Descending to the twilight-zone: changes in coral reef fish assemblages along a depth gradient down to 65 m

Brokovich, Eran, Einbinder, Shai, Shashar, Nadav, Kiflawi, Moshe and Kark, Salit (2008) Descending to the twilight-zone: changes in coral reef fish assemblages along a depth gradient down to 65 m. Marine Ecology Progress Series, 371 253-262. doi:10.3354/meps07591


Author Brokovich, Eran
Einbinder, Shai
Shashar, Nadav
Kiflawi, Moshe
Kark, Salit
Title Descending to the twilight-zone: changes in coral reef fish assemblages along a depth gradient down to 65 m
Journal name Marine Ecology Progress Series   Check publisher's open access policy
ISSN 0171-8630
1616-1599
Publication date 2008-11-19
Year available 2008
Sub-type Article (original research)
DOI 10.3354/meps07591
Open Access Status DOI
Volume 371
Start page 253
End page 262
Total pages 10
Place of publication Oldendorf, Germany
Publisher Inter-Research
Language eng
Abstract In contrast to the abundance of literature on the relationship between fish assemblages and habitat structure in the upper 30 in of coral reefs, the deeper (>40 m) parts of coral reefs are rarely studied. We examined changes in reef fish diversity and habitat structure along an increasing depth gradient, including the unknown deep reef. We ran visual and video transects along a substantial depth gradient (0 to 65 in) in the northern Red Sea and extended the known depth distribution for 48 reef species. We found a change in assemblage composition highly correlated to both the depth gradient and a reduction in the abundance of branching corals with depth. The number of reef fish species declined with depth and we also measured a high species turnover as measured by beta diversity (beta(t), beta(w)) in the deep reef. This pattern is mainly due to the replacement of the abundant damselfishes in the shallow reef, which prey on zooplankton, by zooplanktivorous sea basses and wrasses in the deep reef. The steep reduction in branching corals, which most damselfishes use for cover, may be the main factor contributing to this change. We found a peak in species richness (alpha diversity) at 30 m, a peak in beta(w) at 50 to 65 in, and peaks in beta(t) at 30 to 50 in and 50 to 65 m. The 30 in depth stratum shows species of both shallow and deep assemblages generating a transition zone with characters of both deep and shallow habitats. The fish assemblage continues to change with depth, and future research will determine if there exists a depth threshold at which the assemblage will stabilize.
Formatted abstract
In contrast to the abundance of literature on the relationship between fish assemblages and habitat structure in the upper 30 m of coral reefs, the deeper (>40 m) parts of coral reefs are rarely studied. We examined changes in reef fish diversity and habitat structure along an increasing depth gradient, including the unknown deep reef. We ran visual and video transects along a substantial depth gradient (0 to 65 m) in the northern Red Sea and extended the known depth distribution for 48 reef species. We found a change in assemblage composition highly correlated to both the depth gradient and a reduction in the abundance of branching corals with depth. The number of reef fish species declined with depth and we also measured a high species turnover as measured by beta diversity (βt, βw) in the deep reef. This pattern is mainly due to the replacement of the abundant damselfishes in the shallow reef, which prey on zooplankton, by zooplanktivorous sea basses and wrasses in the deep reef. The steep reduction in branching corals, which most damselfishes use for cover, may be the main factor contributing to this change. We found a peak in species richness (alpha diversity) at 30 m, a peak in βw at 50 to 65 m, and peaks in βt at 30 to 50 m and 50 to 65 m. The 30 m depth stratum shows species of both shallow and deep assemblages generating a transition zone with characters of both deep and shallow habitats. The fish assemblage continues to change with depth, and future research will determine if there exists a depth threshold at which the assemblage will stabilize.
Keyword Depth gradient
Deep reef fish
Gulf of Aqaba
Red Sea
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID 740/04
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Biological Sciences Publications
 
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