GOPS Action 2014
Keywords CDOM (Chromophotic Dissolved Organic Matter), water colour, MODIS satellite, Laucala Bay lagoon (Suva), New Caledonia lagoon, annual cycle, spectrofluorescence
Geographical area South West Pacific, Fiji Islands, New Caledonia
Project sponsor : Cécile Dupouy (UMR MIO) Scientific Manager, CR1, Mediterranean Institute of Oceanography, (UM110) at Centre IRD Nouméa, 101 Promenade Roger Laroque, BP A5 - 98848 Nouméa Cedex, New Caledonia Tel: (687) 26.07.29.
Scientific objectives
The countries of the South Pacific are highly dependent on their coastal zone for food security and tourism. Traditionally, there have been many conflicts between agriculture and mining. The challenges of maintaining the health (good biogeochemical balance) of coastal and coral environments are crucial.
Chromophoric dissolved organic matter (CDOM) can carry contaminants and nutrient salts that have a major impact on the health of lagoon areas, even at great distances from the coast during heavy rainfall events. The DROPS project aims to :
- an overall assessment of the CDOM's land-lagoon transfers to the world's largest enclosed lagoon in New Caledonia, and to the coastal areas of the Fiji Islands
- Satellite mapping of CDOM plumes and feathers is based on daily MODIS 500 m Aqua/Terra radiance data and made available via a geoportal.
- CDOM spectrofluorescence measurements are used to characterise its components and identify its origin (mangroves, resuspension by seagrass beds, coral, terrigenous inputs linked to agricultural activity, PAH pollutants and anthropogenic tracers).
Satellite maps Fiji Islands
Daily CDOM maps from the American MODIS high-resolution water colour sensor (500 metres) repatriated from NASA were re-calculated using different regional algorithms (turbidity Ouillon et al., 2008, CDOM, Chla Wattelez et al., 2016), geographically re-projected onto the Fiji area and masked for land and clouds (in black) by a VALHYSAT processing chain (Dupouy, 2010; Lefèvre, 2010). The products are available online.
Figure 1 (September 2002) shows the enrichments around the main island of Viti Levu for CDOM visible in the north-west and east of the island. Enrichment in small scattering particles (bbp (m-1)) is highest in the north-west. Chlorophyll enrichment extends further offshore, impacting a larger area around the islands and affecting coral zones over larger surfaces. Turbidity remains very low outside the lagoons, and very localised. To the south-east of Viti Levu, a plume localised near the coast (C) occurs southwards from Laucala Bay and is caused by the Ba River in heavy rain.
Figure 1. MODIS maps of the main island of VIti Levu, showing various indicators of lagoon healthOuillon et al, 2008, Lefèvre. Zoom 9 September 2002, particularly clear of clouds and allowing good distinction of enrichment phenomena around the main islands.
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| CDOM (m-1) | bbp (m-1) | chla (mg.m-3) | Turbidity (g.m-3) |
Laucala Bay Lagoon South Fiji
The distribution of CDOM (acdom350 nm) from the first DROPS survey in June 2015 highlights the presence of an enriched zone near the east coast of the Suva peninsula, as well as high values in the Rewa River estuary (values of acdom(350 nm) m-1 > 1 m-1 in red, values typical of CDOM-rich coastal environments).
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Figure 2: Map of measurement stations and CDOM distribution in Laucala Bay lagoon in June 2015. Station 23 is located on the coast just outside Suva Harbour. MapCamelia cartography, courtesy Pascal Douillet. By: Cécile Dupouy and Chloe Martias.
The distributions of CDOM in June, November 2015 and October 2016 (after heavy rainfall) and of its compounds in fluorescence indicate distributions impacted by - the Rewa River, - Suva Bay waters (PAHs), - corals at bay closure.
Budgets
GOPS 2013 : 13.5 keuros allocated to the DROPS project
(1 A/R France-Nouvelle-Calédonie and 1 A/R Noumea-Fiji PhD student, 2 months fixed-term contract (WIGS company), chemistry analyses (Luminy), LAMA, 1 Hydroscat-6 calibration)
JAXA: loan of radiometers and 1 calibration/year
Scripps Institution of Oceanography (HPLC pigments)
ACI - IRD: 9 keuros
University of the South Pacific: field mission by Chloe Martias, 15-26 June 2015 (Halimeda ship).
Partners
Institut de Recherche pour le Développement (IRD), UMR MIO: Cécile Dupouy (project PI), Madeleine Goutx, Marc Tedetti, Chloe Martias, A.M.U. doctoral student.
Jérôme Lefèvre Research Engineer, (UMR LEGOS), New Caledonia
Guillaume Wattelez, Research engineer, statistics, modelling, information systems, and Touraivane, Senior lecturer, University of New Caledonia (New Caledonia)
Hélène Jacot des Combes, Awnesh Singh, University of the South Pacific PaCE-SD (Fiji)
Martine Rodier, EIO UMR 241 (Tahiti)
Rüdiger Röttgers, Helmholtz-Zentrum Geesthacht (Germany)
Robert Frouin, Scripps Institution of Oceanography (USA)
Hiroshi Murakami, JAXA (Japan Aerospace eXploration Agency) (Japan)
Publications
Wattelez G, Dupouy C, Mangeas M, Lefèvre J, Touraivane, Frouin R (2016) A statistical algorithm for estimating chlorophyll concentration in the New Caledonian lagoon. Remote Sensing, 8, 45 p. doi:10.3390/rs8010045
Oral presentations at conferences
Dupouy, C., Röttgers, R., Tedetti , M., Martias, C., Murakami, H., Doxaran, D., Lantoine, F., Rodier, M., Favareto, L., Kampel, M., Goutx, M., Frouin, R., 2014. Influence of CDOM and Particle Composition on Ocean Color of the Eastern New Caledonia Lagoon during the CALIOPE CruisesProc. of SPIE Vol. 9261, 92610M 2014 SPIE.
Dupouy C., Goutx, M., Tedetti, M., Martias, C., Lefèvre, J., N yeurt, A., Singh, A., Jacot des Combes, H., Touraivane, Wattelez, G., Andreoli, R., Lille, D., 2015. Satellite ocean color of the coastal zones around Pacific Islands. Oral paper (presented by Rémi Andreoli, Bluecham), Pacific GIS-RS Conference, Suva, Fiji, 20 November 2015.
Martias, C., Dupouy C., Tedetti, M., Singh, A., N'Yeurt, A., Lal, S., Douillet, P., Drouzy, M., Wattelez, G., Lefevre, J., 2015b. Dynamic of CDOM in the South Pacific: an application of ocean color remote sensing, Oral communication, Pacific GIS-RS Conference Suva, Fiji, 19 November 2015.
Wattelez, G, Dupouy C., Mangeas, M., Lefèvre, J., Touraivane, Singh, A., N'Yeurt, A., Jacot Des Combes, H., Frouin, R, 2015, GIS for environmental issues in the South Pacific: focus on ocean color, Oral communication, Pacific GIS-RS Conference, Suva, Fiji, 16-20 November 2015.
Posters for conferences
Wattelez, G., Dupouy C. Mangeas, M., Lefèvre, J., Touraivane, T., Frouin, R., 2014. A statistical algorithm for estimating chlorophyll concentration from MODIS data, Ocean Remote Sensing and Monitoring from Spaceedited by Robert J. Frouin, Delu Pan, Hiroshi
Murakami, Young Baek Son, Proc. of SPIE Vol. 9261, 92611S 2014 SPIE CCC code: 0277-786X/14/$18 doi: 10.1117/12.2086297.