Limits...
Macrofaunal Patterns in and around du Couedic and Bonney Submarine Canyons, South Australia.

Conlan KE, Currie DR, Dittmann S, Sorokin SJ, Hendrycks E - PLoS ONE (2015)

Bottom Line: Overall, the canyon interiors were not significantly different in community composition from the exterior (H3).However, both canyons had higher abundance and/or biomass, increased species dominance, different species composition and coarser sediments near the canyon heads compared to outside the canyons at the same depth (500 m), suggestive of heightened currents within the canyons that influence community composition there.The large number of species captured, given the relatively low sampling effort and focus on the larger macrofauna, support previous studies that identify the South Australian coast as a high biodiversity area.

View Article: PubMed Central - PubMed

Affiliation: Canadian Museum of Nature, Ottawa, Ontario, Canada.

ABSTRACT
Two South Australian canyons, one shelf-incising (du Couedic) and one slope-limited (Bonney) were compared for macrofaunal patterns on the shelf and slope that spanned three water masses. It was hypothesized that community structure would (H1) significantly differ by water mass, (H2) show significant regional differences and (H3) differ significantly between interior and exterior of each canyon. Five hundred and thirty-one species of macrofauna ≥ 1 mm were captured at 27 stations situated in depth stratified transects inside and outside the canyons from 100 to 1500 m depth. The macrofauna showed a positive relationship to depth in abundance, biomass, species richness and community composition while taxonomic distinctness and evenness remained high at all depths. Biotic variation on the shelf was best defined by variation in bottom water primary production while sediment characteristics and bottom water oxygen, temperature and nutrients defined biotic variation at greater depth. Community structure differed significantly (p<0.01) among the three water masses (shelf-flowing South Australian current, upper slope Flinders current and lower slope Antarctic Intermediate Water) (H1). Although community differences between the du Couedic and Bonney regions were marginally above significance at p = 0.05 (H2), over half of the species captured were unique to each region. This supports the evidence from fish and megafaunal distributions that the du Couedic and Bonney areas are in different bioregions. Overall, the canyon interiors were not significantly different in community composition from the exterior (H3). However, both canyons had higher abundance and/or biomass, increased species dominance, different species composition and coarser sediments near the canyon heads compared to outside the canyons at the same depth (500 m), suggestive of heightened currents within the canyons that influence community composition there. At 1000-1500 m, the canyon interiors were depauperate, typical of V-shaped canyons elsewhere. The large number of species captured, given the relatively low sampling effort and focus on the larger macrofauna, support previous studies that identify the South Australian coast as a high biodiversity area.

Show MeSH

Related in: MedlinePlus

Rarefaction curves of estimated species richness based on the Chao 1 index for the du Couedic and Bonney regions at each depth interval.The x axis represents the number of individuals randomly subsampled with replacement from within the sample. The y axis is the expected mean number of species using the Chao 1 index.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4664417&req=5

pone.0143921.g003: Rarefaction curves of estimated species richness based on the Chao 1 index for the du Couedic and Bonney regions at each depth interval.The x axis represents the number of individuals randomly subsampled with replacement from within the sample. The y axis is the expected mean number of species using the Chao 1 index.

Mentions: Estimated species richness within each depth interval, based on rarefaction curves of the Chao 1 index, is compared for the du Couedic and Bonney regions, respectively (Fig 3). Comparing D 100–1000 with B 100–1000 at the n = 16 runs for the least species-rich location, mean S Chao 1 was 92.2 ± 30.2 vs 126.4 ± 31.8 at 100 m, 115.5 ± 25.0 vs 77.4 ± 14.4 at 200 m, 70.0 ± 13.9 vs 59.6 ± 13.3 at 500 m and 16.0 ± 0.6 vs 25.0 ± 0.9 at 1000 m for the du Couedic vs Bonney regions, respectively. The D 100 and D 200 m curves overlapped at their asymptote while the others did not. The D 100–500 and B 100–200 curves rose rapidly in mean and SD at the upper ends of the curves while the others did not.


Macrofaunal Patterns in and around du Couedic and Bonney Submarine Canyons, South Australia.

Conlan KE, Currie DR, Dittmann S, Sorokin SJ, Hendrycks E - PLoS ONE (2015)

Rarefaction curves of estimated species richness based on the Chao 1 index for the du Couedic and Bonney regions at each depth interval.The x axis represents the number of individuals randomly subsampled with replacement from within the sample. The y axis is the expected mean number of species using the Chao 1 index.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664417&req=5

pone.0143921.g003: Rarefaction curves of estimated species richness based on the Chao 1 index for the du Couedic and Bonney regions at each depth interval.The x axis represents the number of individuals randomly subsampled with replacement from within the sample. The y axis is the expected mean number of species using the Chao 1 index.
Mentions: Estimated species richness within each depth interval, based on rarefaction curves of the Chao 1 index, is compared for the du Couedic and Bonney regions, respectively (Fig 3). Comparing D 100–1000 with B 100–1000 at the n = 16 runs for the least species-rich location, mean S Chao 1 was 92.2 ± 30.2 vs 126.4 ± 31.8 at 100 m, 115.5 ± 25.0 vs 77.4 ± 14.4 at 200 m, 70.0 ± 13.9 vs 59.6 ± 13.3 at 500 m and 16.0 ± 0.6 vs 25.0 ± 0.9 at 1000 m for the du Couedic vs Bonney regions, respectively. The D 100 and D 200 m curves overlapped at their asymptote while the others did not. The D 100–500 and B 100–200 curves rose rapidly in mean and SD at the upper ends of the curves while the others did not.

Bottom Line: Overall, the canyon interiors were not significantly different in community composition from the exterior (H3).However, both canyons had higher abundance and/or biomass, increased species dominance, different species composition and coarser sediments near the canyon heads compared to outside the canyons at the same depth (500 m), suggestive of heightened currents within the canyons that influence community composition there.The large number of species captured, given the relatively low sampling effort and focus on the larger macrofauna, support previous studies that identify the South Australian coast as a high biodiversity area.

View Article: PubMed Central - PubMed

Affiliation: Canadian Museum of Nature, Ottawa, Ontario, Canada.

ABSTRACT
Two South Australian canyons, one shelf-incising (du Couedic) and one slope-limited (Bonney) were compared for macrofaunal patterns on the shelf and slope that spanned three water masses. It was hypothesized that community structure would (H1) significantly differ by water mass, (H2) show significant regional differences and (H3) differ significantly between interior and exterior of each canyon. Five hundred and thirty-one species of macrofauna ≥ 1 mm were captured at 27 stations situated in depth stratified transects inside and outside the canyons from 100 to 1500 m depth. The macrofauna showed a positive relationship to depth in abundance, biomass, species richness and community composition while taxonomic distinctness and evenness remained high at all depths. Biotic variation on the shelf was best defined by variation in bottom water primary production while sediment characteristics and bottom water oxygen, temperature and nutrients defined biotic variation at greater depth. Community structure differed significantly (p<0.01) among the three water masses (shelf-flowing South Australian current, upper slope Flinders current and lower slope Antarctic Intermediate Water) (H1). Although community differences between the du Couedic and Bonney regions were marginally above significance at p = 0.05 (H2), over half of the species captured were unique to each region. This supports the evidence from fish and megafaunal distributions that the du Couedic and Bonney areas are in different bioregions. Overall, the canyon interiors were not significantly different in community composition from the exterior (H3). However, both canyons had higher abundance and/or biomass, increased species dominance, different species composition and coarser sediments near the canyon heads compared to outside the canyons at the same depth (500 m), suggestive of heightened currents within the canyons that influence community composition there. At 1000-1500 m, the canyon interiors were depauperate, typical of V-shaped canyons elsewhere. The large number of species captured, given the relatively low sampling effort and focus on the larger macrofauna, support previous studies that identify the South Australian coast as a high biodiversity area.

Show MeSH
Related in: MedlinePlus