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EXPERIMENTAL WORK |
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ACTION CRUISES |
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RESEARCH PLAN & CALENDAR |
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Y1: year 1 ; Y2: year 2 ;Y3: year32 ; Y4: year 4; |
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| SOLA |
Measurements during the year (SOMLIT) + relevant parameters (TCO2, AT) |
Y1 – Y2 – Y3 – Y4
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Punctual
measurements |
– Y2 |
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3D
physical model (OCKE3D, Banyuls Bay) |
Y1 – Y2 – Y3 – Y4 |
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Carbon
chemistry model |
Y1 |
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Stoichiometric model |
Y1 – |
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Coupling
of sub-models |
Y2 – Y3 – Y4 |
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| Calibration
and validation |
Y2 – Y3 – Y4 |
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| DYFAMED |
Measurements
during the year + relevant parameters (TCO2, AT) |
Y1 – Y2 – Y3 – Y4 |
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Punctual
measurements ( PROOF MELISSA) |
Y2 – Y3 |
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1/3D physical model (model Symphonie, MELISSA) |
Y1 – Y2 – Y3 – Y4 |
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Carbon
chemistry model |
Y1 |
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Stoichiometric model |
Y1 – |
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Coupling
of sub-models |
Y2 – Y3 – Y4 |
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Data assimilation |
Y2 – Y3 – Y4 |
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Calibration
and validation |
Y2 – Y3 – Y4 |
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Satellite imagery |
Y1 – Y2 – Y3 – Y4 |
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| CARBON mooring |
Y1 – Y2 – Y3 – Y4 |
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| Gulf
of Lions |
CARBON mooring |
Y1 – Y2 – Y3 – Y4 |
| ACTION cruises |
Regional
cruises off Alger |
Y1 – Y2 – Y3 – Y4 |
| Cruise
in the Mediterranean Sea |
......................... Y4 |
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Modelling |
3D multidisciplinary OPA model:discussion, organisation |
Y1 – |
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3D multidisciplinary OPA model: coupling |
Y2 – Y3 – Y4 |
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3D
multidisciplinary OPA model: exploitation of results |
Y1 – Y2 – Y3 – Y4 |
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Satellite imagery |
Y1 – Y2 – Y3 – Y4 |
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| Data assimilation |
……….. – Y3 – Y4 |
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Valorisation |
Data base |
Y2 – Y3 – Y4 |
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Publications |
…. – Y3 – Y4 |
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| Web site |
Y2 – Y3 – Y4 |
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a. The time-series stations (DYFAMED and SOLA)
Concerning DYFAMED, monthly measurements of numerous hydrological and biogeochemical variables are available for several years at depths between sea surface and 2000 m. The collection of the relevant data will continue at least during the next four years. Additional data (TCO2 and total alkalinity) will be collected at the DYFAMED station through the ACTION project. Punctual experiments at the DYFAMED site will be also realised during the second and the third year (MELISSA project; Mediterranée LimitationS Saisonnières); these measurements will be available to calibrate and validate the foodweb sub-model.
The experimental contribution to the study of carbon cycle at the SOLA station will encompass: (1) the collection of all the existing scientific data regarding the Bay of Banyuls-sur-Mer, (2) the use of the data collected within the framework of the SOMLIT program, (3) the complementation of the SOMLIT data by other relevant parameters over a year cycle, and (4) the completion of punctual experiments integrating a higher number of parameters but over more restricted period of time (i.e., about one month).
Collection
of existing data
All the published data regarding the functioning of the Bay of Banyuls
ecosystem will be gathered, organised in a bibliographic data base,
and, whenever possible, made available (pdf files) on the Internet
site of the Observatoire Océanologique de Banyuls. In addition,
some unpublished (but pertinent relative to the objectives of ACTION)
data sets will also be made available to ACTION partners. This will
for example be the case for the results of the two “high frequency
surveys” recently carried out at the SOLA station within the
framework of the PNEC (ART1). The results of the one year monitoring
survey of size-fractionated phytoplanktonic biomass and production
recently carried out at the SOLA site (Charles and Lantoine unpublished)
will be made available to ACTION partners as well. Such existing data
will be used to test the adequacy of the biological model when no
similar data could be measured during the curse of ACTION. They will
complete the information regarding some of the parameters measured
during ACTION as well.
Use
of data collected within SOMLIT
The SOLA station (42°29’366N, 03°08’625E) is located
within the Bay of Banyuls-sur-Mer. Its depth is 26.3 m. Since 1997,
this site is monitored for some main biogeochemical parameters within
the national program SOMLIT. During the whole duration of the project
(i.e., 2002-2005), the data collected within this framework will be
made available to calibrate and validate the ACTION food-web submodel.
The routinely measured parameters are: total suspended matter (SPM),
particulate organic carbon (POC), particulate organic nitrogen (PON),
nutrients (NH4, NO3, NO2, PO4, SiO4), O2, phytoplanktonic biomass
(total Chl a). These parameters are measured weekly both at 3 and
24 m depths. All the data (T, S, turbidity, fluorescence) corresponding
to the CTD profiles carried out weekly at the SOLA station will also
be made available. This data set will be complemented by meteorological
data collected at: (1) the Cape Béar Meteo France station (wind,
precipitation), and (2) the Observatoire Océanologique de Banyuls
(wind). In addition, the continuous monitoring of wave characteristics
(wave height and direction), which will start during the first semester
of 2002, will provide continuous data for assessing physical constraints
due to the swell.
The parameters routinely measured at SOLA will constitute the main
sources of data for the calibration and the validation of the biological
submodel. It however appears necessary to complement these data to
improve both the calibration and the validation of the submodel. This
will be achieved in two different ways: (1) a complementary limited
set of parameters over a year cycle, and (2) a high frequency survey
over a restricted period of time.
Other complementary parameters over a year cycle
Direct measurements of current speed and direction at the boundary
of the Hydrodynamic model will be carried out. This will be achieved
through specific cruises during which ADCP measurements will be carried
out at selected sites. It seems unrealistic to plan such a sampling
effort during a whole year cycle. We shall thus define “typical”
situations in conjunction both with meteorological (i.e., Cape Béar)
and hydrodynamical (SARHYGOL data base) conditions. One cruise at
least will be carried out for each of these situations. The so-obtained
data will be used to feed the hydrodynamical model.
In the Bay of Banyuls-sur-Mer, the functioning of the ecosystem and thus the main biogeochimal cycle may be influenced by continental inputs mainly transiting by the Baillaury River. This River is intermittent. It typically flows between autumn and early spring and is dry during summer. The flow of this River will be monitored during ACTION. These measurements will be complemented by periodical assessments of nutrients, POC, PON, DOC, DTN, DTP and chloropigments in the River. All carbon and nitrogen measurements will be carried out using autoanalysers (i.e., Perkin Elmer CHN 2400 and Shimadzu TOC-V). DTP will be assessed by a wet oxidation method and PO4 determinations). Chloropigments will be assessed through spectrofluorometry.
Besides its use of a stoechiometric approach (i .e. coupling of several biogeochemical cycles), one of the main characteristics of the foodweb submodel, which will be used during ACTION is the subdivision of the phytoplanktonic compartment into several size classes. This is especially important in the Mediterranean Sea, which is largely oligotrophic and where picophytoplankton dominates phytoplankton during some periods of the year (Lantoine 1995, Jordana et al. 2001). As stated above, only total Chl a is routinely measured within SOMLIT. In order to improve both the calibration and the validation of this part of the model, it thus seems necessary to assess temporal changes in different size classes of phytoplantonic cells. This will be achieved by measuring temporal changes in concentrations of Chl a within the <2µm and the >2µm size fractions. This will be done on a weekly basis both at 3 and 24 m depth using a spectrofluorometric approach. A similar size-fractionation approach will be used both for POC and PON. Besides phytoplanktonic biomass, primary production will also assessed (in situ incubation using 14C bicarbonate) but with a lower sampling periodicity. Bacteria abundance will be assessed using flow cytometry. It will be converted to biomass using appropriate conversion factors. Bacterial production will also be quantified using the 3H thymidine method.
Both the SOLA station and the whole area around Banyuls-sur-Mer, where the hydrodynamical and the food-web model will be coupled, are shallow areas. It has been shown that resuspension events may enhance the transfer of nutrients from the sediment to the water column with major consequences on bacterial production (Grémare et al. submitted for publication). In this sense, it is thus essential to incorporate the sediment in the food-web submodel. This will be achieved through the inclusion of a nutriment flux. This process will be documented through monthly measurements carried out at the SOLA station using the set of benthic chambers available at Banyuls. The effect of major meteorological events will be assessed based on the results of an existing survey carried out during November 1999 within the framework of the PNEC (ART1) (see above).
Major changes in the composition of benthic macrofauna have been recently documented for the whole Gulf of Lions based on initial observations carried out within the bay of Banyuls-sur-Mer (Grémare et al. 1998a and b, Medernach et al. 2000). The most dramatic change is linked to the increase of the serpulid polychaete Ditrupa arietina, which was almost absent during the late 60s (Guille 1971) and now features abundances up to 3000 ind.m-2, which are really exceptional for an oligotrophic Sea such as the North-Western Mediterranean. This species exhibits a strong tusk-shaped calcareous tube, and Medernach et al. (2000) have shown that the building of this tube results in significant calcification rates, which may interfere with the carbon cycle at the SOLA station. The population dynamics of this particular species will thus be monitored at the SOLA site based on biweekly sampling. Calcification rates will then be computed as proposed by Medernach et al. (2000) and incorporated into the food-web submodel.
Punctual
experiment
One of the potential problems of the use of a one year long data set
in validating the coupling between the hydrodynamic and the food-web
submodels relies in the fact that it will be difficult to feed the
hydrodynamic models with measured boundary conditions over such a
long period of time (see above). It has thus been decided to focus
on much shorter period of time during more punctual experiments. This
approach will associate the use of permanent moorings (Wave buoy,
ADCP, sediment traps, CTD) and high frequency sampling survey (CTD
profiles, SPM, POC, PON, Nutrients, DOC, DON, Chloropigments, Primary
production, Bacterial biomass and production, gross sedimentation
rates, benthic fluxes) carried out on board of the RV Nereis II. The
feasibility of this approach has been demonstrated during the two
operations carried out within the Bay during November 1999 and March-April
2001 with the framework of the ART1 of the PNEC. During the present
project, the punctual experiment will be focussed on the spring bloom
period. High frequency sampling will be achieved on a daily basis
with 4 sampled depths.
Through a collaboration
with Dr. F Louanchi (Institut des Sciences de la Mer et Aménagement
du Littoral, ISMAL, Algeria), for the next three years, N. Aït-Ameur
(CEFREM) will participate in several short cruises off the Algerian
coast. She will collect samples for TCO2, and total alkalinity measurements.
ISMAL staff members will measure other parameters such as temperature,
salinity, and nutrient concentrations.
We plan to request shipping time for a month cruise across the Mediterranean
Sea. The cruise track will be similar to (but not exactly the same)
that of the previous September 1999 PROSOPE cruise. It will extend
from about 5°W to 30°W. There will be approximately 10 stations
along the cruise track. Some of these stations will a repeat of the
PROSOPE stations in order to directly compare the CO2 concentrations
and quantify the absorption of atmospheric CO2 integrated over a few
years. Data from this cruise will be used to constrain/validate the
model parameterization.
