GOPS Action 2011
Project sponsor Martine Rodier (IRD - EIO, in collaboration with C. Dupouy (IRD - MIO)
G. Eldin (IRD - LEGOS)
Keywords Coastal environment, Current variability, Lagoon
Context
The MOISE project is part of a medium- and long-term approach to monitoring the coastal environment in New Caledonia. Initiated at the end of 2011, this monitoring is based on the installation of a fixed mooring with automatic physico-chemical, optical and biological measurement systems. This approach makes it possible to address the different scales of temporal variability characteristic of the dynamics and functioning of the lagoon ecosystem, including the daily scale. Since 2012, this high-frequency in situ monitoring has been supplemented by monthly monitoring with discrete measurements and vertical profiles over the entire water column; the parameters measured and the methods used are modelled on those of the SOMLIT network, with a view to MOISE's accreditation as an observation station.
The MOISE point is located on the Basse Caoui reef: 22°14 798 S - 166°18 954 E at the outlet of Dumbéa Bay. This site is representative of the average oligotrophic lagoon, but may reveal sporadic events linked to anthropogenic and/or natural forcing, such as :
- terrigenous inputs during strong meteorological events because it is located opposite the Dumbéa river;
- atmospheric dust of industrial origin, as it is located in the plume of SLN's nickel processing plant;
- the appearance of diazotrophic algal blooms.
The MOISE mooring is an instrumented 'looking up' mooring fixed to an aluminium frame 1.5 m above the seabed and 8 m below the surface. The various multiparameter probes integrated into the MOISE platform provide access to the speed and direction of currents, the thermohaline structure of the water column, the transparency of the environment, the nutrient status and coloured organic matter CDOM (terrigenous inputs), and the phytoplankton biomass with a focus on cyanobacteria.
Results
At Basse Caoui, the MOISE mooring records the key parameters of climate change almost continuously, making it possible to record A) different periods of current variability linked to tidal cycles, wind forcing and other factors, B) changes in temperature and salinity on a daily and seasonal scale, and C) increases in fluorescence and turbidity (Hydroscat-6 backscatter) lasting from a few days to 1 month on average and of variable amplitude. These sporadic events of little-known lagoon enrichment are of crucial importance for understanding the biogeochemical functioning of the lagoon.
Outlook
This station is unique in the French tropics and the South West Pacific for in situ monitoring of climate change parameters and the study of high-frequency variability. In particular, it enables : i) to monitor changes in the environment at a point in the lagoon that is representative of the lagoon ecosystem but potentially subject to different anthropogenic and natural pressures, ii) to study the natural variability of the environment on different time scales (daily to interannual) and to deconvolute the impact of natural and anthropogenic forcings on the environment, iii) to study/quantify the consequences of this variability on the structure and functioning of the lagoon ecosystem, and in particular on the appearance of algal blooms, iv) to validate the images obtained by various MODIS, VIIRS and Sentinel 3 sensors in shallow environments and to monitor variations in the 'colour of the water' in order to adjust the algorithms for calculating chlorophyll and, finally, v) to validate the numerical models (LEFE GMMC ILIAC project, fine-scale models).
The MOISE mooring is an integral part of research programmes to study dissolved organic matter (TREMOLO/EC2CO, PI C. Dupouy, A.M.U. thesis, Chloe Martias), and diazotrophic and potentially toxic algal blooms (TRICHOTOX/Campus France with Israel, PI I. Berman-Frank, C. Dupouy and TricNTox/Labex Corail, PI C. Dupouy, M. Rodier, S. Bonnet). The data will be used to populate databases and will be provided free of charge to the scientific community. The inclusion of the MOISE site in the SOMLIT network, with the introduction of monthly monitoring and the addition of other key CC parameters (pH and O2), as well as the IRD's application for South Observatory accreditation, will guarantee validated methodologies and a degree of sustainability, as well as national and international visibility. Finally, other optical sensors such as UV-PAR and CDOM (developed by the M.I.O. CE team) could be installed, as well as a nutrient salt sensor (developed by LEGOS to replace the current one) and/or other sensors such as pCO2 and pH.
Budgets
GOPS 2011: 10 keuros allocated to the MOISE project (co-funding: 20 keuros JAXA (Japan Aerospace Exploration Agency, Japan) and 9 keuros by ACI - IRD)
GOPS 2012: €4.3m for the MOISE mooring out of the €20m allocated to the VAHINE-GOPS project (PI S. Bonnet)
TRICHOTOX 2012-2013: €2,000 for a Hydroscat-6/AN calibration
Since 2012: IRD - Observatoires Sud: on average €1,000 / year.
Partners
Martine Rodier (UMR MIO then EIO), in charge of the instrumented mooring system
Cécile Dupouy (UMR MIO) co-responsible for instrumented mooring and monthly monitoring
Gérard Eldin (UMR LEGOS), ADCP data processing
Anne Desnues until 2014 (50/50, US LAMA, UMR MIO), assistant engineer
David Varillon (US IMAGO), design engineer
General services at the IRD centre in Nouméa and IRD-US: electronics technicians (IMAGO US), seagoing resources, technical services (garage, welders) and divers (SEOH service).
Publications
Many Gaël, 2011. Mise au point d'un mouillage instrumenté, application au lagon Sud-ouest de Nouvelle-Calédonie Rapport de licence Pro IUT Chimie de Sète, Université de Montpellier, 29 p.
Dumas Mahé, 2012, Application d'un mouillage instrumenté permanent biogéochimique pour le suivi environnemental dans le lagon Sud de Nouvelle-Calédonie, DEUST report, Université du Littoral Côte d'Opale, 48 p.
Morgane Juette, 2012. High-frequency variability at the MOISE instrumented mooring. M2 University report. Bordeaux, 38 p.
Caroline Velay, Jérôme Lefèvre, Jérôme Aucan, and Yvan Mercier, 2015. Validation and transfer to the government of New Caledonia of a decision chain for lagoon drifts. ENSTA report, 70 p.
Conference presentations
Dupouy C, Rodier, M., Biegala, I., Raimbault, P., Douillet, P., 2015. Lagoon and offshore observation stations to measure anthropogenic and climate change in the tropical south-west Pacific, PACENET+ Workshop "Observation systems in the Pacific", 12-13 June Noumea, New Caledonia.
Martias C., Dupouy C., Marie, L., Röttgers, R. Tedetti, M., Rodier, M., Goutx; M., 2015. Source characterization of chromophoric dissolved organic matter in a tropical lagoon subjected to anthropogenic impacts. Poster WOMS 2015, Sopot, Poland.
Rodier M., 2013. Temporal monitoring of biogeochemical parameters by the MOISE instrumented mooring, Noumea, New Caledonia, GOPS final report, 41 p.