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Long-term effects of the 1998 coral bleaching event on reef fish assemblages
Stockholm University, Faculty of Science, Department of Zoology.
Stockholm University, Faculty of Science, Department of Zoology.
Stockholm University, Faculty of Science, Department of Zoology.
Stockholm University, Faculty of Science, Department of Zoology.
2006 (English)In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 315, 237-247 p.Article in journal (Refereed) Published
Abstract [en]

Coral bleaching events constitute compound disturbances often resulting in coral death as well as successive degradation of the reef framework. The 1997/1998 El Niño Southern Oscillation (ENSO) was the most severe on record and affected coral reefs worldwide. The present study examined the response of fish assemblages in plots of transplanted coral before and after the 1998 bleaching. Multidimensional scaling ordinations (MDS) demonstrate significant changes in assemblage composition related to habitat alteration. Within-site variability increased with disturbance, the increase being most apparent following substrate erosion. The differences in long-term responses as opposed to short-term responses were striking. Six mo after coral death, total abundance as well as taxonomic richness had increased at one of the sites, but not the other, whereas 6 yr later, both measures had decreased significantly at both sites. Functional groups, with documented affiliations with coral, were significantly influenced by the habitat alteration. Herbivore abundance increased as an immediate response to bleaching, but was subsequently decimated in eroded habitat. The loss of structural complexity had major detrimental effects on the entire fish community. In conclusion, we present evidence of severe and long-lasting secondary impacts of a catastrophic bleaching event, with no apparent recovery. The discrepancies between short-term and long-term responses underline the importance of long-term monitoring of fish assemblages following habitat alteration.

Place, publisher, year, edition, pages
2006. Vol. 315, 237-247 p.
Keyword [en]
Habitat structure, Disturbance, Coral degradation, Community ecology, Herbivores, Corallivores, Multivariate analyses, Global warming
National Category
Zoology Ecology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-25795DOI: 10.3354/meps315237OAI: oai:DiVA.org:su-25795DiVA: diva2:200531
Available from: 2009-03-05 Created: 2009-02-25 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Habitat structure, degradation and management effects on coral reef fish communities
Open this publication in new window or tab >>Habitat structure, degradation and management effects on coral reef fish communities
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Coral reefs are among the most diverse and productive ecosystems on earth, and are critical to the survival of tropical marine ecosystems and sustenance of local human populations. However, coral reefs are quite vulnerable to disturbances, both natural and anthropogenic. This thesis looks at how coral reef communities have responded to climactic disturbances, particularly the 1997-98 El Niño Southern Oscillation (ENSO) and subsequent coral bleaching and mortality that affected much of the Indian Ocean, including the coastal waters of Tanzania, where the study was conducted. In particular, it investigates the effects of coral bleaching, habitat degradation and reef spatial arrangement on reef fish assemblages.

Habitat structural complexity and spatial arrangement of reefs had an effect on reef fish communities. Fish communities showed patterns in distribution among habitats and between patch and continuous reefs. Fishes preferred live to bleached/dead or eroded coral, but trophic groups reacted differently to patch and continuous reefs. There were slight changes in fish abundance and significant changes in fish diversity on experimental, bleached branching Acropora coral plots over a period of one year. While fish abundance on one site increased shortly after a bleaching event, 6 years later fish abundance had decreased significantly. Conversely, coral reef communities in northern Tanzania had changed little over an 8-year period, with minor changes associated with the 1997-98 ENSO and the presence or absence of fisheries management. The coral reefs in the region were found to show high variability in community structure and responses of associated fish and invertebrate communities.

The findings of this thesis indicate the importance of habitat structure and spatial arrangement of reefs, the detrimental effects of coral bleaching, and the possibility that some reefs and some (generalist) reef fish taxa may exhibit resilience to climate change.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2011. 46 p.
Keyword
fish assemblages, climate change, coral degradation, Indian Ocean, patch reefs, coral bleaching, resilience
National Category
Ecology Zoology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-62187 (URN)978-91-7447-360-5 (ISBN)
Public defence
2011-10-07, Ahlmannsalen, Geovetenskapens hus, Svante Arrhenius väg 12, 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 3: Manuscript. Paper 4: Manuscript. Available from: 2011-09-15 Created: 2011-09-12 Last updated: 2011-09-13Bibliographically approved
2. Effects of habitat structure on tropical fish assemblages
Open this publication in new window or tab >>Effects of habitat structure on tropical fish assemblages
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Rates of habitat alteration and degradation are increasing worldwide due to anthropogenic influence. On coral reefs, the loss of live coral reduces structural complexity while facilitating algal increase. In many coastal lagoons seagrass and corals are cleared to make room for cultivated macroalgae. This thesis deals with reef and lagoon habitat structure and how fish assemblage patterns may be related to physical and biological features of the habitat. It further examines assemblage change following habitat disturbance. Four studies on East African coral reefs concluded that both the abundance and species richness of recruit and adult coral reef fish were largely predicted by the presence of live coral cover and structural complexity (Papers I-III, VI). Typically, recruits were more selective than adults, as manifested by limited distributions to degraded sites. Paper VI compared short- and long-term responses of fish assemblages to the 1997-1998 bleaching event. The short-term response to coral mortality included the loss of coral dwelling species in favour of species which feed on algae or associated detrital resources. Counterintuitively, fish abundance and taxonomic richness increased significantly at one of two sites shortly after the bleaching. However, the initial increase was later reversed and six years after the death of the coral, only a limited number of fish remained. The influence of fleshy algae on fish assemblages was studied in algal farms (Paper IV), and examined experimentally (Paper V). The effects of algal farming in Zanzibar were significant. Meanwhile, manually clearing algal-dominated patch reefs in Belize from macroalgae resulted in short-term increases of abundance, biomass and activity of a few species, including major herbivores. The findings of this thesis demonstrate the significance of habitat as a structuring factor for tropical fish assemblages and predicts that coral death, subsequent erosion and algal overgrowth may have substantial deleterious impacts on fish assemblage composition, abundance and taxonomic richness, with recovery being slow and related to the recovery of the reef framework.

Place, publisher, year, edition, pages
Stockholm: Zoologiska institutionen, 2007. 39 p.
National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-6767 (URN)91-7155-361-4 (ISBN)
Public defence
2007-06-08, sal G, Arrheniuslaboratorierna, Svante Arrhenius väg 14-18, Stockholm, 13:30
Opponent
Supervisors
Available from: 2007-05-18 Created: 2007-04-11 Last updated: 2011-09-12Bibliographically approved

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