4th International Submarine Canyon Symposium (INCISE2018)
5-7 November 2018, Shenzhen, CHINA
This is the detail of The unknown role of Whittard Canyon: Pathway or sink for organic carbon?
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Sofia Ledin, Sabine Haalboom, Marc Lavaleye, Henko de Stigter, Hans van Haren, Gerard Duineveld
The unknown role of Whittard Canyon: Pathway or sink for organic carbon?
Submarine canyons provide effective connections between the productive shelf waters and the nutrient poor deep-sea, providing important lateral transport pathways for (organic) matter. During two cruises with the RV Pelagia in 2017/2018 these pathways were studied in the easternmost branch of the Whittard Canyon complex to determine which processes affect organic matter dispersal, remineralization and retention following a multidisciplinary approach. CTD transects were carried out to determine the presence of nepheloid layers in the canyon, while landers and moorings were deployed to study particle transport processes through time (days-year). Sediment samples were collected along the canyon axis and on the adjacent slopes to determine organic matter and sedimentation rates, while in situ and ex situ respiration experiments gave a first insight into remineralization processes. CTD transects showed the presence of nepheloid layers between 1200 and 2500 m water depth. Backscatter data collected with landers showed that the resuspension of material is related to internal waves that interact with the canyon topography. Over the year many large particle resuspension events were observed, which lasted from several days up to several weeks. Some events were linked to major storms, like Ophelia, while others are still to be identified. Particle transport during these events is mainly focused along the canyon axis. Clear differences in sediment composition and sedimentation rate were observed between the canyon and slope sediments and with depth. The head of the canyon is characterized by erosional processes and low organic matter contents, as are the slopes of the canyon. A depo center was found at around 2000 m water depth, showing high organic matter values and the presence of turbidites. The deepest part of the canyon is dominated by marine derived material, containing high, but aged organic matter. In situ respiration measurements showed a clear relation to the amount and freshness of organic matter. Highest rates were found near the depocenter, while lower rates were observed in the head of the canyon.
Session 3: Patterns and heterogeneity in submarine canyons