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Effects of elevated water temperature, reduced salinity and nutrient enrichment on the metabolism of the coral Turbinaria mesenterina
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.
2010 (English)In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 88, no 4, 482-487 p.Article in journal (Refereed) Published
Abstract [en]

Water quality is declining in many coastal areas, which has caused coral degradation worldwide. In addition, reduced water quality may aggravate the impacts of seawater temperature. In this study the effects of increased temperature (31 degrees C), nitrate enrichment (+5 mu M NO3-), low salinity (20) and combinations of these stressors were investigated compared to ambient water (25 degrees C, 30, 0.3 mu M NO3-) on the metabolism and survival of the coral Turbinaria mesenterina from the Tonkin Gulf, Vietnam. The results showed that all specimens exposed to a combination of all three stressors (i.e. high temperature + high nitrate + low salinity) died after 24 h exposure, while those that had been exposed to high nitrate + low salinity at ambient temperature did not show any effects on the metabolism or survival. Furthermore, corals exposed to low salinity + high temperature displayed a decrease in gross primary production/respiration (GP/R) ratio and the mortality rate was 50%. In addition, all corals exposed to increased temperature, alone or in combination with another stressor, displayed a GP/R-24h ratio below 1.0, suggesting that they depend on stored energy to cover their metabolic requirements. The results showed that corals may tolerate short-term exposure to stressors such as low salinity + high nitrate concentration in ambient temperature, while additional increased temperature lead to rapid mortality, hence suggesting a synergistic effect. Thus, the effect of climate change might be more severe in nearshore coastal areas where corals already are exposed to several disturbances.

Place, publisher, year, edition, pages
2010. Vol. 88, no 4, 482-487 p.
Keyword [en]
temperature increase, salinity, nutrients, corals, metabolism, stress
National Category
Biological Sciences
Research subject
Marine Ecotoxicology
Identifiers
URN: urn:nbn:se:su:diva-49476DOI: 10.1016/j.ecss.2010.05.008ISI: 000279860800006OAI: oai:DiVA.org:su-49476DiVA: diva2:377600
Note

authorCount :3

Available from: 2010-12-14 Created: 2010-12-14 Last updated: 2017-12-11Bibliographically 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)
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: 2011-10-27 Created: 2011-10-03 Last updated: 2011-10-26Bibliographically approved
2. Coral Reef Habitats and Fish Connectivity: Implications for coastal management and fishery
Open this publication in new window or tab >>Coral Reef Habitats and Fish Connectivity: Implications for coastal management and fishery
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Coral reefs have one of the highest levels of biodiversity of all ecosystems in the world and are important for both human livelihood and food security throughout many tropical countries. However, due to increased anthropogenic pressure on marine ecosystems, especially during the last couple of decades, coral reefs have become critically over-fished, and many reefs are now in a degraded state and are facing additional future threats due to further over-exploitation, chemical pollution, sedimentation, and effects of climate change.

The main aim of this PhD thesis was to understand effects of anthropogenic disturbances on tropical coastal ecosystems and fish connectivity for coastal management purposes. Therefore, linkages between anthropogenic disturbance and corals were investigated (Paper I), as well as interactions between coral reef habitat and associated fish assemblage (Paper II). Furthermore, connectivity between coral reefs and other tropical coastal ecosystems was explored (Paper III), as well as fish migration to reproduction sites (Paper IV), and evaluations of spatial ecology methods (Paper V).

The result showed that coral reefs that are already exposed to disturbances, such as freshwater and nutrient run-offs, may be more sensitive to climate change, in terms of increased sea surface temperatures (Paper I). In addition, there were also clear linkages between coral reef quality, in terms of coral coverage, and fish assemblages, which displayed high spatial variability and suggesting patchy recovery after the 1997/1998 bleaching and subsequent coral mass mortality event (Paper II). This highlights the importance of understanding effects of disturbances on corals, especially in terms of synergistic effects between increased water temperatures and other coastal stressors such as decreased salinity and increased nutrients; and the indirect effects of habitat degradation on the fish community.

Linkages between fish and different coastal habitats were further explored. The results showed that coral reefs were strongly connected with mangrove and seagrass beds, through ontogenetic migration of fish (Paper III). Migrations to spawning sites of groupers were related to lunar activities when thousands of fish gather for reproduction purposes during new moon, which increases the risk of over-exploitation (Paper IV). The results emphasises the importance of protecting key areas such as nursing grounds and reproduction sites. Furthermore, acoustic telemetry has become an increasingly common method in studies of fish movement, and the results showed that efficiency of acoustic arrays may increase depending on deployment strategies and habitat characteristics (Paper V).

In conclusion, the results from this PhD thesis emphasises the importance of protecting coral reef habitats, as well as identifying related susceptible tropical coastal areas, such as nursing grounds and reproduction sites. Indeed, a better scientific understanding of coral reef ecology and indirect and direct effects on fish assemblages are needed for efficient and accurate coastal management decisions.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University, 2016. 80 p.
Keyword
anthropogenic disturbance, coral reef habitat, fish community, coastal ecosystems, conservation management, spatial ecology, seascape perspective, holistic approach
National Category
Biological Sciences
Research subject
Marine Ecotoxicology
Identifiers
urn:nbn:se:su:diva-125595 (URN)978-91-7649-337-3 (ISBN)
Public defence
2016-03-11, Vivi Täckholmsalen (Q-salen), NPQ-huset, Svante Arrhenius väg 20, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.

Available from: 2016-02-17 Created: 2016-01-14 Last updated: 2017-02-20Bibliographically approved

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