Food-web structure in canyon and slope-associated fauna revealed by stable isotopes

Food webs and associated trophic linkages among organisms are central themes in ecology that provide insight into the structure and function of ecosystems. In the deep sea, food webs rely on particulate flux raining from surface waters for energy (Klages et al. 2003), except for chemosynthetic communities, which rely on in situ production via chemosynthesis (Van Dover 2007). In general, the deep sea is a food limited environment because only a small percentage of organic carbon produced in surface waters settles to the seafloor (Gage and Tyler 1991, Klages et al. 2003, De La Rocha and Passow 2007). In contrast, relative to more quiescent slope environments, canyons can experience dynamic flow and turbulence. Internal tides can enhance turbulent mixing near the canyon seafloor leading to resuspension of sediments. Channeling of organic matter in deepsea canyons can enhance benthic productivity leading to high biodiversity (Vetter and Dayton 1998, 1999) and trophic complexity (Stefanescu et al. 1994, Cartes and Sorbe 1999). Thus, there may be a decoupling between the benthic-productivity relationships in canyon environments where food limitation may not be a driving factor influencing community structure. However, there have been only a few studies, often limited in depth range and spatial scale, that have examined the trophic pathways of deepsea canyons relative to adjacent slope environments (Duineveld et al. 2001, Fanelli et al. 2009, Cartes et al. 2010, Jeffreys et al. 2011).