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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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Distribution of abundance (a and d), biomass (b and e) and species richness (c and f) among the major taxa, shown as pie charts for each station in Fig 2. Upper panel: du Couedic region; lower panel: Bonney region.Major taxa and their colour codes are, annelids (red); arthropods (yellow); echinoderms (green); molluscs (turquoise); colonial organisms (mainly sponges) (navy); other solitary organisms (e.g., an enteropneust at BW 1500 and a nemertean at BW 1500) (purple).
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pone.0143921.g005: Distribution of abundance (a and d), biomass (b and e) and species richness (c and f) among the major taxa, shown as pie charts for each station in Fig 2. Upper panel: du Couedic region; lower panel: Bonney region.Major taxa and their colour codes are, annelids (red); arthropods (yellow); echinoderms (green); molluscs (turquoise); colonial organisms (mainly sponges) (navy); other solitary organisms (e.g., an enteropneust at BW 1500 and a nemertean at BW 1500) (purple).

Mentions: Among the six major taxa, annelids and arthropods accounted for the largest proportion of abundance on the shelf (up to 94.5% at 100–200 m) while on the slope (500–1500 m), the arthropods (primarily peracarids) declined in proportion, leaving the annelids (primarily polychaetes with some oligochaetes) as the sole abundance dominants (up to 84.9%) at most stations (Fig 5a and 5d). The only case where another taxon was the dominant was when abundance was very low, giving a few species a large proportion of the abundance (e.g. a calcareous sponge at DC1500 and a nemertean at BE1500).


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)

Distribution of abundance (a and d), biomass (b and e) and species richness (c and f) among the major taxa, shown as pie charts for each station in Fig 2. Upper panel: du Couedic region; lower panel: Bonney region.Major taxa and their colour codes are, annelids (red); arthropods (yellow); echinoderms (green); molluscs (turquoise); colonial organisms (mainly sponges) (navy); other solitary organisms (e.g., an enteropneust at BW 1500 and a nemertean at BW 1500) (purple).
© Copyright Policy
Related In: Results  -  Collection

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

pone.0143921.g005: Distribution of abundance (a and d), biomass (b and e) and species richness (c and f) among the major taxa, shown as pie charts for each station in Fig 2. Upper panel: du Couedic region; lower panel: Bonney region.Major taxa and their colour codes are, annelids (red); arthropods (yellow); echinoderms (green); molluscs (turquoise); colonial organisms (mainly sponges) (navy); other solitary organisms (e.g., an enteropneust at BW 1500 and a nemertean at BW 1500) (purple).
Mentions: Among the six major taxa, annelids and arthropods accounted for the largest proportion of abundance on the shelf (up to 94.5% at 100–200 m) while on the slope (500–1500 m), the arthropods (primarily peracarids) declined in proportion, leaving the annelids (primarily polychaetes with some oligochaetes) as the sole abundance dominants (up to 84.9%) at most stations (Fig 5a and 5d). The only case where another taxon was the dominant was when abundance was very low, giving a few species a large proportion of the abundance (e.g. a calcareous sponge at DC1500 and a nemertean at BE1500).

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