submarine canyons: how important are they for connecting …€¦ · over 270 submarine canyons are...
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Submarine canyons: how important are they for connecting coastal and deep-sea ecosystems?
Daniel Leduc, Max Gibbs, Joshu Mountjoy, Scott Nodder, Arne Pallentin, Ashley Rowden, Andrew Swales
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Ecosystem connectivity
Well-known connection between catchments, rivers/lakes, and coastal ecosystems
Does this connectivity extend beyond the coast?
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Ecosystem connectivity
Recent evidence* shows accumulation of NZ Pinusradiata pollen in deepest parts of Kermadec and Tonga trenches
(Leduc & Rowden, in press; Ecosystems)
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Ecosystem connectivity
More than 200 million tons of sediment washed out to sea by rivers around NZ every year
Much of the organic material likely decomposed or ingested within coastal areas
However the fate of this material is not always clear
River plume
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Ecosystem connectivity
Over 270 submarine canyons are found along NZ’s continental margin
Presence of submarine canyons may accelerate downslope transport of material to the deep
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Our approach
1. Quantify connectivity between land and deep sea in two canyons
2. Extrapolate findings from two study canyons to other NZ canyons
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1. Quantifying connectivity
Kaikōura Canyonand main catchments
Hokitika Canyonand main catchments
• Comparative approach focusing on two canyons with different productivity levels
• We will compare sediment organic matter levels and abundance of seabed fauna
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1. Quantifying connectivity• Use chemical tracers to
study origins of organic matter in canyon sediments
• We sampled riverine source of land-derived organic matter and offshore sediments
• We will also analyse some of the fauna (food web)
River Canyon
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Offshoremarine
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2. Extrapolating to other canyons
Complete a New Zealand wide quantification of canyons, and produce a canyon classification
Area (km2)
Length (km)
Head depth
(m)
Mouth depth
(m)Sinuosity
Distance from coast
(km)Roughness
Length:Widthratio
Kaikōura 515 61 50 1916 1.52 1.5 8.0 3.3
Hokitika 2725 533 410 3687 1.74 23.7 9.3 31.4
All 270 canyons
Morphometric and biological variables
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2. Extrapolating to other canyons
Kaikōura
Hokitika
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2. Extrapolating to other canyons
Kaikōura
Hokitika
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Consequences of connectivity between land and deep sea
Deep-sea food webs and productivity
Pollutants
Export of carbon
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Ki uta ki tai: mountains to the sea
A holistic approach to environmental management, similar to concepts of EBM
Unprecedented magnitude of change on land means that it may be necessary to extend this concept beyond the coast
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Links to other Dynamic Seas programmes
• Ecosystem connectivity: tracking biochemical fluxes to inform EBM
• Stressor footprints and dynamics
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Thank youThanks to: Sharyn Goldstien (Te Korowai, University of Canterbury), Francois Tumahai (Te Runanga o Ngati Waewae), Kate Neill, Sadie Mills, David Bowden, Phil Barnes (NIWA)
Co-funding: MPI, MBIE
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Kaikōura earthquakeOpportunistic sampling by NIWA shortly after earthquake shows evidence of sediment flows (turbidite) extending 300 km from Kaikōura coast
KaikōuraCanyon
Cook Strait
Kaikōuratownship
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Kaikōura earthquakeComparison of seabed images taken in 2006 and January 2017 from Kaikōura canyon show stark contrast –vast areas buried under fresh sediments transported from shallow part of canyon