Rate and amplitudes of climate change

: are there tipping points in marine ecosystems

Abstract

Climate change results in warming, acidification, and deoxygenation, changing the physical and chemical properties of the ocean. While the response to these environmental changes is fundamental for our assessment of potential impacts on marine ecosystems, impacts are usually assessed in the laboratory which are too short to assess potentials for acclimation and adaptation.
The Paleocene–Eocene Thermal Maximum (PETM) is an often-investigated geological analogue to study the response of marine organisms to climate perturbation. I contrasted the PETM with the smaller environmental change during the Eocene Thermal Maximum 2 (ETM2). The comparison of these two intervals was chosen to assess the importance of the amplitude of the climate change for the ecological impact. I contrast benthic and planktic foraminifers and hence deep sea and surface ocean ecosystem responses focussing on size, calcification, and eco-groups defined by depth habitat and symbiosis.
In Chapter 2, I analyse two species of benthic foraminifera using CT scanning to investigate their morphological and calcification responses. The results highlight negative impacts on calcification in the two studied benthic foraminifera species during the PETM with a reduction in calcification at high latitudes but a lack of response at a sSite below the subtropical gyre. In chapter 3, I quantify potential impacts on test sizes and and calcification reconstructed via size normalized weights in the tropics, mid and high latitudes. The calcification data is compromised by infilling. The size data shows unexpected resilience, with minor short-lived increases associated with the appearance of excursion taxa and migration of thermophilic genus in polar/subpolar regions. In Chapter 4, at the same locations I quantify the impact on planktic ecological groups. Mixed layer clades dominate the assemblage regionally and temporally with high resilience to environmental perturbations.

Date of Award	22 Mar 2022
Original language	English
Awarding Institution	University of Bristol
Sponsors	Petroleum Technology Development Fund (PTDF) Nigeria
Supervisor	Laura Cotton (Supervisor) & Daniela N Schmidt (Supervisor)