Food web structure and seasonality of slope megafauna in the NW Mediterranean elucidated by stable isotopes: Relationship with available food sources

摘要: Abstract The food-web structure and seasonality of the dominant taxa benthopelagic megafauna (fishes decapods) on middle slope Catalan Sea (Balearic Basin, NW Mediterranean) were investigated using carbon nitrogen stable isotope ratios 29 species. Macrofauna (infauna, suprabenthos zooplankton) also analysed as potential prey. Samples collected a seasonal basis from 600 to 1000 m depth between February 2007 2008. fishes decapods classified into feeding groups based literature: benthic feeders (including suprabenthos) zooplankton feeders, latter further separated migratory non-migratory Decapods exhibited depleted δ 15 N enriched 13 C compared fishes. Annual mean ranged − 19.15‰ ( Arctozenus risso ) − 16.65‰ Phycis blennoides 7.27‰ Lampanyctus crocodilus 11.31‰ Nezumia aequalis ). values − 18.94‰ Sergestes arcticus − 14.78‰ Pontophilus norvegicus ), 6.36‰ Sergia robusta 9.72‰ Paromola cuvieri Stable isotopes distinguished well amongst 3 guilds established priori , pointing high levels resource partitioning in deep-sea communities. trophic community was function position predators along benthic–pelagic gradient, with isotopically relative pelagic feeders. This difference allowed identification two food webs versus consumption. Prey predator sizes important structuring community. most generalised pattern depletion winter spring summer, especially macroplankton suggests greater consumption prey, likely related increases production or ontogenic migrations organisms mid-water Benthic Boundary Layer (BBL). enrichment detected periods water column stratification, particularly feeder Megafauna relied single source nutrition after peaks surface production, presumably marine snow. Conversely, larger array sources, probably advection, sustained stratification. both positively correlated fluorescence measured 5 m above seabed negatively total organic sediments, being sources for deposit macroinfauna. Macroplankton linked environmental variables vertical transport i.e. lipids chlorophyll their degradation products, due stronger reliance sinking phytodetritus through planktonic