An algorithm for detecting &amp;lt;i&amp;gt;Trichodesmium&amp;lt;/i&amp;gt; surface blooms in the South Western Tropical Pacific

Dupouy, Cécile; Benielli-Gary, D.; Neveux, Jacques; Dandonneau, Yves; Westberry, T. K.

doi:10.5194/bgd-8-5653-2011

Cited by 13 publications

(25 citation statements)

References 77 publications

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“…R/V Alis) and ships of opportunity. Some of these visual observations were confirmed by water samples analyzed with 25 photomicrographs confirming the presence of abundant Trichodesmium (Dupouy et al, 2011). Airborne visual observations were also gathered in December 2014 in the vicinity of New Caledonia during the REMMOA program (Laran et al, 2016).…”

Section: In Situ Observationsmentioning

confidence: 85%

“…It includes the Trichodesmium mat observations published in Dupouy et al (2011). These observations were done between 1998 and 2010, from aircraft, French Navy ships, research vessels (e.g.…”

Section: In Situ Observationsmentioning

confidence: 99%

“…these issues as reflectance from the floating algae can be wrongly interpreted as aerosols or clouds. It is a main concern in this region as the blooming period of Trichodesmium (mainly November to March (Dupouy et al, 2011)) coincides with the South Pacific Convergence Zone, i.e. heavy cloudiness making difficult the identification of coincident in-situ mats in satellite imagery.…”

Section: Introductionmentioning

confidence: 99%

“…Trichodesmium blooms have long been detected by satellite in the region, mostly around New Caledonia and Vanuatu (Dupouy et al, 2000(Dupouy et al, , 2011, and later confirmed by microscopic enumerations (Shiozaki et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…By using specific optical properties of Trichodesmium, among which pigment absorption (mainly phycoerythrin, PE) and particle backscattering (Subramaniam et al, 1999a(Subramaniam et al, , 1999b, several biooptical algorithms have been developed to detect Trichodesmium blooms in real time from various satellite sensors , i.e. the ones of Hood et al (2002); Westberry et al (2005); Dupouy et al (2011) for SeaWiFS, the ones of Gower et al (2014) for MERIS, and the ones of Hu et al (2010) and McKinna et al (2011) for MODIS-Aqua (review in Mckinna (2015)). 30 The application of these algorithms to MODIS imagery revealed several issues, some of which had already been raised and discussed in the aforementioned articles.…”

Section: Introductionmentioning

confidence: 99%

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Remote Sensing of <i>Trichodesmium</i> spp. mats in the Western Tropical South Pacific

Rousset¹,

Boissieu²,

Menkès³

et al. 2018

Preprint

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Abstract.Trichodesmium is the main nitrogen-fixing species in the South Pacific region, a hotspot for diazotrophy. Due to the paucity of in situ observations, methods for detecting Trichodesmium presence on a large scale have been investigated to assess the regional-to-global impact of these species on primary production and carbon cycling. A number of satellite-derived algorithms have been developed to identify Trichodesmium surface blooms, but determining with confidence their accuracy 20 has been difficult, chiefly because of the scarcity of sea-truth information at time of satellite overpass. Here, we use a series of new cruises as well as airborne observational surveys in the South Pacific to quantify statistically the ability of these algorithms to discern correctly Trichodesmium surface blooms in the satellite imagery. The evaluation, performed on MODIS data at 250m and 1km resolution acquired over the South West Pacific, shows limitations due to spatial resolution, clouds, and atmospheric correction. A new satellite-based algorithm is designed to alleviate some of these limitations, by exploiting 25 optimally spectral features in the atmospherically corrected reflectance at 531, 645, 678, 748, and 869 nm. This algorithm outperforms former ones near clouds, limiting false positive detection, and allowing regional scale automation. Compared with observations, 80% of the detected mats are within a 2 km range, demonstrating the good statistical skill of the new algorithm. 2 taking into account environment properties (wind, sea surface temperature, …), fluorescence, and spatial structure of filaments, and a better understanding of Trichodesmium dynamics, including aggregation processes to generate surface mats. Such submesoscales aggregation processes for Trichodesmium are yet to be understood.

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Section: In Situ Observationsmentioning

confidence: 85%

Section: In Situ Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Remote Sensing of <i>Trichodesmium</i> spp. mats in the Western Tropical South Pacific

Rousset¹,

Boissieu²,

Menkès³

et al. 2018

Preprint

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Large‐scale impact of the island mass effect through nitrogen fixation in the western South Pacific Ocean

Shiozaki

Kodama

Furuya

2014

Geophysical Research Letters

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We describe a new mechanism for the island mass effect fueled by nitrogen fixation. The nitrogen fixation activities and δ 15 N of suspended particles in the surface water in the South Pacific were examined. Active nitrogen fixation and abundant Trichodesmium spp. were observed near islands in the western subtropical region, which was attributable to the material supplied by land runoff. High primary production was extensively centered around the islands and was characterized by low δ 15 N of suspended particles and a reduction in phosphate concentrations at the surface compared with the subtropical gyre and eastern equatorial upwelling. This suggested that Trichodesmium spp. were advected to areas remote from these islands, and consequently, the elevated primary production fueled by nitrogen fixation extended over a large area around them. Because the proposed island mass effect is triggered by a terrigenous nutrient supply, this ecosystem is potentially vulnerable to human activity on small islands.

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An optical system for detecting and describing major algal blooms in coastal and oceanic waters around India

Gokul

Shanmugam

2016

JGR Oceans

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An optical system is developed with the aim to detect and monitor three major algal blooms (including harmful algal blooms ''HABs'') over ecologically relevant scales around India and to strengthen algal forecasting system. This system is designed to be capable of utilizing remote sensing, in situ, and radiative transfer techniques to provide species-specific data necessary for increasing capabilities of an algal forecasting system. With the ability to measure in-water optical properties by means of remote sensing and in situ observations, the optical system developed infers the desired phytoplankton signal from spectral distributions and utilize these data in a numerical classification technique to generate species-specific maps at given spatial and temporal scales. A simple radiative transfer model is adopted for this system to provide a means to optimally interpolate to regions with sparse in situ observation data and to provide a central component to generate in-water optical properties from remotely sensed data. For a given set of inherent optical properties along with surface and bottom boundary conditions, the optical system potentially provides researchers and managers coverage at different locations and depths for tracking algal blooms in the water column. Three major algal blooms focused here include Noctiluca scintillans/miliaris, Trichodesmium erythraeum, and Cochlodinium polykrikoides, which are recurring events in coastal and oceanic waters around India. Because satellite sensors provide a synoptic view of the ocean, both spatially and temporally, our initial efforts tested this optical system using several MODIS-Aqua images and ancillary data. Validation of the results with coincident in situ data obtained from either surface samples or depth samples demonstrated the robustness and potential utility of this approach, with an accuracy of 80-90% for delineating the presence of all three blooms in a heterogeneous phytoplankton community. Despite its limitation in detecting specific species during their prebloom phases and indicating whether a particular bloom is toxic or harmful, the proposed optical system will provide managers with the specific phytoplankton bloom maps to structure monitoring efforts and a powerful tool for studying the dynamics of algal blooms at various temporal and spatial scales.

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An algorithm for detecting <i>Trichodesmium</i> surface blooms in the South Western Tropical Pacific

Cited by 13 publications

References 77 publications

Remote Sensing of <i>Trichodesmium</i> spp. mats in the Western Tropical South Pacific

Remote Sensing of <i>Trichodesmium</i> spp. mats in the Western Tropical South Pacific

Large‐scale impact of the island mass effect through nitrogen fixation in the western South Pacific Ocean

An optical system for detecting and describing major algal blooms in coastal and oceanic waters around India

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An algorithm for detecting &lt;i&gt;Trichodesmium&lt;/i&gt; surface blooms in the South Western Tropical Pacific

Cited by 13 publications

References 77 publications

Remote Sensing of &lt;i&gt;Trichodesmium&lt;/i&gt; spp. mats in the Western Tropical South Pacific

Remote Sensing of &lt;i&gt;Trichodesmium&lt;/i&gt; spp. mats in the Western Tropical South Pacific

Large‐scale impact of the island mass effect through nitrogen fixation in the western South Pacific Ocean

An optical system for detecting and describing major algal blooms in coastal and oceanic waters around India

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Product

Resources

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An algorithm for detecting <i>Trichodesmium</i> surface blooms in the South Western Tropical Pacific

Remote Sensing of <i>Trichodesmium</i> spp. mats in the Western Tropical South Pacific

Remote Sensing of <i>Trichodesmium</i> spp. mats in the Western Tropical South Pacific