Hyperspectral reflectance spectra of floating matters derived from Hyperspectral Imager for the Coastal Ocean (HICO) observations

Hu, Chuanmin

doi:10.5194/essd-14-1183-2022

Cited by 13 publications

(3 citation statements)

References 26 publications

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“…Furthermore, our green Noctiluca spectra showed relatively high reflectance in the NIR wavelengths (~706 to ~825 nm) during SGN blooms (Figure 2B and 3A,G). This feature has never previously been reported in studies of green Noctiluca blooms, but has been observed in the reflectance spectra of red Noctiluca (Astoreca et al, 2005;Van Mol et al, 2007;Qi et al, 2019), floating macroalgae (Hu, 2022), and land vegetation (Govender et al, 2007). Reflectances higher than 700 nm are typically low because of high water absorption.…”

Section: Spectral Characteristics Of Green Noctiluca Blooms and Other...mentioning

confidence: 54%

MODIS-derived green Noctiluca blooms in the upper Gulf of Thailand: Algorithm development and seasonal variation mapping

Luang-on

Ishizaka²,

Buranapratheprat³

et al. 2023

Front. Mar. Sci.

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In recent decades, red tides of non-toxic harmful algal blooms have frequently occurred in monsoon-influenced tropical areas, particularly the green form of Noctiluca scintillans (hereafter green Noctiluca). However, our understanding of the mechanism of red tide formation is hindered by spatial and temporal constraints of field data. In this study, we used moderate resolution imaging spectroradiometer (MODIS) ocean color data along with a locally developed algal-bloom classification algorithm to investigate the seasonal variability of dominant red tides across the upper Gulf of Thailand (uGoT). During our July 2018 observation, a super green Noctiluca bloom with extraordinarily high chl-a (>1,469 mg m-3) displayed a distinct spectral reflectance characteristic among red tides in blue-to-green and red-to-near infrared wavelengths. According to the distinctive in situ hyperspectral characteristics of uGoT algal blooms, we developed a classification algorithm for MODIS normalized at 488, 531, and 667 nm, which successfully discriminated green Noctiluca in three levels of blooms, namely, super (100%), strong (>80%), and weak (>40%), from other algal blooms (i.e., dinoflagellates, diatoms, cyanobacteria, and mixed red tide species) as well as non-bloom oceanic and coastal waters using MODIS data, as confirmed by uGoT red tide reports. Monthly MODIS-based discrimination composites from 2003 to 2021 revealed seasonal variability in the surface distribution and bloom frequency of green Noctiluca and other red tides according to the Asian monsoon seasons: the southwest monsoon (May–September) and the northeast monsoon (October–January of the following year). Green Noctiluca blooms occurred farther from the shore and estuaries than other red tides (dinoflagellates and cyanobacteria), and were much more frequent than other red tides between the Tha Chin and Chao Phraya River mouths during the non-monsoon period (February to April). The frequency and distribution of green Noctiluca blooms, as well as other algal blooms, varied with the monsoon season. By comparing MODIS-derived algal blooms to monsoon-induced factors (i.e., sea surface winds, precipitation, and river discharge), we present an unprecedented overview of the spatial and temporal dynamics of red tides throughout the uGoT under Asian monsoon conditions. This research contributes to our understanding of the impact of climate change on phytoplankton dynamics.

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Section: Spectral Characteristics Of Green Noctiluca Blooms and Other...mentioning

confidence: 54%

MODIS-derived green Noctiluca blooms in the upper Gulf of Thailand: Algorithm development and seasonal variation mapping

Luang-on

Ishizaka²,

Buranapratheprat³

et al. 2023

Front. Mar. Sci.

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“…Ocean Colour Climate Change Initiative (Valente et al, 2022), National Aeronautics and Space Administration Hyperspectral Imager for the Coastal Ocean reflectance of floating matters (Hu, 2022) or Belgian lakes water quality properties (Castagna et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

Bio-optical properties of cyanobacterium Nodularia spumigena

Garaba

Albinus

Bonthond

et al. 2023

Preprint

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Abstract. In the last century an increasing number of extreme weather events have been experienced across the globe. These events have also been linked to changes in water quality especially due to heavy rains, flooding, or droughts. In terms of blue economic activities, one major threat are harmful algal bloom events that tend to be widespread and can last up to several days. We present and discuss advanced measurements of a bloom involving the cyanobacterium Nodularia spumigena conducted by hyperspectral optical technologies through experiments-of-opportunity. Absorption coefficients, absorbance and fluorescence were measured in the laboratory and these are available via (https://doi.org/10.4121/21610995.v1 (Wollschläger et al., 2022), https://doi.org/10.4121/21822051.v1 (Miranda et al., 2023) and https://doi.org/10.4121/21904632.v1 (Miranda and Garaba, 2023). Data used to derive the above-water reflectance is available via https://doi.org/10.4121/21814977.v1 (Garaba, 2023) and https://doi.org/10.4121/21814773.v1 (Garaba and Albinus, 2023). Additionally, hyperspectral fluorescence measurements of the dissolved compounds in the water were done. The hyperspectral measurements were conducted over a wide spectrum (200–2500 nm). Identification of the cyanobacterium was completed by visual analyses under a microscope. Diagnostic optical features were determined using robust statistical techniques. Water clarity was inferred from Secchi disk measurements https://doi.org/10.1594/PANGAEA.951239 (Garaba and Albinus, 2022). Full sequences were obtained of the 16S rRNA and rbcL genes revealing a very strong match to Nodularia spumigena, data available via GenBank https://www.ncbi.nlm.nih.gov/nuccore/OP918142/ (Garaba and Bonthond, 2022b) and https://www.ncbi.nlm.nih.gov/nuccore/OP925098 (Garaba and Bonthond, 2022a). The chlorophyll-a and phycocyanin levels determined are in open-access https://doi.org/10.4121/21792665.v1 (Rohde et al., 2023). Our experiments-of-opportunity echo the importance of sustainable, simplified, coordinated and continuous water quality monitoring as a way to thrive for the targets 2 set in the United Nations Sustainable Goals (e.g., Goals 6, 11, 12 and 14) or European Union Framework Directives (e.g. Water, Marine Strategy).

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“…Thus, our high-quality in situ dataset is expected to contribute to algorithm development and potential operational monitoring of similar blooms from current or planned hyperspectral satellite missions such as those of the German Aerospace Center (Environmental Mapping and Analysis Program -EnMAP), the Japan Aerospace Exploration Agency (Hyperspectral Imager Suite -HISUI), the National Aeronautics and Space Administration (Plankton, Aerosol, Cloud, ocean Ecosystem -PACE), or the Italian Space Agency (Hyperspectral Precursor of the Application Mission -PRISMA). The current dataset has a unique geographic location, timescale and satellite overpass match-up window (∼ 2 h) as well as hyperspectral measurements that can be considered an addition to related datasets, such as the updated European Space Agency (ESA) Ocean Colour Climate Change Initiative (Valente et al, 2022) and the National Aeronautics and Space Administration Hyperspectral Imager for the Coastal Ocean reflectance of floating matters (Hu, 2022), or Belgian lake water quality properties (Castagna et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

Bio-optical properties of the cyanobacterium Nodularia spumigena

Garaba,

Albinus,

Bonthond

et al. 2023

Earth Syst. Sci. Data

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Abstract. In the last century, an increasing number of extreme weather events have been experienced across the globe. These events have also been linked to changes in water quality, especially due to heavy rains, flooding, or droughts. In terms of blue economic activities, harmful algal bloom events can pose a major threat, especially when they become widespread and last for several days. We present and discuss advanced measurements of a bloom dominated by the cyanobacterium Nodularia spumigena conducted by hyperspectral optical technologies via experiments of opportunity. Absorption coefficients, absorbance and fluorescence were measured in the laboratory, and these data are available at https://doi.org/10.4121/21610995.v1 (Wollschläger et al., 2022), https://doi.org/10.4121/21822051.v1 (Miranda et al., 2023) and https://doi.org/10.4121/21904632.v1 (Miranda and Garaba, 2023). Data used to derive the above-water reflectance are available from https://doi.org/10.4121/21814977.v1 (Garaba, 2023) and https://doi.org/10.4121/21814773.v1 (Garaba and Albinus, 2023). Additionally, hyperspectral fluorescence measurements of the dissolved compounds in the water were carried out. These hyperspectral measurements were conducted over a wide spectrum (200–2500 nm). Diagnostic optical features were determined using robust statistical techniques. Water clarity was inferred from Secchi disc measurements (https://doi.org/10.1594/PANGAEA.951239, Garaba and Albinus, 2022). Identification of the cyanobacterium was completed via visual analysis under a microscope. Full sequences of the 16S rRNA and rbcL genes were obtained, revealing a very strong match to N. spumigena; these data are available via GenBank: https://www.ncbi.nlm.nih.gov/nuccore/OP918142/ (Garaba and Bonthond, 2022b) and https://www.ncbi.nlm.nih.gov/nuccore/OP925098 (Garaba and Bonthond, 2022a). The chlorophyll-a and phycocyanin levels determined are available from https://doi.org/10.4121/21792665.v1 (Rohde et al., 2023). Our experiments of opportunity echo the importance of sustainable, simplified, coordinated and continuous water quality monitoring as a way to thrive with respect to the targets set in the United Nations Sustainable Development Goals (e.g. 6, 11, 12 and 14) or the European Union Framework Directives (e.g. the Water Framework Directive and Marine Strategy Framework Directive).

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Hyperspectral reflectance spectra of floating matters derived from Hyperspectral Imager for the Coastal Ocean (HICO) observations

Cited by 13 publications

References 26 publications

MODIS-derived green Noctiluca blooms in the upper Gulf of Thailand: Algorithm development and seasonal variation mapping

MODIS-derived green Noctiluca blooms in the upper Gulf of Thailand: Algorithm development and seasonal variation mapping

Bio-optical properties of cyanobacterium Nodularia spumigena

Bio-optical properties of the cyanobacterium Nodularia spumigena

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