Comparison of numerical models for computing underwater light fields

Mobley, Curtis D.; Gentili, Bernard; Gordon, Howard R.; Jin, Zhonghai; Kattawar, George W.; Morel, A.; Reinersman, Phillip N.; Stamnes, Knut; Stavn, Robert H.

doi:10.1364/ao.32.007484

Cited by 465 publications

(267 citation statements)

References 44 publications

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“…Underwater scalar irradiance with a spectral resolution of 5 nm and each 5-m depth was derived by the Hydrolight model (Mobley et al, 1993;Mobley and Sundman, 2013), which allows us to compute the contributions to E of the solar irradiance, the Raman scattering, and the chlorophyll a fluorescence, independently. Simulations were run using in situ chlorophyll a profiles and clear sky irradiance at Solar Zenith Angle of 30°as inputs.…”

Section: Identity Of Light Signals Possibly Driving Dphmentioning

confidence: 99%

Diatom Phytochromes Reveal the Existence of Far-Red-Light-Based Sensing in the Ocean

et al. 2016

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The absorption of visible light in aquatic environments has led to the common assumption that aquatic organisms sense and adapt to penetrative blue/green light wavelengths but show little or no response to the more attenuated red/far-red wavelengths. Here, we show that two marine diatom species, Phaeodactylum tricornutum and Thalassiosira pseudonana, possess a bona fide red/far-red light sensing phytochrome (DPH) that uses biliverdin as a chromophore and displays accentuated red-shifted absorbance peaks compared with other characterized plant and algal phytochromes. Exposure to both red and far-red light causes changes in gene expression in P. tricornutum, and the responses to far-red light disappear in DPH knockout cells, demonstrating that P. tricornutum DPH mediates far-red light signaling. The identification of DPH genes in diverse diatom species widely distributed along the water column further emphasizes the ecological significance of far-red light sensing, raising questions about the sources of far-red light. Our analyses indicate that, although far-red wavelengths from sunlight are only detectable at the ocean surface, chlorophyll fluorescence and Raman scattering can generate red/far-red photons in deeper layers. This study opens up novel perspectives on phytochrome-mediated far-red light signaling in the ocean and on the light sensing and adaptive capabilities of marine phototrophs.

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Section: Identity Of Light Signals Possibly Driving Dphmentioning

confidence: 99%

Diatom Phytochromes Reveal the Existence of Far-Red-Light-Based Sensing in the Ocean

et al. 2016

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“…In Eq.2, Γ is the water-to-air divergence factor (Mobley 1994), and (1-ς r rs ) accounts for the internal reflection of the water-air interface, which is important when r rs values are high for very shallow and/or very turbid waters.…”

Section: Hyperspectral Optimization Process Exemplar Model (Hope)mentioning

confidence: 99%

“…First, a database of R rs spectra corresponding to various water depths, bottom reflectance spectra, water-column IOPs, sky conditions, and viewing geometries is assembled. This database is constructed using a special version of the HydroLight radiative transfer numerical model (Mobley et al 1993; Mobley 1994) (www.hydrolight.info), which provides an exact solution of the unpolarized RTE for the given input. Each HydroLight-generated R rs spectrum in the database is tagged by indices that identify the bottom depth, bottom reflectance spectrum, water IOPs (absorption, scatter, and backscatter spectra), sun zenith angle, etc.…”

Section: Comprehensive Reflectance Inversion Based On Spectrum Matchimentioning

confidence: 99%

Intercomparison of shallow water bathymetry, hydro‐optics, and benthos mapping techniques in Australian and Caribbean coastal environments

Dekker

Phinn

Anstee

et al. 2011

Limnology & Ocean Methods

270

232

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Science, resource management, and defense need algorithms capable of using airborne or satellite imagery to accurately map bathymetry, water quality, and substrate composition in optically shallow waters. Although a variety of inversion algorithms are available, there has been limited assessment of performance and no work has been published comparing their accuracy and efficiency. This paper compares the absolute and relative accuracies and computational efficiencies of one empirical and five radiative-transfer-based published approaches applied to coastal sites at Lee Stocking Island in the Bahamas and Moreton Bay in eastern Australia. These sites have published airborne hyperspectral data and field data. The assessment showed that (1) radiative-transfer-based methods were more accurate than the empirical approach for bathymetric retrieval, and the accuracies and processing times were inversely related to the complexity of the models used; (2) all inversion methods provided moderately accurate retrievals of bathymetry, water column inherent optical properties, and benthic reflectance in waters less than 13 m deep with homogeneous to heterogeneous benthic/substrate covers; (3) slightly higher accuracy retrievals were obtained from locally parameterized methods; and (4) no method compared here can be considered optimal for all situations. The results provide a guide to the conditions where each approach may be used (available image and field data and processing capability). A re-analysis of these same or additional sites with satellite hyperspectral data with lower spatial and radiometric resolution, but higher temporal resolution would be instructive to establish guidelines for repeatable regional to global scale shallow water mapping approaches.Optically shallow waters, those where the bottom is visible from the water surface and measurably influences the waterleaving radiance, include inland waters through to estuarine and tropical coral reef and temperate coastal ecosystems. Over

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“…The underwater light field was modeled using measured inherent optical properties of the water (IOPs) and radiative transfer software (Hydrolight 4.1, Sequoia Scientific) (see Mobley et al [1993] and Johnsen [2002] for further details and justification). Depth profiles of inherent optical properties were measured using a dual path, multiband absorption/ attenuation meter (ac-9, WETLabs) and backscattering meters (a-␤eta and HydroScat-2, HOBILabs) at a site 80 km from the coast of Portsmouth, New Hampshire (42Њ47ЈN 70Њ05ЈW, 1106 h local time, 30 June 2000).…”

Section: Calculation Of Underwater Radiances and Irradiances-mentioning

confidence: 99%

Cryptic coloration and mirrored sides as camouflage strategies in near‐surface pelagic habitats: Implications for foraging and predator avoidance

Johnsen

Sosik

2003

Limnology & Oceanography

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Mirrored and colored surfaces are common adaptations for crypsis in pelagic habitats. Although highly successful when optimized for a particular situation, either may become less successful if it is then viewed in a different situation. In this study we examine the relative robustness of these two strategies by determining how visible an organism becomes when viewed under optical conditions different from those under which the camouflage is optimal. Underwater radiance distributions were calculated using inherent optical properties measured in coastal waters 80 km off the coast of New Hampshire. These radiance distributions were then used to calculate optimally cryptic diffuse and specular reflectance spectra as a function of depth, solar elevation, viewing angle, and azimuth. Then the visibilities of organisms cryptic in one situation viewed in a different situation were calculated, using the Atlantic Cod, Gadus morhua, as the viewer. In contrast to benthic organisms, pelagic organisms cryptic under one set of optical conditions were quite visible under a different set, particularly when viewed from a different azimuth. The crypsis afforded by mirrored surfaces was generally more robust than that resulting from colored surfaces. However, because mirrored surfaces could never be perfectly cryptic when viewed in the azimuth of the sun, neither strategy clearly outperformed the other. In general, crypsis by colored or mirrored surfaces was not robust in nearsurface water, which may help explain both the predominance of transparent species in near-surface pelagic habitats and the vertical migration of many colored and mirrored species. The results also show that three common foraging strategies-circling, crepuscular activity, and driving prey toward the surface-all increase the visibility of cryptically colored or mirrored prey.

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Comparison of numerical models for computing underwater light fields

Cited by 465 publications

References 44 publications

Diatom Phytochromes Reveal the Existence of Far-Red-Light-Based Sensing in the Ocean

Diatom Phytochromes Reveal the Existence of Far-Red-Light-Based Sensing in the Ocean

Intercomparison of shallow water bathymetry, hydro‐optics, and benthos mapping techniques in Australian and Caribbean coastal environments

Cryptic coloration and mirrored sides as camouflage strategies in near‐surface pelagic habitats: Implications for foraging and predator avoidance

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