Search

Underwater images often suffer from degradation due to scattering and absorption. With the development of artificial intelligence, fully supervised learning-based models have been widely adopted to solve this problem. However, the enhancement performance is susceptible to the quality of the reference images, which is more pronounced in underwater image enhancement tasks because the ground truths are not available. In this paper, we propose a light-enhanced pixel fusion network (LEPF-Net) to solve this problem. Specifically, we first introduce a novel light enhancement block (LEB) based on the residual block (RB) and the light enhancement curve (LE-Curve) to restore the cast color of the images. The RB is adopted to learn and obtain the feature maps from an original input image, and the LE-Curve is used to renovate the color cast of the learned images. To realize the superb detail of the repaired images, which is superior to the reference images, we develop a pixel fusion subnetwork (PF-SubNet) that adopts a pixel attention mechanism (PAM) to eliminate noise from the underwater image. The PAM adapts weight allocation to different levels of a feature map, which leads to an enhancement in the visibility of severely degraded areas. The experimental results show that the proposed LEPF-Net outperforms most of the existing underwater image enhancement methods. Furthermore, among the five classic no-reference image quality assessment (NRIQA) indicators, the enhanced images obtained by LEPF-Net are of higher quality than the ground truths from the UIEB dataset., Peer Reviewed, Postprint (published version)

In ice-covered polar lakes, a narrow ice-free moat opens up in spring or early summer, and then persists at the edge of the lake until complete ice loss or refreezing. In this study, we analyzed the horizontal gradients in Ward Hunt Lake, located in the High Arctic, and addressed the hypothesis that the transition from its nearshore open-water moat to offshore ice-covered waters is marked by discontinuous shifts in limnological properties. Consistent with this hypothesis, we observed an abrupt increase in below-ice concentrations of chlorophyll a beyond the ice margin, along with a sharp decrease in temperature and light availability and pronounced changes in benthic algal pigments and fatty acids. There were higher concentrations of rotifers and lower concentrations of viruses at the ice-free sampling sites, and contrasts in zooplankton fatty acid profiles that implied a greater importance of benthic phototrophs in their inshore diet. The observed patterns underscore the structuring role of ice cover in polar lakes. These ecosystems do not conform to the traditional definitions of littoral versus pelagic zones, but instead may have distinct moat, icemargin and ice-covered zones. This zonation is likely to weaken with ongoing climate change.

Dataset: Edmunds et al. MarBio 2019a: Data in support of energy budget calculations, Light data from surveys in Great Lameshur Bay, St. John, US Virgin Islands in 2017 used to calculate photosynthetic input to coral energy budget as in Edwards et al. (2019). These data were used in Edmunds et al. (2019). For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793581, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Kd data, Light data (Kd) from surveys conducted in Great Lameshur Bay, St. John, US Virgin Islands in 2017. These data were used in Edmunds et al. (2019) in Figure 2. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793571, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Light and rainfall data, Light and rainfall data from surveys conducted at Windswept Beach and Great Lameshur Bay, St. John, US Virgin Islands in 2016 and 2017. These data were used in Edmunds et al. (2019) in Figure 1. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793461, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Transmission data, Light data (transmission) from surveys conducted in Great Lameshur Bay, St. John, US Virgin Islands in 2017. These data were used in Edmunds et al. (2019) in Figure 2. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793561, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Transmission data, Light data (transmission) from surveys conducted in Great Lameshur Bay, St. John, US Virgin Islands in 2017. These data were used in Edmunds et al. (2019) in Figure 2. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793561, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Light and rainfall data, Light and rainfall data from surveys conducted at Windswept Beach and Great Lameshur Bay, St. John, US Virgin Islands in 2016 and 2017. These data were used in Edmunds et al. (2019) in Figure 1. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793461, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Data in support of energy budget calculations, Light data from surveys in Great Lameshur Bay, St. John, US Virgin Islands in 2017 used to calculate photosynthetic input to coral energy budget as in Edwards et al. (2019). These data were used in Edmunds et al. (2019). For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793581, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Kd data, Light data (Kd) from surveys conducted in Great Lameshur Bay, St. John, US Virgin Islands in 2017. These data were used in Edmunds et al. (2019) in Figure 2. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793571, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Data in support of energy budget calculations, Light data from surveys in Great Lameshur Bay, St. John, US Virgin Islands in 2017 used to calculate photosynthetic input to coral energy budget as in Edwards et al. (2019). These data were used in Edmunds et al. (2019). For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793581, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Light and rainfall data, Light and rainfall data from surveys conducted at Windswept Beach and Great Lameshur Bay, St. John, US Virgin Islands in 2016 and 2017. These data were used in Edmunds et al. (2019) in Figure 1. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793461, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Transmission data, Light data (transmission) from surveys conducted in Great Lameshur Bay, St. John, US Virgin Islands in 2017. These data were used in Edmunds et al. (2019) in Figure 2. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793561, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

Dataset: Edmunds et al. MarBio 2019a: Kd data, Light data (Kd) from surveys conducted in Great Lameshur Bay, St. John, US Virgin Islands in 2017. These data were used in Edmunds et al. (2019) in Figure 2. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/793571, NSF Division of Ocean Sciences (NSF OCE) OCE-1801335

In ice-covered polar lakes, a narrow ice-free moat opens up in spring or early summer, and then persists at the edge of the lake until complete ice loss or refreezing. In this study, we analyzed the horizontal gradients in Ward Hunt Lake, located in the Canadian High Arctic, and addressed the hypothesis that the transition from its nearshore open-water moat to offshore ice-covered waters is marked by discontinuous shifts in limnological properties. Consistent with this hypothesis, we observed an abrupt increase in below-ice concentrations of chlorophyll a beyond the ice margin, along with a sharp decrease in temperature and light availability and pronounced changes in benthic algal pigments and fatty acids. There were higher concentrations of rotifers and lower concentrations of viruses at the ice-free sampling sites, and contrasts in zooplankton fatty acid profiles that implied a greater importance of benthic phototrophs in their inshore diet. The observed patterns underscore the structuring role of ice cover in polar lakes. These ecosystems do not conform to the traditional definitions of littoral versus pelagic zones but instead may have distinct moat, ice-margin, and ice-covered zones. This zonation is likely to weaken with ongoing climate change.

Camouflage in marine environments requires matching all of the background optical properties: spectral, intensity and polarization components all of which can change dynamically in space and time. Current research suggests that polarization detection is more sensitive than other conventional detection methods in scattering media such as the ocean, hence underscoring the need to develop polarized camouflage technology. Our research investigates the biological challenge of camouflage in the near-shore littoral zone and near-surface marine environments in two distinct water types found in coastal environments around the globe (oligotrophic and eutrophic) with particular emphasis on the polarization properties. We aim to characterize the dynamic light field along with the behavioral and cellular response of camouflaging animals in these environments. Our long-term goal is to identify the biological pathways for concealment against the underwater spectral-polarized light field enabling us to identify design principles for future naval camouflage.

The primary focuses of this research are to understand the requirements of the inverse modeling of seasurface processes on the accuracy, resolution, and coverage of underwater unpolarized and polarized light-field measurements, to master the theoretical constraints and computational resources required of the modeling and simulation, and to improve the forward theoretical and simulation prediction capabilities in terms of accuracy and efficiency. We aim to investigate the feasibility and limitations of achieving the inverse problem of modeling the ocean surface using underwater light measurements. Our ultimate goal is to establish an efficacious, robust framework for the unique and efficient solution of the inverse problem in terms of both the statistical characterization and direct phase-resolved prediction of the ocean surface.

Camouflage in marine environments requires matching all of the background optical properties: spectral, intensity and polarization components all of which can change dynamically in space and time. Current research suggests that polarization detection is more sensitive than other conventional detection methods in scattering media such as the ocean, hence underscoring the need to develop polarized camouflage technology. Our research investigates the biological challenge of camouflage in the near-shore littoral zone and near-surface marine environments in two distinct water types found in coastal environments around the globe (oligotrophic and eutrophic) with particular emphasis on the polarization properties. We aim to characterize the dynamic light field along with the behavioral and cellular response of camouflaging animals in these environments. Our long-term goal is to identify the biological pathways for concealment against the underwater spectral-polarized light field enabling us to identify design principles for future naval camouflage., The original document contains color images.

SeaWiFS data converted to optical properties of the ocean in the form of vertical and horizontal underwater visibility products are compared to in-water diver and optical instrument measurements during the Model Diver Visibility (MoDiV) experiment. Results were collected from 19 to 21 August in the Mississippi Bight region of the United States. The SeaWiFS satellite data was processed with the Automated Processing System (APS), developed by the Naval Research Laboratory (Code 7333). APS converted radiance values into specific parameters studied: the beam attenuation coefficient, the diffuse attenuation coefficient, vertical visibility and horizontal visibility. These values were compared to the AC-9instrument, a-Beta instrument, Secchi disk and the observed visibilities from the divers. The results indicated that the beam attenuation coefficient and the diffuse attenuation coefficient are underestimated as compared to the in-situ measurements. These values then overestimate the vertical and horizontal visibility as compared to the Secchi disk and diver sightings. The visibility products from SeaWiFS should be used on an experimental basis for Naval Operational Planning. It is recommended that the use of in-water diver reports noting variability of SeaWiFS visibility product estimates are necessary for validation and offers feedback to the research and development field for algorithm improvement., http://archive.org/details/acomparisonofins109451082, Lieutenant, United States Navy, Approved for public release; distribution is unlimited.

This project is part of the Radiance in a Dynamic Ocean (RaDyO) program which aims at developing an understanding of variability in underwater light field and its relation to dynamic processes within the ocean-atmosphere boundary layer. We investigate fluctuations in underwater light field produced by sea surface waves under various boundary conditions. Our objectives focus on the characterization of wave-induced fluctuations in downwelling irradiance and radiance as a function of various environmental parameters and depth of observation. The central theme of our study is to characterize the most intense light fluctuations at shallow depths produced by surface wave focusing under sunny conditions. The focusing events occur in the form of high-amplitude short-duration pulses, which we refer to as light flashes. The specific objectives of this project over the past year were to analyze field data collected during the RaDyO experiments carried out in 2008 and 2009 with special emphasis on the characterization of methodology for investigating wave-induced light fluctuations and probability distributions of instantaneous irradiance within the near-surface ocean under sunny conditions.

Camouflage in marine environments requires matching all of the background optical properties: spectral, intensity and polarization components all of which can change dynamically in space and time. Current research suggests that polarization detection is more sensitive than other conventional detection methods in scattering media such as the ocean, hence underscoring the need to develop polarized camouflage technology. Our research investigates the biological challenge of camouflage in the near-shore littoral zone and near-surface marine environments in two distinct water types found in coastal environments around the globe (oligotrophic and eutrophic) with particular emphasis on the polarization properties. We aim to characterize the dynamic light field along with the behavioral and cellular response of camouflaging animals in these environments. Our long-term goal is to identify the biological pathways for concealment against the underwater spectral-polarized light field enabling us to identify design principles for future naval camouflage.

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2011, The ocean depths provide an ever changing and complex imaging environment. As scientists and researches strive to document and study more remote and optically challenging areas, specifically scatter-limited environments. There is a requirement for new illumination systems that improve both image quality and increase imaging distance. One of the most constraining optical properties to underwater image quality are scattering caused by ocean chemistry and entrained organic material. By reducing the size of the scatter interaction volume, one can immediately improve both the focus (forward scatter limited) and contrast (backscatter limited) of underwater images. This thesis describes a relatively simple, cost-effective and field-deployable low-power dynamic lighting system that minimizes the scatter interaction volume with both subjective and quantifiable improvements in imaging performance.

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2011, The ocean depths provide an ever changing and complex imaging environment. As scientists and researches strive to document and study more remote and optically challenging areas, specifically scatter-limited environments. There is a requirement for new illumination systems that improve both image quality and increase imaging distance. One of the most constraining optical properties to underwater image quality are scattering caused by ocean chemistry and entrained organic material. By reducing the size of the scatter interaction volume, one can immediately improve both the focus (forward scatter limited) and contrast (backscatter limited) of underwater images. This thesis describes a relatively simple, cost-effective and field-deployable low-power dynamic lighting system that minimizes the scatter interaction volume with both subjective and quantifiable improvements in imaging performance.

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2011, The ocean depths provide an ever changing and complex imaging environment. As scientists and researches strive to document and study more remote and optically challenging areas, specifically scatter-limited environments. There is a requirement for new illumination systems that improve both image quality and increase imaging distance. One of the most constraining optical properties to underwater image quality are scattering caused by ocean chemistry and entrained organic material. By reducing the size of the scatter interaction volume, one can immediately improve both the focus (forward scatter limited) and contrast (backscatter limited) of underwater images. This thesis describes a relatively simple, cost-effective and field-deployable low-power dynamic lighting system that minimizes the scatter interaction volume with both subjective and quantifiable improvements in imaging performance.

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2011, The ocean depths provide an ever changing and complex imaging environment. As scientists and researches strive to document and study more remote and optically challenging areas, specifically scatter-limited environments. There is a requirement for new illumination systems that improve both image quality and increase imaging distance. One of the most constraining optical properties to underwater image quality are scattering caused by ocean chemistry and entrained organic material. By reducing the size of the scatter interaction volume, one can immediately improve both the focus (forward scatter limited) and contrast (backscatter limited) of underwater images. This thesis describes a relatively simple, cost-effective and field-deployable low-power dynamic lighting system that minimizes the scatter interaction volume with both subjective and quantifiable improvements in imaging performance.

This project is part of the Radiance in a Dynamic Ocean (RaDyO) program which aims at developing an understanding of variability in underwater radiance distribution and its relation to dynamic processes within the ocean-atmosphere boundary layer.

Camouflage in marine environments requires matching all of the background optical properties: spectral, intensity and polarization components- all of which can change dynamically in space and time. Our research investigates the biological challenge of camouflage in the near-shore littoral zone and near-surface marine environments in two distinct water types found in coastal environments around the globe (oligotrophic and eutrophic). We aim to characterize the dynamic light field along with the behavioral and cellular response of camouflaging animals in these environments. Our longterm goal is to identify the biological pathways for concealment against the underwater spectral-polarized light field enabling us to identify design principles for future naval camouflage.

Native submersed macrophyte growth is often limited by underwater light availability in eutrophic aquatic systems. Control of canopy-forming exotic species does not necessarily lead to greater light penetration because eutrophic systems usually sustain high algal biomass in the form of cyanobacterial blooms that can rapidly attenuate light near the lake surface. High phosphorus (P) loading from bottom sediments often represents an important source for algal uptake that needs to be controlled in order to drive aquatic systems toward P-limitation of growth and improve underwater light condition for restoration of native submersed macrophyte populations. Aluminum (Al) sulfate application represents an effective management technique for binding P in sediment and reducing flux into the water column for algal uptake. However, research is needed to determine the dosage of alum required to bind sediment P. The objective of this research was to examine Al:P stoichiometry in relation to extractable forms of sediment P in order to improve the accuracy of alum dosage determination to control sediment P loading in aquatic systems.

Direct biomass control programs (i.e., herbicide, biocontrol, mechanical) that target non-native macrophyte species may not always produce the desired goal of restoring native macrophyte community dominance in shallow aquatic systems. Native reestablishment is often complicated by eutrophic conditions, enhanced nutrient recycling, and frequent nuisance algal blooms that result in poor light penetration and limited colonizable macrophyte habitat. Half Moon Lake is a eutrophic, urban oxbow lake exhibiting high densities of the non-native Potamogeton crispus in early summer followed by high chlorophyll, total phosphorus, and light attenuation. These patterns are, unfortunately, typical for many lakes located in agricultural regions of the upper midwestern United States. Although Half Moon Lake is shallow and supports a native submersed macrophyte community, poor underwater light conditions limit their growth and propagation. The purpose of this research was to examine algal, nutrient, light attenuation characteristics, and underwater light habitat for submersed macrophyte growth and to project changes in these variables and improvement in light penetration as a result of managing the lake to control internal phosphorus loads.

The principal objective of our project is to measure wave-induced fluctuations in underwater light field under various sea-surface boundary conditions. The specific objectives include the characterization of wave-induced fluctuations in downwelling irradiance and radiance as a function of various environmental parameters such as wind/wave conditions, sky radiance distribution, direction of radiance observation, depth of observation, and water optical properties. The central theme of our study is to characterize light fluctuations at shallow depths caused by surface wave focusing under clear skies. The focusing events are the most intense fluctuations that occur on temporal scales of a fraction of a second. The most prominent manifestation of this phenomenon is high-amplitude shortduration pulses of focused light, which we refer to as light flashes (Dera and Stramski, 1986; Stramski, 1986). The two primary objectives for this reporting period were: (i) analysis of data collected during the RaDyO experiment in the Santa Barbara Channel in September 2008, and (ii) collection of data during the Hawaii RaDyO experiment in August-September, 2009.

Optical properties derived from ocean color imagery represent vertically-integrated values from roughly the first attenuation length in the water column, thereby providing no information on the vertical structure. Robotic, in situ gliders, on the other hand, are not as synoptic, but provide the vertical structure. By linking measurements from these two platforms we can obtain a more complete environmental picture. We merged optical measurements derived from gliders with ocean color satellite imagery to reconstruct vertical structure of particle size spectra (PSD) in Antarctic shelf waters during January 2007. Satellite-derived PSD was estimated from reflectance ratios using the spectral slope of paniculate backscattering. Average surface values (0-20 m depth) of were spatially coherent (I to 50 km resolution) between space and in-water remote sensing estimates. This agreement was confirmed with shipboard vertical profiles of spectral backscattering (llydroScat-6). It is suggested the complimentary use of glider-satellite optical relationships, ancillary data (e.g., wind speed) and ecological interpretation of spatial changes on particle dynamics (e.g., phytoplankton growth) to model underwater light fields based on cloud-free ocean color imagery., Published in the Proceedings of SPIE, v7459, p74590N-1 - 74590N-9, 2009.

Characterization of 3-D underwater light fields from above the sea surface requires passive and active remote sensing measurements. In this work, we suggest the use of passive ocean color sensors and lidar (Light Detection and Ranging) to examine the vertical structure of optical properties in marine waters of the Northern Part of the Gulf of Alaska (NGOA). We collected simultaneous airborne remote sensing reflectance (Rrs) in the spectral range 443-780 nm (MicroSAS, Satlantic) and lidar-derived volume backscattering (beta) profiles (0-20 m depth, wavelength = 532 nm) during August 17 2002 in shelf waters situated south of Kodiak Island off Alaska (57.48 degrees-58.04 degrees N, 152.91 degrees-151.67 degrees W). We evaluated the spectral response of Rrs to perturbations on the vertical distribution of beta by comparing the spatial variability between aggregated (250 m horizontal resolution x 1 m vertical resolution) Rrs spectral ratios and different lidar statistics per bin (Maximum beta per bin, mean beta per bin, beta(sub m), standard deviation of beta per bin, beta(sub std), integrated beta per bin, beta(sub int) or group of bins (lidar volume extinction coefficient of beta between 0 and 5 m depth). Sub-surface changes of beta(sub m), beta(sub int), and beta(sub std) were mainly correlated with Rrs (490)/Rrs (555) variability along the flight-track (Semi-partial correlation coefficients = 0.12 to 0.21). Our results evidenced linkages between above and below-sea surface optical properties that can be used to derive water optical constituents as a function of depth based on combined passive-active data., Published in the Proceedings of SPIE, v7459, Ocean Remote Sensing: Methods and Applications, p74590F-1 to 74590F-9, 2009. Presented at the Conference on Ocean Remote Sensing: Methods and Applications held in San Diego, CA, on 2 Aug 2009. Prepared in collaboration with the Northern Gulf Institute, Mississippi State University, Mississippi State, MS and the Earth System Research Laboratory (NOAA), Boulder, CO.

This project is part of the Radiance in a Dynamic Ocean (RaDyO) program which aims at developing an understanding of variability in underwater radiance distribution and its relation to dynamic processes within the ocean-atmosphere boundary layer. The principal objective of our project is to measure wave-induced fluctuations in underwater light field under various sea-surface boundary conditions. The specific objectives include the characterization of wave-induced fluctuations in downwelling irradiance and radiance as a function of various environmental parameters such as wind/wave conditions, sky radiance distribution, direction of radiance observation, depth of observation, and water optical properties. Because of the complexity of the problem and multiplicity of factors affecting the light field fluctuations, achieving a comprehensive characterization of all these effects is unrealistic within the timeframe of the RaDyO program. Our study will focus on selected problems and environmental factors as the project progresses throughout the phase of main field experiments. The central theme of our study is to characterize light fluctuations at shallow depths caused by surface wave focusing under clear skies. The focusing events are the most intense fluctuations that occur on temporal scales of a fraction of a second. The primary objectives for this reporting period were focused on the execution of two major field experiments, first the test experiment at the Scripps Pier in January 2008, and second, the main RaDyO experiment on FLIP and KILO MOANA in the Santa Barbara Channel in September 2008. The central idea of our project is to conduct in situ measurements of high-frequency fluctuations in underwater light field produced by surface waves under various boundary conditions. Our approach towards this objective builds largely on our past research experience in the area of wave-induced light fluctuations.

Simulation of underwater light is essential for modeling marine ecosystems. A new model of underwater light attenuation is presented and compared with previous models. In situ data collected in Monterey Bay, CA. during September 2006 are used for validation. It is demonstrated that while the new light model is computationally simple and efficient it maintains accuracy and flexibility. When this light model is incorporated into an ecosystem model, the correlation between modeled and observed coastal chlorophyll is improved over an eight-year time period. While the simulation of a deep chlorophyll maximum demonstrates the effect of the new model at depth., The original document contains color images. All DTIC reproductions will be in black and white. Pub. in Optics Express, v16 n21 p16581-16591, 13 Oct 2008.

The long-term goal of this project is to measure, understand and be able to predict the propagation of light through the air-sea interface under various sea states. The objectives include: (1) Characterization of the point spread function of underwater light that has gone through the air water interface with exact coincident measurement of the surface wave field. (2) Analysis of this data to formulate either empirical or theoretical relationships between the sea surface and the observed light spreading. (3) Incorporation of the above results into an analysis and understanding of how difficult it will be to obtain detailed images through the air-sea interface as a function of sea state.

We present a new approach that incorporates two models to estimate the underwater light field from remote sensing of ocean color. The first employs a sense of analytical. semi-analytical, and empirical algorithms to retrieve the spectrum of inherent optical properties (IOPs), including the absorption and backscatter coefficients, from the spectrum of remote sensing reflectance. The second model computes the profile of photosynthetically available radiation EO, PAR(z) for a vertically homogeneous water column using the information of the retrieved IOPs and the ambient optical environment. This computation is based on an improved look-up table technology that possesses high accuracy, comparable with the full solution of the radiative transfer equations, and meets the computational requirement of remote sensing application. This new approach was validated by in situ measurements and an extensive model-to-model comparison with a wide range of IOPs. We successfully mapped the compensation depth by applying this new approach to process the SeaWiFS imagery. This research suggests that E0, PAR(z) can be obtained routinely from ocean-color data and may have significant implications for the estimation of global heat and carbon budget., The original document contains color images. Pub. in Jnl. of Oceanography, v62 p235-248, 2006.

The spatial and angular structure of light radiance in the depth of sea water can be precisely computed with such numerical programs as Hydrolight. Unfortunately, such calculations demand a lot of computational time if used for problems of visibility of submerged objects. In this case, due to the much greater computational efficiency and logarithmic dependence of visibility parameters on radiance values, analytical radiative transfer methods are preferable. In this presentation, a new analytical radiative transfer method is proposed to solve visibility problems in sea water. The angular structure of depth-dependent light radiance in the sea is obtained in the framework of previously published self-consistent approximation. The analytical expressions proposed in this paper allow one to compute a horizontal visibility of submerged objects. This approach can be applied to problems of diver visibility in shallow water bodies of arbitrary turbidity and illumination., Presented at the Conference on "Remote Sensing and Modeling of Ecosystems for Sustainability" held in Denver, CO on 2-4 Aug 2004. Published in Proceedings of SPIE, v5544, p372-379. Sponsored through program number VSF-73-6641-04-5.

A simulation model has been developed that focuses on the ability of two competing submersed macrophytes, meadow-forming and canopy-forming, to maintain their biomass under different environmental conditions. Vallisneria americana (American wildcelery) serves as the example for meadow-forming plants and Stuckenia pectinata (until recently known as Potamogeton pectinatus or sago pondweed) for canopy-forming plants. The model can be used to predict changes in species composition of submersed vegetation as a result of changes in the availability of resources in shallow freshwater bodies. In the model, the two plant species compete for light and exhibit different species-specific relationships between plant tissue nitrogen (N):phosphorus (P) ratio and plant biomass production. The latter species-specific relationships have not been determined in V. americana and P. pectinatus, and, therefore, for calibration of the model, the specific relationships between plant tissue N:P ratio and reduction in plant biomass production of Zannichellia palustris and Elodea canadensis were used. The latter species have habitat preferences similar to those of V. americana and P. pectinatus. Competition for light proved to be a far more important determinant of species composition than the availabilities of N and P in the sediment. Intraspecific competition for light did not occur in V. americana in a temperate climate, but it was observed at densities > 8-9 plants m-2 in a more southern climate. It occurred in P. pectinatus at plant densities >4-5 plants m-2. Coexistence of both species occurred only at V. americana:P. pectinatus plant density ratios of 28:2 to 26:4 plants m-2 in the absence of N and P limitation of growth, irrespective of climate (temperate and more southern climates tested). At density ratios higher than 28:2, V. americana excludes P. pectinatus, and at density ratios lower than 26:4, P. pectinatus excludes V. americana.

We examined sediment resuspension dynamics and light availability in relation to the potential for macrophytes to improve water quality conditions in Peoria Lake, Illinois. The lake exhibited high total suspended sediment (TSS) loading and retention of predominantly fine-grained particles during 2000. Large fetches along the prevailing wind rose, coupled with shallow morphometry and sediment particles composed of > 90 percent silt and clay, resulted in frequent periods of sediment resuspension in September. The tau(sub c) of sediment in the vicinity of the resuspension monitoring station, determined experimentally using a particle entrainment simulator, was 2.3 dynes/sq cm. This value was in close agreement with tau(sub c), determined by direct examination of variations in in situ turbidity as a function of tau, calculated using wave theory, at the resuspension monitoring station during the month of September. As calculated tau increased above tau(sub c), turbidity increased substantially at the resuspension monitoring station during the month of September. Net TSS resuspension was very high in relation to TSS loading from the Illinois River during September. The settling velocity of particles in the water column was estimated as 0.004 cm/sec, based on analysis of five particle-size fractions ranging between < 1.95 and > 62.5 micrometers. Using a resuspension model, we reasonably predicted resuspension events that occurred in September at the resuspension station. Model explorations suggested that establishment of submersed aquatic macrophytes could substantially reduce sediment resuspension in Peoria Lake. However, K(sub d) was very high, while Secchi transparency was low at in-lake stations, and the silt fraction (i.e., < 62.5 and > 1.95 micrometers) strongly influenced K(sub d). Thus, in order to establish a persistent macrohpyte population in the lake to control resuspension, the underwater light regime must initially improve quite dramatically., Original contains color plates: All DTIC reproductions will be in black and white.

The goals of this project were to better define the characteristics of spectral fluorescence quantum yields of particulate and soluble material in the ocean. Methods were developed for improved estimates of soluble absorption coefficients of oceanic material to improve estimates of the absorbed quantum flux that is needed to estimate The yields. These methods were implemented in numerous cruises in the California Current Indian Ocean and Sea of Japan. Fluorescence excitation and emission spectra were determined and scaled to known fluorescence standards to estimate quantum yields. Coastal waters of the Southern California Bight and San Diego Bay exhibited nearly linear response of fluorescence per absorbed quanta for 350 nm excitation and 450 nm emission suggesting that The quantum yield is relatively invariant. Cultures of phytoplankton were grown to evaluate the spectral quantum yield of in vivo chlorophyll a fluorescence. We determined that mycosporine amino acids with UV absorption, and xanthophyll pigments with absorption near 490 nm dramatically suppress The quantum yield of fluorescence. The results we have obtained could be used to improve models of trans-spectral sources for underwater light fields.

The effects of microbial and mineral particles, and of dissolved substances, on marine light fields were investigated using a database of single-particle optical properties as input to the Hydrolight radiative transfer numerical model. This database now includes 24 microbial species as well as generic mineral particles, organic detritus, and microbubbles. Significant results include: (1) It is possible to define generic prochlorophyes and Synechococcus species, but this cannot be done for nanoplankton. (2) The detailed species composition of small nanoplankton is not crucial, so long as the various-sized particles obey a Junge size distribution overall, with the same total concentration of these particles. (3) The natural variability in the parameters used in simple bio-optical models for dissolved substances and detritus can have effects on the remote-sensing reflectance that are as large as a factor-of-two change in the chlorophyll concentration. (4) Organic detritus can have a large effect on remotely sensed signals and therefore deserves more research attention. An improved methodology for estimating the remote-sensing reflectance from above-water measurements is presented., Prepared in cooperation with Scripps Inst. of Oceanography, San Diego, CA.

My principal goal is to understand the mechanistic basis for changes in the flourescent signatures, both host and algal symbiont, of corals. Changes in the spectral quantity and quality of visible and ultraviolet radiation will have effects of the quantum yield of photosynthesis and affect the fluorescent signatures of the algal symbionts as will changes in the temperature of the surrounding seawater. Since the reef environment is very dynamic, the challenge is to understand what environmental factors are responsible for the greatest variability in these fluorescent optical signatures at small to large scales and understand sufficiently to model them over space and time., See also ADM002252.

The long-term goal of this study is to examine the vertical structure in bio-optical properties and to classify features that persist at large scales, particularly with a view to application in remote sensing of the underwater light field and of the water-column primary productivity at basin to global scales. In the present proposal, we emphasise issues related to the vertical structure of the water column: (1) the use of coupled models to improve our understanding of the vertical structure of the water column, and (2) the use of information other than just chlorophyll-a to refine optical models. The work will be oriented towards examining the implications of vertical structure for penetration of light underwater and for remote sensing of primary production., See also ADM002252. Prepared in cooperation with Bedford Institute of Oceanography, Dartmouth, Nova Scotia.

The development of an optical methodology, valid for Case II coastal waters, for the remote classification of the sea bottom including sediment type (calcareous/quartz sand, clay, mud), benthic flora (benthic diatom and algal mats, seagrasses, green and red macrophytes), and bottom structure (reef, rock). The methodology will exploit elastic and inelastic spectral information as well as 3-dimensional size, shape, and texture information determined by optical methods. The deconvolution of the components of the underwater and water-leaving light fields in coastal waters. The determination of feature vectors, including 3-D morphology, which hold information unique to different bottom types and structure for use in an automatic classification strategy. The significant challenge inherent in this work is the need to identify and address all significant factors affecting the underwater light field., See also ADM002252.

Our goal is to develop a more detailed understanding of the role of fluorescence as a source of trans-spectral energy in the underwater light field and the biological and chemical causes for variations in the spectral source terms. We will (1) determine the spectral quantum yield of cDOM and photosynthetic pigments; (2) assess the impact of steady state growth conditions on phytoplankton pigment in vivo quantum yields; (3) run model sensitivity analyses to determine the importance of transspectral sources in defining the submarine light field; and (iv) assess the implications of trans-spectral sources for hyperspectral remote sensors. The proposed work is significant for the ONR optics program because no systematic, quantitative evaluation of the trans-spectral source terms have been accomplished and the quantum yields of the different components, which are essential for modeling and prediction, are poorly specified. The work is also of importance for the biology/chemistry programs since, despite the ubiquitous use of fluorescence as a tool to study cDOM and phytoplankton, the fundamental understanding of the processes in terms of quantum fluxes is not well known. We anticipate that our work will enhance the ability to predict optical, chemical and biological processes in the ocean. Our goal is to study the quantum yields of fluorescence of various components including dissolved, detrital particulate and phytoplankton. We will assess the role of fluorescence of these various components to contribute trans-spectral sources within the water column and environmental conditions that govern the fluorescence of biological and chemical components. Combining laboratory work and radiative transfer modeling, we will define which sources must be accounted for to understand the intensity of irradiance in the ocean for sources other than the natural solar flux and Raman., See also ADM002252.

This paper discusses the results of two decades on in situ measurements of the ocean color index. which is defined as the ratio of two upward light radiances measured at nadir at both 540 and 420 nm. An optical classification of ocean waters based on the color index is proposed. This classification is compared to other optical water classifications. The color index distributions for specific regions of interest were compiled and compared with the water dynamics. The ranges of the color index variability were also estimated for these ocean regions. It was shown that the color index regressions can be successfully used for the interpretation of spaceborne and airborne optical remote information., Presented at the third International Airborne Remote Sensing Conference and Exhibition, v2, Copenhagen, Denmark, 7-10 Jul 97

The results are presented of a preliminary mathematical modelling study of optical image propagation in water using Monte Carlo methods. Mathematical models, Images, Propagation, Monte Carlo method, Underwater, Range gating, Imaging systems

A report on the verification of a suite of mathematical models related to propagation of light in water. The developed models were assessed by comparison with experimental results for forward scattering and backscattering, in addition to image propagation, using the high performance underwater imaging system.

This optical oceanography project provided support to researchers doing ocean optics experiments by developing analytical methods for solving multiple-scattering inverse and forward problems of radiative transfer, including: (1) Solutions of inverse problems that can be used to determine the spatial dependence of internal sources and/or inherent optical properties (IOPs). The sources of interest can arise from inelastic scattering effects, bioluminescence, or fluorescence, while the IOPs of interest are the absorption and scattering coefficients and the scattering phase function. (2) Analytical solutions of forward problems that assist in the understanding of the underwater light field and in determining IOPS. Such problems typically involve measurements of the downward and/upward irradiances, and sometimes the corresponding scalar irradiances and selected radiances, followed by the determination of the spatial dependence of internal sources and/or optical properties.

This project was concerned with advancing the understanding of both the theoretical underpinnings of underwater image formation theory and also the experimental development of a new system for obtaining three dimensional information about ocean optical properties. Theoretical results from a Monte Carlo simulation of underwater radiance fields the average cosine of the radiance field does not achieve its asymptote for an omnidirectional source, even after 15 attenuation lengths. In addition, limits to the computation of the absorption coefficient, using an omnidirectional light source are explored. Experimental results of lab simulations of a volumetric imaging system based on fluorescence emission from a sheet of stimulating light laser light indicated that the system can be used to measure the 3-dimensional distribution of chlorophyl-a over a broad range of concentrations., Original contains color plate: All DTIC/NTIS reproducrtions will be in black and white