Publication Abstract

Trophodynamic linkage between river runoff and coastal fishery yield elucidated by stable isotope data in the Gulf of Lions (NW Mediterranean).

Trophodynamic linkage between river runoff and coastal fishery yield elucidated by stable isotope data in the Gulf of Lions (NW Mediterranean).

A.M. Darnaude, C. Salen-Picard, N.V.C. Polunin and M.L. Harmelin-Vivien

The link between climate-driven river runoff and sole fishery yields observed in the Gulf of Lions (NW Mediterranean) was analysed using carbon- and nitrogenstable isotopes along the flatfish food webs. Off the RhoneRiver, the main terrestrial (river POM) and marine(seawater POM) sources of carbon differed in δ13C(-26.11‰ and −22.36‰, respectively). Surface sedimentand suspended POM in plume water exhibited low δ13C(-24.38‰ and −24.70‰, respectively) that differed morefrom the seawater POM than from river POM, demonstratingthe dominance of terrestrial material in thosecarbon pools. Benthic invertebrates showed a wide range in δ15N (mean 4.30‰ to 9.77‰) and δ13C (mean−23.81‰ to −18.47‰), suggesting different trophiclevels, diets and organic sources. Among the macroinvertebrates,the surface (mean δ13C −23.71‰) and subsurface(mean δ13C −23.81‰) deposit-feeding polychaetes wereparticularly 13C depleted, indicating that their carbon wasmainly derived from terrestrial material. In flatfish, δ15N(mean 9.42 to 10.93‰) and δ13C (mean −19.95‰ to−17.69‰) varied among species, indicating differences in food source and terrestrial POM use. A significant negative correlation was observed between the percentage by weight of polychaetes in the diet and the δ13C of flatfish white muscle. Solea solea (the main polychaete feeder) had the lowest mean δ13C, Arnoglossus laterna and Buglossidium luteum (crustacean, mollusc and polychaete feeders) had intermediate values, and Solea impar(mollusc feeder) and Citharus linguatula (crustacean and fish feeder) exhibited the highest δ13C. Two different benthic food webs were thus identified off the Rhone River, one based on marine planktonic carbon and the nother on the terrestrial POM carried by the river. Depositfeeding polychaetes were responsible for the main transfer of terrestrial POM to upper trophic levels, linking sole population dynamics to river runoff fluctuations.

Reference:

A.M. Darnaude, C. Salen-Picard, N.V.C. Polunin and M.L. Harmelin-Vivien (2004) Trophodynamic linkage between river runoff and coastal fishery yield elucidated by stable isotope data in the Gulf of Lions (NW Mediterranean). Oecologia, 138: 325-332

A.M. Darnaude*, C. Salen-Picard, N.V.C. Polunin and M.L. Harmelin-Vivien

Oecologia, 138: 325-332