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Aquatic Living Resources | 2003

Structure of the Gironde estuarine fish assemblages: a comparison of European estuaries perspective

Jérémy Lobry; Laetitia Mourand; Eric Rochard; Pierre Elie

An estuary is an ecotone. It plays various vital roles in the functioning of the different fish species encountered. Each estuary has its own geographical, hydraulic, sedimentological and biological characteristics. These specific features influence the makeup and structure of the fish assemblages and the dynamics of the fish populations. The Gironde estuary is the biggest estuary in France and one of the largest in Europe. It is considered to be relatively unspoilt. The aim of this study is to provide an initial reference document on the specific composition of its fish assemblage. This study establishes a list of the fish species sampled by two different and complementary methods which have been regularly undertaken since 1979. A typology is recognized according to a series of ecological criteria. The relative proportion of fish species that spend all their life cycle in the Gironde estuary is very small. Moreover, the Gironde would appear to be the European estuary with the largest migratory amphihaline fish assemblage. Considering the study made by Elliott and Dewailly (1995), the Gironde estuarine fish population can be compared to those of 17 other European estuaries. The classification we obtained, raised a number of questions on the particularities of estuarine environment, with regard to ecological diagnostics and comparisons. Important points include the need for an inter-calibration of sampling practices, the relevance of taking into account the physical dimension of the environment (tidal range, upstream limit of saline intrusion, etc.), the degree of anthropogenic influence and its evolution.


Marine Pollution Bulletin | 2010

Development of a fish-based index to assess the ecological quality of transitional waters: the case of French estuaries.

C. Delpech; Anne Courrat; Stéphanie Pasquaud; Jérémy Lobry; O. Le Pape; D. Nicolas; Philippe Boët; Michel Girardin; Mario Lepage

The Water Framework Directive requires the assessment of the ecological status of transitional waters considering the fish component. An original methodology, based on a pressure-impact approach, was established to develop a multimetric fish-based index to characterize the ecological quality of French estuaries. An index of contamination, based on the chemical pollution affecting aquatic systems, was used as a proxy of anthropogenic pressure. The fish metric selection was based on their response to disturbances tested via statistical models (generalized linear models) taking into account sampling strategy and estuarine features. Four metrics, for which discriminating responses to level of pressure were demonstrated, were retained to constitute the estuarine multimetric fish index. This new tool appeared particularly relevant to detect the contamination effects on fish communities in estuaries. It could help managers to take decisions in order to maintain or reach the good status required by the Water Framework Directive for 2015.


Hydrobiologia | 2007

Facing the necessity of describing estuarine ecosystems: a review of food web ecology study techniques

Stéphanie Pasquaud; Jérémy Lobry; Pierre Elie

Estuarine areas are sites of human pressures and degradation. In order to maintain and/or restore the quality of estuarine ecosystems, it is necessary to describe their structure and functioning. For that reason, many recent scientific works focus on food webs, which are depicted as being good indicators of the functioning of aquatic ecosystems. Hence it is necessary to question how estuarine food webs can be described. This paper proposes a pragmatic and practical review of the most widely used techniques (stomach/gut content analysis, stable isotope ratios and biochemical markers) with emphasis on their main advantages, drawbacks and bias according to possible ecological goals (ecological quality objectives). These approaches, although quite different, provide complementary information about the trophic relationships in the system, that is to say the sources of organic matter and the description of energy flows between the different compartments of the food web. In trophic models, all these results can be integrated to a global picture of the estuarine trophic structure. This is considered to be an essential step towards the understanding of the functioning of these ecosystems.


Aquatic Living Resources | 2003

La biodiversité spécifique des ressources démersales du plateau continental guinéen : utilisation d'indices classiques pour un diagnostic sur l'évolution de l'écosystème

Jérémy Lobry; Didier Gascuel; François Domain

Fish biodiversity of the Guinean demersal resources. Use of classical indices for a diagnosis on the evolution of the ecosystem. Species diversity is usually regarded as a key factor of ecosystem resiliency facing human impact and especially fishing pressure. This study analyzed the impact of fishing on fish species diversity. We focused on the Guinean coastal demersal resources which have recently undergoes very fast and significant increase in fishing pressure. Within a period of 15 years, the demersal resources evolved from a “virgin status” to a globally overexploited situation. This quick evolution can be regarded as a “model” of the history of an exploitation. The analysis is based on the data of 18 demersal trawling scientific campaigns carried out in the coastal zone between 1985 and 1992. The level of the species diversity was quantified for each campaign and by trawl using different indices: species richness, the Shannon and equitability indices. The indices by trawl were analyzed by ANOVA methods in order to release a temporal evolution of the indicators. The rank/frequencies diagrams of each campaign were also drawn. The Shannon and equitability indices remained appreciably constant, whereas abundance and species richness decreased significantly during the period. The least abundant species, and particularly species from the Sparidae community, tended to disappear from the samples. Lastly, all diversity indices were weak in 1989. This can be related to suitable environmental conditions for the recruitment of some species. Relevance of the indices used is discussed.


PLOS ONE | 2017

Toward a phenological mismatch in estuarine pelagic food web

Xavier Chevillot; Hilaire Drouineau; Patrick Lambert; Laure Carassou; Benoît Sautour; Jérémy Lobry

Alterations of species phenology in response to climate change are now unquestionable. Until now, most studies have reported precocious occurrence of life cycle events as a major phenological response. Desynchronizations of biotic interactions, in particular predator-prey relationships, are however assumed to strongly impact ecosystems’ functioning, as formalized by the Match-Mismatch Hypothesis (MMH). Temporal synchronicity between juvenile fish and zooplankton in estuaries is therefore of essential interest since estuaries are major nursery grounds for many commercial fish species. The Gironde estuary (SW France) has suffered significant alterations over the last three decades, including two Abrupt Ecosystem Shifts (AES), and three contrasted intershift periods. The main objective of this study was to depict modifications in fish and zooplankton phenology among inter-shift periods and discuss the potential effects of the resulting mismatches at a community scale. A flexible Bayesian method was used to estimate and compare yearly patterns of species abundance in the estuary among the three pre-defined periods. Results highlighted (1) an earlier peak of zooplankton production and entrance of fish species in the estuary and (2) a decrease in residence time of both groups in the estuary. Such species-specific phenological changes led to changes in temporal overlap between juvenile fish and their zooplanktonic prey. This situation questions the efficiency and potentially the viability of nursery function of the Gironde estuary, with potential implications for coastal marine fisheries of the Bay of Biscay.


Environmental Science & Technology | 2017

Evidence for the Trophic Transfer of Perfluoroalkylated Substances in a Temperate Macrotidal Estuary

Gabriel Munoz; Hélène Budzinski; Marc Babut; Hilaire Drouineau; Mathilde Lauzent; Karyn Le Menach; Jérémy Lobry; Jonathan Selleslagh; Caroline Simonnet-Laprade; Pierre Labadie

The present survey examines the trophodynamics of a suite of 19 perfluoroalkyl substances (PFASs) in a temperate macrotidal estuary (Gironde, SW France). Across the 147 biota samples (18 taxa) collected, perfluorooctane sulfonate (PFOS), perfluorooctane sulfonamide (FOSA), and C8-C14 perfluoroalkyl carboxylates (PFCAs) were the most-recurrent analytes. ΣPFASs ranged between 0.66-45 ng per g of wet weight of the whole body. Benthic organisms had relatively high ΣPFASs compared to demersal organisms and displayed specific composition profiles with higher relative abundances of C8 and C9 PFCAs. Trophic magnification factors (TMFs) were determined through the use of linear mixed effect models including censored data, thereby considering data below detection limits as well as the interspecific variability of δ15N and PFAS levels (random effects). TMFs were almost consistently >1 in the benthic food web as well as when considering all data pooled together, providing evidence for the biomagnification of several PFASs in estuarine environments. In addition, in contrast with previous observations, TMFs determined in the estuarine benthic web were found to significantly decrease with increasing chain length for C8-C14 PFCAs and C6-C8 perfluoroalkyl sulfonates. This suggests that PFAS chemical structure might not be necessarily predictive of TMFs, which are also influenced by the trophic web characteristics.


Science of The Total Environment | 2018

Beyond classic ecological assessment: The use of functional indices to indicate fish assemblages sensitivity to human disturbance in estuaries

Nils Teichert; Mario Lepage; Jérémy Lobry

Assessing ecological health of aquatic ecosystems is crucial in the current context of biodiversity loss to guide and prioritize management actions. Although several fish-based indices were developed to assess the ecological status of estuarine ecosystems, they do not provide guidance on the causal responses of communities to disturbances. The functional trait-based approach provides an understanding of how human disturbance affects the composition of biological and ecological traits in assemblages, as well as their consequences for ecosystem functioning. Here, we evaluate the responses of fish assemblages to human disturbance in 30 French estuaries using several taxonomic and functional indices (e.g. diversity, evenness or redundancy). We tested whether these indices can provide additional information on the human impacts and health of assemblages that are not reflected by the ecological indicator (fish-based index ELFI). Results indicated that high values of local human disturbances were associated to a decrease in fish abundance, decrease in species richness and reduced functional redundancy, whereas taxonomic and functional evenness increased. In contrast, the functional richness remained stable suggesting that the functional traits of species removed by stressors were maintained by more tolerant species. Indeed, we found that the local disturbances mainly resulted in a decrease in the proportions of small benthic species feeding on macro-invertebrates, which were dominant in the studied estuaries. Some functional alterations were detected by the fish-based index, but the decline of functional redundancy was not reflected, highlighting a serious concern for management. Indeed, the abrupt collapse of functional redundancy in response to local disturbances can decrease the ability of assemblages to maintain certain species traits in the face of future environmental disturbance, including climate change. From a management perspective, the application of such functional redundancy measure in monitoring programs can help stakeholders identify sensitive areas where conservation efforts need to be planned.


Ecosystems | 2018

Global Changes Jeopardize the Trophic Carrying Capacity and Functioning of Estuarine Ecosystems

Xavier Chevillot; Samuele Tecchio; Aurélie Chaalali; Géraldine Lassalle; Jonathan Selleslagh; Gérard Castelnaud; Valérie David; Guy Bachelet; Nathalie Niquil; Benoît Sautour; Jérémy Lobry

Abstract At the interface between terrestrial and marine biomes, estuaries display high ecological productivity and provide goods and services to humans. Associated with many ecological functions, they are nursery, refuge, and growing areas for many species fish. These ecological functions and services depend on both their ecological production and trophic carrying capacity and the durability of food web functioning. These transitional key habitats undergo both strong anthropogenic pressures and climatic influences that impact the structure and dynamics of estuarine biodiversity. In this context, we explore, here, three decades of the Gironde estuary ecosystem history to detect the food web’s response to global changes-induced effect on biodiversity. At least two Ecological Abrupt Shifts associated with deep modifications in the biodiversity at most trophic levels have been documented for this particular ecosystem. Three food web models were thus calibrated, one for each of the three periods discriminated by the two shifts that occurred at the end of the 1980s and the beginning of the 2000s. Results highlighted that the ecotrophic efficiency estimate for subtidal macrofauna and shrimps reached the maximum possible values during the last period. This could mean that the Gironde estuary fully reached its trophic carrying capacity due to a food limitation especially for benthos demersal fish. We also observed a significant decrease in some food web indicators (such as Average Mutual Information, System Omnivory Index, and Average Path Length) usually associated with ecosystem stress, suggesting a significant impact of global change on the Gironde estuary ecosystem health and questioning the sustainability of the ecological functions associated with this ecosystem.


Estuarine Coastal and Shelf Science | 2009

Anthropogenic disturbance on nursery function of estuarine areas for marine species

Anne Courrat; Jérémy Lobry; D. Nicolas; Pascal Laffargue; Rachid Amara; Mario Lepage; Michel Girardin; O. Le Pape


Marine Ecology Progress Series | 2008

Diversity and stability of an estuarine trophic network

Jérémy Lobry; Valérie David; Stéphanie Pasquaud; Mario Lepage; Benoît Sautour; Eric Rochard

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