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Differences in physiological response to increased seawater temperature in nearshore and offshore corals in northern Vietnam
Stockholm University, Faculty of Science, Department of Systems Ecology.
Stockholm University, Faculty of Science, Department of Systems Ecology.
Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre.
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2011 (English)In: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 71, no 3, 225-233 p.Article in journal (Refereed) Published
Abstract [en]

Effects of elevated seawater temperature show high spatial heterogeneity and variation within and among coral species. The objective of this study was to investigate how two coral species, Porites lutea and Galaxea fascicularis, from two high latitude reefs differently exposed to chronic disturbance, respond to elevated seawater temperatures. Corals were collected from reefs nearshore (i.e. subjected to high sediment load, higher chlorophyll α concentrations, turbidity etc.) and offshore (i.e. less exposed). The corals were exposed in the lab to gradually increasing temperatures (25.5–33.5 °C) for 72 h after which they were allowed to recover to ambient temperature (25.5 °C) for 24 h. Production and respiration were measured after 24, 48, 72 and 96 h. The results show that P. lutea from nearshore reefs suffered an initial decrease in gross primary production/respiration (GP/R) ratio after 24 h, after only a moderate temperature increase (+2 °C, from 25.5 to 27.5 °C), while there was no difference in GP/R ratio between heat-exposed and controls the other days, indicating that the chronic disturbance in the nearshore reef had no effect on their thermotolerance. Furthermore, P. lutea from the offshore reef showed a decrease in GP/R ratio both after 24 h and 72 h (33.5 °C) of exposure.

In comparison, G. fascicularis showed a decrease in GP/R ratio after 48 h, 72 h and 96 h of exposure for the nearshore corals. Also, after 72 h these corals had withdrawn their polyps. There were no differences between heat-treated and controls for the offshore G. fascicularis. This implies that the chronically disturbed G. fascicularis had lower thermotolerance when exposed to a temperature increase.

This study, hence, shows that the response of corals to elevated seawater temperature varies with species and environmental background history.

Place, publisher, year, edition, pages
2011. Vol. 71, no 3, 225-233 p.
Keyword [en]
Increased water temperature, Galaxea fascicularis, Porites lutea, Disturbance, Physiological responses, High latitude reefs, Vietnam
National Category
Natural Sciences
Research subject
Marine Ecotoxicology
Identifiers
URN: urn:nbn:se:su:diva-62845DOI: 10.1016/j.marenvres.2011.01.007ISI: 000288780400010OAI: oai:DiVA.org:su-62845DiVA: diva2:445212
Available from: 2011-10-03 Created: 2011-10-03 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Coral reefs in the Anthropocene: The effects of stress on coral metabolism and symbiont composition
Open this publication in new window or tab >>Coral reefs in the Anthropocene: The effects of stress on coral metabolism and symbiont composition
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Coral reefs constitute some of the most prolific and diverse ecosystems on our planet, but also among the most threatened.

This thesis investigates the effects of environmental stressors on corals’ metabolism and symbiont diversity. Paper I shows that the coral Turbinaria mesenterina withstood a single stressor while a combination of two stressors (decreased salinity and increased seawater temperature) lead to decreased metabolism. Increased seawater temperature in combination with two stressors (enhanced nutrients and decreased salinity) lead to rapid mortality of all specimens. Paper II shows that chronic stress in combination with increased seawater temperature affects coral species differently. Porites lutea did not show any difference in response to temperature increase, regardless of environmental disturbance history, while Galaxea fascicularis’ metabolism was negatively affected in chronically disturbed corals but not in corals from less disturbed areas. The main explanation for the difference in response between the two species is different compositions of endosymbionts as found in paper III. P. lutea only harboured the symbiont C15, regardless of environment, whilst D1a dominated the nearshore G. fascicularis and C1 dominated offshore corals. In paper IV there was a clear inshore-offshore pattern of D1a along the whole coast of Vietnam, where D1a dominated inshore. In contrast, the five symbionts belonging to group C displayed a strong latitudinal gradient, with diversity increasing from north to south. The coral host showed higher diversity offshore than inshore.

The thesis emphasizes the importance of improving water quality (paper I and II) and protecting marginal areas since tolerant coral hosts and symbionts can be found there (paper III and IV), as well as safeguarding areas with high symbiont diversity (paper IV) to increase the ability of corals to withstand future environmental changes.

Place, publisher, year, edition, pages
Stockholm: Department of Systems Ecology, Stockholm University, 2011. 53 p.
Keyword
Corals, Disturbance, Galaxea fascicularis, ITS2, Metabolism, mtDNA, Pollution, Porites lutea, Symbiodinium, Temperature, Turbinaria mesenterina, Vietnam
National Category
Natural Sciences
Research subject
Marine Ecotoxicology
Identifiers
urn:nbn:se:su:diva-62867 (URN)978-91-7447-383-4 (ISBN)
Public defence
2011-11-18, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:30 (English)
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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: 2011-10-27 Created: 2011-10-03 Last updated: 2011-10-26Bibliographically approved

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