Microcyclus tortuosus, lower Givetian, Aferdou el Mrakib (Morocco), UAM Tc/B/AM/01. A. Transmitted-light view; the corallite has been mostly recrystallised to a uniform, fine calcite crystal mosaic (MS) with rare ghosts of the original fibrous texture (FB). Note the presence of a cement-filled boring (arrow). B. CL pattern showing the dark blue-luminescent (BL) centre of the corallite and its red-luminescent outer parts (RL). Note also a contrasting luminescence pattern of a boring (arrow; see A for a transmitted-light view). C. SEM view showing invariably small (microspar to small spar), irregular calcite crystals indicative of strong recrystallisation of the skeleton. D-F: Palaeocyclus porpitus, Telychian, Gotland (Sweden), UAM Tc/B/GO/01. D. Transmitted-light photomicrograph; note recrystallisation of the original skeletal material to small sparry calcite crystals (SP) and the entire lack of visible original microstructural features. The interseptal spaces were partially occluded by early diagenetic cements (arrows). E. CL view; the specimen shows uniform red luminescence (RL) with only interseptal spaces filled by yellow to orange-luminescent cements (YL, arrows—see D for a transmitted-light view). F. SEM photomicrograph illustrating complete transformation of the original corallite microstructure into a uniform, fine calcite crystal mosaic. G-L: Calceola sandalina, upper Eifelian, Holy Cross Mountains (Poland), UAM Tc/B/SK/50. G-H. Transmitted-light views showing well-defined original growth increments in the inner part (IN) of the corallite walls, and more advanced recrystallisation of the outer (OUT) skeleton portions. I. CL view of a corallite portion shown in H; note distinct contrast between laminated, dull to faintly-red luminescent (DL), inner part of the wall and homogenously red-luminescent (RL) outer portion of the corallite. J-L. SEM photomicrographs showing well-defined lamellar ultrastructure of the corallite wall.
Mentions: Of the two Moroccan representatives of Microcyclus, the M. roberti specimen from Madène el Mrakib still shows well-defined traces of original fibrous stereome and centres of calcification, similar to those found in M. praecox. These are mostly preserved as ghosts not coinciding with the current calcite crystal outlines (Fig 3G and 3H). SEM analyses show the presence of microspar to small spar crystal mosaic, but the sites of the original centres of calcification are still well visible (Fig 3K and 3L). The M. roberti corallite shows no luminescence in the central and upper portion of the skeleton, whereas the lower part of the corallite gives red luminescence responses (Fig 3I). A thin layer of calcitic cement rimming the corallite has a distinct red to orange luminescence (Fig 3J). A skeleton of M. tortuosus from the Aferdou el Mrakib locality, in turn, consists mostly of microspar to fine spar cloudy calcite crystals, with few remnants of the original fibrous texture (Fig 4A), no visible centres of calcification, and a very homogenous calcite crystal mosaic visible under SEM (Fig 4C). The corallite shows dark blue luminescence in its central part, and only borings and peripheral portions of the skeleton luminesce red to orange (Fig 4B).

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