Long-term changes in the composition and diversity of deep-slope megabenthos and trophic webs off Catalonia (western Mediterranean): Are trends related to climatic oscillations?

• Published in: Progress in Oceanography
• Main Authors: Cartes, Joan Enric, Maynou, Francesc, Fanelli, Emanuela, Papiol, Vanesa, Lloris, Domingo
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2009
• Subjects: North Atlantic; North Atlantic oscillation; Zooplankton
• Online Access: http://hdl.handle.net/10261/15206; https://doi.org/10.1016/j.pocean.2009.03.003

15 pages, 9 figures, 4 tables For depths ranging between 650 and 1700 m we have compared recent (2007–2008) to older (from 1988 to 1992) data, searching for long-term changes in the distribution, abundance and composition of deep megafauna (fish and decapods) off the central Catalonian coasts (western Mediterranean). Overall, in the depth interval between 600 and 1100 m, we found higher abundance of fish in 1988–1992 than in 2007, a decrease simultaneous with an increase of decapod crustaceans. Older and more recent haul replicates (after 20 years) had similar assemblage composition in the depth range 1300–1700 m, whereas we found significant changes at 1000 m. Diversity of fish was greater in 1988–1992 than in 2007, while diversity of decapod crustaceans increased between the two periods. Thus, there was a reorganization in benthopelagic communities, rather than a loss of biodiversity. This was in agreement with long-term changes described for diversity of (neritic) zooplankton in the western Mediterranean. We found a dominance of plankton-suprabenthos feeders (e.g. fish such as Lepidion lepidion, Hymenocephalus italicus and Alepocephalus rostratus; the decapods Plesionika spp. and Sergestes arcticus) in 1988–1992. In 2007 by contrast, dominance of plankton-suprabenthos feeders decreased, and assemblages were increasingly composed of benthos-feeding decapods (e.g. Aristeus antennatus, Pontophilus norvegicus and some hermit crabs) preying for instance on polychaetes. These results coincided with low/negative North Atlantic Oscillation index (NAO) in 2007 and in the period immediately before (2004–2006) 2007 (increase of benthos feeders), and with high average NAO in 1988–1992 (decrease of benthos feeders, which in turn may enhance abundance of plankton feeders). The benthic decapod Calocaris macandreae and suprabenthos (small crustaceans, mostly peracarids, living on and just beneath the sediment surface) are key prey in food webs off Catalonian margins, acting as links between surface oceanographic processes ...