Title: Geochemical Evidence of the Seasonality, Affinity and Pigmenation of Solenopora jurassica

Abstract

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 inferredmore » 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.« less

Authors:

Barden, Holly E. ^[1]; Behnsen, Julia ^[1]; Bergmann, Uwe ^[2]; Leng, Melanie J. ^[3]; Manning, Phillip L. ^[1]; Withers, Philip J. ^[1]; Wogelius, Roy A. ^[1]; van Dongen, Bart E. ^[1]; Silva, Lucas C. R. ^[4]

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+ Show Author Affiliations

1. Univ. of Manchester (United Kingdom)
2. SLAC National Accelerator Lab., Menlo Park, CA (United States)
3. NERC Isotope Geosciences Facilities and Univ. of Nottingham, Nottingham (United Kingdom)
4. Univ. of California, Davis, CA (United States)

Publication Date:

Mon Sep 14 00:00:00 EDT 2015

Research Org.:

SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1224051

Grant/Contract Number:  

AC02-07CH11359

Resource Type:

Accepted Manuscript

Journal Name:

PLoS ONE

Additional Journal Information:

Journal Volume: 10; Journal Issue: 9; Journal ID: ISSN 1932-6203

Publisher:

Public Library of Science

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES