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Effects of habitat structure on tropical fish assemblages
Stockholm University, Faculty of Science, Department of Zoology.
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: urn:nbn:se:su:diva-6767ISBN: 91-7155-361-4 (print)OAI: oai:DiVA.org:su-6767DiVA: diva2:197013
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
List of papers
1. The influence of habitat structure on the abundance of Pomacentrus sulfureus, a western Indian Ocean reef fish
Open this publication in new window or tab >>The influence of habitat structure on the abundance of Pomacentrus sulfureus, a western Indian Ocean reef fish
2000 In: Environmental biology of fishes, ISSN 0378-1909, Vol. 59, no 3, 243-252 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-24203 (URN)
Note
Part of urn:nbn:se:su:diva-6767Available from: 2007-05-18 Created: 2007-04-11Bibliographically approved
2. Coral and fish distribution patterns in Mafia Island Marine Park, Tanzania: Fish-habitat interactions
Open this publication in new window or tab >>Coral and fish distribution patterns in Mafia Island Marine Park, Tanzania: Fish-habitat interactions
2003 In: Hydrobiologia, ISSN 0018-8158, Vol. 498, no 1-3, 191-211 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-24204 (URN)
Note
Part of urn:nbn:se:su:diva-6767Available from: 2007-05-18 Created: 2007-04-11Bibliographically approved
3. Non-random habitat use by coral reef fish recruits in Mafia Island Marine Park, Tanzania
Open this publication in new window or tab >>Non-random habitat use by coral reef fish recruits in Mafia Island Marine Park, Tanzania
2007 (English)In: African Journal of Marine Science, ISSN 1814-232X, Vol. 29, no 2, 187-199 p.Article in journal (Refereed) Published
Abstract [en]

The habitat use by nearly 3 000 reef fish recruits, comprising 56 taxa, at seven sites in Mafia Island Marine Park, Tanzania, were examined. The study was carried out following the 1998 global coral bleaching event and all sites but one were dominated by dead coral and rubble. Mean recruit densities ranged between 0.1 m-2 and 0.7 m-2 among sites. Although live coral represented only 15% of the overall substrate composition, almost half of all observed recruits were found associated with this substrate. Pooled across all sites, 46% of the recruits used live coral cover in disproportion to availability. Principal component analyses were applied to explore microhabitat use by the 11 most common recruit taxa in comparison to availability. Among these taxa, 10 exhibited nonrandom microhabitat use and six associated with live coral in disproportion to availability. A comparison with the adult fish community revealed that adult abundances of four of the six coral selective recruit taxa were significantly correlated with live coral. The study demonstrated that reef fish recruits use microhabitats non-randomly and that a substantial proportion is selective towards live coral.

Place, publisher, year, edition, pages
Informa plc, 2007
Keyword
DISTURBANCE; EAST AFRICA; HABITAT ALTERATION; LARVAL SUPPLY; SELECTION; SETTLEMENT; WESTERN INDIAN OCEAN
National Category
Microbiology
Identifiers
urn:nbn:se:su:diva-24205 (URN)10.2989/AJMS.2007.29.2.4.187 (DOI)000249759400004 ()
Note
Part of urn:nbn:se:su:diva-6767Available from: 2007-05-18 Created: 2007-04-11 Last updated: 2010-12-14Bibliographically approved
4. Influences of algal farming on fish communities
Open this publication in new window or tab >>Influences of algal farming on fish communities
2001 In: Marine Pollution Bulletin, ISSN 0025-326X, Vol. 42, no 12, 1379-1389 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-24206 (URN)
Note
Part of urn:nbn:se:su:diva-6767Available from: 2007-05-18 Created: 2007-04-11Bibliographically approved
5. Response of fishes to whole patch reef algal reductions on Glovers Reef Belize
Open this publication in new window or tab >>Response of fishes to whole patch reef algal reductions on Glovers Reef Belize
Show others...
2000 In: Marine Ecology Progress Series, ISSN 0171-8630, Vol. 206, 273-282 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-24207 (URN)
Note
Part of urn:nbn:se:su:diva-6767Available from: 2007-05-18 Created: 2007-04-11Bibliographically approved
6. Long-term effects of the 1998 coral bleaching event on reef fish assemblages
Open this publication in new window or tab >>Long-term effects of the 1998 coral bleaching event on reef fish assemblages
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.

Keyword
Habitat structure, Disturbance, Coral degradation, Community ecology, Herbivores, Corallivores, Multivariate analyses, Global warming
National Category
Zoology Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-25795 (URN)10.3354/meps315237 (DOI)
Available from: 2009-03-05 Created: 2009-02-25 Last updated: 2017-12-13Bibliographically approved

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