Sediment water interface is an important transition zone and is classically characterized by a well define oxic horizon with geochemical... » More

Sediment water interface is an important transition zone and is classically characterized by a well define oxic horizon with geochemical gradients. In reality, in coastal sediments, fauna activity and patchy distribution of organic matter introduce another level of complexity and initiate a heterogenic pattern of microzones. Thus the investigation of benthic processes and exchange rates needs to resolve temporal and spatial variations on different scales and requires the use of innovative approaches to investigate benthic ecosystems. In this perspective, a closed-circulation, water jacket-insulated laboratory basins called benthocosms of 1.6 m2 surface area have been used to preserve sediment of the 350-m-deep Laurentian Trough under in situ conditions of salinity and temperature. After a period of equilibration, an experiment of organic matter stress has been carried for 20 days with two approaches: a high intensity disturbance for a short period of time (“pulse”) and a regular and chronic disturbance over a long period (“press”). Benthocosm incubations have been realized before and all along the experiment to measure fluxes of oxygen, nitrate, ammonium, phosphate at sediment water interface. Other parameters like abundance of bacteria, meiofauna, macrofauna are also available and allow to have a global understanding of ecosystem functioning of this environment.

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