Potential Impacts of Climate Change on Photochemistry of <i>Zostera Marina</i> L.

<p>Seagrasses account for approximately 10% of the ocean’s total carbon storage, although photosynthesis of seagrasses is carbon limited at today’s oceanic pH. Therefore, increasing atmospheric CO₂ concentration, which results in ocean acidification/carbonation, is predicted to have a positive impact on seagrass productivity. Previous studies have confirmed the positive influence of increasing CO₂ on photosynthesis and survival of the temperate eelgrass <em>Zostera marina L</em>., but the acclimation of photoprotective mechanisms in this context has not been characterized. This study aimed to quantify the long-term impacts of ocean acidification on photochemical control mechanisms that promote photosynthesis while simultaneously protecting eelgrass from photodamage. Eelgrass were grown in controlled outdoor aquarium tanks at different aqueous CO₂ concentrations ranging from ~50 to ~2100 μM from May 2013 to October 2014, and compared for differences in optical properties and photochemistry. Even with daily and seasonal variations of temperature and light, CO₂ enrichment consistently increased plant size, leaf thickness and chlorophyll use efficiency, and decreased pigment content and the package effect while maintaining similar light harvesting efficiency. These CO₂ responses resembled high light acclimation suggesting a common photosynthetic sensory function, such as redox regulation, controls long-term acclimation of leaf morphology. Laboratory incubations resolved this mutual regulation of redox state via carbon and light availability, by measuring O₂ production, total CO₂ uptake and fluorescence of the acclimated leaves. The morphological acclimations due to CO₂ enrichment were facilitated by improved photosynthetic capacity. Increasing CO₂ availability, relative to oxygen concentrations, maximized chlorophyll specific photosynthesis to its physiological limits at pH 6.2 by minimizing photorespiration, and increased the light requirement to saturate photosynthesis. The instantaneous increase of photosynthesis up to 8 fold reduced the role of alternative electron pathways and non-photochemical quenching for photoprotection, therefore increasing quantum yield of oxygen production. These findings explained how seagrasses resist photodamage in shallow high light environments, while maintaining long daily period of light-saturated photosynthesis to compensate carbon limitation and sustain growth. The quasi-mechanistic models generated by this study provide a pathway for including the photoprotection and photoacclimation processes in understanding the dynamic response of seagrasses to fluctuating coastal environments and climate change.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Ocean & Earth Sciences

Year dc:date.available

2016

Author dc:creator

• Celebi, Billur

Contributors dc:contributor

• Richard C. Zimmerman
• Victoria J. Hill
• Alexander Bochdansky
• Mark J. Butler IV

• Ocean acidification
• Photo-protection
• Photorespiration
• Photosynthesis
• Seagrass
• Zostera marina
• Climate
• Oceanography
• Plant Sciences

Statement dc:rights

• <p>In Copyright. URI: <a href="http://rightsstatements.org/vocab/InC/1.0/">http://rightsstatements.org/vocab/InC/1.0/</a> This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).</p>

Identifier

9781369536973

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:oeas_etds-1003