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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.

Show MeSH
Relative abundance of Acropora, Pocillopora, Porites and other corals in (A) the juvenile (≤50 mm) and (B) adult assemblages among the three sectors.
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pone-0057788-g003: Relative abundance of Acropora, Pocillopora, Porites and other corals in (A) the juvenile (≤50 mm) and (B) adult assemblages among the three sectors.

Mentions: A total of 2,801 juvenile corals, from 28 genera and 8 families, were recorded across all sites, giving a mean of 6.92 juveniles ±0.25 SE per m2. Densities of juvenile corals ranged from 0 to 38 per m2 among quadrats, and was extremely variable even among quadrats situated along the same transect. The densities of juvenile corals varied significantly among reefs and sites, but displayed no significant variation among latitudes. Most of the variation (62.6%) occured within sites (Table 1A). Variation among reefs was most pronounced in the southern GBR where mean juvenile density varied 3.9-fold, from 2.8±0.3 ind.m−2 on Heron Island South to 11.08±1.4 ind.m−2 on Heron Island North (Fig. 2A). Juvenile assemblages were dominated by three genera (Acropora, Pocillopora, and Porites) that collectively accounted for 84.1% of all juveniles recorded. Taxonomic composition varied significantly among sectors, reefs and sites (Table 2A), with relative proportions of juvenile Acropora higher at the southern sector (57.4%), Pocillopora corals higher at the central sector (13.7%) and Porites corals higher at the northern sector (30.5%, Fig. 3A).


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)

Relative abundance of Acropora, Pocillopora, Porites and other corals in (A) the juvenile (≤50 mm) and (B) adult assemblages among the three sectors.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0057788-g003: Relative abundance of Acropora, Pocillopora, Porites and other corals in (A) the juvenile (≤50 mm) and (B) adult assemblages among the three sectors.
Mentions: A total of 2,801 juvenile corals, from 28 genera and 8 families, were recorded across all sites, giving a mean of 6.92 juveniles ±0.25 SE per m2. Densities of juvenile corals ranged from 0 to 38 per m2 among quadrats, and was extremely variable even among quadrats situated along the same transect. The densities of juvenile corals varied significantly among reefs and sites, but displayed no significant variation among latitudes. Most of the variation (62.6%) occured within sites (Table 1A). Variation among reefs was most pronounced in the southern GBR where mean juvenile density varied 3.9-fold, from 2.8±0.3 ind.m−2 on Heron Island South to 11.08±1.4 ind.m−2 on Heron Island North (Fig. 2A). Juvenile assemblages were dominated by three genera (Acropora, Pocillopora, and Porites) that collectively accounted for 84.1% of all juveniles recorded. Taxonomic composition varied significantly among sectors, reefs and sites (Table 2A), with relative proportions of juvenile Acropora higher at the southern sector (57.4%), Pocillopora corals higher at the central sector (13.7%) and Porites corals higher at the northern sector (30.5%, Fig. 3A).

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