JERICO (The European Coastal Ocean Observing System) is a pan-European research infrastructure committed to observing, analyzing, understanding, and forecasting changes in coastal marine systems. It encompasses a wide range of scientific disciplines, including physical oceanography, biogeochemistry, marine biology, and hydrology. Its objective is to provide integrated solutions to address key scientific challenges related to climate change, anthropogenic pressures, extreme events, biodiversity loss and the sustainable management of coastal resources.JERICO’s scientific vision is to create a coherent observation framework to enhance the understanding of coastal ecosystems by combining multidisciplinary data and innovative approaches. Its mission is based on delivering high-quality observations, FAIR (Findable, Accessible, Interoperable, Reusable) data, and access to advanced services and technologies, while strengthening international scientific collaboration.JERICO pushes the boundaries of science by integrating new interdisciplinary dimensions with a multiplatforms approach. This includes fixed and moving platforms with the development of real-time physical, biological and chemical observations (e.g., smart sensors, marine robots), the transition to systems fully compatible with artificial intelligence, and the design of environmentally friendly infrastructures. These advancements enable better monitoring of essential oceanic variables and support the sustainable management of coastal ecosystems within the framework of the European Green Deal.The multidisciplinary impact of JERICO is significant. It builds bridges between marine, terrestrial, and atmospheric disciplines, addressing critical gaps in the European scientific landscape. It bridges coastal and open-ocean data, fostering synergies with existing RIs. To enhance coordination, JERICO established links with several RIs, including DANUBIUS, ICOS, EMBRC, and EMSO. These partnerships strengthen synergies, improve data interoperability, and support joint initiatives addressing coastal and environmental observation challenges.

Three scenarios for the future of the French agro-food system were specified for the territory draining into the Seine Bight, comprising Paris megacity and the Seine watershed. The first scenario assumes the pursuit of the current trend of opening and specialization of agriculture, as well as of concentration of population within the Paris agglomeration. The second scenario assesses the generalization of agro-ecological practices and a healthier human diet. A third, hybrid, scenario was elaborated assuming that agro-ecological practices were implemented in some protected areas (namely Regional Natural Parks and drinking water protection areas, making up about one-third of the total watershed area), while the rest of the territory will follow the trends of the first scenario. We use a unique modelling chain (GRAFS-Riverstrahler-ECOMARS3D) that couples the biogeochemical functioning of the river basin, the estuary and the adjacent bay. It allows exploring the implications of changes in terrestrial activities throughout the aquatic continuum in a consistent way and assessing to what extent changes in population, agricultural practices, food consumption, and sanitation may sustain the current trend of recovery in the Seine River or either increase stress on the system. Results show that only the full agro-ecological scenario would be able to restore good water quality everywhere in the river network, as well as decrease significantly the risks of toxic algal blooms in the coastal zone. Intermediate situations, such as the protection of specific areas, however attractive as a solution, are not enough to offset the impacts of intensive human activities unless the protected areas dedicated to compensating for damage are sufficiently large.

The model ECO-MARS3D, successfully applied thus far to coastal ecosystems, has been extended to encompass the Seine estuary up to Poses, at the limit between the river and the estuary. We used updated bathymetric data and thoroughly calibrated the hydrodynamics and the sedimentary dynamics in the turbidity maximum zone (TMZ). Biogeochemical processes related to oxygen were newly implemented, and freshwater phytoplankton and zooplankton groups were added to the existing marine groups. The simulations allowed us to evaluate the filter effect of the estuary with regard to the main nutrients (N, P, and Si). Today, this filter role appears quite limited and variable depending on the hydrology. On average, considering three different hydrological years, the estuary was able to retain (at least temporarily) 19 kt N yr(-1), 10 kt Si yr(-1), and 0.7 kt P yr(-1), amounting to -13%, -11%, and -27% of the total N, Si, and P inputs, respectively. Seasonal differences in the filtering capacity (lower in winter than in summer) were similar between wet and dry years. Nutrient retention was higher in the upstream fluvial estuary than in the TMZ, the former being mostly characterized by uptake, the latter by remineralization. At the coastal zone, the dry year showed greater risk of eutrophication. Despite lower discharge and lower nutrient fluxes, inputs were confined into a shallower layer, close to the coastline, where nutrients were concentrated and allowed phytoplankton to thrive. Differences in the N : P : Si ratios (lower P-deficit during dry years) could also underpin the larger proliferations, and notably the larger dinoflagellate blooms during dry years.

To understand and predict the physical, chemical, and biological processes at play in coastal and nearshore marine areas requires an integrated, interdisciplinary approach. The case study of the French structuration of coastal ocean and nearshore observing systems provides an original overview on a federative research infrastructure named ILICO. It is a notable example of national structuration and pan-institution efforts to investigate the forefront of knowledge on the processes at work within the critical coastal zone. ILICO comprises, in a pluridisciplinary approach, eight distributed network-systems of observation and data analysis that are accredited and financially supported by French research institutions and the French Ministry for Higher Education, Research, and Innovation. ILICO observation points are implemented along metropolitan and overseas French coasts, where coastline dynamics, sea level evolution, physical and biogeochemical water properties, coastal water dynamics, phytoplankton composition, and health of coral reefs are monitored in order to address a wide range of scientific questions. To give an overview of the diversity and potential of the observations carried out, this paper offers a detailed presentation of three constituting networks: Service Observation en Milieu LITtoral (SOMLIT), with homogeneous sampling strategies, DYNALIT, with heterogeneous sampling strategies adapted to different environments, and Mediterranean Ocean Observing System for the Environment (MOOSE), an integrated, pluri-disciplinary coastal/offshore regional observatory in the north-western Mediterranean Sea. ILICO was conceived using a European framework. It addresses the great challenges of the next decade in terms of sustainability, cost-efficiency, interoperability, and innovation. This paper emphasizes the added-value of federating these systems, and highlights some recommendations for the future.

The continental coastal waters of the Eastern Channel, from Normandy to Hauts-de-France, are subject to the major influence of unbalanced nutrient inputs from inflowing rivers. Several episodes of harmful algal blooms (HABs) compromising fishing and shellfish farming activities have been observed at the coast. For a better understanding of how the land-to-sea aquatic continuum functions, the GRAFS-RIVERSTRAHLER river biogeochemical model was implemented to cover the watersheds of 11 rivers flowing into this area (including the Seine) and chained with the ecological marine ECO-MARS3D model, applied to the French Northern coastal zone. Human activities strongly impact on the functioning of coastal ecosystems. Specifically, for these fertile soils of Northern France, intensive agricultural nitrogen (N) deliveries in excess over silica (Si) and phosphorus (P), essentially of diffuse origin, are potentially responsible for coastal eutrophication. Phosphorous is today equally supplied by diffuse and point sources, after a drastic reduction of inputs from wastewater treatment plants since the 2000s, and is better balanced regarding Si, as shown by the indicators of coastal eutrophication potential (P-ICEP versus N-ICEP). However, despite this drastic P reduction, HABs still appear repeatedly. Exploration of several scenarios of agro-food chain reorganization shows that (i) further progress in urban wastewater treatment to fully comply with current European regulations will not result in a significant reduction of nutrient fluxes to the sea, hence including HABs, and (ii) radical structural changes in agriculture, based on generalization of long and diversified organic crop rotations, reconnection of crop and livestock farming and changes in the human diet have the capacity to significantly reduce nutrient flows, coastal eutrophication and HABs.

Phytoplankton primary production varies considerably with environmental parameters especially in dynamic ecosystems like estuaries. The aim of this study was to investigate short-term primary production along the salinity gradient of a temperate estuary over the course of 1 year. The combination of carbon incorporation and fluorescence methods enabled primary production estimation at short spatial and temporal scales. The electron requirement for carbon fixation was investigated in relation with physical-chemical parameters to accurately estimate primary production at high frequency. These results combined with the variability of the photic layer allowed the annual estimation of primary production along the estuary. Phytoplankton dynamics was closely related to salinity and turbidity gradients, which strongly influenced cells physiology and photoacclimatation. The number of electrons required to fix 1 mol of carbon (C) was ranged between 1.6 and 25 mol electron mol C −1 with a mean annual value of 8 ± 5 mol electron mol C −1 . This optimum value suggests that in nutrient replete conditions like estuaries, alternative electron flows are low, while electrons transfer from photosystem II to carbon fixation is highly efficient. A statistical model was used to improve the estimation of primary production from electron transport rate as a function of significant environmental parameters. Based on this model, daily carbon production in the Seine estuary (France) was estimated by considering light and photic zone variability. A mean annual daily primary production of 0.12 ± 0.18 g C m −2 day −1 with a maximum of 1.18 g C m −2 day −1 in summer was estimated which lead to an annual mean of 64.75 g C m −2 year −1 . This approach should be applied more frequently in dynamic ecosystems such as estuaries or coastal waters to accurately estimate primary production in those valuable ecosystems.

The population dynamics of different Pseudo-nitzschia species, along with particulate domoic acid (pDA) concentrations, were studied from May 2012 to December 2013 in the Bay of Seine (English Channel, Normandy). While Pseudo-nitzschia spp. blooms occurred during the two years of study, Pseudo-nitzschia species diversity and particulate domoic acid concentrations varied greatly. In 2012, three different species were identified during the spring bloom (P. australis, P. pungens and P. fraudulenta) with high pDA concentrations (∼1400 ng l−1) resulting in shellfish harvesting closures. In contrast, the 2013 spring was characterised by a P. delicatissima bloom without any toxic event. Above all, the results show that high pDA concentrations coincided with the presence of P. australis and with potential silicate limitation (Si:N < 1), while nitrate concentrations were still replete. The contrasting environmental conditions between 2012 and 2013 highlight different environmental controls that might favour the development of either P. delicatissima or P. australis. This study points to the key role of Pseudo-nitzschia diversity and cellular toxicity in the control of particulate domoic acid variations and highlights the fact that diversity and toxicity are influenced by nutrients, especially nutrient ratios.

Eutrophication of the Seine estuary and the Bay of Seine is a crucial environmental issue for the management of ecosystems and economic activities related to fisheries and tourism in the region. A large quantity of nutrients, especially nitrogen, is brought to the coastal zone by the Seine River, the main input into that area, but also by smaller rivers along the Normandy coast. This large delivery of nitrogen leads to an imbalance between nitrogen (N), phosphorus (P) and silica (Si), which affects the growth of planktonic organisms and can exacerbate the occurrence of harmful algal blooms (HABs). These events can be damaging for shellfish fisheries, an important economic resource for the region. The study describes a new modelling chain coupling a riverine and a marine model (the Seneque/Riverstrahler and the ECO-MARS3D, respectively), which allows us to explore the effects on the coast of 2 scenarios of watershed management. The first one, focused on an upgrade of wastewater treatment plants, decreases the P fluxes by 5 to 35 kg P km(-2) yr(-1) on average over the 2000 to 2006 period, depending on the watershed, and would reduce about 3-fold the concentration of dinoflagellates in the adjacent coastal zone. The second one explores a hypothetical scenario of generalisation of organic farming in all agricultural areas of the basin. Although this is not realistic, it shows the best theoretical results we can achieve. With this scenario, the N fluxes decrease by almost 50%, and the dinoflagellate blooms and thus possibly the Dinophysis spp. blooms are drastically reduced by a factor of 20 to 40. Nevertheless, diatoms, which are the main primary producers in the bay and sustain the marine food web, are not significantly affected by this drastic scenario.

The Seine River is a highly artificialised catchment in Europe, comprising both productive agricultural areas and intense industrial and commercial activity. Due to its strategic importance, monitoring programs in the river started as early as the 1970s. The present study compiles and analyses this valuable data set (1970-2014), thoroughly describing the riverine section downstream of Paris and the estuary. We identify long-term trends and shifting patterns in nutrients and oxygen, and pay special attention to the river's evolution after the year 2000, when the European Water Framework Directive came into force. The study has a manifest management perspective, and the results are discussed on the basis of the environmental quality standards proposed in current environmental regulations. The data show that water quality has improved remarkably over the past two decades, with sharp reductions of ammonium and phosphate and a progressive increase of dissolved oxygen levels. The amelioration is prominent in the estuary, where summer anoxic episodes have nearly disappeared. As a result, these three parameters are nowadays in good or very good condition throughout the year. The successful abatement of point sources contrasts, however, with the low effectiveness of the measures provided for the control of nutrients from diffuse sources. Nitrate concentration has increased by 150% since the early 1980s, and only very recently has the upward trend been reversed. Bold agri-environmental management measures are required if we are to prevent chronic pollution problems and truly restore the good ecological status of rivers. (C) 2016 Elsevier Ltd. All rights reserved.

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. (c) 2015 Elsevier Ltd. All rights reserved.

The dynamics of the phytoplankton assemblage, the physical, chemical and biological parameters, and primary productivity and production were monitored in the central English Channel along a transect between Ouistreham and Portsmouth from January to December 2010. The spatial patterns of the phytoplankton assemblage were controlled by the hydrological characteristics of the water masses, and the annual structure of the phytoplankton assemblage was characteristic of the central English Channel and was controlled by seasonality. The spring bloom was dominated by a single species, Chaetoceros socialis, and associated with low microphytoplankton evenness and Shannon-Wiener indices, whereas the evenness index was high from late spring to winter and associated with the proliferation of pico- and nanophytoplankton cells. We identified 2 species responsible for harmful algal blooms, Phaeocystis globosa, which dominated the community in the northern part of the Seine Bay in May, and Lepidodinium chlorophorum, which dominated the community near the French coast in September. We examined the relationship between microphytoplankton diversity and maximum primary production and productivity. We found a negative parabolic relationship between the diversity indices (evenness and Shannon-Wiener) and maximum primary production, and a positive parabolic relationship between the number of taxa (richness) and maximum primary production. However, we found no relationship between maximum productivity and the evenness or richness indices. High levels of productivity were measured during the increasing abundance of pico and nanophytoplankton cells, highlighting the importance of taking the dominant functional group into account, rather than the degree of diversity, when explaining the level of productivity.

Hydrological and photosynthetic parameters were investigated monthly from November 2009 to December 2010 using an opportunity ship, along a transect in the central part of the English Channel. A powerful statistical method, a Partial Triadic Analysis (PTA), was applied on the physicochemical data set and highlighted the functioning of four different ecosystems: (i) the French coast area (FRcoast) subjected to large freshwater inputs, (ii) the North of the Seine Bay (NSBay) influenced by nutrient inputs from the river Seine and offshore, (iii) the centre of the English Channel (CentreEC) characterized by nutrient offshore inputs and (iv) the English coast area (UKcoast) which exhibits low nutrient concentrations despite the proximity of the English coast. In the FRcoast and the NSBay the phytoplankton biomass peaked from mid-January to June. In contrast, in the UKcoast the phytoplankton biomass peak occurred from mid-November to March. In addition, we noticed that these coastal ecosystems showed two types of photosynthetic regulations. Photoacclimation mechanisms were observed in the FRcoast and the NSBay and a control of the photosynthetic parameters by nutrients in the UKcoast. This study highlights the importance of a “top down” control in winter/spring and underlines a complex situation in autumn with an uncoupling between rETRmax and the Chlorophyll a biomass. In order to understand this uncoupling it is necessary to estimate the loss due to zooplankton grazing and viral lysis as well as carbon excretion.

We provide data on nutrient export for 28 rivers in southwestern Europe and analyze long-term changes in the context of anthropogenic pressures and regulation policies. Special attention is given to seasonal variations, because the integrated annual values that are usually provided do not allow us to establish comparisons with seasonal phytoplankton dynamics. The eutrophication risk associated with river inputs is addressed by means of an indicator (Index of Coastal Eutrophication Potential, ICEP, Billen and Garnier, Mar Chem 106:148–160, 2007). An overview of the temporal evolution and the intra-annual variability of the ICEP is discussed for specific rivers and integrated coastal regions. The annual dynamics of the eutrophication indicator is analyzed to delimit those periods when the risk of eutrophication is particularly high. The trends in nutrient fluxes and coastal phytoplankton are compared by means of a case study (Seine Bay). The decrease in phosphorus matches a general decrease in phytoplankton biomass in the summer. However, sustained high values of nitrogen still foster the emergence of harmful algal blooms, and we found an increase in the summer abundance of dinoflagellates. The abatement of phosphorus alone is not enough to shortcut harmful blooms and toxic outbreaks in the Seine Bay. A reduction in nitrogen inputs may be necessary to effectively minimize eutrophication problems.