Abstract
Fossil remnants of benthic foraminifera consist of carbonate tests and their organic linings.
The macromolecular and stable isotopic composition of these benthic foraminiferal organic
linings was characterized to evaluate their potential use as paleoclimate proxies. Using Curie
point pyrolysis–GC–MS (Py–GC–MS) we show that benthic foraminiferal organic linings consist
of protein and polysaccharides, bound together in a complex macromolecular structure.
Both chitin derivatives and traces of guaiacols and syringols, usually assigned to lignin, are
found. Although the five species of benthic foraminifera all contain chitin derivatives and
proteins, the relative contribution of these compounds tends to vary considerably. Oxygen
stable isotopic analyses of the organic linings of the benthic foraminiferal species Ammonia
tepida indicates that δ18OOL values are in line with fractionation between seawater and organic
matter. In contrast a δ13C deliberate tracer experiment showed that metabolic carbon is the
main source for the carbon fixed in the organic lining. The different pathways of carbon and
oxygen stable isotopes into the foraminiferal linings have important implications for future
proxy development as they reflect different components of the environment compared to the
carbonate bound stable isotopes. Still, the future application of benthic foraminiferal organic
linings and their isotopic values critically relies on improvements in calibration and sample size
required for isotopic analyses.
The macromolecular and stable isotopic composition of these benthic foraminiferal organic
linings was characterized to evaluate their potential use as paleoclimate proxies. Using Curie
point pyrolysis–GC–MS (Py–GC–MS) we show that benthic foraminiferal organic linings consist
of protein and polysaccharides, bound together in a complex macromolecular structure.
Both chitin derivatives and traces of guaiacols and syringols, usually assigned to lignin, are
found. Although the five species of benthic foraminifera all contain chitin derivatives and
proteins, the relative contribution of these compounds tends to vary considerably. Oxygen
stable isotopic analyses of the organic linings of the benthic foraminiferal species Ammonia
tepida indicates that δ18OOL values are in line with fractionation between seawater and organic
matter. In contrast a δ13C deliberate tracer experiment showed that metabolic carbon is the
main source for the carbon fixed in the organic lining. The different pathways of carbon and
oxygen stable isotopes into the foraminiferal linings have important implications for future
proxy development as they reflect different components of the environment compared to the
carbonate bound stable isotopes. Still, the future application of benthic foraminiferal organic
linings and their isotopic values critically relies on improvements in calibration and sample size
required for isotopic analyses.
| Original language | English |
|---|---|
| Qualification | Doctor of Philosophy |
| Awarding Institution |
|
| Supervisors/Advisors |
|
| Award date | 25 Jan 2019 |
| Place of Publication | Utrecht |
| Publisher | |
| Print ISBNs | 978-90-6266-522-8 |
| Publication status | Published - 25 Jan 2019 |