Understanding the changes in the ecological functioning of foraminifera during the Palaeocene-Eocene thermal maximum using biological trait analysis

Nwojiji, CN ORCID: 0000-0002-7561-5961
(2018) Understanding the changes in the ecological functioning of foraminifera during the Palaeocene-Eocene thermal maximum using biological trait analysis. Doctor of Philosophy thesis, University of Liverpool.

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Understanding the changes in the ecological functioning of foraminifera during the Palaeocene-Eocene Thermal Maximum using Biological Trait Analysis Biological Trait Analysis (BTA) has been used to examine the changes in foraminiferal taxa and traits composition during the Palaeocene -Eocene Thermal Maximum (PETM), 56 million years ago. BTA is a multivariate ordination method used in describing the biological characteristics/behaviour of species and how they are related to the functioning of their ecosystem. It uses a series of life history, morphological and behavioural characteristics of species present in assemblages to indicate their role in ecological functioning (defined as the maintenance and regulation of ecosystem processes). This study investigated benthic and planktonic foraminifera taxa and trait composition from the Pacific Ocean (ODP Sites 1209, 1212B, 1215A), Atlantic Ocean (ODP Site1265A) and Alamedilla section in Southern, Spain. Thirteen (13) foraminiferal traits and over 60 trait categories were perceived to be crucial for the foraminiferal ecological functioning in the marine environment. However, BTA recognised test composition, chamber arrangement/ shape, ornamentation, primary aperture position, perforations and living/feeding habit as the most important foraminiferal trait in the benthic ecosystem. Also, bi/tri-serial, planispiral and trochospiral test; spherical/oval and triangular/trapezoid chamber shapes; depressed/ raised sutures or taxa with no ornament were highlighted as the most resilient traits during the period of ecological disturbance. The results from this study demonstrated for the first time that BTA could detect changes/disturbance in microfossil (foraminifera) ecology. The technique produced a more integrated and quantitative picture of palaeoecological changes across a wide range of locations when compared to the conventional faunal assemblage approach. The mapping of foraminiferal traits to ecological functions indicated that test composition is related to carbon sequestration and ocean acidification. Test shape and chamber arrangement are linked to productivity, ecological disturbance and oxygen concentration. Ornamentation is also related to ecological disturbance and ocean acidification. Perforation, aperture position and accessories in foraminifera are associated with nutrient/food utilisation, productivity and oxygen concentration. In addition, the living habit can provide a clue to ocean acidification, productivity, oxygen concentration, competition, nutrient/food utilisation in the marine ecosystem. Our data showed that foraminiferal taxonomic composition experienced extreme biotic turnover that resulted in extensive mortalities and extinction of both planktonic and benthic fauna during the PETM. The faunal assemblage is predominantly made of cosmopolitan taxa indicating ecological disturbance during the PETM. The taxa composition and non-metric multi-dimensional scaling (nmMDS) suggested that the foraminiferal communities in the Atlantic Ocean experienced ecological perturbation before and during the CIE but stabilised during the recovery period. Evidence of disturbance in bottom waters before the CIE supports the theory that the source of the light carbon that caused the PETM may have originated in the Atlantic Ocean causing benthic ecological disturbance and progressively reaching the surface of the ocean. In the Pacific and Tethys Oceans, ecological disturbance was only recorded at the CIE interval. The scanning electron microscope (SEM) image of some recovered foraminifera revealed evidence of dissolution/etching, extreme recrystallization/neomorphism and secondary calcite cementation on the test. The amount of coccoliths incorporated in the test of some deep infauna species requires further investigation to understand if some foraminiferal taxa construct their test in the dual process of secreting hyaline calcite and incorporation of coccolith plates by agglutinated processes in the later stage of their life history.

Item Type: Thesis (Doctor of Philosophy)
Divisions: Faculty of Science and Engineering > School of Environmental Sciences
Depositing User: Symplectic Admin
Date Deposited: 21 Aug 2019 11:36
Last Modified: 19 Jan 2023 01:02
DOI: 10.17638/03033183
URI: https://livrepository.liverpool.ac.uk/id/eprint/3033183