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Seagrass Respiration: An assessment of oxygen consumption patterns of temperate marine macrophytes
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.ORCID iD: 0000-0003-4297-0956
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In coastal seas, the abundance of marine macrophytes has profound influence on the flows of oxygen and inorganic carbon through the water. Vast amounts of carbon dioxide are taken up by photosynthesis and part of this is respired back into the water column. The photosynthetic carbon uptake of the most common seagrasses of the northern hemisphere is nowadays extensively studied at both community- and individual levels, and its impact on coastal carbon- and oxygen fluxes is quite well defined. However, the coinciding release of carbon dioxide and consumption of oxygen by the processes of mitochondrial respiration and photorespiration in these organisms has as yet not been given much attention, especially concerning how these processes are affected by external factors. For estimations of the rates of mitochondrial respiration, the common approach has been to use values obtained during darkness and treat them as being constant over the day. This approach is questioned in this thesis where the effects of different abiotic and biotic factors on oxygen consumption were examined to elucidate possible variations of seagrass respiration rates (with primary focus on the species Zostera marina), explored mainly using gas exchange techniques. The initial aim was to investigate whether the rates of respiration are at all fluctuating. This was found to be the case. Secondly, impacts of various factors on the respiration process were examined on Z. marina, with additional studies on the seagrass Ruppia maritima and the common green alga Ulva intestinalis. It was found that respiration rates were lower in the light for all three species. Specific investigations on Z. marina showed that respiration rates also varied with time of the day. Moreover, the rates of both respiration and photosynthesis differed between Z. marina shoots of different age as well as among different parts of the leaves. These differences were observed at both ambient (19.1oC) and elevated (29.1oC) temperatures. Photorespiration, previously considered insignificant in seagrasses, was found to have a profound role, as high rates were observed in productive bays, i.e. in settings with low inorganic carbon availability and high oxygen. Overall, this thesis has identified important external and developmental factors influencing the patterns of oxygen consumption and associated carbon dioxide release of two common temperate seagrasses. Clearly, respiration in seagrasses is a dynamic process that responds to a variety of external and developmental factors, which should be carefully considered when assessing the carbon budget of coastal vegetated areas.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University , 2015. , 54 p.
Keyword [en]
Mitochondrial respiration, Photorespiration, Seagrass productivity, Zostera marina, Marine carbon budgets, Ruppia maritima, Ulva intestinalis
National Category
Other Biological Topics
Research subject
Plant Physiology
Identifiers
URN: urn:nbn:se:su:diva-120156ISBN: 978-91-7649-230-7 (print)OAI: oai:DiVA.org:su-120156DiVA: diva2:850869
Public defence
2015-10-09, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript.

Available from: 2015-09-17 Created: 2015-09-02 Last updated: 2015-09-16Bibliographically approved
List of papers
1. Determining light suppression of mitochondrial respiration for three temperate marine macrophytes using the Kok method
Open this publication in new window or tab >>Determining light suppression of mitochondrial respiration for three temperate marine macrophytes using the Kok method
2014 (English)In: Botanica Marina, ISSN 0006-8055, E-ISSN 1437-4323, Vol. 57, no 6, 483-486 p.Article in journal (Refereed) Published
Abstract [en]

To properly calculate the carbon budgets of coastal marine habitats, potential fluctuations in oxygen consumption due to mitochondrial respiration must be taken into account. As mitochondrial respiration is sometimes inhibited in light, we used the Kok method to estimate whether such suppression occurs in the seagrasses Zostera marina and Ruppia maritima as well as in the macroalga Ulva intestinalis. For Z. marina and U. intestinalis, the respiration rate was clearly downregulated in light, a finding that might be important when determining the impact of respiration on estimated net primary productivity in these marine habitats.

Keyword
coastal primary production, Kok effect, mitochondrial respiration in light
National Category
Biological Sciences
Research subject
Plant Physiology
Identifiers
urn:nbn:se:su:diva-111404 (URN)10.1515/bot-2014-0046 (DOI)000345632100008 ()
Note

AuthorCount:2;

Available from: 2015-01-05 Created: 2015-01-02 Last updated: 2017-12-05Bibliographically approved
2. Respiratory oxygen consumption in the seagrass Zostera marina is affected by light and varies on a diel basis: a combined gas exchange and gene expression study
Open this publication in new window or tab >>Respiratory oxygen consumption in the seagrass Zostera marina is affected by light and varies on a diel basis: a combined gas exchange and gene expression study
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Other Biological Topics
Research subject
Plant Physiology
Identifiers
urn:nbn:se:su:diva-120159 (URN)
Available from: 2015-09-02 Created: 2015-09-02 Last updated: 2016-01-29Bibliographically approved
3. Effects of increased temperature on respiration and photosynthesis differ among different leaf parts and with tissue age of the seagrass Zostera marina
Open this publication in new window or tab >>Effects of increased temperature on respiration and photosynthesis differ among different leaf parts and with tissue age of the seagrass Zostera marina
(English)Manuscript (preprint) (Other academic)
National Category
Other Biological Topics
Research subject
Plant Physiology
Identifiers
urn:nbn:se:su:diva-120158 (URN)
Available from: 2015-09-02 Created: 2015-09-02 Last updated: 2016-01-29Bibliographically approved
4. Photorespiration and carbon limitation determine productivity in temperate seagrasses
Open this publication in new window or tab >>Photorespiration and carbon limitation determine productivity in temperate seagrasses
2013 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 12, e83804Article in journal (Refereed) Published
Abstract [en]

The gross primary productivity of two seagrasses, Zostera marina and Ruppia maritima, and one green macroalga, Ulva intestinalis, was assessed in laboratory and field experiments to determine whether the photorespiratory pathway operates at a substantial level in these macrophytes and to what extent it is enhanced by naturally occurring shifts in dissolved inorganic carbon (DIC) and O2 in dense vegetation. To achieve these conditions in laboratory experiments, seawater was incubated with U. intestinalis in light to obtain a range of higher pH and O2 levels and lower DIC levels. Gross photosynthetic O2 evolution was then measured in this pretreated seawater (pH, 7.8–9.8; high to low DIC:O2 ratio) at both natural and low O2concentrations (adjusted by N2 bubbling). The presence of photorespiration was indicated by a lower gross O2 evolution rate under natural O2 conditions than when O2 was reduced. In all three macrophytes, gross photosynthetic rates were negatively affected by higher pH and lower DIC. However, while both seagrasses exhibited significant photorespiratory activity at increasing pH values, the macroalga U. intestinalis exhibited no such activity. Rates of seagrass photosynthesis were then assessed in seawater collected from the natural habitats (i.e., shallow bays characterized by high macrophyte cover and by low DIC and high pH during daytime) and compared with open baymouth water conditions (where seawater DIC is in equilibrium with air, normal DIC, and pH). The gross photosynthetic rates of both seagrasses were significantly higher when incubated in the baymouth water, indicating that these grasses can be significantly carbon limited in shallow bays. Photorespiration was also detected in both seagrasses under shallow bay water conditions. Our findings indicate that natural carbon limitations caused by high community photosynthesis can enhance photorespiration and cause a significant decline in seagrass primary production in shallow waters.

National Category
Botany
Research subject
Plant Physiology
Identifiers
urn:nbn:se:su:diva-100015 (URN)10.1371/journal.pone.0083804 (DOI)000328745100145 ()
Available from: 2014-01-23 Created: 2014-01-23 Last updated: 2017-12-06Bibliographically approved

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