seamount ophiuroids: diversity, extent, reliability and patterns
TRANSCRIPT
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Seamount Ophiuroids:diversity, extent, reliability and patterns of distribution and endemism
Dr Tim O’Hara
Senior curator of marine invertebrates
Museum VictoriaAustralia
Brittle star on black coral. J Mallefet
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Outline• Ophiuroids
• Seamount ophiuroid faunas in the SW Pacific
― Community analyses
― Latitude, longitude, depth
• Seamount endemicity
• Seamount species richness
• Impact of mining/dredging
• Future
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Ophiuroids (Brittle-stars)
Conocladus australis (Sth Aust)
Ophiarachna incrassata (coral reefs)
Ophiopsammus assimilis (Sth Aust)
Clarkcoma canaliculata (Sth Aust)
Amphiophiuraconfecta
(Tasman Sea)
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Echinoderms
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Ophiuroids• Reasonable taxonomy
• Diversity/abundance
• Rich enough for statistical approaches
• Not too rich to be impossible to process
• Occur in all benthic habitats
• Various life histories:
viviparous, lecithotrophic, planktotrophic
fissiparous
Astroporpa australensis(NE NZ, NIWA)
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Ophiuroid datasetCombined collection data from:
Australia (AM, MV, QM, NTM, SAM, WAM, TM)NZ (NIWA, NMNZ)Europe (MNHN, BM, ZMA, ZMUC)Historical publications
All habitats (not just seamounts)Ophionereis schayeri(Sth Aust) J Mallefet
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Ophiuroid dataset -Reliability• Most material identified by a single taxonomist
• Historical identifications checked or reliably
illustrated
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Projects
• Ophiuroid bioregionalisation of
Australian deep-sea waters
(National Oceans Office)
• Macro-ecology of ophiuroids in SW Pacific
• Latitudinal patterns from Arctic – Antarctic
• SW Pacific seamounts
Ophiomyxa sp nov(NZ seamounts - NIWA)
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SW Pacific Seamounts
Norfolk
Lord Howe
Tasmantid
Tasmanian
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Results – multivariate analysisSeamount regions
Tas seamounts
Lord Howe Rise
Norfolk Ridge
Tasmantid seam
SW WA
Stress: 0.1
ANOSIM Global statistic: R= 0.579
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Results – Environmental matching• BIO-ENV analysis
Longitude: ρ = 0.419
Latitude: ρ = 0.398
Depth: ρ = 0.366
• Location and depth - importantOphiothrix proteus – Lizard Is, G. Rouse
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Results - latitudeOnly 10-15% of fauna is common to New Caledonia and Tasmania/NZ at depths of 200-2000 m
Temperature - 2000m2.3-2.4°C
Salinity - 2000m34.64-34.68
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Results – latitudinal study200-1500 m
Tropical
S. temperateSouthern Ocean
N. temperate??
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Results - longitude
Richer de Forges et al. (2000). Nature 405
also found significant differences between these regions
Seamount longitude
Lord Howe Rise
Norfolk Ridge
Tasmantid seamou
Stress: 0.1
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Longitudal variation•Sampling artefact?
•Patchiness at biogeographicscales?
•Cryptic species?
Ophiacantha fuscina
Amphiura magellanica
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Results - depthSeamount depth
2000
1000
500
Stress: 0.07
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Results – depth range
0
500
1000
1500
2000
2500
3000
3500
Dept
h Min depthMax depthAvg depth
•Seamount species bathymetric range increases with depth
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Summary: E Indo-W Pacific
• Latitude - biogeographic boundaries• Longitude - patchiness at regional to local scales
• Ecology (especially depth)• History
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Seamount endemics •191 seamount ophiuroids in SW Pacific•23 only recorded from seamounts (12%)•Only 3 described, 12 from a single sample•All but one restricted to one region
No of seamount endemics
0
1
2
3
4
5
6
7
8
9
E NZ LordHowe
Norfolk WestNorfolk
SouthNorfolk
Tasmatid Tasmania
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Seamount endemics • Many seamount species also
found on along continental margins
• Seamount habitats include•Hard & soft substrates•Epifauna & cryptofauna
Solenosmilia
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What is a species?•Current analyses based on morpho-species •Genetic studies of shallow water species
- numerous cryptic species - sympatric, various ages
•Fragmented habitat- seamounts – millions years- epifauna
•Limited dispersal capacity- Viviparity/lecithotrophy- Fissiparity Asteronyx loveni – Japan
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Seamount endemics •Expect endemism to
decrease with depth•Not restricted to shallow water
0
500
1000
1500
2000
2500
3000
Am
phiu
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Asp
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Dep
th (m
)
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Species richnessSpecies richness is higher in
Solenosmila beds on seamounts.
Mean species richness/sample
0
2
4
6
8
10
12
14
16
Two Rocks PerthCanyon
Bald Island Albany AlbanySeamount
Pt Hillier
No
spec
ies
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Summary• Communities change with latitude,
longitude & depth• Seamount fauna in SW Pacific includes
• Many continental species• Some endemics
At all depthsFurther surveys Genetics
• Seamounts often species rich
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Dredging/mining impact•Destruction of slow-growing sessile animals•Removal of habitat•Damage to deeper habitat – rock falls, tailings
Restoration•Limited dispersal capacity
– infrequent dispersal events•Longevity – species and communities•Re-colonisation from local refuge habitats
– habitat corridors on every seamount (>30%)
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Future studies - baseline data• Genetic studies
• what are morpho-species?• choose taxa with care? • bar code of life
• Taxonomic specialists required• para-taxonomists unable to deal with unknown fauna from ‘voyage of discoveries’• need to compare animals, examine types etc• prepare image catalogs