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Acid-base regulation in the sea urchin Parechinus angulosus during CO₂-induced seawater acidification
Ocean acidification is predicted to have adverse effects on the physiologies of marine organisms, particularly those that produce calcified structures. Extracellular homeostasis is considered to be critical to mediating the effects of ocean acidification. Due to their low metabolic rates and weak ab...
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2014
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| _version_ | 1867613337195380736 |
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| access_status_str | Open Access |
| author | Dyer, Alexei |
| author2 | Lucas, Mike |
| author_browse | Dyer, Alexei Lucas, Mike |
| author_facet | Lucas, Mike Dyer, Alexei |
| author_sort | Dyer, Alexei |
| collection | Thesis |
| description | Ocean acidification is predicted to have adverse effects on the physiologies of marine organisms, particularly those that produce calcified structures. Extracellular homeostasis is considered to be critical to mediating the effects of ocean acidification. Due to their low metabolic rates and weak ability to regulate ion exchange, sea urchins are thought to be particularly weak acid-base regulators. Recent findings showing species-specific capacities for extracellular pH regulation however suggest that species currently exposed to natural CO₂ elevations, such as upwelling events, may have a higher capacity tolerate elevated CO₂. The sea urchin Parechinus angulosus currently experiences natural CO₂ variations within the Benguela upwelling system and is therefore predicted to possess the capacity to compensate moderate acid-base disturbances. Urchins were submitted to control (8.0), intermediate (7.7) and low (7.4) seawater pH treatments for 14 days to investigate the capacity to regulate extracellular acid-base status. Extracellular pH changes induced by exposure to intermediate (pH 7.7) seawater acidification were fully compensated through the accumulation of approximately 2.0 mmol l-1 of bicarbonate. The bicarbonate accumulation was only sufficient to partially compensate extracellular acid-base status during exposure to low (7.4) seawater pH. Results from acute (24 hour) exposure to low (7.4) seawater pH reveal that bicarbonate accumulation, despite being evident within 24 hours, is not sufficient to compensate extracellular pH. This study provides further support that sea urchins exposed to natural CO₂ variability possess a limited capacity to regulate extracellular acid-base disturbances. P.angulosus may therefore already be adapted to deal with a moderate reduction in seawater pH to 7.7, but lacks the iono-regulatory capacity to accumulate sufficient bicarbonate to deal with a reduction of seawater pH to 7.3. Long-term studies are needed to assess the role of acid-base regulation as a mediator of broader physiological tolerance to ocean acidification, and its consequences at the level of the whole organism. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/7631 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:34:32.198Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/7631 Acid-base regulation in the sea urchin Parechinus angulosus during CO₂-induced seawater acidification Dyer, Alexei Lucas, Mike Ocean acidification is predicted to have adverse effects on the physiologies of marine organisms, particularly those that produce calcified structures. Extracellular homeostasis is considered to be critical to mediating the effects of ocean acidification. Due to their low metabolic rates and weak ability to regulate ion exchange, sea urchins are thought to be particularly weak acid-base regulators. Recent findings showing species-specific capacities for extracellular pH regulation however suggest that species currently exposed to natural CO₂ elevations, such as upwelling events, may have a higher capacity tolerate elevated CO₂. The sea urchin Parechinus angulosus currently experiences natural CO₂ variations within the Benguela upwelling system and is therefore predicted to possess the capacity to compensate moderate acid-base disturbances. Urchins were submitted to control (8.0), intermediate (7.7) and low (7.4) seawater pH treatments for 14 days to investigate the capacity to regulate extracellular acid-base status. Extracellular pH changes induced by exposure to intermediate (pH 7.7) seawater acidification were fully compensated through the accumulation of approximately 2.0 mmol l-1 of bicarbonate. The bicarbonate accumulation was only sufficient to partially compensate extracellular acid-base status during exposure to low (7.4) seawater pH. Results from acute (24 hour) exposure to low (7.4) seawater pH reveal that bicarbonate accumulation, despite being evident within 24 hours, is not sufficient to compensate extracellular pH. This study provides further support that sea urchins exposed to natural CO₂ variability possess a limited capacity to regulate extracellular acid-base disturbances. P.angulosus may therefore already be adapted to deal with a moderate reduction in seawater pH to 7.7, but lacks the iono-regulatory capacity to accumulate sufficient bicarbonate to deal with a reduction of seawater pH to 7.3. Long-term studies are needed to assess the role of acid-base regulation as a mediator of broader physiological tolerance to ocean acidification, and its consequences at the level of the whole organism. 2014-09-22T12:00:16Z 2014-09-22T12:00:16Z 2013 Bachelor Thesis Honours BSc http://hdl.handle.net/11427/7631 eng application/pdf Department of Biological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Dyer, Alexei Acid-base regulation in the sea urchin Parechinus angulosus during CO₂-induced seawater acidification |
| thesis_degree_str | Bachelor's / Honours |
| title | Acid-base regulation in the sea urchin Parechinus angulosus during CO₂-induced seawater acidification |
| title_full | Acid-base regulation in the sea urchin Parechinus angulosus during CO₂-induced seawater acidification |
| title_fullStr | Acid-base regulation in the sea urchin Parechinus angulosus during CO₂-induced seawater acidification |
| title_full_unstemmed | Acid-base regulation in the sea urchin Parechinus angulosus during CO₂-induced seawater acidification |
| title_short | Acid-base regulation in the sea urchin Parechinus angulosus during CO₂-induced seawater acidification |
| title_sort | acid base regulation in the sea urchin parechinus angulosus during co₂ induced seawater acidification |
| url | http://hdl.handle.net/11427/7631 |
| work_keys_str_mv | AT dyeralexei acidbaseregulationintheseaurchinparechinusangulosusduringco2inducedseawateracidification |