Chlorophyll Reflectance Research Articles

A potential relationship between soil disinfestation efficacy and leaf green reflectance.

Soil disinfestation with steam was evaluated as an alternative to fumigation. Following soil disinfestation, plant health has traditionally been measured using plant size and yield. Plant health can be measured in a timely manner more efficiently, more easily and non-destructively using image analysis. We hypothesized that plant health could be quantified and treatments can be differentiated using an RGB (Red, Green, Blue) image analysis program, particularly by observing the greenness of plant leaves. However, plant size or the proportion of green area could be unreliable due to plant loss and camera's position and angle. To this end, we decided to evaluate plant health by analyzing the RGB codes associated with the green color only, which detects the chlorophyll reflectance and nutrient status, noting that the degree of greenness within the green-leaf-area was not affected by the plant size. We identified five RGB codes that are commonly observed in the plant leaves and ordered them from dark green to light green. Among the five RGB codes, the relative percentage covered by the darkest green to the lightest green was significantly different between the steam and chloropicrin treatments and the control, and it was not significantly different between the steam and chloropicrin treatments. Furthermore, the result was correlated with the total yield, and the trend observed in the first year was replicated in the second year of this experiment. In this study, we demonstrate that the RGB image analysis can be used as an early marker of the treatment effect on the plant health and productivity.

Turning the Tide on Mapping Marginal Mangroves with Multi-Dimensional Space–Time Remote Sensing

Mangroves are a globally important ecosystem experiencing significant anthropogenic and climate impacts. Two subtypes of mangrove are particularly vulnerable to climate-induced impacts (1): tidally submerged forests and (2) those that occur in arid and semi-arid regions. These mangroves are either susceptible to sea level rise or occur in conditions close to their physiological limits of temperature and freshwater availability. The spatial extent and impacts on these mangroves are poorly documented, because they have structural and environmental characteristics that affect their ability to be detected with remote sensing models. For example, tidally submerged mangroves occur in areas with large tidal ranges, which limits their visibility at high tide, and arid mangroves have sparse canopy cover and a shorter stature that occur in fringing and narrow stands parallel to the coastline. This study introduced the multi-dimensional space–time randomForest method (MSTRF) that increases the detectability of these mangroves and applies this on the North-west Australian coastline where both mangrove types are prevalent. MSTRF identified an optimal four-year period that produced the most accurate model (Accuracy of 80%, Kappa value 0.61). This model was able to detect an additional 32% (76,048 hectares) of mangroves that were previously undocumented in other datasets. We detected more mangrove cover using this timeseries combination of annual median composite Landsat images derived from scenes across the whole tidal cycle but also over climatic cycles such as EÑSO. The median composite images displayed less spectral differences in mangroves in the intertidal and arid zones compared to individual scenes where water was present during the tidal cycle or where the chlorophyll reflectance was low during hot and dry periods. We found that the MNDWI (Modified Normalised Water Index) and GCVI (Green Chlorophyll Vegetation Index) were the best predictors for deriving the mangrove layer using randomForest.

Effects of wood distillate and soy lecithin on the photosynthetic performance and growth of lettuce (Lactuca sativa L.)

This study investigated the effectiveness of foliar application of sweet chestnut wood distillate on the photosynthetic performance and growth of lettuce (Lactuca sativa L. cv ‘Canasta’), both alone and in combination with soybean lecithin used as biosurfactant. Seedlings of lettuce were treated with a foliar application of either mineral water (control), or 1:500 solutions of 3% soy lecithin, wood distillate and wood distillate plus 3% soy lecithin. After 1 week, the chlorophyll content, chlorophyll fluorescence, chlorophyll reflectance and dry biomass were measured. The results showed that both wood distillate and lecithin exerted a positive effect on chlorophyll content and biomass production, but the joint use of wood distillate and lecithin quickly stimulated a ca. 50% increase in these parameters and is thus recommended.

Spectral Reflectance in Silver Birch Genotypes from Three Provenances in Finland

The goal of this study was to investigate the variation in the leaf spectral reflectance and its association with other leaf traits from 12 genotypes among three provenances of origin (populations) in a common garden for Finnish silver birch trees in 2015 and 2016. The spectral reflectance was measured in the laboratory from the detached leaves in the wavelength range of visible and near-infrared (VNIR, 400–1000 nm) and shortwave infrared (SWIR, 1000–2500 nm). The variation among the provenance was initially visualized with principal component analysis (PCA) and a clear separation among the provenances was detected with the discriminant analysis of principal components (DAPC) and partial least squares discriminant analysis (PLS-DA) depicting a less strong variation among the genotypes within the provenances. Wavelengths contributing to the separation of the genotypes and provenances were identified from the contribution plot of DAPC and the red edge was strongly related to the differences. Chlorophyll content showed clear provenance variation and was associated with the separation among the genotypes and provenances in the DAPC space. The normalized difference vegetation index (NDVI705,750) and chlorophyll reflectance index (CRI) showed clear significance among the provenances, whereas NDVI670,780 showed no variation. The variation in the chlorophyll content and the CRI and red edge-based NDVI indices indicated seasonal variation as the chlorophyll content starts increasing in early June. The correlation of foliar chlorophyll content and the chlorophyll-related spectral indices for the discrimination of provenances and genotypes are reported for the first time in a naturally occurring tree species consecutively for two years.

Hyperspectral core logging for fire reconstruction studies

Lacustrine sediments contain a wide range of proxies that enable paleoenvironmental reconstructions. For instance, charcoal can be used to document past fire regime changes. In order to analyse high-temporal- and spatial-resolution records, however, it is necessary to develop fast, low-cost and high-stratigraphic-resolution methods. We developed a new paleo-fire proxy by studying a lacustrine core from the Esterel Massif, SE France, an area affected by two recent fire events, in AD 1987 and 2003. For this purpose, we searched for charcoal deposited and preserved in the lake sediments by combining a number of complementary methods, including: classic macrocharcoal tallying, scanning spectrophotometry, scanning hyperspectral imaging and high pressure liquid chromatography analyses. Macrocharcoal quantification is efficient, but time-consuming, and only provides intermediate-resolution data (cm scale). Spectrophotometry, used classically to quantify colour, is very fast, provides high-resolution data (4 mm) and is non-destructive (core preservation). Hyperspectral data have the same advantages as spectrophotometry, but offer higher spatial resolution (64-µm pixel size) and higher spectral resolution (6 nm) for core logging applications. The main result of this research is based on hyperspectral analysis at very high stratigraphic resolution using the I-band index. This index usually measures reflectance values at [660, 670 nm] corresponding to the trough in red reflectance produced by Chlorophyll a and its diagenetic products. This [660, 670 nm] reflectance trough, however, is also affected by the presence of altered organic matter and decreases with altered organic matter such as charcoal particles. Charcoal effect on the reflectance of Chlorophyll a and its diagenetic products is identified on first derivative spectra by a characteristic pattern around 675 nm, which is also in agreement with the Chlorophyll a concentrations measured by high-pressure liquid chromatography and charcoal particles. The I-band index is hence suitable for detecting burned organic matter, by quantifying the dilution of the chlorophyll signal by the charcoal signal. Thus, this adaptation of the I-band index can be applied in fire reconstruction studies.

A Sight for Sore Eyes: The Return of True Color to Geostationary Satellites

Abstract In 1967, at the dawn of the satellite era, the Applications Technology Satellite 3 (ATS-3) provided the first full-disk “true color” images of Earth. With its depiction of blue oceans, golden deserts, and green forestlands beneath white clouds, the imagery captured the iconic Blue Marble in a way that resonates strongly with human perception. After ATS-3, the standard fare of geostationary satellites entailed a single visible band with additional infrared spectral channels. While single-band visible satisfied the basic user requirements of daytime imagery, the loss of true-color capability and its inherent capability to distinguish myriad atmospheric and surface features via coloration left a notable void. Nearly half a century later, with the launch of Japan’s Himawari-8 in October 2014, there is once again a geostationary sensor—the Advanced Himawari Imager (AHI)—containing the multispectral visible bands required notionally for true color. However, it soon became apparent that AHI’s “green” band, centered at 0.51 μm, was not aligned with the chlorophyll reflectance signature near 0.55 μm. As a result, vegetation appears browner and deserts appear redder than legacy true-color imagery. Here, we describe a technique that attempts to mitigate these issues by blending information from a ref lective-infrared band at 0.86 μm to form a “hybrid” green band. When combining this method with Rayleigh corrections, AHI’s true-color performance is found to be consistent with that of the optimal 0.55-μm band, offering a stopgap solution adaptable to future satellites of similar design.

TOWARDS OPTICAL DETECTION OF PLASMOPARA VITICOLA INFECTION IN THE FIELD

Chlorophyll fluorescence, UV-induced fluorescence and reflectance signals of grapevine leaf tissue naturally infected by Plasmopara viticola were inspected in three susceptible grapevine cultivars (Cabernet Sauvignon, Pinot Blanc and Pinot Gris). Distribution of FV/FM parameter over the leaf was found to be effective to discriminate symptomatic and asymptomatic leaf tissue. Reduction of FV/FM parameter ~ 25% was found in all infected leaf spots. Infected leaves also expressed significantly changed chlorophyll fluorescence induction kinetics expressing much slower electron transport rate on donor and acceptor site of photosystem II. Symptomatic leaves emitted high fluorescence signal under UV excitation 320nm, centered at 395nm, emanated mainly from highly fluorescent compound 2,4,6-trihydroxyphenanthrene-2-O- glucoside. Increase of this compound was found in all inspected grapevine varieties, while its concentration was strongly dependent on resveratrol concentration. Concentration of trans- resveratrol ranged in asymptomatic leaves from 0.1μg·g-1 (CS) to 0.2μg·g-1 (PB, PG). Highest increase of trans-resveratrol in infected leaf tissue was found in PB (4.4μg·g-1), followed by CS (1.6μg·g-1) and PG (1.1μg·g-1). 2,4,6-trihydroxyphenanthrene-2-O-glucoside concentrations varied from 0.41 (PB), 0.75 (PG) to 1.01μg·g-1 (CS) in asymmptomatic leaves, since its concentration rapidly increase with severity of infection [71.09 (PB), 79.37 (PG), and 26.14 μg·g- 1 (CS)]. Reflectance vegetation indices SRI R750/R700, (R780-R710)/(R780-R680) and CRI700 were the most powerful to follow changes in chlorophylls and carotenoids contents under Plasmopara viticola infection. Infected leaves also exhibited lower chlorophyll a (~50 %) and carotenoids (~70%) content. Combination of these optical signals can be used as an effective, non-invasive tool for an early detection of Plasmopara viticola in field.

Chlorophyll content retrieve of vegetation using Hyperion data based on empirical models

Modeling using empirical methods based on Hyperion is a fast and accurate way to retrieve vegetation chlorophyll content. In this paper,the measured spectra and simulated Hyperion spectra were analyzed,the correlation between chlorophyll content and reflectance with its change forms and the relation between chlorophyll content and red edge parameters as well as vegetation indexes were calculated to obtain the most accurate modeling method. The vegetation index of modified simple ratio( MSR) has a significant correlation with chlorophyll content, and its regression model can retrieve chlorophyll concentration accurately. Using MSR and measured chlorophyll content,the authors built the regression model based on Hyperion data and then established the chlorophyll concentration profile. The chlorophyll concentration profile of Zhangye City was computed and a high- accuracy was achieved,with its relative error less than 5%.

Early Detection of Soybean Plant Injury from Glyphosate by Measuring Chlorophyll Reflectance and Fluorescence

Early detection of crop injury from off-target drift of herbicide is critical in crop production. Subtle changes in canopy reflectance could present useful information to detect the onset of crop stress. This study was conducted in a greenhouse to evaluate a portable spectroradiometer and a portable chlorophyll fluorometer for the detection of crop injury caused by glyphosate spray. Non-glyphosate resistant soybean (Glycine max L. Merr.) plants were sprayed with glyphosate using a pneumatic track sprayer in a spray chamber. Four plants received a rate of 0.86 kg ae/ha glyphosate and four plants received 0.086 kg ae/ha. Additional four non-sprayed plants were used as controls. After the glyphosate spray, the chlorophyll reflectance of the plants was measured with the spectroradiometer at 4, 24, 48, and 72 hours to determine the plant response to herbicide. Simultaneously, fluorescence induction kinetics of the crop under stress was measured with the portable chlorophyll fluorometer. Results of the statistical mean separation indicated that the plant chlorophyll reflectance measurement could be used to differentiate crop stress from glyphosate at 24 hours after spray among treatments and to identify the effect of herbicide at 24 hours after spray in each treatment. Moreover, linear discriminant analysis with the reflectance data showed that the crop stress of the soybean plants from glyphosate could be identified at 24 hours or more post application. Results of the statistical mean separation also indicated that use of plant chlorophyll fluorescence measurement could not differentiate crop stress until 48 hours after spray among treatments while it could identify the effect of herbicide 24 hours after spray in each treatment. These findings demonstrate that chlorophyll reflectance and fluorescence measurements both could be used for early detection of crop stress.

Degradation of Cyanobacterial Biosignatures by Ionizing Radiation

Primitive photosynthetic microorganisms, either dormant or dead, may remain today on the martian surface, akin to terrestrial cyanobacteria surviving endolithically in martian analog sites on Earth such as the Antarctic Dry Valleys and the Atacama Desert. Potential markers of martian photoautotrophs include the red edge of chlorophyll reflectance spectra or fluorescence emission from systems of light-harvesting pigments. Such biosignatures, however, would be modified and degraded by long-term exposure to ionizing radiation from the unshielded cosmic ray flux onto the martian surface. In this initial study into this issue, three analytical techniques--absorbance, reflectance, and fluorescence spectroscopy--were employed to determine the progression of the radiolytic destruction of cyanobacteria. The pattern of signal loss for chlorophyll reflection and fluorescence from several biomolecules is characterized and quantified after increasing exposures to ionizing gamma radiation. This allows estimation of the degradation rates of cyanobacterial biosignatures on the martian surface and the identification of promising detectable fluorescent break-down products.

Study of the Relationship between Rice Chlorophyll Concentration and Rice Reflectance

By the field experiment,we achieve the chlorophyll concentration and reflectance of nine groups of rice leaves and investigate the quantitative relationships between them by correlation analysisThe results reveal that they have good relationship in the range of 450～686 nm and 750～770 nm, and the peak of the correlation is at the wavelength of 686nmMeanwhile, we find strong correlation between the wavelength of the Red edge inflection point and the chlorophyll concentration of the rice leaves(R\+2=088), and then discuss the feasibility of exploring the rice chlorophyll concentration by way of hyperspectral remote sensing.

Nitrogen Status Determination of Rice by Leaf Chlorophyll Fluorescence and Reflectance Properties

Nitrogen Status Determination of Rice by Leaf Chlorophyll Fluorescence and Reflectance Properties Hao Hu1, Kefeng Zheng1 ∗, Xiaoming Zhang2, Yanting Lu2, and Hao Zhang1 1Institute of Digital Agriculture, Zhejiang Academy of Agriculture Sciences, Zhejiang, Hangzhou 310021, P. R. China 2Institute of Crops and Nuclear Technology Utilization, Zhejiang Academy of Agriculture Sciences, Zhejiang, Hangzhou 310021, P. R. China

LEAF CHLOROPHYLL CONTENT ESTIMATION IN THE MONARCH BUTTERFLY BIOSPHERE RESERVE

Chlorophyll is an essential element of photosynthesis and its content in plant leaves indicates their photosynthetic capacity as well as the presence of stress or diseases. The purpose of this work was to evaluate the feasibility of estimating chlorophyll content in the Monarch Butterfly Biosphere Reserve forest (Sierra Chincua sanctuary, México) based on vegetation indices calculated by using hyperspectral reflectance measurements of plant leaves. This study focused on oyamel (Abies religiosa L.) which is the main tree specie of this area. Leaf samples were taken on 140 trees and analyzed for chlorophyll a and b, nitrogen and carbon content. The hyperspectral reflectance spectra were measured on each sample and different vegetation indices were calculated. Results showed that the indices best correlated with chlorophyll content were the red edge position index (r = 0.531) and the red edge position chlorophyll reflectance index (r = 0.506), followed by the MERIS terrestrial chlorophyll index (r = 0.497) and the green chlorophyll reflectance index (r = 0.472). Although there was a significant correlation between nitrogen and chlorophyll content, none of the indices studied here correlated with nitrogen content. The influence of various environmental factors (altitude, slope, vegetation density and aspect) on leaf composition (nitrogen, carbon chlorophyll content and chlorophyll a/b ratio) and on the vegetation indices was studied. Environmental factors had an influence on both leaf composition and vegetation indices. Chlorophyll and nitrogen content were influenced mostly by the altitude and slope of the site while vegetation indices were affected mostly by its orientation.

Spectral identification of ozone‐damaged pine needles

Needles were collected from ponderosa and Jeffrey pine trees at three sites in the Sierra Nevada, and were assembled into 504 samples and grouped according to five dominant live needle conditions – green, winter fleck, sucking insect damage, scale insect damage, and ozone damage – and a random mixture. Reflectance and transmittance measurements of abaxial and adaxial surfaces were obtained at ca 0.3 nm spectral resolution from 400–800 nm, and binned to simulate Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) data. There were no significant differences in optical properties between the two surfaces. Ozone‐damaged needles were collected from Jeffrey pine trees at one site, and exhibited significantly different (family‐wise α = 0.01) reflectance and transmittance signatures – and significantly different signature slopes – at both spectral resolutions, from green and winter fleck needles from the same site. Ozone‐damaged needles had significantly different (family‐wise α = 0.01) abaxial surface reflectance and reflectance slope signatures from all other groups of needles, at both spectral resolutions. In comparison with three chlorophyll reflectance indices, a new red fall index (RFI) provides high classification accuracies for ozone‐damaged and non‐ozone‐damaged pine needles (overall acc. = 94%; κ = 59%). Thus, ozone‐damaged Jeffrey pine needles have a unique spectral signature in relation to dominant needle conditions of ponderosa and Jeffrey pine trees.

Comparison of measurements and FluorMOD simulations for solar‐induced chlorophyll fluorescence and reflectance of a corn crop under nitrogen treatments

Laboratory and field measurements previously acquired from foliage and canopies of corn (Zea mays L.) under controlled nitrogen (N) fertilization were used to parameterize and evaluate a new spectral vegetation Fluorescence Model (FluorMOD) developed to include the effects of steady‐state solar‐induced chlorophyll fluorescence (SIF) on canopy reflectance. These data included biophysical properties, fluorescence (F) and reflectance spectra for leaves; reflectance spectra of canopies and soil; solar irradiance; plot‐level leaf area index (LAI); and canopy SIF emissions determined using the Fraunhofer line‐depth (FLD) principle for the atmospheric telluric oxygen absorption features at 688 nm (O2β) and 760 nm (O2α). FluorMOD simulations implemented in the default mode did not reproduce the observed magnitudes of leaf F, canopy SIF, or canopy reflectance. However, simulations for all of these parameters agreed with observations when the default FluorMOD information was replaced with measurements, although N treatment responses were underestimated. The observed shift in the red/far‐red SIF ratio (from <1 to ∼2) that occurred in scaling from leaves to canopies, partially attributed to the paucity of abaxial leaf information incorporated in the model, was not expressed in the simulations. Recommendations were provided to enhance the potential utility of FluorMOD in support of SIF field experiments and studies of agriculture and ecosystems.

Chlorophyll Detection and Mapping of Shallow Water Impoundments Using Image Spectrometry

There exists a common perception that chlorophyll a concentrations in tidal coastal waters are unsuitable to be captured by remote sensing techniques because of high water turbidity. In this study, we use band index measurements to separate active chlorophyll pigments from other constituents in the water. Published single- and multiband spectral indices are used to establish a relationship between algal chlorophyll concentration and reflectance data. We find an index which is suitable to map chlorophyll gradients in the impoundments, ditches, and associated waterways of the Hackensack Meadowlands (NJ, USA). The resulting images clearly depict the spatial distribution of plant pigments and their relationship with the biological conditions of the waters in the estuary. Since these biological conditions are often determined by land usage, the methods in this paper provide a simple tool to address water quality management issues in fragmented urban estuaries.

(347) Identifying Common Reflectance Properties in Diverse Ornamental Species to Nondestructively Determine Nitrogen Status

Nitrogen (N) is often supplied to plants in excess to minimize the possibility of encountering N deficiency that would reduce the plant quality due to leaf chlorosis and necrosis. This is not only costly, but it can reduce the quality of plants, predispose the plants to biotic stress such as Botrytisgray mold, and extend the production cycle. Several tools can be used to identify N deficiency in plants, and most are based on chlorophyll reflectance or transmittance. While sensitive when plants are experiencing N deficiency, spectral signals can saturate in an ample N supply and make it difficult to discern sufficient and supra-optimal N nondestructively. Three diverse ornamental species (begonia, Begoniacea×tuberhybrida; butterflybush, Buddlejadavidii; and geranium, Pelargonium×hortorum) were grown with a broad range of N supplied (1.8 to 58 mm) in three separate studies that resulted in a range of 1.8% to 6% tissue N concentration. Using a spectroradiometer, we measured reflectance from the whole plants twice over a period of 3 weeks. A first-derivative analysis of the data identified six wavebands that were strongly correlated to both begonia and butterflybush tissue N concentration (r2 ∼ 0.9), and two of these also correlated well to geranium N concentration. These wavebands did not correlate to chlorophyll peak absorbance, but rather blue, green, red, and far-red “edges” of known plant pigments. These wavebands hold promise for use as a nondestructive indicator of N status over a much broader range of tissue N concentration than current sensors can reliably predict.

Visual Biology of Hawaiian Coral Reef Fishes. III. Environmental Light and an Integrated Approach to the Ecology of Reef Fish Vision

In the previous two papers in this three-part series, we have examined visual pigments, ocular media transmission, and colors of the coral reef fish of Hawaii. This paper first details aspects of the light field and background colors at the microhabitat level on Hawaiian reefs and does so from the perspective and scale of fish living on the reef. Second, information from all three papers is combined in an attempt to examine trends in the visual ecology of reef inhabitants. Our goal is to begin to see fish the way they appear to other fish. Observations resulting from the combination of results in all three papers include the following. Yellow and blue colors on their own are strikingly well matched to backgrounds on the reef such as coral and bodies of horizontally viewed water. These colors, therefore, depending on context, may be important in camouflage as well as conspicuousness. The spectral characteristics of fish colors are correlated to the known spectral sensitivities in reef fish single cones and are tuned for maximum signal reliability when viewed against known backgrounds. The optimal positions of spectral sensitivity in a modeled dichromatic visual system are generally close to the sensitivities known for reef fish. Models also predict that both UV-sensitive and red-sensitive cone types are advantageous for a variety of tasks. UV-sensitive cones are known in some reef fish, red-sensitive cones have yet to be found. Labroid colors, which appear green or blue to us, may be matched to the far-red component of chlorophyll reflectance for camouflage. Red cave/hole dwelling reef fish are relatively poorly matched to the background they are often viewed against but this may be visually irrelevant. The model predicts that the task of distinguishing green algae from coral is optimized with a relatively long wavelength visual pigment pair. Herbivorous grazers whose visual pigments are known possess the longest sensitivities so far found. “Labroid complex colors” are highly contrasting complementary colors close up but combine, because of the spatial addition, which results from low visual resolution, at distance, to match background water colors remarkably well. Therefore, they are effective for simultaneous communication and camouflage.

Study of the effects of suspended marine clay on the reflectance spectra of phytoplankton

A controlled experiment was set up to study the reflectance spectra of phytoplankton cultures isolated from marine and fresh waters in Singapore. Typical reflectance of chlorophyll was observed in the green band (540-570 nm), whereas absorption was mainly in the blue band (400-500 nm) and red band (∼650 nm). Additional reflectance peaks were observed in the near-infrared (NIR) region at 687 nm, 719 nm and 760 nm. A comparison of the spectral profiles at high and low chlorophyll concentrations indicates that there is a significantly greater increase in the overall reflectance in the (NIR) band compared to that in the visible band. Colour ratios and first derivatives at selected reflectance peaks were correlated with chlorophyll a content. The red-NIR ratio and first derivative at 687 nm (NIR) give the best correlations with chlorophyll a . When marine clays were added to the pure algal culture, a preferential increase in reflectance of light at certain wavebands was observed. When natural marine clay was added, there was a greater increase in the visible band, especially the green wavelengths, compared to that in the NIR band. In contrast, when combusted marine clay (organic content removed) was added, a relatively greater increase in reflectance in the NIR band was seen. The experimental results were able to partially explain the trends observed in spectral reflectance measurements of the coastal waters of Singapore.

Spectral mixture analysis of inland tropical waters

Abstract This letter presents results of experiments conducted to assess the use of linear mixing models to unmix the reflectance spectra of water. The model was tested with 11 reflectance spectra measured at Tucurui reservoir, Brazilian Amazon. The results showed that the fraction of chlorophyll reflectance accounting for the reflectance spectra of the various samples correlate significantly with the chlorophyll concentration in the 600 to 700 nm spectral region.