Action #2: Impacts of river discharge to coastal ecosystems

Objectives: This Action deals with the quantification and characterization of riverine inputs of particles as well as nutrients and contaminants and estimates their potential impact in the coastal adjacent area (accumulation rates and impact on benthos, partition between deposit and plume). Mediterranean rivers are characterized by short-term but violent flash-flood events. There is a need to augment and coordinate regional river observations of riverine particle load and their coastal impacts and develop scenarios of how riverine inputs and flooding may affect coastal ecosystems and how they should be observed.

Action Lead and other Partners (with contact persons): CNRS (Bourrin), CNR (Cantoni), UPC (del Rio)

JERICO-S3 Platforms included: ILICO gliders, coastal buoy (CNRS), HF radar network (CNR), Corsica Channel mooring with imaging (CNR), Coastal Ocean Observing, Forecasting and Monitoring System (SOCIB), OBSEA Expandable Seafloor Observatory (UPC), PORTUS observing and forecasting system (PdE).

Additional infrastructure: Gliders (SOCIB), HF radars (CNRS, PdE), buoys (CNRS, PdE, SOCIB), tide gauges (PdE), coastal moorings, river stations (CNRS, SAIH Ebro), monitoring by R/V (SOCIB, CNRS).

Other data sources and external partners for implementation: IFREMER (Verney, Pairaud) for land to sea interface particle fluxes and behavior in the coastal area for the Rhône River. Ocean colour data (COPERNICUS) for turbidity in front of rivers. DANUBIUS-RI (Ebro delta, Vicente Gracia Garcia, UPC)

Overall timetable of action: January 2021-August 2022

Description of action: We will focus on 3 sub-actions:
A) We need to increase transnational access to databases for river input data in terms of river discharge, particle and nutrient loads. There are national databases (Spain, France, Italy) and even local databases which need to be gathered and mentioned in the same document.

Timetable: due at the end of 2021.

B) Extreme events such as flash-floods are typical of the Mediterranean climate and can have a strong impact (economic, coastal erosion, and biological impact). There is a need to access high-frequency and high-resolution data through coastal monitoring stations (buoys, gliders) and satellite data, to address those impacts. We propose here to focus on extreme events (i.e. Gloria events of January 2020) which affected the whole NWMED Sea to access the impact of such events in the coastal area. We will gather all available data or papers from this extreme event and analyse the impact on each side of the NW-MED PSS.

Timetable: due in August 2022

C) We propose here to design a suitable research infrastructure and conduct experiments to monitor the impact of extreme events (i.e. flash-flood and storm) on the coastal ecosystem in the Mediterranean environment. Joint monitoring of river inputs (from river quality station), coastal buoys, HF radar and glider will be set in the Ebro ROFI in fall 2021 to address the impact of potential events in the coastal area. A similar experiment was designed in the Rhone ROFI inside the DeltaRhone French project and will focus on the impact of riverine inputs to the delta and prodelta bottom sediments and associated benthic ecosystem.

Timetable: due in August 2022

The definition of common questions should lead to answers based on the local dataset. It should be followed by an enhanced collaboration across river-coastal systems to define commonalities and differences between the systems. This would lead to a better understanding of the main common constraints on these marine systems, and thus a better understanding of the main drivers of their functioning. These actions would require the organisation of an inter-system workshop (or mini-conference with round tables) at the JERICO level for several river-coastal systems (with all PSSs and IRSs having river coastal activities).

Best practices used or developed: The Action will apply best practices defined in DANUBIUS to the JERICO-S3 river system network

Data flows: The Action will check the interoperability of river quality databases. Experimental data (gliders, buoys, river stations, HF radar) will be available to the JERICO-S3 consortium.

Data QC routines: QC routines from regional observatories will be adapted to those employed in DANUBIUS-RI.

Data management issues: Databases are hosted by different national agencies and there is no common database.

Expected results: Gather regional river databases following DANUBIUS-RI best practices and QC routines. Define a research strategy to observe river inputs and their impact in the coastal area at the level of Mediterranean systems (and others). An example experiment following the defined research strategy will be tested in the Ebro delta in fall 2021.

Users of results: National water agencies, marine protected areas

Dissemination of results: Results will be disseminated in the NW-Med PSS meeting and J3 general assembly. Results could also be disseminated inside DANUBIUS-RI meetings.

Links: Link to Po River system in the Adriatic system (WP3), Ebro River in DANUBIUSRI (WP2).