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Photosynthetic activity of seagrasses and macroalgae in temperate shallow waters can alter seawater pH and total inorganic carbon content at the scale of a coastal embayment
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Prince Songkla University, Thailand.
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
2013 (English)In: Marine and Freshwater Research, ISSN 1323-1650, E-ISSN 1448-6059, Vol. 64, no 11, 1040-1048 p.Article in journal (Refereed) Published
Abstract [en]

Many studies have reported fluctuations in pH and the concentration of dissolved inorganic carbon (DIC) in shallow coastal waters as a result of photosynthetic activity; however, little is known about how these fluctuations vary with degree of exposure among habitats, and at different scales. In the present study, diel variation in seawater pH was apparent in aquaria experiments with Zostera marina and Ruppia maritima. These pH variations were affected by light regime, biomass level and plant species. Subsequently, the natural variability in seawater pH and the concentration of DIC was assessed in six shallow embayments (three sheltered and three exposed) during sunny days. From the outer part towards the interior part of each bay, the following four habitats were identified and studied: the bay-mouth open water, seagrass beds, mixed macrophyte belts and unvegetated bottoms. The two vegetated habitats and unvegetated bottoms were characterised by higher pH and a lower concentration of DIC than in the bay-mouth water. The mixed macrophytes habitat showed slightly higher pH and a lower concentration of DIC than the seagrass and unvegetated habitats. No significant effect of exposure was detected. Our findings clearly showed that the photosynthetic activity of marine macrophytes can alter the coastal pH and the concentration of DIC and that the effects can be observed at the scale of a whole bay.

Place, publisher, year, edition, pages
2013. Vol. 64, no 11, 1040-1048 p.
Keyword [en]
ocean acidification, temperate environment
National Category
Biological Sciences Oceanography, Hydrology, Water Resources
Identifiers
URN: urn:nbn:se:su:diva-96674DOI: 10.1071/MF12124ISI: 000326166400005OAI: oai:DiVA.org:su-96674DiVA: diva2:667294
Note

AuthorCount:3;

Available from: 2013-11-26 Created: 2013-11-25 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Beyond carbon-limitation: A re-evaluation of the ecological role of photorespiration and direct oxygen photoreduction in seagrasses
Open this publication in new window or tab >>Beyond carbon-limitation: A re-evaluation of the ecological role of photorespiration and direct oxygen photoreduction in seagrasses
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Seagrasses living in shallow coastal waters are regularly subjected to changes in environmental conditions including the two essential factors for photosynthesis: dissolved inorganic carbon (DIC) and irradiance. This thesis focuses on the photosynthetic responses of seagrasses to carbon limitation induced by community metabolism and/or high light intensities. Field sampling conducted in seagrass-dominated embayments along the Swedish west coast revealed that high pH and low levels of DIC caused by community photosynthesis are common in shallow coastal waters. These effects were found on a scale of a whole bay and were affected by the composition of the vegetation. Such carbon limitation and at the same time an increase in O2 concentration negatively affected photosynthesis of the seagrass species Zostera marina L. and Ruppia maritima L. by compromising carbon assimilation as well as enhancing photorespiration.  In contrast to the results from the two seagrasses, it was found that gross photosynthetic rates did not increase under low O2 concentrations in the green alga Ulva intestinalis L., suggesting that its efficient carbon acquisition mechanisms are able to suppress photorespiration. The role of photorespiration in seagrass photosynthesis was further investigated in Z. marina. It was found that under conditions of carbon limitation, photorespiration provides the major alternative sink for electrons, sustaining substantial electron transport via photosystem II while the Mehler reaction has a smaller contribution as an alternative electron sink. Photorespiration was however not a significant component of the photoprotective mechanisms in Z. marina under high irradiance. Here the down-regulation of electron transport via non-photochemical quenching appeared to be the more efficient mechanism for dissipating excess energy. Overall, this study highlights the role of O2 in seagrass photosynthesis which appears to be of greater importance than previously envisaged, particularly in the productive waters where carbon availability is occasionally limited. 

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University, 2014. 49 p.
Keyword
Carbon limitation, Chlorophyll fluorescence, Electron transport rate, Irradiance, Mehler reaction, Non-photochemical quenching, Photorespiration, Photosynthetic activity
National Category
Botany
Research subject
Plant Physiology
Identifiers
urn:nbn:se:su:diva-99434 (URN)978-91-7447-850-1 (ISBN)
Public defence
2014-02-21, Föreläsningssalen, Institutionen för Ekologi, Miljö och Botanik, Lilla Frescativägen 5, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2014-01-30 Created: 2014-01-13 Last updated: 2014-01-28Bibliographically approved

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