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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.

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Cross-canyon abundance (circle), biomass (square) and species richness (diamond) inshore (a and b), at the canyon head (c and d), on the upper slope (e and f) and on the lower slope (g and h) inside (C) and outside (to west (W) and east (E)) of du Couedic (D) and Bonney (B) Canyons.“Upper and lower slope” are relative terms spanning the range of this study. There were no data for (f) or for DE 1000. Distances between stations are shown in Fig 2. Station codes are as in Fig 2.
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pone.0143921.g006: Cross-canyon abundance (circle), biomass (square) and species richness (diamond) inshore (a and b), at the canyon head (c and d), on the upper slope (e and f) and on the lower slope (g and h) inside (C) and outside (to west (W) and east (E)) of du Couedic (D) and Bonney (B) Canyons.“Upper and lower slope” are relative terms spanning the range of this study. There were no data for (f) or for DE 1000. Distances between stations are shown in Fig 2. Station codes are as in Fig 2.

Mentions: When the samples were compared as cross-canyon transects (Fig 6), different patterns emerged. Inshore, at 100 m, there were more than two orders of magnitude increases in biomass to the east (E) of the central canyon axis (C) and the western transect (W) in both the du Couedic (27.2 to 4343.5 g m-2) and Bonney (13.1 to 2516.0 g m-2) regions (Fig 6a and 6b). A near order of magnitude increase in abundance (437 to 3341 ind m-2) and species richness (31 to 121 species) corresponded with the biomass increase in the du Couedic region but not in the Bonney region, where abundance and species richness instead declined from W to E (3164 to 2000 ind m-2 and 129 to 95 species).


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)

Cross-canyon abundance (circle), biomass (square) and species richness (diamond) inshore (a and b), at the canyon head (c and d), on the upper slope (e and f) and on the lower slope (g and h) inside (C) and outside (to west (W) and east (E)) of du Couedic (D) and Bonney (B) Canyons.“Upper and lower slope” are relative terms spanning the range of this study. There were no data for (f) or for DE 1000. Distances between stations are shown in Fig 2. Station codes are as in Fig 2.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0143921.g006: Cross-canyon abundance (circle), biomass (square) and species richness (diamond) inshore (a and b), at the canyon head (c and d), on the upper slope (e and f) and on the lower slope (g and h) inside (C) and outside (to west (W) and east (E)) of du Couedic (D) and Bonney (B) Canyons.“Upper and lower slope” are relative terms spanning the range of this study. There were no data for (f) or for DE 1000. Distances between stations are shown in Fig 2. Station codes are as in Fig 2.
Mentions: When the samples were compared as cross-canyon transects (Fig 6), different patterns emerged. Inshore, at 100 m, there were more than two orders of magnitude increases in biomass to the east (E) of the central canyon axis (C) and the western transect (W) in both the du Couedic (27.2 to 4343.5 g m-2) and Bonney (13.1 to 2516.0 g m-2) regions (Fig 6a and 6b). A near order of magnitude increase in abundance (437 to 3341 ind m-2) and species richness (31 to 121 species) corresponded with the biomass increase in the du Couedic region but not in the Bonney region, where abundance and species richness instead declined from W to E (3164 to 2000 ind m-2 and 129 to 95 species).

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