Macrobenthic communities of soft intertidal shores in the Nord – Pas-de-Calais coastline (France) : Structure, relationships with wintering shorebirds and conservation issues

Les zones intertidales meubles sont reconnues comme des écosystèmes d’interface majeurs, procurant un habitat transitoire et/ou permanent pour la reproduction, l’alimentation et la migration de nombreuses espèces. Cependant, dans le contexte d’une anthropisation croissante des zones littorales, ces zones d’interface sont aujourd’hui menacées. Il apparaît donc primordial d’étudier leur biodiversité et leur fonctionnement écologique afin de mettre en place des mesures de gestion et de conservation efficaces. Pour répondre à cette problématique, les relations entre la macrofaune benthique (proies) et les oiseaux limicoles (parmi leurs principaux prédateurs) ont été étudiées à l’échelle du littoral Nord – Pas-de-Calais. Les principales questions de ce travail étaient : (1) Quelles sont les communautés macrobenthiques présentes dans ces zones intertidales ? (2) Quelles sont leurs relations avec les limicoles hivernants dans un cadre spatial ? (3) De potentiels forçages anthropiques affectent-ils ces deux compartiments (i.e. benthique et/ou avifaune) ? Ce travail de thèse a permis de caractériser la diversité, l’abondance, la biomasse et la distribution spatiale des communautés macrobenthiques des sédiments meubles intertidaux selon la classification d’habitats EUNIS et d’étudier les relations (approche fonctionnelle) entre ces communautés et leurs prédateurs principaux, les limicoles, en période hivernale. Des sites d’importance écologique ont pu être mis en évidence et doivent être ciblés en priorité pour la mise en place de mesures de gestion et de conservation à l’échelle régionale.Soft intertidal areas are recognized as major interface ecosystems providing permanent or transitory habitat for reproduction, feeding and migration of many species. However, in the context of increasing human impact on coastal areas, beaches and estuaries are highly threatened. Studying their biodiversity and ecological functioning is therefore required to implement effective management and conservation strategies. As a contribution to achieve this goal, the relationship between benthic macrofauna (preys) and shorebirds (among their most important predators) were studied at the scale of Northern France. The main questions of this study were: (1) What are the macrobenthic communities found in soft intertidal areas (beaches and estuaries)? (2) What are their relationships with wintering shorebirds in a spatial context? (3) Do human forcings potentially affect these two biological compartments (i.e. benthic communities and shorebirds)? This work enabled, in a first step, the characterization of macrozoobenthic communities located in soft intertidal areas (diversity, abundance, biomass and spatial distribution) according to the EUNIS habitat classification. The relationship (functional approach) between these communities and their major predators (shorebirds) in winter has been investigated in a second step. Ecologically important sites have been identified and should be targeted as a priority for the implementation of management and conservation strategies at the regional scale

A Multilevel Core Sampler Device to Directly Estimate Food Supply Accessible to Waders

International audienceTo understand food webs functioning in intertidal soft-sediments, it is critical to assess the macrobenthic prey fraction accessible to waders. Here we describe a simple core sampler device allowing to directly relating the vertical distribu- tion of macrozoobenthos to waders bill length. Bill length measurements were used as a proxy of probing depth to esti- mate the amount of food supply accessible. Several metal plates can be inserted in the core sampler at different heights according to the bill length data of the studied species. These data are provided in a literature survey. For each species, the bill length variability is then explicitly taken into account in the estimation of food accessibility. The core is trans- parent to check for the quality of the sample. It could also be used to estimate a Benthic Habitat Quality index (BHQ) based on characteristics of the vertical structure of the sediment. This multilevel core is easy to build and to adapt to any studied wader species of the intertidal zone, floodplains or other wetlands. The samples are obtained with the same ef-fort as with usual circular cores leading to the possibility to survey large area. With one core sample, the ecological in-formation that can be achieved at once is threefold: 1) benthic community structure (partitioned in several depths), 2) estimate of the accessible food fraction to waders (range of values) and 3) habitat quality index assessmen

Linking macrobenthic communities structure and zonation patterns on sandy shores : Mapping tool toward management and conservation perspectives in Northern France

International audienceIn a context of intensifying anthropogenic pressures on sandy shores, the mapping of benthic habitat appears as an essential first step and a fundamental baseline for marine spatial planning, ecosystem-based management and conservation efforts of soft-sediment intertidal areas. Mapping allows representing intertidal habitats that are basically characterised by abiotic (e.g sediments, exposure to waves…) and biotic factors such as macrobenthic communities. Macrobenthic communities are known to show zonation patterns across sandy beaches and many studies highlighted the existence of three biological zones. We tested this general model of a tripartite biological division of the shore at a geographical scale of policy, conservation and management decisions (i.e. Northern France coastline), using multivariate analyses combined with the Direct Field Observation (DFO) method. From the upper to the lower shores, the majority of the beaches exhibited three macrobenthic communities confirming the existence of the tripartite biological division of the shore. Nevertheless, in some cases, two or four zones were found: (1) two zones when the drying zone located on the upper shore was replaced by littoral rock or engineering constructions and (2) four zones on beaches and estuaries where a muddy-sand community occurred from the drift line to the mid shore. The correspondence between this zonation pattern of macrobenthic communities and the EUNIS habitat classification was investigated and the results were mapped to provide a reference state of intertidal soft-sediment beaches and estuaries. Our results showed evidence of the applicability of this EUNIS typology for the beaches and estuaries at a regional scale (Northern France coastline) with a macroecological approach. In order to fulfil the requirements of the European Directives (WFD and MFSD), this mapping appears as a practical tool for any functional study on these coastal ecosystems, for the monitoring of anthropogenic activities and for the implementation of management plans concerning effective conservation strategies

Contrôle de surveillance benthique de la Directive Cadre sur l’Eau (2000/60/CE). Année 2021. District Artois-Picardie

This report deals with results of monitoring carried out in 2021 for the area concerned by the Artois-Picardie water district.Ce rapport présente les résultats des opérations menées en 2021, sur l’ensemble des masses d’eau côtières et de transition rattachées au district Artois-Picardie

Anthropogenic impact on macrobenthic communities and consequences for shorebirds in Northern France : a complex response

International audienceShorebird populations are declining worldwide due to the combined effect of climate change and anthropogenic forcing, the ongoing coastal urbanisation amplifying the alteration of their habitat in both rate and magnitude. By focusing on a highly anthropogenically-influenced region in Northern France, we studied the impact of a seawall construction on wintering shorebird populations through potential alterations in the abundance and availability of their food resources. We concurrently investigated changes in the spatial distribution of muddy-sand beach macrobenthic communities between two periods of contrasting anthropogenic impacts and examined year-to-year trends of wintering shorebirds. Our study reveals that the seawall construction led to a major spatial reorganisation of the macrobenthic communities with a drastic reduction of the muddy-sand community. However, no relation between macrobenthic changes and shorebird abundances was detected. Fluctuations in shorebird abundances appeared to be congruent with flyway population trends. This result suggests that the response of shorebirds to human-induced perturbations is much more complex than expected. While an assessment of potential disturbances induced by coastal engineering constructions is needed, the pathways by which alterations could propagate through an ecosystem are not linear and as such difficult to determine. Ecosystems appear as complex adaptive systems in which macroscopic dynamics emerge from non-linear interactions at entangled smaller/larger scales. Our results confirm that an in-depth knowledge of the local, regional and global factors that influence trends of shorebirds and their habitat use is essential for accurate and effective management and conservation strategies

Contrôle de surveillance benthique de la Directive Cadre sur l’Eau (2000/60/CE). Année 2020. District Artois-Picardie

This report deals with results of monitoring carried out in 2020 for the area concerned by the Artois-Picardie water district.Ce rapport présente les résultats des opérations menées en 2020, sur l’ensemble des masses d’eau côtières et de transition rattachées au district Artois-Picardie

Quantification of pepsin in rennet using a monoclonal antibody-based inhibition ELISA

6 graph.Pepsin and chymosin are milk-clotting enzymes found in rennets. They differ in their pH and temperature sensitivities and their milk-clotting activity (MCA)/proteolytic activity ratio which impact cheese technology. Therefore, characterization of rennet should not be limited to its total MCA, but also its enzymatic composition. Monoclonal antibodies against pepsin, obtained from mice immunized with purified pepsin, were characterized. A specific inhibition enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of pepsin in rennets. The limit of quantification was 143 ng pepsin/ mL. The precision within runs ranged from 7.0 to 9.4%, for rennets with low and high pepsin concentrations, respectively. The precision among runs also ranged from 8.8 to 11.4%. Satisfying recovery, from 84.7 to 100.3%, was found with spiked samples. The applicability of the developed inhibition ELISA for pepsin quantification was assessed by analyzing commercial rennets, and compared to the standard chromatographic method 110A of International Dairy Federation. The relation and agreement between methods were evaluated using Deming regression analysis and Bland-Altman plot. A good agreement was found with a fixed bias. By means of bias subtraction, inhibition ELISA could be a reliable alternative for rapid and sensitive determination of pepsin in rennet

Development and evaluation of a monoclonal antibody-based inhibition ELISA for the quantification of chymosin in solution

Chymosin is the major enzyme of natural rennet, traditionally used in cheese making for its high milk-clottingactivity. For technical reasons, an accurate characterization of rennet should include its total clotting activity and also its enzymatic composition. Monoclonal antibodies specific to chymosin were obtained from mice immunized with purified bovine chymosin, and an inhibition enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of chymosin in solution. No cross-reactivity was observed with other milk-clotting enzymes commonly used in cheese making. The limit of detection and limit of quantification were 125 and 400 ng/mL, respectively. The values of precision within and among runs were 7.23 and 7.39%, respectively, and satisfying recovery, from 92 to 119%, was found for spiked samples. The inhibition ELISA was successfully applied to commercial rennets, and the results were consistent with those obtained using the standard chromatographic method (IDF 110: A, 1987)