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Justin B Ries - One of the best experts on this subject based on the ideXlab platform.
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Research Article DOI: 10.2110/jsr.2006.051 ARAGONITIC ALGAE IN CALCITE SEAS: EFFECT OF SEAWATER Mg/Ca RATIO ON ALGAL SEDIMENT PRODUCTION
2015Co-Authors: Justin B RiesAbstract:ABSTRACT: Secular variation in seawater Mg/Ca would have subjected the aragonite-producing codiacean algae to two intervals of low-Mg calcite seas (mMg/Ca, 2) and two intervals of aragonite + high-Mg calcite seas (mMg/Ca. 2) seas since their origin in the Ordovician. It is asserted that the aragonite + high-Mg calcite affinity of modern and Recent tropical seas (mMg/Ca. 2) has enabled the aragonitic Codiaceae to act as major carbonate sediment producers in these seas. To test this assertion, specimens of the sediment-producing codiacean alga Udotea flabellum were grown in artificial seawaters formulated at mMg/Ca ratios (1.0, 2.5, 5.2) that have occurred in the oceans throughout the geologic history of the Codiaceae. While the U. flabellum algae produced exclusively aragonite in both the artificial boundary seawater (mMg/Ca 5 2.5) and the artificial aragonite + high-Mg calcite seawater (modern seawater; mMg/Ca 5 5.2), the algae produced a portion (25 6 3%) of their CaCO3 as low-Mg calcite ( # 4 mol % MgCO3) in the artificial calcite seawater (mMg/Ca 5 1.0), suggesting that their CaCO3 polymorph control can be partially overridden by ambient seawater chemistry. Primary productivity, calcification, and linear growth of the algae decreased with reductions in ambient Mg/Ca, despite increases in absolute Ca concentration of the seawater. Reduced calcification in the lower Mg/Ca seawaters is probably due to kinetic difficulties of producing aragonite from seawater that favors the nucleation of calcite. The decreased linear growth and primary production are likely associated with reductions in the ambient CO2 available for photosynthesis, resulting from the reduced calcification
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aragonite production in calcite seas effect of seawater mg ca ratio on the calcification and growth of the calcareous alga penicillus capitatus
Paleobiology, 2005Co-Authors: Justin B RiesAbstract:Abstract Previous studies have shown that secular variation in the Mg/Ca ratio of seawater throughout the Phanerozoic would have subjected the aragonite-producing codiacean algae to at least three transitions between the low-Mg calcite (molar Mg/Ca 2) nucleation fields in the oceans, since their origin in the Ordovician. These studies have asserted that major sediment production by codiacean algae in Recent tropical seas is permitted by the Mg/Ca ratio of modern seawater (molar Mg/Ca ∼5.2) remaining within the aragonitic/high-Mg calcite nucleation field (molar Mg/Ca >2). Here I present the results of experiments conducted to determine the effects of ambient Mg/Ca on the mineralogy, growth rate, primary productivity, calcification rate, and biomechanics of the codiacean alga Penicillus capitatus. P. capitatus specimens were grown in three artificial seawater treatments that mimic ancient seawater of differing Mg/Ca ratios, corresponding to the low-Mg calcit...
Frederick W. Zechman - One of the best experts on this subject based on the ideXlab platform.
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PHYLOGENETIC ANALYSES OF THE BRYOPSIDALES (ULVOPHYCEAE, CHLOROPHYTA) BASED ON RUBISCO LARGE SUBUNIT GENE SEQUENCES1
Journal of Phycology, 2006Co-Authors: Daryl W. Lam, Frederick W. ZechmanAbstract:Current taxonomy of the Bryopsidales recognizes eight families; most of which are further categorized into two suborders, the Bryopsidineae and Halimedineae. This concept was supported by early molecular phylogenetic analyses based on rRNA sequence data, but subsequent cladistic analyses of morphological characters inferred monophyly in only the Halimedineae. These conflicting results prompted the current analysis of 32 taxa from this diverse group of green algae based on plastid-encoded RUBISCO large subunit (rbcL) gene sequences. Results of these analyses suggested that the Halimedineae and Bryopsidineae are distinct monophyletic lineages. The families Bryopsidaceae, Caulerpaceae, Codiaceae, Derbesiaceae, and Halimediaceae were inferred as monophyletic, however the Udoteaceae was inferred as non-monophyletic. The phylogenetic position of two taxa with uncertain subordinal affinity, Dichotomosiphon tuberosus Lawson and Pseudocodium floridanum Dawes & Mathieson, were also inferred. Pseudocodium was consistently placed within the halimedinean clade suggesting its inclusion into this suborder, however familial affinity was not resolved. D. tuberosus was the inferred sister taxon of the Halimedineae based on analyses of rbcL sequence data and thus a possible member of this suborder.
Daryl W. Lam - One of the best experts on this subject based on the ideXlab platform.
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PHYLOGENETIC ANALYSES OF THE BRYOPSIDALES (ULVOPHYCEAE, CHLOROPHYTA) BASED ON RUBISCO LARGE SUBUNIT GENE SEQUENCES1
Journal of Phycology, 2006Co-Authors: Daryl W. Lam, Frederick W. ZechmanAbstract:Current taxonomy of the Bryopsidales recognizes eight families; most of which are further categorized into two suborders, the Bryopsidineae and Halimedineae. This concept was supported by early molecular phylogenetic analyses based on rRNA sequence data, but subsequent cladistic analyses of morphological characters inferred monophyly in only the Halimedineae. These conflicting results prompted the current analysis of 32 taxa from this diverse group of green algae based on plastid-encoded RUBISCO large subunit (rbcL) gene sequences. Results of these analyses suggested that the Halimedineae and Bryopsidineae are distinct monophyletic lineages. The families Bryopsidaceae, Caulerpaceae, Codiaceae, Derbesiaceae, and Halimediaceae were inferred as monophyletic, however the Udoteaceae was inferred as non-monophyletic. The phylogenetic position of two taxa with uncertain subordinal affinity, Dichotomosiphon tuberosus Lawson and Pseudocodium floridanum Dawes & Mathieson, were also inferred. Pseudocodium was consistently placed within the halimedinean clade suggesting its inclusion into this suborder, however familial affinity was not resolved. D. tuberosus was the inferred sister taxon of the Halimedineae based on analyses of rbcL sequence data and thus a possible member of this suborder.
Petra Empt - One of the best experts on this subject based on the ideXlab platform.
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sterane biomarkers as indicators of palaeozoic algal evolution and extinction events
Palaeogeography Palaeoclimatology Palaeoecology, 2006Co-Authors: Lorenz Schwark, Petra EmptAbstract:Abstract Algae are among the oldest organisms known to inhabit the Earth's biosphere with a record dating back some 2.7 Ga. Only few marine algae produce hard parts that can be preserved over geologic time and consequently their fossil record is incomplete. Molecular fossils or biomarkers add complementary information to the fossil palynomorph record. Steroids are important constituents of eukaryotic cell-membranes and are preserved in sediments as steranes. C28- and C29-steranes are indicators for the presence of green and C27-steranes for the presence of red algae, respectively. The relative abundance of steranes allows the investigation of the fossil record for Palaeozoic algal diversification and evolution. In this study, 500 Palaeozoic rock samples, representing a broad facies variety from the Upper Ordovician to the P/T-boundary were investigated for sterane compositions. In addition three profiles covering the Hirnantian, the F/F and the Hangenberg-Event were analyzed for possible shifts in the sterane distribution associated with extinction events. A sharp increase of the C28/C29-sterane ratio from 0.70 at the Devonian/Carboniferous boundary implies a fundamental change in the green algae assemblage from more primitive, mainly C29-sterane-producing algae, to modern C28-sterane-producing algae. For all investigated extinction events a pronounced but short-lived rise in the C28-sterane content occurs that is attributed to an episodic increase in prasinophytes. The gradual radiation of algae may have been triggered by frequent mass extinctions in the Upper Devonian culminating with the massive decline of acritarchs at the D/C-boundary. The coeval rise in the C28/C29-sterane ratio indicates the presence of an non-encysting algal group and coincides with the global augmentation of numerous filamentous Codiacea (Siphonales) and the rise of euspondyle and metaspondyle Dasycladales.
Tsuneyoshi Kuroiwa - One of the best experts on this subject based on the ideXlab platform.
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Isolation of organellar DNA from Codium fragile (Codiaceae, Codiales, Ulvophyceae)
Phycological Research, 1997Co-Authors: Masaya Satoh, Atsushi Sakai, Shizue Hamazaki, Yuki Takashima, Tsuneyoshi KuroiwaAbstract:SUMMARY Organellar DNA was isolated from Codium fragile (Suringar) Hariot (Codiaceae, Codiales, Ulvophyceae) by CsCI-buoyant density centrifugation in the presence of Hoechst dye 33258. Three bands were formed by ultracentrifugation and each fraction of DNA was identified by Southern hybridization. The uppermost fraction was identified as chloroplast DNA, the middle fraction was nuclear DNA and the bottom fraction was mitochondrial DNA. Nuclear rDNA was isolated in the same fraction as mitochondrial DNA. The estimated genome size of mitochondrial DNA by analysis with restriction endonucleases was more than 141.6 kb, which was larger than that of microalgae but smaller than land plants. Restriction endonuclease analysis of the chloroplast DNA showed no difference with that known of C. fragile in New York.