Evaluating ecosystem-level anthropogenic impacts in a stressed transitional environment: The case of the Seine estuary

Type Article
Date 2016-02
Language English
Author(s) Tecchio Samuele1, Chaalali Aurelie1, 2, Raoux Aurore1, 3, Rius Armonie Tous1, Lequesne Justine4, Girardin Valerie4, Lassalle Geraldine5, Cachera Marie6, Riou Philippe7, Lobry Jeremy5, Dauvin Jean-Claude3, Niquil Nathalie1
Affiliation(s) 1 : Normandie Univ UNICAEN, UMR BOREA MNHN, UPMC, CNRS 7208,IRD 207,CS 14032, Caen, France.
2 : IFREMER, Res Unit Fisheries Ecol & Modelling, F-44311 Nantes 3, France.
3 : Normandie Univ UNICAEN, UMR UCN M2C, UR, CNRS 6143, F-14000 Caen 5, France.
4 : Univ Caen Normandie, Lab Math Nicolas Oresme, UMR 6139, F-14032 Caen, France.
5 : IRSTEA, UR EABX Aquat Ecosyst & Global Changes, F-33612 Cestas, France.
6 : UBO, Lab Sci Environm Mann LEMAR, UMR CNRS 6539, IUEM, F-29280 Plouzane, France.
7 : IFREMER, Environm & Shellfish Resources Lab, F-14520 Port En Bessin, France.
Source Ecological Indicators (1470-160X) (Elsevier Science Bv), 2016-02 , Vol. 61 , P. 833-845
DOI 10.1016/j.ecolind.2015.10.036
WOS© Times Cited 42
Keyword(s) Linear inverse model, Estuarine ecosystem, Seine estuary, English Channel
Abstract During 2002–2005, a new container terminal in the commercial harbour of Le Havre, named “Port2000”, was built on the northern flank of the Seine estuary, northern France. This extension is already known to have modified the estuary current and sediment dynamics, as well as reducing biomass of the suprabenthos assemblage, for the whole downstream part of the system. However, studies on other biotic communities were largely inconclusive, and an ecosystem-wide analysis was still lacking. Here, we performed a before/after study of ecosystem dynamics of the different habitats of the Seine estuary, using a Linear Inverse Modelling technique (LIM-MCMC) to estimate all flows occurring in the food web. Ecological Network Analysis indices were calculated, summarising ecosystem functioning traits and giving indications about the habitat health status. Results showed that the southern flank (FS, Fosse Sud) exhibits all characteristics to be considered as the least stressed habitat of the estuary: system activity and functional specialisation of flows were stable between periods, ecosystem recycling processes and detrital dynamics were also stable; an increase in trophic specialisation (decrease in system omnivory) was the only change confirming a general ecological succession. The northern flank (FN, Fosse Nord), where the actual terminal was built, showed a food web with increased importance of lower trophic levels (increased detritivory and carbon recycling), increased stability and flow efficiency, but possibly regressed to a previous step in ecological succession. In the central navigation channel (CH), patterns of network indices were overall inconclusive and the general image is one of a constantly shifting food web, a condition possibly caused by the year-round dredging activities. The functioning of the Seine estuary – especially of FN and FS – seems to have been modified by the combination of harbour construction and the related mitigation measures. Network indices partially captured this combination of changes and, although not fully operational yet, they are promising tools to comply with the European Union mandate of defining ecosystem health status.
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Tecchio Samuele, Chaalali Aurelie, Raoux Aurore, Rius Armonie Tous, Lequesne Justine, Girardin Valerie, Lassalle Geraldine, Cachera Marie, Riou Philippe, Lobry Jeremy, Dauvin Jean-Claude, Niquil Nathalie (2016). Evaluating ecosystem-level anthropogenic impacts in a stressed transitional environment: The case of the Seine estuary. Ecological Indicators, 61, 833-845. Publisher's official version : https://doi.org/10.1016/j.ecolind.2015.10.036 , Open Access version : https://archimer.ifremer.fr/doc/00288/39916/