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Impact of herbivore identity on algal succession and coral growth on a Caribbean reef.

Burkepile DE, Hay ME - PLoS ONE (2010)

Bottom Line: On new substrates, rapid grazing by ocean surgeonfish and princess parrotfish kept communities in an early successional stage dominated by short, filamentous algae and crustose coralline algae that did not suppress coral growth.These patterns contrast with patterns from established communities not undergoing primary succession; on established substrates redband parrotfish significantly reduced upright macroalgal cover while ocean surgeonfish and princess parrotfish allowed significant increases in late successional macroalgae.The species-specific effects of herbivorous fishes suggest that a species-rich herbivore fauna can be critical in providing the resilience that reefs need for recovery from common disturbances such as coral bleaching and storm damage.

View Article: PubMed Central - PubMed

Affiliation: School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America. deron.burkepile@fiu.edu

ABSTRACT

Background: Herbivory is an important top-down force on coral reefs that regulates macroalgal abundance, mediates competitive interactions between macroalgae and corals, and provides resilience following disturbances such as hurricanes and coral bleaching. However, reductions in herbivore diversity and abundance via disease or over-fishing may harm corals directly and may indirectly increase coral susceptibility to other disturbances.

Methodology and principal findings: In two experiments over two years, we enclosed equivalent densities and masses of either single-species or mixed-species of herbivorous fishes in replicate, 4 m(2) cages at a depth of 17 m on a reef in the Florida Keys, USA to evaluate the effects of herbivore identity and species richness on colonization and development of macroalgal communities and the cascading effects of algae on coral growth. In Year 1, we used the redband parrotfish (Sparisoma aurofrenatum) and the ocean surgeonfish (Acanthurus bahianus); in Year 2, we used the redband parrotfish and the princess parrotfish (Scarus taeniopterus). On new substrates, rapid grazing by ocean surgeonfish and princess parrotfish kept communities in an early successional stage dominated by short, filamentous algae and crustose coralline algae that did not suppress coral growth. In contrast, feeding by redband parrotfish allowed an accumulation of tall filaments and later successional macroalgae that suppressed coral growth. These patterns contrast with patterns from established communities not undergoing primary succession; on established substrates redband parrotfish significantly reduced upright macroalgal cover while ocean surgeonfish and princess parrotfish allowed significant increases in late successional macroalgae.

Significance: This study further highlights the importance of biodiversity in affecting ecosystem function in that different species of herbivorous fishes had very different impacts on reef communities depending on the developmental stage of the community. The species-specific effects of herbivorous fishes suggest that a species-rich herbivore fauna can be critical in providing the resilience that reefs need for recovery from common disturbances such as coral bleaching and storm damage.

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Plot of axes from nonmetric multidimensional scaling (NMDS) describing the similarity of the algal communities among the treatments.Data are for (A) Year 1 and (B) Year 2. Values within parentheses show % of variance explained by each axis. Symbols are as in Fig. 1. Lines connect replicates within treatment.
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pone-0008963-g003: Plot of axes from nonmetric multidimensional scaling (NMDS) describing the similarity of the algal communities among the treatments.Data are for (A) Year 1 and (B) Year 2. Values within parentheses show % of variance explained by each axis. Symbols are as in Fig. 1. Lines connect replicates within treatment.

Mentions: Resampling statistics showed no significant effects of herbivore richness on individual algal groups (Fig. 1 & 2). The decrease in replication in several treatments following intrusion by moral eels (see Materials and Methods) may have decreased our statistical power making it more difficult to detect differences between some mixed-species and single-species treatments. However, this did not affect the detection of herbivore richness effects on established substrates [16], and did not appear to be a problem here because the mixed-species treatment was usually intermediate between the two single-species treatments rather then either higher or lower than both single-species treatments, the sign of a richness effect. Nonmetric multidimensional scaling (NMDS) analysis of the algal communities showed that the surgeonfish-only and mixed-herbivore treatments clustered closely together in axis space (Fig. 3A). The redband-only treatment clustered in distinctly different axis space, being most similar to the exclosure treatments. In feeding assays, neither redband parrotfish nor ocean surgeonfish consumed detectable amounts of adult Dasycladus vermicularis (2.1±2.1% removed, P>0.5, df = 5; 2.3±1.6% removed, P>0.5, df = 7, respectively).


Impact of herbivore identity on algal succession and coral growth on a Caribbean reef.

Burkepile DE, Hay ME - PLoS ONE (2010)

Plot of axes from nonmetric multidimensional scaling (NMDS) describing the similarity of the algal communities among the treatments.Data are for (A) Year 1 and (B) Year 2. Values within parentheses show % of variance explained by each axis. Symbols are as in Fig. 1. Lines connect replicates within treatment.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2813280&req=5

pone-0008963-g003: Plot of axes from nonmetric multidimensional scaling (NMDS) describing the similarity of the algal communities among the treatments.Data are for (A) Year 1 and (B) Year 2. Values within parentheses show % of variance explained by each axis. Symbols are as in Fig. 1. Lines connect replicates within treatment.
Mentions: Resampling statistics showed no significant effects of herbivore richness on individual algal groups (Fig. 1 & 2). The decrease in replication in several treatments following intrusion by moral eels (see Materials and Methods) may have decreased our statistical power making it more difficult to detect differences between some mixed-species and single-species treatments. However, this did not affect the detection of herbivore richness effects on established substrates [16], and did not appear to be a problem here because the mixed-species treatment was usually intermediate between the two single-species treatments rather then either higher or lower than both single-species treatments, the sign of a richness effect. Nonmetric multidimensional scaling (NMDS) analysis of the algal communities showed that the surgeonfish-only and mixed-herbivore treatments clustered closely together in axis space (Fig. 3A). The redband-only treatment clustered in distinctly different axis space, being most similar to the exclosure treatments. In feeding assays, neither redband parrotfish nor ocean surgeonfish consumed detectable amounts of adult Dasycladus vermicularis (2.1±2.1% removed, P>0.5, df = 5; 2.3±1.6% removed, P>0.5, df = 7, respectively).

Bottom Line: On new substrates, rapid grazing by ocean surgeonfish and princess parrotfish kept communities in an early successional stage dominated by short, filamentous algae and crustose coralline algae that did not suppress coral growth.These patterns contrast with patterns from established communities not undergoing primary succession; on established substrates redband parrotfish significantly reduced upright macroalgal cover while ocean surgeonfish and princess parrotfish allowed significant increases in late successional macroalgae.The species-specific effects of herbivorous fishes suggest that a species-rich herbivore fauna can be critical in providing the resilience that reefs need for recovery from common disturbances such as coral bleaching and storm damage.

View Article: PubMed Central - PubMed

Affiliation: School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America. deron.burkepile@fiu.edu

ABSTRACT

Background: Herbivory is an important top-down force on coral reefs that regulates macroalgal abundance, mediates competitive interactions between macroalgae and corals, and provides resilience following disturbances such as hurricanes and coral bleaching. However, reductions in herbivore diversity and abundance via disease or over-fishing may harm corals directly and may indirectly increase coral susceptibility to other disturbances.

Methodology and principal findings: In two experiments over two years, we enclosed equivalent densities and masses of either single-species or mixed-species of herbivorous fishes in replicate, 4 m(2) cages at a depth of 17 m on a reef in the Florida Keys, USA to evaluate the effects of herbivore identity and species richness on colonization and development of macroalgal communities and the cascading effects of algae on coral growth. In Year 1, we used the redband parrotfish (Sparisoma aurofrenatum) and the ocean surgeonfish (Acanthurus bahianus); in Year 2, we used the redband parrotfish and the princess parrotfish (Scarus taeniopterus). On new substrates, rapid grazing by ocean surgeonfish and princess parrotfish kept communities in an early successional stage dominated by short, filamentous algae and crustose coralline algae that did not suppress coral growth. In contrast, feeding by redband parrotfish allowed an accumulation of tall filaments and later successional macroalgae that suppressed coral growth. These patterns contrast with patterns from established communities not undergoing primary succession; on established substrates redband parrotfish significantly reduced upright macroalgal cover while ocean surgeonfish and princess parrotfish allowed significant increases in late successional macroalgae.

Significance: This study further highlights the importance of biodiversity in affecting ecosystem function in that different species of herbivorous fishes had very different impacts on reef communities depending on the developmental stage of the community. The species-specific effects of herbivorous fishes suggest that a species-rich herbivore fauna can be critical in providing the resilience that reefs need for recovery from common disturbances such as coral bleaching and storm damage.

Show MeSH
Related in: MedlinePlus