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An experimental study on post-mortem dissolution and overgrowth processes affecting coccolith assemblages: A rapid and complex process
- 1.0562161 - GLÚ 2024 RIV GB eng J - Journal Article
Holcová, K. - Scheiner, Filip
An experimental study on post-mortem dissolution and overgrowth processes affecting coccolith assemblages: A rapid and complex process.
Geobiology. Roč. 21, č. 2 (2023), s. 193-209. ISSN 1472-4677. E-ISSN 1472-4669
R&D Projects: GA ČR(CZ) GA20-05872S
Institutional support: RVO:67985831
Keywords : coccolith abundance * coccolith corrosion * coccolith overgrowths * dissolution-resistant taxa * pH fluctuations
OECD category: Paleontology
Impact factor: 2.7, year: 2023
Method of publishing: Limited access
https://onlinelibrary.wiley.com/doi/full/10.1111/gbi.12528
Coccolith dissolution together with post-mortem morphological features are immensely important phenomena that can affect assemblage compositions, complicate taxonomic identification as well as provide valuable palaeoenvironmental insights. This study summarizes the effects of pH oscillations on post-mortem coccolith morphologies and the abundances and compositions of calcareous nannoplankton assemblages in three distinct types of material—(i) Cretaceous chalk, (ii) Miocene marls, and (iii) late Holocene calcareous ooze. Two independent experimental runs within a semi-enclosed system setting were realized to observe assemblage alterations. One experiment was realized with the presence of bacteria and, in contrast, the second one inhibited their potential effect on the studied system. The pH was gradually decreased within the range of 8.3–6.4 using a reaction of CO2 with H2O forming weak carbonic acid (H2CO3), thereby affecting [CO2−3]. Further, a subsequent overgrowth study was carried out during spontaneous degassing accompanied by a gradual pH rise. The experiment revealed that the process and intensity of coccolith corrosion and subsequent overgrowth build-ups are influenced by a plethora of different factors such as (i) pH and associated seawater chemistry, (ii) mineral composition of the sediment, (iii) the presence of coccoliths within a protective substrate (faecal pellets, pores, pits), and (iv) the presence/absence of bacteria. Nannoplankton assemblages with corroded coccoliths or with coccoliths with overgrowth build-ups showed that the observed relative abundances of taxa experienced alteration from the original compositions. Additionally, extreme pH oscillations may result in enhanced morphological changes that make coccoliths unidentifiable structures, and might even evoke the absence of coccoliths in the fossil record.
Permanent Link: https://hdl.handle.net/11104/0341402
Number of the records: 1