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Spatial variation in abundance, size and orientation of juvenile corals related to the biomass of parrotfishes on the Great Barrier Reef, Australia.

Trapon ML, Pratchett MS, Hoey AS - PLoS ONE (2013)

Bottom Line: Size-class structure, orientation on the substrate and taxonomic composition of juvenile corals varied significantly among latitudinal sectors.The abundance of juvenile corals varied both within (6-13 ind.m(-2)) and among reefs (2.8-11.1 ind.m(-2)) but was fairly similar among latitudes (6.1-8.2 ind.m(-2)), despite marked latitudinal variation in larval supply and settlement rates previously found at this scale.While numerous studies have advocated the importance of parrotfishes for clearing space on the substrate to facilitate coral settlement, our results suggest that at high biomass they may have a detrimental effect on juvenile coral assemblages.

View Article: PubMed Central - PubMed

Affiliation: ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia. melanie.trapon@my.jcu.edu.au

ABSTRACT
For species with complex life histories such as scleractinian corals, processes occurring early in life can greatly influence the number of individuals entering the adult population. A plethora of studies have examined settlement patterns of coral larvae, mostly on artificial substrata, and the composition of adult corals across multiple spatial and temporal scales. However, relatively few studies have examined the spatial distribution of small (≤50 mm diameter) sexually immature corals on natural reef substrata. We, therefore, quantified the variation in the abundance, composition and size of juvenile corals (≤50 mm diameter) among 27 sites, nine reefs, and three latitudes spanning over 1000 km on Australia's Great Barrier Reef. Overall, 2801 juveniles were recorded with a mean density of 6.9 (±0.3 SE) ind.m(-2), with Acropora, Pocillopora, and Porites accounting for 84.1% of all juvenile corals surveyed. Size-class structure, orientation on the substrate and taxonomic composition of juvenile corals varied significantly among latitudinal sectors. The abundance of juvenile corals varied both within (6-13 ind.m(-2)) and among reefs (2.8-11.1 ind.m(-2)) but was fairly similar among latitudes (6.1-8.2 ind.m(-2)), despite marked latitudinal variation in larval supply and settlement rates previously found at this scale. Furthermore, the density of juvenile corals was negatively correlated with the biomass of scraping and excavating parrotfishes across all sites, revealing a potentially important role of parrotfishes in determining distribution patterns of juvenile corals on the Great Barrier Reef. While numerous studies have advocated the importance of parrotfishes for clearing space on the substrate to facilitate coral settlement, our results suggest that at high biomass they may have a detrimental effect on juvenile coral assemblages. There is, however, a clear need to directly quantify rates of mortality and growth of juvenile corals to understand the relative importance of these mechanisms in shaping juvenile, and consequently adult, coral assemblages.

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Comparison of surface orientation use by juvenile scleractinian corals across the northern (n = 135), central (n = 135) and southern reefs (n = 135) on the GBR, for (A) Acropora sp, (B) Pocillopora sp, and (C) Porites sp.
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pone-0057788-g005: Comparison of surface orientation use by juvenile scleractinian corals across the northern (n = 135), central (n = 135) and southern reefs (n = 135) on the GBR, for (A) Acropora sp, (B) Pocillopora sp, and (C) Porites sp.

Mentions: The majority of juvenile corals surveyed in all sites, reefs and sectors were recorded on horizontal (47.5%) and vertical (32.5%) surfaces, but orientation of the three main genera varied among sectors (Table 3B; Fig. 5). In the central GBR, juvenile Acropora, Pocillopora and Porites were found less often on vertical surfaces (23.8%, 19.2%, and 29.5%, respectively) and more often immersed in crevices (14.9, 31.1, and 21.5%, respectively) compare to the northern or southern reefs (Fig. 5). In contrast, the occurrence of juvenile Acropora, Pocillopora and Porites under existing structures was low especially on the southern reefs (2.8%, 3.8%, and 0%, respectively), compared to the central (11.8%, 9.9%, and 3.3%) and northern (12.5%, 12.1%, and 5.2%) reefs (Fig. 5).


Spatial variation in abundance, size and orientation of juvenile corals related to the biomass of parrotfishes on the Great Barrier Reef, Australia.

Trapon ML, Pratchett MS, Hoey AS - PLoS ONE (2013)

Comparison of surface orientation use by juvenile scleractinian corals across the northern (n = 135), central (n = 135) and southern reefs (n = 135) on the GBR, for (A) Acropora sp, (B) Pocillopora sp, and (C) Porites sp.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585139&req=5

pone-0057788-g005: Comparison of surface orientation use by juvenile scleractinian corals across the northern (n = 135), central (n = 135) and southern reefs (n = 135) on the GBR, for (A) Acropora sp, (B) Pocillopora sp, and (C) Porites sp.
Mentions: The majority of juvenile corals surveyed in all sites, reefs and sectors were recorded on horizontal (47.5%) and vertical (32.5%) surfaces, but orientation of the three main genera varied among sectors (Table 3B; Fig. 5). In the central GBR, juvenile Acropora, Pocillopora and Porites were found less often on vertical surfaces (23.8%, 19.2%, and 29.5%, respectively) and more often immersed in crevices (14.9, 31.1, and 21.5%, respectively) compare to the northern or southern reefs (Fig. 5). In contrast, the occurrence of juvenile Acropora, Pocillopora and Porites under existing structures was low especially on the southern reefs (2.8%, 3.8%, and 0%, respectively), compared to the central (11.8%, 9.9%, and 3.3%) and northern (12.5%, 12.1%, and 5.2%) reefs (Fig. 5).

Bottom Line: Size-class structure, orientation on the substrate and taxonomic composition of juvenile corals varied significantly among latitudinal sectors.The abundance of juvenile corals varied both within (6-13 ind.m(-2)) and among reefs (2.8-11.1 ind.m(-2)) but was fairly similar among latitudes (6.1-8.2 ind.m(-2)), despite marked latitudinal variation in larval supply and settlement rates previously found at this scale.While numerous studies have advocated the importance of parrotfishes for clearing space on the substrate to facilitate coral settlement, our results suggest that at high biomass they may have a detrimental effect on juvenile coral assemblages.

View Article: PubMed Central - PubMed

Affiliation: ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia. melanie.trapon@my.jcu.edu.au

ABSTRACT
For species with complex life histories such as scleractinian corals, processes occurring early in life can greatly influence the number of individuals entering the adult population. A plethora of studies have examined settlement patterns of coral larvae, mostly on artificial substrata, and the composition of adult corals across multiple spatial and temporal scales. However, relatively few studies have examined the spatial distribution of small (≤50 mm diameter) sexually immature corals on natural reef substrata. We, therefore, quantified the variation in the abundance, composition and size of juvenile corals (≤50 mm diameter) among 27 sites, nine reefs, and three latitudes spanning over 1000 km on Australia's Great Barrier Reef. Overall, 2801 juveniles were recorded with a mean density of 6.9 (±0.3 SE) ind.m(-2), with Acropora, Pocillopora, and Porites accounting for 84.1% of all juvenile corals surveyed. Size-class structure, orientation on the substrate and taxonomic composition of juvenile corals varied significantly among latitudinal sectors. The abundance of juvenile corals varied both within (6-13 ind.m(-2)) and among reefs (2.8-11.1 ind.m(-2)) but was fairly similar among latitudes (6.1-8.2 ind.m(-2)), despite marked latitudinal variation in larval supply and settlement rates previously found at this scale. Furthermore, the density of juvenile corals was negatively correlated with the biomass of scraping and excavating parrotfishes across all sites, revealing a potentially important role of parrotfishes in determining distribution patterns of juvenile corals on the Great Barrier Reef. While numerous studies have advocated the importance of parrotfishes for clearing space on the substrate to facilitate coral settlement, our results suggest that at high biomass they may have a detrimental effect on juvenile coral assemblages. There is, however, a clear need to directly quantify rates of mortality and growth of juvenile corals to understand the relative importance of these mechanisms in shaping juvenile, and consequently adult, coral assemblages.

Show MeSH