Geochemical Evidence of the Seasonality, Affinity and Pigmenation of Solenopora jurassica.
Geochemical Evidence of the Seasonality, Affinity and Pigmenation of Solenopora jurassica.
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DOI：
10.1371/journal.pone.0138305
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
van Dongen BE
中科院分区：
文献类型：
--
作者：
Barden HE;Behnsen J;Bergmann U;Leng MJ;Manning PL;Withers PJ;Wogelius RA;van Dongen BE
Solenopora Jurassica是一种钙质藻类化石，在古生代是一种重要的造礁生物。由于其独特但鲜为人知的粉色和白色条带，它具有重大的古生物学意义。尽管被广泛认为是一种藻类，但关于它的分类相似性仍然存在争议，最近的研究认为，它应该被重新归类为海绵毛虫。这种条带被认为是季节性的，但没有确凿的证据证明这一点。然而，最近的其他研究表明，在S.Jurassica的粉红色条带中存在一种独特的有机含硼粉红色/红色颜料。我们提出了有关沙门氏菌季节性和色素沉着的新的地球化学证据。X射线照相显示了方解石密度的差异，并通过改变条带的δ13C组成证明了季节性的生长周期。由于Mg/Ca摩尔比和δ18O数据产生的相互冲突的模式，很难准确地限制带内的温度变化。波动的氯水平表明白色带中的盐度增加，与同位素数据相结合，这表明白色带形成期间的海洋条件更多，粉色带降水(δ18O)期间的淡水成分更大(氯度较低)。根据δ13C，与白色带相比，粉色带内的光合作用增强。裂解气相色谱-质谱分析(Py-GCMS)和傅立叶变换红外光谱(FTIR)分析表明，样品中含有四甲基吡咯、蛋白质部分和羧酸基，暗示红藻色素藻红蛋白的存在。这与S.Jurassica的粉红色是一致的。由于藻红蛋白只存在于藻类和蓝藻中，没有检测到细菌或海绵的生物标志物证据，因此我们得出结论：海藻很可能是一种藻类。色素分析是一种可靠的藻类化石分类方法。
Solenopora jurassica is a fossil calcareous alga that functioned as an important reef-building organism during the Palaeozoic. It is of significant palaeobiological interest due to its distinctive but poorly understood pink and white banding. Though widely accepted as an alga there is still debate over its taxonomic affinity, with recent work arguing that it should be reclassified as a chaetetid sponge. The banding is thought to be seasonal, but there is no conclusive evidence for this. Other recent work has, however demonstrated the presence of a unique organic boron-containing pink/red pigment in the pink bands of S. jurassica. We present new geochemical evidence concerning the seasonality and pigmentation of S. jurassica. Seasonal growth cycles are demonstrated by X-ray radiography, which shows differences in calcite density, and by varying δ13C composition of the bands. Temperature variation in the bands is difficult to constrain accurately due to conflicting patterns arising from Mg/Ca molar ratios and δ18O data. Fluctuating chlorine levels indicate increased salinity in the white bands, when combined with the isotope data this suggests more suggestive of marine conditions during formation of the white band and a greater freshwater component (lower chlorinity) during pink band precipitation (δ18O). Increased photosynthesis is inferred within the pink bands in comparison to the white, based on δ13C. Pyrolysis Gas Chromatography Mass Spectrometry (Py-GCMS) and Fourier Transform Infrared Spectroscopy (FTIR) show the presence of tetramethyl pyrrole, protein moieties and carboxylic acid groups, suggestive of the presence of the red algal pigment phycoerythrin. This is consistent with the pink colour of S. jurassica. As phycoerythrin is only known to occur in algae and cyanobacteria, and no biomarker evidence of bacteria or sponges was detected we conclude S. jurassica is most likely an alga. Pigment analysis may be a reliable classification method for fossil algae.