Submarine canyons: how important are they for connecting coastal and deep-sea ecosystems? (innovation fund)

Computer image of Kaikoura Canyon

New Zealand’s deep submarine canyons vary in shape, physical characteristics and ecological productivity. To investigate what is behind this difference in productivity, we are using forensic chemistry to track the chemical ‘signatures’ of land- and coastal-derived plant material in the canyon’s sediment and food webs.

Project leader: Daniel Leduc, NIWA

Comparing submarine canyons’ productivity and role in transport of organic materials

New Zealand has large areas of narrow continental shelf punctuated by numerous deep submarine canyons, which vary in shape and physical characteristics. These differences are likely to influence which canyons funnel debris and organic matter into deeper environments – they determine to what extent a canyon connects land and deep seabed ecosystems.

Ecological productivity is a measure of how much biomass (living organisms) an ecosystem can generate. Kaikoura Canyon’s seabed communities have exceptionally high ecological productivity – the canyon is one of the most productive deep sea habitats known – while Hokitika Canyon has low productivity.

To investigate what is behind this difference, which may be partly influenced by organic matter from rivers, we are comparing the amount of land- and coastalderived plant material in the sediment and food webs using forensic chemistry to track the chemical ‘signatures’ of the organic matter. The findings, in combination with a new biologically-focused canyon classification scheme, will be used to assess the regional influence of other canyons on the productivity of New Zealand’s deep seabed communities.

This research will provide valuable insights into the food webs of seabed communities, and so help predict how changes in food supply due to natural or human causes may affect their function. It is also of global interest because it will help clarify the fate of the vast quantities of fine, land-derived organic matter that enters the oceans, but which is not preserved in marine sediments.

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