Title :

Reorganization of a marine trophic network along an inshore-offshore gradient due to stronger pelagic-benthic coupling in coastal areas

Author(s) :

Kopp, Dorothée [Auteur]
Institut Français de Recherche pour l'Exploitation de la Mer [IFREMER]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Lefebvre, Sébastien [Auteur]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Cachera, Marie [Auteur]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Villanueva, Maria Ching [Auteur]
Institut Français de Recherche pour l'Exploitation de la Mer [IFREMER]
Ernande, Bruno [Auteur]
Institut Français de Recherche pour l'Exploitation de la Mer [IFREMER]

Journal title :

Progress in Oceanography

Pages :

157-171

Publisher :

Elsevier

Publication date :

2015

ISSN :

0079-6611

HAL domain(s) :

Planète et Univers [physics]

English abstract : [en]

Recent theoretical considerations have highlighted the importance of the pelagic-benthic coupling in marine food webs. In continental shelf seas, it was hypothesized that the trophic network structure may change along an ...
Show more >Recent theoretical considerations have highlighted the importance of the pelagic-benthic coupling in marine food webs. In continental shelf seas, it was hypothesized that the trophic network structure may change along an inshore-offshore gradient due to weakening of the pelagic-benthic coupling from coastal to offshore areas. We tested this assumption empirically using the eastern English Channel (EEC) as a case study. We sampled organisms from particulate organic matter to predatory fishes and used baseline-corrected carbon and nitrogen stable isotope ratios (δ<SUP>13</SUP>C and δ<SUP>15</SUP>N) to determine their trophic position. First, hierarchical clustering on δ<SUP>13</SUP>C and δ<SUP>15</SUP>N coupled to bootstrapping and estimates of the relative contribution of pelagic and benthic carbon sources to consumers' diet showed that, at mesoscale, the EEC food web forms a continuum of four trophic levels with trophic groups spread across a pelagic and a benthic trophic pathway. Second, based on the same methods, a discrete approach examined changes in the local food web structure across three depth strata in order to investigate the inshore-offshore gradient. It showed stronger pelagic-benthic coupling in shallow coastal areas mostly due to a reorganization of the upper consumers relative to the two trophic pathways, benthic carbon sources being available to pelagic consumers and, reciprocally, pelagic sources becoming accessible to benthic species. Third a continuous approach examined changes in the mean and variance of upper consumers' δ<SUP>13</SUP>C and δ<SUP>15</SUP>N with depth. It detected a significant decrease in δ<SUP>13</SUP>C variance and a significant increase in δ<SUP>15</SUP>N variance as depth increases. A theoretical two-source mixing model showed that an inshore-offshore decrease in the pelagic-benthic coupling was a sufficient condition to produce the δ<SUP>13</SUP>C variance pattern, thus supporting the conclusions of the discrete approach. These results suggest that environmental gradients such as the inshore-offshore one should be accounted for to better understand marine food webs dynamics.Show less >

Language :

Anglais

Peer reviewed article :

Oui

Audience :

Internationale

Popular science :

Non

Collections :

• Laboratoire d'Océanologie et de Géosciences (LOG) - UMR 8187

Source :

Harvested from HAL