A Review of Ocean Color Algorithms to Detect Trichodesmium Oceanic Blooms and Quantify Chlorophyll Concentration in Shallow Coral Lagoons of South Pacific Archipelagos

Cécile Dupouy (1, 2, 3) , Andra Whiteside (1, 2) , Jing Tan (4) , Guillaume Wattelez (5, 6) , Hiroshi Murakami (7) , Rémi Andréoli (8) , Jérôme Lefèvre (9, 10) , Rüdiger Röttgers (11) , Awnesh Singh (2) , Robert Frouin

1 MIO - Institut méditerranéen d'océanologie
2 PACE-SD
3 IRD [Polynésie] - Institut de Recherche pour le Développement
4 SIO - UC San Diego - Scripps Institution of Oceanography
5 UNC - Université de la Nouvelle-Calédonie
6 LIRE - Laboratoire Interdisciplinaire de recherches en éducation
7 JAXA - Japan Aerospace Exploration Agency [Tsukuba]
8 Bluecham SAS [Nouméa]
9 ENTROPIE [Réunion] - Ecologie marine tropicale dans les Océans Pacifique et Indien
10 IRD - Institut de Recherche pour le Développement
11 Centre for Materials and Coastal Research [Geesthacht]

The oceanic waters of the Southwest Tropical Pacific occupy a vast region including multiple Pacific Island Countries. The state of these waters is determinant for fisheries and the blue economy. Ocean color remote sensing is the main tool to survey the variability and long-term evolution of these large areas that are important for economic development but are affected by climate change. Unlike vast oligotrophic gyres, tropical waters are characterized by numerous archipelagos and islands, with deep and shallow lagoons subjected to the large impacts of the land. Strikingly large dendritic phytoplankton (Trichodesmium) blooms with high levels of chlorophyll, developing within archipelagos, as well as coastal enrichments from various origins may be observed. Algorithms to detect the presence of Trichodesmium have been developed or adapted, as well as algorithms to estimate the chlorophyll concentration ([Chl-a)]. Adapting existing [Chl-a] algorithms does not always yield high, i.e., sufficient, accuracy. A review of published regional bio-optical algorithms developed taking into account the specific phytoplankton composition and minimizing the adverse impacts of particles and the seabed bottom on [Chl-a] determination is presented, as well the bio-optical database that allowed their development. The interest of such algorithms for a variety of applications and scientific accomplishments is highlighted, with a view to further addressing the main biology and biogeochemistry questions, e.g., to determine the true impact of diazotrophs and assess lagoon [Chl-a] variability with the highest confidence. This work anticipates the use of future coarse and high-spatial-resolution and multi- and hyper-spectral satellite imagery in the Pacific.

Mots clés: chlorophyll-a concentration; ocean color; Trichodesmium blooms; bathymetry; water column attenuation correction; MODIS; MERIS; Sentinel 2; remote sensing; reflectance; algorithms; inversion method; seabed mapping; clustering; support vector machine; New Caledonia; Fiji Islands; Southwestern Tropical Pacific; chlorophyll-a concentration ocean color Trichodesmium blooms bathymetry water column attenuation correction MODIS MERIS Sentinel 2 remote sensing reflectance algorithms inversion method seabed mapping clustering support vector machine New Caledonia Fiji Islands Southwestern Tropical Pacific; chlorophyll-a concentration

Domaines: Optique / photonique; Traitement du signal et de l'image [eess.SP]; Biodiversité et Ecologie

Cécile Dupouy, Andra Whiteside, Jing Tan, Guillaume Wattelez, Hiroshi Murakami, et al.. A Review of Ocean Color Algorithms to Detect Trichodesmium Oceanic Blooms and Quantify Chlorophyll Concentration in Shallow Coral Lagoons of South Pacific Archipelagos. Remote Sensing, 2023, 15 (21), pp.5194. ⟨10.3390/rs15215194⟩. ⟨hal-04458757⟩