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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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Unconstrained non-metric multidimensional scaling plot of station dissimilarities based on community composition.DC 1500 is not shown because its dissimilarity to other stations was so high that it prevented resolution of the relationships of the other stations. Station codes are as in Fig 2.
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pone.0143921.g007: Unconstrained non-metric multidimensional scaling plot of station dissimilarities based on community composition.DC 1500 is not shown because its dissimilarity to other stations was so high that it prevented resolution of the relationships of the other stations. Station codes are as in Fig 2.

Mentions: Community composition changed significantly with water mass (p = 0.001 and 0.003) when the canyon interiors were defined by the “central canyon axis” and “topographically distinct interior”, respectively (H1) (Table 4). The regions were close to being significantly different (p = 0.06 and 0.07, respectively) (H2). There was no significant difference between the interior and exterior of the canyons by either definition of canyon interior (H3). Interactions were not significant. The change in community composition with depth (and therefore water mass since the three water masses stratify by depth) is evident in the unconstrained multidimensional scaling (MDS) ordination (Fig 7). Shallower (100–500 m) stations grouped more tightly than the deep (1000–1500 m stations). There was high resemblance between the station at the head of du Couedic Canyon (DC 200) and the stations at the same depth to west and east (DW 200 and DE 200). At 500 and 1000 m, though, community composition in the centre of du Couedic Canyon was quite different from outside. Community composition at the head of Bonney Canyon (BC 500) was not as distinctive relative to the canyon exterior (BW 500 and BE 500) as at du Couedic Canyon. There was not a consistent distinction of du Couedic from Bonney samples (H2) although some same-region samples showed close similarity within the same depth (e.g., du Couedic samples at 200 m). Similarly, samples from the interior (H3) (DC and BC) of the canyons did not separate from exterior samples (DW, DE, BW and BE).


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)

Unconstrained non-metric multidimensional scaling plot of station dissimilarities based on community composition.DC 1500 is not shown because its dissimilarity to other stations was so high that it prevented resolution of the relationships of the other stations. 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.g007: Unconstrained non-metric multidimensional scaling plot of station dissimilarities based on community composition.DC 1500 is not shown because its dissimilarity to other stations was so high that it prevented resolution of the relationships of the other stations. Station codes are as in Fig 2.
Mentions: Community composition changed significantly with water mass (p = 0.001 and 0.003) when the canyon interiors were defined by the “central canyon axis” and “topographically distinct interior”, respectively (H1) (Table 4). The regions were close to being significantly different (p = 0.06 and 0.07, respectively) (H2). There was no significant difference between the interior and exterior of the canyons by either definition of canyon interior (H3). Interactions were not significant. The change in community composition with depth (and therefore water mass since the three water masses stratify by depth) is evident in the unconstrained multidimensional scaling (MDS) ordination (Fig 7). Shallower (100–500 m) stations grouped more tightly than the deep (1000–1500 m stations). There was high resemblance between the station at the head of du Couedic Canyon (DC 200) and the stations at the same depth to west and east (DW 200 and DE 200). At 500 and 1000 m, though, community composition in the centre of du Couedic Canyon was quite different from outside. Community composition at the head of Bonney Canyon (BC 500) was not as distinctive relative to the canyon exterior (BW 500 and BE 500) as at du Couedic Canyon. There was not a consistent distinction of du Couedic from Bonney samples (H2) although some same-region samples showed close similarity within the same depth (e.g., du Couedic samples at 200 m). Similarly, samples from the interior (H3) (DC and BC) of the canyons did not separate from exterior samples (DW, DE, BW and BE).

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