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Upholding the coral loop: Resilience, alternative stable states and feedbacks in coral reefs
Stockholm University, Faculty of Science, Department of Systems Ecology. (Natural resource management)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Coral reefs are suffering unprecedented declines in coral cover and species diversity. These changes are often associated with  substantial shifts in community structure to new dominant organisms. Ultimately, these “phase shifts” can be persistent and very difficult to return from. Building insurance against degradation and decreasing the likelihood of reefs undergoing shifts to undesirable states will require sustainable management practices that uphold coral reef resilience. This thesis consists of five papers that contribute new knowledge useful for managing the resilience of coral reefs, and other marine ecosystems. Paper I shows how the morphology of natural substrate (dead coral colonies) can significantly influence coral recruitment patterns. Paper II focuses on larval lipid levels, a key determinant of coral dispersal potential, in a common Caribbean coral (Favia fragum). It shows that i) lipid levels exhibit a significant, non-linear reduction throughout the larval release period of F. fragum and ii) exposure to a common pollutant (copper) could potentially lead to a more rapid lipid consumption in the larvae. Paper III presents a broader analysis of the different undesirable states a coral reef can shift to as a consequence of reef degradation. It concludes that different states are caused by different driving factors and that management must explicitly acknowledge this. Paper IV proposes a suite of resilience indicators that can help managers assess when a coral-dominated reef might be moving towards a shift to an undesirable state. These indicators capture key-processes occuring on different temporal and spatial scales and signal resilience loss early enough for managers to take appropriate measures. Finally, Paper V reviews the feedback loops that reinforce the undesirable states of five important marine ecosystems and suggests certain strategies that can ease the restoration back to healthier conditions. Managing these critical feedbacks will recquire monitoring the processes underpinning these feedbacks, breaking already established feedbacks loops through large-scale management trials and acknowledging transdisciplinary solutions that move management beyond the discipline of ecology

Place, publisher, year, edition, pages
Stockholm: Department of Systems Ecology, Stockholm University , 2010. , 39 p.
Keyword [en]
resilience, alternative stable states, regimes, feedbacks, recruitment, coral reefs, marine ecosystem management, regime shifts, phase shifts
National Category
Ecology
Research subject
Natural Resources Management
Identifiers
URN: urn:nbn:se:su:diva-34037ISBN: 978-91-7155-997-5 (print)OAI: oai:DiVA.org:su-34037DiVA: diva2:284081
Public defence
2010-01-29, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 09:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 5: In progress.Available from: 2010-01-07 Created: 2010-01-04 Last updated: 2010-01-07Bibliographically approved
List of papers
1. Influence of dead coral substrate morphology on patterns of juvenile coral distribution
Open this publication in new window or tab >>Influence of dead coral substrate morphology on patterns of juvenile coral distribution
2007 (English)In: Marine Biology, ISSN 0025-3162, Vol. 150, no 6, 1145-1152 p.Article in journal (Refereed) Published
Abstract [en]

This study examines the abundances of three morphological categories of juvenile corals (massive, branching and encrusting) on two different types of natural substratum, dead massive and dead branching corals. The overall results show that the morphological characteristics of dead coral substratum have a significant influence on the coral recruitment patterns with respect to the morphology of the recruits: juvenile corals of massive and branching types were more abundant on substrates of corresponding morphology. The results obtained from this study suggest that dead coral might attract coral larvae that are morphologically similar. On the other hand, it may be the result of post-settlement mortality. Whatever the mechanism shaping the patterns is, it seems that the physical morphology of the dead coral substrate has a significant influence on the coral recruit assemblage. Hence, we suggest that substrate morphology can be an important qualitative factor for coral settlement and a possible determinant of community structure.

Identifiers
urn:nbn:se:su:diva-10877 (URN)10.1007/s00227-006-0458-2 (DOI)000244454900010 ()
Available from: 2008-01-08 Created: 2008-01-08 Last updated: 2010-01-07Bibliographically approved
2. Lipid contents of Favia fragum larvae: changes during planulation period and effects of copper exposure
Open this publication in new window or tab >>Lipid contents of Favia fragum larvae: changes during planulation period and effects of copper exposure
(English)Article in journal (Refereed) Submitted
Abstract [en]

Lipid contents of the planulae larvae of the brooding scleractinian coral Favia fragum were analysed throughout a monthly planulation period. Lipid levels exhibited a significant non-linear decrease during the planulation period, with a significant drop occurring between the 5th and 6th planulation day. The mean lipid content of F. fragum planulae released during the first 5 days of the planulation period was 47% by dry weight, compared to 34% during the final 4 days. Larval lipid content was also used to investigate the physiological response of F. fragum larvae to sub-lethal copper exposure (20 μg l-1) for 4 days. Copper exposure resulted in a faster rate of lipid consumption (6% day-1) compared to control treatments (1.3% day-1).

Keyword
Favia fragum, larvae, lipid, planulation, copper
National Category
Ecology
Research subject
Natural Resources Management; Systems Ecology
Identifiers
urn:nbn:se:su:diva-34304 (URN)
Available from: 2010-01-07 Created: 2010-01-07 Last updated: 2010-01-07Bibliographically approved
3. Alternative states on coral reefs: beyond coral-macroalgal phase shifts
Open this publication in new window or tab >>Alternative states on coral reefs: beyond coral-macroalgal phase shifts
2009 (English)In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 376, 295-306 p.Article in journal (Refereed) Published
Abstract [en]

Degradation of coral reefs is often associated with changes in community structure where macroalgae become the dominant benthic life form. These phase shifts can be difficult to reverse. The debate on coral reef phase shifts has not focused on reports of coral reefs becoming dominated by other life forms following disturbance. A review of the primary and grey literature indicates that reefs dominated by corallimorpharia, soft corals, sponges and sea urchins can enter an alternative state as a result of a phase shift. Shifts can be triggered by pulse disturbances that cause large-scale coral mortality, and may become stable as a result of positive feedback mechanisms. However, they may differ from the archetypical coral-macroalgae shift, depending on the factors driving the shift; whereas coral-macroalgae and coral-urchin shifts seem to be driven by loss of top-down control through overfishing, shifts to corallimorpharian, soft coral and sponge dominance seem more associated with changes in bottom-tip dynamics. Understanding the differences and similarities in mechanisms that cause and maintain this variety of alternative states will aid management aimed at preventing and reversing phase shifts of coral reefs.

Keyword
Phase shifts, Coral reefs, Alternative states, Corallimorpharia, Soft coral, Sponge, Urchin barren
National Category
Oceanography, Hydrology, Water Resources Ecology
Identifiers
urn:nbn:se:su:diva-34132 (URN)10.3354/meps07815 (DOI)000263999900024 ()
Available from: 2010-01-06 Created: 2010-01-06 Last updated: 2012-11-09Bibliographically approved
4. Capturing the cornerstones of coral reef resilience: linking theory to practice
Open this publication in new window or tab >>Capturing the cornerstones of coral reef resilience: linking theory to practice
2008 (English)In: Coral reefs (Print), ISSN 0722-4028, E-ISSN 1432-0975, Vol. 27, no 4, 795-809 p.Article in journal (Refereed) Published
Abstract [en]

Coral reefs can undergo unexpected and dramatic changes in community composition, so called phase shifts. This can have profound consequences for ecosystem services upon which human welfare depends. Understanding of this behavior is in many aspects still in its infancy. Resilience has been argued to provide insurance against unforeseen ecosystem responses in the face of environmental change, and has become a prime goal for the management of coral reefs. However, diverse definitions of resilience can be found in the literature, making its meaning ambiguous. Several studies have used the term as a theoretical framework and concern regarding its practical applicability has been raised. Consequently, operationalizing theory to make resilience observable is an important task, particularly for policy makers and managers dealing with pressing environmental problems. Ultimately this requires some type of empirical assessments, something that has proven difficult due to the multidimensional nature of the concept. Biodiversity, spatial heterogeneity, and connectivity have been proposed as cornerstones of resilience as they may provide insurance against ecological uncertainty. The aim of this article is to provide an overview of the divergent uses of the concept and to propose empirical indicators of the cornerstones of coral reef resilience. These indicators include functional group approaches, the ratios of "good" and "bad" colonizers of space, measurements of spatial heterogeneity, and estimates of potential space availability against grazing capacity. The essence of these operational indicators of resilience is to use them as predictive tools to recognize vulnerability before disturbance occurs that may lead to abrupt phase shifts. Moving toward operationalizing resilience theory is imperative to the successful management of coral reefs in an increasingly disturbed and human-dominated environment.

Keyword
Diversity, Functional groups, Management, Phase shifts, Coral reefs, Resilience
National Category
Ecology
Identifiers
urn:nbn:se:su:diva-15628 (URN)10.1007/s00338-008-0426-z (DOI)000260616400011 ()
Available from: 2008-12-07 Created: 2008-12-07 Last updated: 2012-11-12Bibliographically approved
5. Steering feedbacks toward healthier marine ecosystems
Open this publication in new window or tab >>Steering feedbacks toward healthier marine ecosystems
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Marine ecosystem decline is accelerating. At some point degradation may pass a tipping point beyond which ecosystems become trapped in alternative degraded states, as a result of changes in critical feedbacks. Self-reinforcing feedbacks pose a major challenge for managers and policy-makers seeking remedial actions to curb the marine crisis. Here we synthesize the dynamics of critical feedbacks of the degraded states in five socio-economically important marine ecosystems; coral reefs, kelp forests, seagrass beds, shallow unvegetated soft-bottom habitats, and coastal pelagic food webs. A better understanding of the way human actions influence the strength and direction of feedbacks, how different feedbacks interact and at what scales they operate, is crucial for successful implementation of marine ecosystem management. We advocate a critical-feedback management approach that ventures beyond traditionally discipline boundaries, as an essential element of marine ecosystem management.

National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-34306 (URN)
Available from: 2010-01-07 Created: 2010-01-07 Last updated: 2013-07-10Bibliographically approved

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