«

»

Mass transfer and biogeochemistry of the Gulf of Lion – Meeting for MERITE Action « Fishing Grounds »– June 6th-7th 2016 – Montpellier, France

 

The meeting was divided into three parts: Presentation of the new MerMex organization (MERITE, PEARL, PEACETIME) and assessment of work in MerMex Phase 1 ; General discussion on the expectations and project participation ; Major scientific issues and inclusion in MerMex.

 

“Carbon, nutrients, sediment, contaminant transport and transformation from Rivers to canyon export in the Gulf of Lion”

This sub-topic aims at understanding the transfer and transformation of bio-elements (C, nutrients) and contaminants associated with particulate matter from their input by large and small rivers (Rhone, Heraut, Tet), their transfer through the Gulf of Lion shelf and their export to the deep-sea through Western canyons (Cap de Creus, Lacaze-Duthiers). A particular emphasis will be put on the interaction between marine production, intense events and transfers of carbon, nutrients and contaminants.

 

Organization: C. Estournel, C. Rabouille, Y. Leredde, B. Mostajir
List of participants: I. Pairaud, F. Vidussi, F. Bourrin, R. Verney (video), G. Gregori, C. Estournel, C. Rabouille, Y. Leredde, B. Mostajir
Apologies: P. Conan S. Charmasson D. Lefevre, M. Thyssen

 

  1. Part 1 (Monday mornig, 06/06/2016):


Presentation of the new MerMex organization (MERITE, PEARL, PEACETIME)

Common interfacing points required by MERITE (presented by Ivane Pairaud)

    1. Typology of studied contaminants – choice of biological and abiotic contaminated compartments
    2. Define a consistency in biogeochemical processes approaches studied in common way in different parts of MERITE in temporal or spatial approaches:
  • Interfaces process: water-sediment; air-sea; continent-ocean;
  • Consistency in approach of observations to the particle-plankton interface;
  • Targeted contaminants process;
    1. Characterization in terms of trophic environment, structuring habitats dynamic, life cycle, dissolved / particle / plankton coupling and transfer of target contaminants in food webs;
    2. Contribution to integrated approach of the fate of contaminants in the Gulf of Lions (between urbanized bays and fishing zones);
    3. Integrated modeling of hydrodynamic / ecological; spatial and temporal extent;

Need for convergence between actions of the same sub-project.

 

Assessment of work in MerMex Phase 1 (WP3)

    1. Observation of hydro-sedimentary transfers: Rhone and canyons area (ACCESS, TUCPA and MAtugli campaigns with gliders equipped with turbidity). Satellite measurements are associated with the quantification of suspended particulate matters (SPM).
    2. Biogeochemistry: coastal stations of Gulf of Lion (SOMLIT and HF; Mesurho, Bessete, POEM), observation in the benthic zone in Rhone prodelta
    3. Ecosystem: High Resolution Measures of planktonic abundances by flow cytometry

Summary table of observation periods with observed parameters and observation means (campaign, station, glider…)

 

  1. Part 2 (Monday afternoon, 06/06/2016): General discussion on the expectations and project participation

 

    1. General objectives: interactions between living (bacteria, phyto, zoo) and nonliving (organic and inorganic detrital particles, dissolved matter) organisms, connection between hydro-sedimentary transfers and biogeochemistry, pelagic-benthic coupling, strong interaction between models and observations, intense / quiet periods events
    2. Link with MERITE / Fishing grounds: biotic particles (organisms) and detrital particles = carriers of contaminants, primary production = entry in the trophic chain, base for the resource and its contamination
    3. Clarification on the contributions of each group: observations (fixed stations, mobile platforms and campaign) and modeling

The innovative features key for such a project: the HF platforms, which should ensure homogeneity of the measured parameters, gliders and eventually bios profilers. It was noted a large lack of submissions on the mid-sheld mud belt.

Is it possible to add a mooring taht minimize the risk of loss? This also applies to biogeochemistry, given the coastal nature of SOMLIT. It would also be interesting to follow the middle shelf over a period to be determined.

Adapted elements strategy to scientific context: events on campaigns (to be defined) in addition to HF and gliders monitoring of conventional campaigns.

 

  1. Discussion restricted to the organizers (Tuesday, 07/07/2016)

 

Major scientific issues and inclusion in MerMex


Relations between hydro-sedimentary transfers and various components of the pelagic (and benthic) food web are poorly understood or ignored. However, coastal environments are characterized by resuspension, turbidity or hydro-sedimentary transfer. Such phenomena modify habitats and exert a massive transfer of carbon, biogenic elements and contaminants potentially.

How does biota react to these transfers? Is there a link between the beginning of some blooms and resuspension events? This refers to the connection between living and non-living organisms.

Moreover, the role of intense events is unclear, although their importance is now documented. Resuspension events, floods and transfers by the induced currents during storms will play a major role in the connection between living and nonliving and perhaps in the spatial and temporal structure of pelagic ecosystems.

Also, one could propose to study the issues of relationship between hydro-sedimentary transfer and biogeochemical/food web with the aim of a model coupling circulation model, biogeochemical model and hydro-sedimentary model. This model would be developed for the Golfe du Lion from observations that integrate these disciplines taken from various platforms: fixed with high frequency and low frequency, mobile in targeted ecological periods.

Beyond in-situ observations, laboratory and mesocosm experiments can be conducted to deepen the interactions between living (bacteria, phytoplankton and zooplankton) and non-living particles (detrital organic particles, inorganic sediment and materials dissolved).

It is proposed to work on the joint development of two projects related to Mermex:

  • An ANR project for the general project described above, it would be tabled in 2016 (letter of intent) for a start at the earliest in 2018,
  • An EC2CO project on the intense events study (floods, storms) and their impacts on the biogeochemical cycles across the plateau of Golfe du Lion (coupling between HF station and modeling).

All these studies should be used as basis for further studies in « Fishing Grounds » with the rise of various locks such as the description of the transport of SPM as contaminant vector and the representation by models of planktonic groups and element flow between them.

It would also be interesting to benefit from our approach to the existing approach on understanding the variability of small pelagic fish. We did not go further on a possible synergy between experimental and modeling approaches of the different actions of Fishing grounds. This will be discussed with the Pis of MERITE at a meeting probably in autumn 2016.