Remote sensing of <i>Trichodesmium</i> spp. mats in the western tropical South Pacific
<p><i>Trichodesmium</i> is the major nitrogen-fixing species in the western tropical South Pacific (WTSP) region, a hot spot of diazotrophy. Due to the paucity of in situ observations, remote-sensing methods for detecting <i>Trichodesmium</i> presence on a large scal...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2018-08-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/5203/2018/bg-15-5203-2018.pdf |
| _version_ | 1828240223619776512 |
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| author | G. Rousset F. De Boissieu C. E. Menkes J. Lefèvre R. Frouin M. Rodier V. Ridoux V. Ridoux S. Laran S. Bonnet C. Dupouy |
| author_facet | G. Rousset F. De Boissieu C. E. Menkes J. Lefèvre R. Frouin M. Rodier V. Ridoux V. Ridoux S. Laran S. Bonnet C. Dupouy |
| author_sort | G. Rousset |
| collection | DOAJ |
| description | <p><i>Trichodesmium</i> is the major nitrogen-fixing species in the western
tropical South Pacific (WTSP) region, a hot spot of diazotrophy. Due to the
paucity of in situ observations, remote-sensing methods for detecting
<i>Trichodesmium</i> presence on a large scale have been investigated to
assess the regional-to-global impact of this organism on primary production
and carbon cycling. A number of algorithms have been developed to identify
<i>Trichodesmium</i> surface blooms from space, but determining with
confidence their accuracy has been difficult, chiefly because of the scarcity
of sea-truth information at the time of satellite overpass. Here, we use a series
of new cruises as well as airborne surveys over the WTSP to evaluate their
ability to detect <i>Trichodesmium</i> surface blooms in the satellite
imagery. The evaluation, performed on MODIS data at 250 m and 1 km resolution
acquired over the region, 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 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. Application to
MODIS imagery acquired during the February-March 2015 OUTPACE campaign
reveals the presence of surface blooms northwest and east of New Caledonia
and near 20° S–172° W in qualitative agreement with measured nitrogen
fixation rates. Improving <i>Trichodesmium</i> detection requires measuring
ocean color at higher spectral and spatial (< 250 m) resolution than MODIS,
taking into account environment properties (e.g., wind, sea surface
temperature), fluorescence, and spatial structure of filaments, and a better
understanding of <i>Trichodesmium</i> dynamics, including aggregation
processes to generate surface mats. Such sub-mesoscale aggregation processes
for <i>Trichodesmium</i> are yet to be understood.</p> |
| first_indexed | 2024-04-12T21:37:36Z |
| format | Article |
| id | doaj.art-2e23847d0c1e4faea221051a602809cd |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-04-12T21:37:36Z |
| publishDate | 2018-08-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-2e23847d0c1e4faea221051a602809cd2022-12-22T03:15:51ZengCopernicus PublicationsBiogeosciences1726-41701726-41892018-08-01155203521910.5194/bg-15-5203-2018Remote sensing of <i>Trichodesmium</i> spp. mats in the western tropical South PacificG. Rousset0F. De Boissieu1C. E. Menkes2J. Lefèvre3R. Frouin4M. Rodier5V. Ridoux6V. Ridoux7S. Laran8S. Bonnet9C. Dupouy10IRD (Institut de Recherche pour le Développement), UMR ESPACE DEV, Nouméa, New CaledoniaInstitut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), UMR TETIS, Montpellier, FranceIRD-Sorbonne Universités (UPMC, Université Paris 06)-CNRS-MNHN, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques (LOCEAN), IRD Nouméa BP A5, 98848 Nouméa CEDEX, New CaledoniaIRD Nouméa, Laboratoire d'Etudes en Géophysique et Océanographie Spatiales (LEGOS), Nouméa, New CaledoniaScripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0224, USAEIO (Ecosystèmes Insulaires Océaniens), Institut de Recherche pour le Développement-Université de la Polynésie Française-Institut Malarmé-Ifremer, Papeete, French PolynesiaObservatoire Pelagis, UMS3462, Université de la Rochelle/CNRS, La Rochelle, FranceCentre d'Etude de Chizé, UMR7273 – CNRS- Université de La Rochelle, 2 Rue Olympe de Gouges, 17000 La Rochelle, FranceObservatoire Pelagis, UMS3462, Université de la Rochelle/CNRS, La Rochelle, FranceAix Marseille Université-CNRS-INSU, IRD, Mediterranean Institute of Oceanography (MIO), UM110, IRD Nouméa, BP A5, 98848 Nouméa CEDEX, New CaledoniaAix Marseille Université-CNRS-INSU, IRD, Mediterranean Institute of Oceanography (MIO), UM110, IRD Nouméa, BP A5, 98848 Nouméa CEDEX, New Caledonia<p><i>Trichodesmium</i> is the major nitrogen-fixing species in the western tropical South Pacific (WTSP) region, a hot spot of diazotrophy. Due to the paucity of in situ observations, remote-sensing methods for detecting <i>Trichodesmium</i> presence on a large scale have been investigated to assess the regional-to-global impact of this organism on primary production and carbon cycling. A number of algorithms have been developed to identify <i>Trichodesmium</i> surface blooms from space, but determining with confidence their accuracy has been difficult, chiefly because of the scarcity of sea-truth information at the time of satellite overpass. Here, we use a series of new cruises as well as airborne surveys over the WTSP to evaluate their ability to detect <i>Trichodesmium</i> surface blooms in the satellite imagery. The evaluation, performed on MODIS data at 250 m and 1 km resolution acquired over the region, 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 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. Application to MODIS imagery acquired during the February-March 2015 OUTPACE campaign reveals the presence of surface blooms northwest and east of New Caledonia and near 20° S–172° W in qualitative agreement with measured nitrogen fixation rates. Improving <i>Trichodesmium</i> detection requires measuring ocean color at higher spectral and spatial (< 250 m) resolution than MODIS, taking into account environment properties (e.g., wind, sea surface temperature), fluorescence, and spatial structure of filaments, and a better understanding of <i>Trichodesmium</i> dynamics, including aggregation processes to generate surface mats. Such sub-mesoscale aggregation processes for <i>Trichodesmium</i> are yet to be understood.</p>https://www.biogeosciences.net/15/5203/2018/bg-15-5203-2018.pdf |
| spellingShingle | G. Rousset F. De Boissieu C. E. Menkes J. Lefèvre R. Frouin M. Rodier V. Ridoux V. Ridoux S. Laran S. Bonnet C. Dupouy Remote sensing of <i>Trichodesmium</i> spp. mats in the western tropical South Pacific Biogeosciences |
| title | Remote sensing of <i>Trichodesmium</i> spp. mats in the western tropical South Pacific |
| title_full | Remote sensing of <i>Trichodesmium</i> spp. mats in the western tropical South Pacific |
| title_fullStr | Remote sensing of <i>Trichodesmium</i> spp. mats in the western tropical South Pacific |
| title_full_unstemmed | Remote sensing of <i>Trichodesmium</i> spp. mats in the western tropical South Pacific |
| title_short | Remote sensing of <i>Trichodesmium</i> spp. mats in the western tropical South Pacific |
| title_sort | remote sensing of i trichodesmium i spp mats in the western tropical south pacific |
| url | https://www.biogeosciences.net/15/5203/2018/bg-15-5203-2018.pdf |
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