Bioavailability of sinking organic matter in the Blanes canyon and the adjacent open slope (NW Mediterranean Sea)

Abstract

Abstract. Submarine canyons are sites of intense energy and material exchange between the shelf and the deep adjacent basins. To test the hypothesis that active submarine canyons represent preferential conduits of available food for the deep-sea benthos, two mooring lines were deployed at 1200 m depth from November 2008 to November 2009 inside the Blanes canyon and on the adjacent open slope (Catalan Margin, NW Mediterranean Sea). We investigated the fluxes, biochemical composition and food quality of sinking organic carbon (OC). OC fluxes in the canyon and the open slope varied among sampling periods, though not consistently in the two sites. In particular, while in the open slope the highest OC fluxes were observed in August 2009, in the canyon the highest OC fluxes occurred in April–May 2009. For almost the entire study period, the OC fluxes in the canyon were significantly higher than those in the open slope, whereas OC contents of sinking particles collected in the open slope were consistently higher than those in the canyon. This result confirms that submarine canyons are effective conveyors of OC to the deep sea. Particles transferred to the deep sea floor through the canyons are predominantly of inorganic origin, significantly higher than that reaching the open slope at a similar water depth. Using multivariate statistical tests, two major clusters of sampling periods were identified: one in the canyon that grouped trap samples collected in December 2008, concurrently with the occurrence of a major storm at the sea surface, and associated with increased fluxes of nutritionally available particles from the upper shelf. Another cluster grouped samples from both the canyon and the open slope collected in March 2009, concurrently with the occurrence of the seasonal phytoplankton bloom at the sea surface, and associated with increased fluxes of total phytopigments. Our results confirm the key ecological role of submarine canyons for the functioning of deep-sea ecosystems, and highlight the importance of canyons in linking episodic storms and primary production occurring at the sea surface to the deep sea floor.

Contrasting particle fluxes and composition in a submarine canyon affected by natural sediment transport events and bottom trawling

“…Sediment transported during storms and DSWC generally have relatively low particulate organic matter content and is composed of aged terrestrial organic carbon (OC) eroded from the continental shelf (Sanchez-Vidal et al, 2008;Tesi et al, 2010;Martıń et al, 2011;Hsu et al, 2014;Sparkes et al, 2015). However, when these events occur in coincidence with phytoplankton blooms, particulate matter enriched with marine OC is transferred into submarine canyons (Fabres et al, 2008;Pasqual et al, 2010;Lopez-Fernandez et al, 2013a).…”

Nematode diversity patterns at different spatial scales in bathyal sediments of the Mediterranean Sea

“…As observed for terrestrial ecosystems (Gaston, 2000), the presence of different habitats (such as canyons, open slopes, landslides, and bathyal and hadal plains) can certainly influence the distributions of deep-sea species (Rex et al, 2006;Vanreusel et al, 2010). Deepsea canyons, for instance, are characterised by high hydrodynamism, as they are "fast-track" corridors for materials and organisms that are rapidly transported from the land to the deep sea (Canals et al, 2006;Tyler et al, 2009;Pusceddu et al, 2010aPusceddu et al, , b, 2013López-Fernández et al, 2013). Some of these systems, such as seamounts, deep-water corals and cold seeps, contain many deep-sea species and have a high level of endemism, which are possibly linked to the peculiar environmental and geomorphological conditions (Raes and Vanreusel, 2006;Roberts et al, 2006;Vanreusel et al, 2009).…”

Deep-sea benthic ecosystem collapse and recovery after an intense Dense Shelf Water Cascading event

“…Deep-sea ecosystems respond rapidly to the seasonal primary productivity pulses leading to the exportation of OM from the upper ocean (Billet et al 2001;Wigham et al, 2003). However, an increasing number of studies now documents atmosphere and climate-driven episodic events, that might favour the transfer of sedimentary OM Figures from the upper part of the continental margin down to the deep margin and basin (Klein et al, 1999;Heussner et al, 2006;Sanchez-Vidal et al, 2008López-Fernández et al, 2012b). The DSWC event in late winter-early spring 2005 is one of the most intensive events ever recorded along the North Catalan margin, which transported huge amounts of material down to the deep-sea margin through the CCC .…”