4th International Submarine Canyon Symposium (INCISE2018)

5-7 November 2018, Shenzhen, CHINA

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This is the detail of Quantifying the transfer of terrestrial organic matter into two contrasting New Zealand submarine canyon systems using bulk and compound-specific stable isotopes

< Back to List Version: 1012:1017 Status: Approved Edit Time: 2018/9/7 10:19:40

Daniel Leduc
Max Gibbs1, Andrew Swales1, Andrew Kingston1, Scott Nodder1, Ashley Rowden1, Fabio De Leo2, Craig Smith3, Joshu Mountjoy1, Brittany Graham1, Arne Pallentin1
Abstarct Title
Quantifying the transfer of terrestrial organic matter into two contrasting New Zealand submarine canyon systems using bulk and compound-specific stable isotopes
Abstarct Body
The extent to which canyons can facilitate the transfer of land-derived organic matter to the deep sea depends on factors such as canyon geomorphology, their position relative to the coast, and proximity to sediment sources, such as rivers. We used bulk stable isotope and compound-specific isotope analyses to determine the sources of organic matter in sediments of two contrasting canyon systems on either side of the active plate boundary and associated uplifted mountain divide of the South Island off New Zealand: Kaikōura Canyon, a steep canyon close to the shore on the eastern seaboard, and Hokitika Canyon, a narrow and lower gradient canyon further from the coast on the western side of the island. In Kaikōura Canyon, high concentrations of land-derived organic matter were found in areas near the coast and down to 1000 m, but very little land-derived material was found further away from the coast (25 km) and deeper in the canyon, where marine-derived organic matter predominated. The nearshore areas with high input of land-derived organic matter were characterized by high biomass of benthic fauna. In contrast, sediment organic matter in Hokitika Canyon was comprised almost entirely of land-derived material, down to 2000 m and up to 200 km from the coast. Despite this relatively high input of organic matter from nearby rivers, the biomass of benthic fauna was low across the entire canyon, suggesting that land-derived organic material alone may be insufficient to support deep-sea benthic communities. The compound-specific stable isotope results indicate that some local rivers contribute more to canyon sediment organic matter than others, which may be related to river catchment sediment yields, the geomorphology of river mouths, their position relative to the canyon head, and local oceanographic hydrodynamics in the coastal zone and on the continental shelf. The significant differences in the local sources and quantity and quality of organic matter observed in the two contrasting canyon systems mirror the predominant sediment transport processes. The Kaikōura Canyon is driven largely by geologically significant episodes of canyon flushing, probably related to the cycle of large plate boundary earthquakes and local ground-shaking. In contrast, the Hokitika Canyon is more representative of a continually fed sediment system driven by a near-constant supply of material derived from a proximal, rapidly eroding and uplifting mountain range, the Southern Alps.
Session 3: Patterns and heterogeneity in submarine canyons
Presentation Type
Oral Presentation
Stable isotopes, compound-specific stable isotopes, fatty acids, terrestrial organic matter, connectivity, food web

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