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Title: Quantification of the effects of ocean acidification on benthic foraminifera
Author: Guamán Guevara, Luis Fabricio
ISNI:       0000 0004 7963 198X
Awarding Body: University of St Andrews
Current Institution: University of St Andrews
Date of Award: 2019
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The global ocean has experienced an alteration of its seawater chemistry due to the continuing uptake of anthropogenic carbon dioxide (CO₂) from the atmosphere. This ongoing process called Ocean acidification (OA) has reduced seawater pH levels, carbonate ion concentrations (CO₃⁻℗ø) and carbonate saturation state (Î♭) with implications for the diversity and functioning of marine life, particularly for marine calcifiers such as foraminifera. The vulnerability of this ubiquitous calcifying group to future high ̧˜łCO₂ /low pH scenarios has been assessed naturally and experimentally in the last decades. However, little is known about how benthic foraminifera from coastal environments such as intertidal environments will respond to the effects of OA projected by the end of the century. This research aimed to quantify the effects of OA on a series of biological parameters measured on the benthic foraminifera ̧˜Œ̧˜Ư̧˜ł̧˜♭̧˜®̧˜Æ̧˜®̧˜œ̧˜ʼ ̧˜ı̧˜®̧˜Ư̧˜Ư̧˜®̧˜Ø̧˜ʼ̧˜þ̧˜ʻ̧˜¯̧˜® and ̧˜̧˜Ø̧˜ð̧˜¯̧˜Œ̧˜þ̧˜®̧˜¯̧˜Ø ̧˜·̧˜Œ̧˜đ̧˜ʼ̧˜Ø̧˜¯̧˜®̧˜Þ̧˜Ø through a laboratory-based experimental approach where future scenarios of a high CO₂ atmosphere and low seawater pH were explored. Experimental evidence revealed that survival rates, test weight and size-normalized weight (SNW) of ̧˜Œ. ̧˜ı̧˜®̧˜Ư̧˜Ư̧˜®̧˜Ø̧˜ʼ̧˜þ̧˜ʻ̧˜¯̧˜® were negatively affected by OA. Whereas ̧˜. ̧˜·̧˜Œ̧˜đ̧˜ʼ̧˜Ø̧˜¯̧˜®̧˜Þ̧˜Ø was positively affected (i.e. enhanced growth rates) showing a species-specific response to OA at 13℗ʻC. However, the combined effect of OA and temperature (15℗ʻC) reduced survival and growth rates for ̧˜Œ̧˜Ư̧˜ł̧˜♭̧˜®̧˜Æ̧˜®̧˜œ̧˜ʼ ̧˜ı̧˜®̧˜Ư̧˜Ư̧˜®̧˜Ø̧˜ʼ̧˜þ̧˜ʻ̧˜¯̧˜® and ̧˜̧˜Ø̧˜ð̧˜¯̧˜Œ̧˜þ̧˜®̧˜¯̧˜Ø ̧˜·̧˜Œ̧˜đ̧˜ʼ̧˜Ø̧˜¯̧˜®̧˜Þ̧˜Ø. Test morphology (i.e. test surface and feeding ornamentation) of live ̧˜Œ. ̧˜ı̧˜®̧˜Ư̧˜Ư̧˜®̧˜Ø̧˜ʼ̧˜þ̧˜ʻ̧˜¯̧˜® and ̧˜. ̧˜·̧˜Œ̧˜đ̧˜ʼ̧˜Ø̧˜¯̧˜®̧˜Þ̧˜Ø were severely affected after 6 weeks by OA, negatively influencing the uptake of 13C-labelled diatoms of ̧˜•̧˜Ø̧˜ʺ̧˜®̧˜Þ̧˜œ̧˜Ư̧˜Ø ̧˜þ̧˜ł., notably for ̧˜Œ. ̧˜ı̧˜®̧˜Ư̧˜Ư̧˜®̧˜Ø̧˜ʼ̧˜þ̧˜ʻ̧˜¯̧˜®. Test dissolution rates were enhanced by OA and negatively affected foraminiferal morphology of recently dead assemblages with implications for net accumulation and preservation. These results imply that the long-term storage of inorganic carbon and cycling of carbon in coastal benthic ecosystems will be considerably altered by future OA.
Supervisor: Austin, William E. N. ; Streeter, Richard Thomas Sponsor: Ecuador. Secretaría de Educación Superior, Ciencia, Tecnología e Innovación ; "This work was supported by the National Institution of Higher Education, Science, Technology and Innovation of Ecuador (SENESCYT)." -- Acknowledgements
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Ocean acidification ; pH ; Benthic foraminifera ; Calcium carbonate ; Survival rates ; Growth ; Calcification ; CO2 ; Mesocosm ; Morphology ; Dissolution ; Carbon cycling ; CaCO3 production ; Coastal waters ; Vulnerability ; Benthic habitats ; Mid-latitude marine environments ; Climate change