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Title: The pelagic record of ocean acidification
Author: Williams, Maria C.
ISNI:       0000 0004 5920 4534
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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Ocean acidification (OA) as a result of anthropogenic CO2 accumulation has major implications for the calcification of marine organisms. Assessing the calcification response of coccolithophores and planktic foraminifera to OA in particular is paramount as together they produce the majority of pelagic carbonate burial and thus impact biogeochemical cycling and oceanic CO2 uptake. In this thesis, two sediment cores from Eirik Drift and the Norwegian Sea are used to reconstruct the natural calcification response of marine plankton since the Last Glacial Maximum and compare these changes to recent anthropogenic influences over the last 200 years. Reconstructions of the bottom water dynamics and thus sedimentation at Eirik Drift infers the suitability of the core for palaeo-analysis of plankton calcification. The calcification response of three foraminiferal species and two morphotypes of the dominant polar species Neogloboquadrina pachyderma are significantly correlated throughout the Holocene suggesting similar calcification mechanisms between and within species. Although the drivers of calcification appear to vary temporally and geographically, down-core planktic foraminiferal Mg/Ca and faunal assemblage counts point towards the importance of sea surface temperature and optimal growth conditions on the calcification of N pachyderma. Unlike Globigerina bulloides, N pachyderma shows little sensitivity to CO2 changes across the last deglaciation Since the beginning of industrialisation, foraminiferal calcification fluctuates within the natural long-term trends observed over the last 22 kyrs inferring minimal anthropogenic impacts on foraminiferal calcification. Interspecies-specific responses are evident, as the test weight of G. bulloides increases since the early 1900s in response to a warming North Altantic Current, whilst Neogloboquadrina incompta shows little change over the last 200 years. Furthermore, an increase in the degree of calcification of the abundant coccolithophore Emiliania huxleyi occurs in response to accelerated 20th century climate change pointing towards increased carbonate burial in the sub-polar North Atlantic under future global change.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available