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/bg-8-3631-2011

Cited by 58 publications

(51 citation statements)

References 76 publications

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“…Bright areas, indicating high signals, are discussed in the text.5460J. Gower et alThese observations of Trichodesmium agree well with those ofDupouy et al (2011), who used Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data to show the distribution of near-surface blooms near New Caledonia in 1998-2010. Their algorithm responds to specific radiance patterns at wavelengths from 410 to 665 nm (SeaWiFS water colour bands) to detect near-surface colour changes.…”

supporting

confidence: 69%

Global remote sensing of Trichodesmium

Gower

King²,

Young

2014

International Journal of Remote Sensing

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The maximum chlorophyll index (MCI) from the Medium Resolution Imaging Spectrometer (MERIS) satellite imager gives a robust indicator of the presence of a variety of floating slicks, near-surface vegetation, and intense surface plankton blooms. The index responds to the presence of surface slicks of Trichodesmium due to the 'red edge' increase in radiance with increasing wavelength near 700 nm. Global composite images of this index can be used to map the distribution of surface slicks of Trichodesmium, showing seasonal and long-term variations. The MCI also responds to the 'red edge' in the spectral signature of Sargassum. The two species share some areas of common occurrence and it is important to distinguish between them. We have developed spectral techniques of distinguishing between these two, and for discriminating a variety of other confusing targets that occur in different areas. We feel that MERIS MCI can be a useful tool in monitoring global Trichodesmium spatial distribution, and its short-and long-term variation.

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supporting

confidence: 69%

Global remote sensing of Trichodesmium

Gower

King²,

Young

2014

International Journal of Remote Sensing

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“…Examination of isotope values calculated from biological samples collected during the Nectalis cruises suggests the contribution of diazotrophs to phytoplankton composition as previously observed in the area (Campbell et al, 2005;Dupouy et al, 2011). Two distinct water masses were encountered in the studied area.…”

Section: Variablesmentioning

confidence: 68%

“…Lower primary production was observed in the downwelling (anticyclonic) eddy at station 9 during Nectalis2 (eddy K). In downwelling areas lateral advection from fluid convergence can concentrate floating organisms (Dandonneau et al, 2003) such as the diazotrophic cyanobacterium Trichodesmium which can be quite frequent in the region (Dupouy et al, 2011). At station 9 (Nectalis 2) a higher proportion of large phytoplankton cells with higher concentration Table 4 Correlations between estimates of micronekton biomasses.…”

Section: Horizontal Advection Mesoscale and Submesoscale Phenomenamentioning

confidence: 98%

Seasonal oceanography from physics to micronekton in the south-west Pacific

Menkès

Allain

Rodier

et al. 2015

Deep Sea Research Part II: Topical Studies in Oceanography

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a b s t r a c tTuna catches represent a major economic and food source in the Pacific Ocean, yet are highly variable. This variability in tuna catches remains poorly explained. The relationships between the distributions of tuna and their forage (micronekton) have been mostly derived from model estimates. Observations of micronekton and other mid-trophic level organisms, and their link to regional oceanography, however are scarce and constitute an important gap in our knowledge and understanding of the dynamics of pelagic ecosystems. To fill this gap, we conducted two multidisciplinary cruises (Nectalis1 and Nectalis2) in the New Caledonian Exclusive Economic Zone (EEZ) at the southeastern edge the Coral Sea, in 2011 to characterize the oceanography of the region during the cool (August) and the hot (December) seasons. The physical and biological environments were described by hydrology, nutrients and phytoplankton size structure and biomass. Zooplankton biomass was estimated from net sampling and acoustics and micronecton was estimated from net sampling, the SEAPODYM ecosystem model, a dedicated echosounder and non-dedicated acoustics. Results demonstrated that New Caledonia is located in an oligotrophic area characterized by low nutrient and low primary production which is dominated by a high percentage of picoplankton cyanobacteria Prochlorococcus (490%). The area exhibits a large-scale north-south temperature and salinity gradient. The northern area is influenced by the equatorial Warm Pool and the South Pacific Convergence Zone and is characterized by higher temperature, lower salinity, lower primary production and micronekton biomass. The southern area is influenced by the Tasman Sea and is characterized by cooler temperature, higher salinity, higher primary production and micronekton biomass. The dynamic oceanography and the complex topography create a myriad of mesoscale features including eddies, inducing patchy structures in the ecosystem. During the cool season, a tight coupling existed between the ocean dynamics and primary production, while there was a stronger decoupling during the hot season. There was little difference in the composition of mid-trophic level organisms (zooplankton and micronekton) between the two seasons. This may be due to different turnover times and delays in the transmission of primary production to upper trophic levels. Examination of various sampling gears for zooplankton and micronekton showed that net biomass estimates and

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“…In the western South Pacific, where nitrogen fixation has not been investigated widely, previous studies demonstrated that Trichodesmium spp. blooms with active nitrogen fixation (>10 nmol N L À1 d À1 ) often occur near islands in the oligotrophic regions [Campbell et al, 2005;Garcia et al, 2007;Shiozaki et al, 2010;Dupouy et al, 2011]. In this region, biological production has been recognized to be enhanced extensively around the islands [Dandonneau and Charpy, 1985].…”

Section: Citationmentioning

confidence: 99%

“…This is because diatoms are capable of growing more rapidly than other phytoplankton under light-saturated and nutrient-replete conditions [Furuya et al, 1986]. However, recent studies have recognized another unique phytoplankton distribution in the oligotrophic region; large-sized filamentous diazotrophs in the genus Trichodesmium also flourish around some islands [Campbell et al, 2005;Shiozaki et al, 2010;Dupouy et al, 2011], and the nitrogen fixation activities are enhanced compared with the open ocean [Shiozaki et al, 2010]. Diazotrophs use dinitrogen gas as a nitrogenous nutrient, and hence, their growth is not limited by nitrogen.…”

Section: Introductionmentioning

confidence: 99%

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

Cited by 58 publications

References 76 publications

Global remote sensing of Trichodesmium

Global remote sensing of Trichodesmium

Seasonal oceanography from physics to micronekton in the south-west Pacific

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

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