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A basis is provided for the feasibility of air-borne laser fluorosensing not only of chlorophyll but also of pollutants such as oils and chemicals. There was a satisfactory correlation between the laser data and those obtained manually. The absolute determination of the chlorophyll concentration is discussed.
Mesoscale biological patterns and processes in productive coastal waters were studied. The physical and biological processes leading to chlorophyll variability were investigated. The ecological and evolutionary significance of this variability, and its relation to the prediction of fish recruitment and marine mammal distributions was studied. Seasonal primary productivity (using chlorophyll as an indication of phytoplankton biomass) for the entire Southern California Bight region was assessed. Complementary and contemporaneous ship and satellite (Nimbus 7-CZCS) bio-optical data from the Southern California Bight and surrounding waters were obtained and analyzed. These data were also utilized for the development of multi-platform sampling strategies and the optimization of algorithms for the estimation of phytoplankton biomass and primary production from satellite imagery.
Ocean view images from the Ocean Color Experiment (OCE) were produced at three widely separated locations on the Earth. Digital computer enhancement and band ratioing techniques were applied to radiometrically corrected OCE spectral data to emphasize patterns of chlorophyll distribution and, in one shallow, clear water case, bottom topography. The chlorophyll pattern in the Yellow Sea between China and Korea was evident in a scene produced from Shuttle Orbit 24. The effects of the discharge from the Yangtze and other rivers were also observed. Two scenes from orbits 30 and 32 revealed the movement of patches of plankton in the Gulf of Cadiz. Geometrical corrections to these images permitted the existing ocean current velocities in the vicinity to be deduced. The variability in water depth over the Grand Bahama Bank was estimated by using the blue-green OCE channel. The very clear water conditions in the area caused bottom reflected sunlight to produce a sensor signal which was related inversely to the depth of the water.
A remote sensing instrument was mounted on a 50-ft tower overlooking North Inlet Estuary, South Carolina in order to conduct a remote sensing study of benthic microalgae. The instrument was programmed to take multispectral imagery data along a 90 deg horizontal frame in six spectral bands ranging from 400-1050 nm and had a ground resolution of about 3 cm. Imagery measurements were encoded in digital form on magnetic tape and were stored, decoded, and manipulated by computer. Correlation coefficients were calculated on imagery data and chlorophyll a concentrations derived from ground truth data. The most significant correlation occurred in the blue spectral band with numerical values ranging from -0.81 to -0.88 for three separate sampling periods. Mean values of chlorophyll a for a larger section of mudflat were estimated using regression equations. The scanner has provided encouraging results and promises to be a useful tool in sampling the biomass of intertidal benthic microalgae.
Near-concurrent Landsat Multispectral Scanner (MSS) and ground data were obtained for 60 lakes distributed in two Landsat scene areas. The ground data included measurement of secchi disk depth, chlorophyll-a, total phosphorous, turbidity, color, and total nitrogen, as well as Carlson Trophic State Index (TSI) values derived from the first three parameters. The Landsat data best correlated with the TSI values. Prediction models were developed to classify some 100 'test' lakes appearing in the two analysis scenes on the basis of TSI estimates. Clouds, wind, poor image data, small lake size, and shallow lake depth caused some problems in lake TSI prediction. Overall, however, the Landsat-predicted TSI estimates were judged to be very reliable for the secchi-derived TSI estimation, moderately reliable for prediction of the chlorophyll-a TSI, and unreliable for the phosphorous value. Numerous Landsat data extraction procedures were compared, and the success of the Landsat TSI prediction models was a strong function of the procedure employed.
Utilization of a two-color airborne lidar system in the systematic study of a major oceanographic feature is reported here for the first time. An excimer pumped dye laser was optically and electronically integrated into the NASA Airborne Oceanographic Lidar for simultaneous use with a frequency doubled Nd:YAG laser. The output beams exit the laser system along parallel paths after being produced on an alternating pulse basis at a combined rate of 12.5 pps. Results are presented for missions flown over a Gulf Stream Warm Core Ring (WCR) as well as over shelf, slope, Gulf Stream, and Sargasso Sea waters. From the airborne data a high coherence is shown between the two-color chlorophyll a data and between the Nd:YAG chlorophyll a and phycoerythrin responses within each of these water masses. However, distinct differences in the response patterns of these photopigments are shown to exist between the differing water masses. At certain of the boundaries separating the water masses a sharp transition is seen to occur, while at others a wider transition zone was observed in which the correlation between the photopigments appears to degrade.
The chlorophyll content of didemnid asidians with symbiotic algae (Prochloron) from oligotropic tropical marine waters around Palau, Western Carolin Islands is discussed. Several species contain as much chlorophyll per unit dry weight as many herbaceous crop plants and more than do other symbiotic associations such as lichens, green Hydra, etc. Their chlorphyllA/B ratios (3-9) were generally much lighter than those of angiosperms (2-4). Where they abound, Prochloron - ascidian symbiosis could make a major contribution to the productivity, especially in localized areas of tropical marine waters characterized by low nutrient levels and high irradiance.
Prokaryotic green algae (prochlorophytes), which contain chlorophylls a and b but no bilin pigments, may be phylogenetically related to ancestral chloroplasts if symbiogenesis occurred. They may be otherwise related to eukaryotic chlorophytes. They could have evolved from cyanophytes by loss of phycobilin and gain of chlorophyll b synthesis. These possibilities are briefly discussed. Relevant evidence from biochemical studies in many collaborative laboratories is now becoming available for the resolution of such questions.
Ocean color and infrared imagery from U2 aircraft and satellite sensors are used to study upwelling interaction between Gulf Stream and continental shelf waters in the Georgia Bight. The photographic data are combined with in situ measurements of currents, chlorophyll, temperature, salinity, coastal winds, and sea-level in observations of five different upwelling events including a near-short wind-driven upwelling caused by topographic effects, three filament-induced upwellings in the Gulf Stream, and a possible meander-induced upwelling event in the Gulf Stream. Chlorophyll distributions are used to trace the circulation and propagation of filaments along the advective routes by which the water moves offshore. Photographic and mooring array measurements of temperature time series are found to provide nearly identical results for the phase speeds of each event. Field measurements of surface pigments, and Nimbus/7 coastal zone color scanner (CZCS) estimates are found to agree well over the range of concentrations 0.1 to 0.7 mg/m to the third. Examples of U2/Ocean Color Scanner and Nimbus 7 CZCS photographs are provided.
A valuable input to crop growth and yield models would be estimates of current crop condition. If multispectral reflectance indicates crop condition, then remote sensing may provide an additional tool for crop assessment. The effects of nitrogen fertilization on the spectral reflectance and agronomic characteristics of winter wheat (Triticum aestivum L.) were determined through field experiments. Spectral reflectance was measured during the 1979 and 1980 growing seasons with a spectroradiometer. Agronomic data included total leaf N concentration, leaf chlorophyll concentration, stage of development, leaf area index (LAI), plant moisture, and fresh and dry phytomass. Nitrogen deficiency caused increased visible, reduced near infrared, and increased middle infrared reflectance. These changes were related to lower levels of chlorophyll and reduced leaf area in the N-deficient plots. Green LAI, an important descriptor of wheat canopies, could be reliably estimated with multispectral data. The potential of remote sensing in distinguishing stressed from healthy crops is demonstrated. Evidence suggests multispectral imagery may be useful for monitoring crop condition.
To evaluate the possible application of sunlight-illuminated fluorescence at 685 nm for remote sensing of phytoplankton concentrations, an ocean-color scanner is flown on an aircraft. The results of an analysis of the scanner data, obtained from a series of test flights conducted along the Elbe River and its estuary in the North Sea, show that 685 nm fluorescence is a promising remote-sensing method. The observation of a strong correlation between the fluorescence yields and the chlorophyll concentrations determined by the absorption method which uses the reflectance ratio of blue/green channels, is discussed. The two methods are compared and it is shown that the fluorescence method has an edge over the other due to the data-processing algorithm and its applicability for surveying bio-resources in all types of water. Photographs of the chlorophyll patterns are presented.
Two sets of TM data taken over the ocean off the coast of the Southeastern U.S. Bight were studied for the applicability of TM data to marine environments. First, the results of applying TM and TMS data to determine chlorophyll concentration in the ocean are presented. Chlorophyll quantification in the range of 0.5 to 2.0 mg/cu m was achieved by taking the ratio of TM band-1/band-2. Second, the results of applying TM band-6 data to monitor sea surface temperature are described. A comparison of TM data with AVHRR data shows TM readings coincide with AVHRR data within a scatter of 0.5 deg C in most of the areas studied. Lastly, the results of a technique to map the water depths of coral reefs in the Great Bahama Bank are demonstrated. Depths from 0 to 20 meters were delineated using TM band-1. The classification accuracy and origins of anomalous depth points are discussed.
In October 1978, the first satellite-borne color sensor, the Coastal Zone Color Scanner (CZCS), was launched aboard Nimbus-7 with four visible and two infrared bands, permitting a sensitivity about 60 times that of the Landsat-1 multispectral scanner. The CZCS radiance data can be utilized to estimate ocean chlorophyll concentrations by detecting shifts in sea color, particularly in oceanic waters. The obtained data can be used in studies regarding problems of overfishing, and, in addition, in investigations concerning the consequences of man's accelerated extraction of nitrogen from the atmosphere and addition of carbon to the atmosphere. The satellite data base is considered along with a simulation analysis, and ships providing ground-truth chlorophyll measurements in the ocean.
The use of remote sensing to determine seasonal changes in agronomic and spectral properties of winter wheat canopies with different levels of N fertilization is investigated. Field experiments were conducted at Purdue Agronomy Farm, West Lafayette, IN during the 1978-1979 and 1979-1980 growing season. Spectral reflectance, total leaf N concentration, leaf chlorophyll concentration, leaf are index (LAI), and fresh and dry phytomass are measured and analyzed. Three distinct wheat canopies are detected for the O, 60, and 120 kg N/ha levels of fertilization; it is observed that with an increase in N the reflectance in the visible, and middle IR wavelengths decrease, and the IR reflectance is increased. The canopies with 120 kg N/ha display the highest LAI, maintain green leaf area the longest, and increase in fresh and dry phytomass. The relationship between spectral and agronomic variables is examined; the effect of changing chlorophyll concentration and LAI on the reflectance is studied.
The temperature-plant pigment-optical structure of a mesoscale anticyclonic eddy consistently found in shipboard surveys and satellite-sensed data several hundred kilometers southwest of Point Conception, CA, is described on three different time scales (100-day mesoscale, annual, and several-year). The satellite coastal zone color scanner (CZCS) ocean color imagery detected the near-surface chlorophyll structure of the eddy, but in situ optical and plant pigment data suggest that such imagery does not provide a good estimate of the integrated chlorophyll field of the eddy. The temperature and plant pigment boundaries of the eddy, as determined from two-dimensional gradients of advanced very high resolution radiometer (AVHRR) and CZCS imagery, do not coincide spatially. This and in situ temperature, plant pigment, and optical structure provide additional evidence that some eddy systems in the California Current are not isolated vortex systems but rather continuously entrain waters of nonlocal origin laterally into their upper layers. Within the California Current a ratio of AVHRR/CZCS data is useful for separating inshore from oceanic water masses and following their surface entrainment by offshore vortices. The historical 28-year California Cooperative Oceanic Fisheries Investigations data for the Point Conception region of the California Current and remotely sensed data over this region show that the Point Conception eddy is a recurrent feature in the offshore California Current. Moreover, the available data provide evidence that a large number of warm-core mesoscale eddies occur simultaneously in a transition zone between coastal and oceanic regimes, that these features recur at preferred locations within the transition zone, and that this family of eddies should impose a significant offshore boundary condition on the flow of the California Current.
In many regions of the ocean, the phytoplankton population dominates both the attenuation and scattering of light. In other regions, non-phytoplankton contributions to the absorption and scattering may change the remote sensing reflectance and thus affect the ability to interpret remotely sensed ocean color. Hence, variations in the composition of both the phytoplankton population and of the non-phytoplankton material in the water can affect the optical properties of the sea. The effects of these contributions to the remote sensing reflectance and the submarine light field are modeled using scattering and absorption measurements of phytoplankton cultures obtained at the Friday Harbor Laboratory of the University of Washington. These measurements are used to develop regional chlorophyll algorithms specific to the summer waters of Puget Sound for the Coastal Zone Color Scanner, Thematic Mapper and future Ocean Color Imager, and their accuracies are compared for high chlorophyll waters with little or no Gelbstoff, but with variable detrital and suspended material.
Visible IR Intelligent Spectrometer (VIRIS) reflectance data have been found to have similar features that are related to air-pollution-induced forest decline and visible damage in both the red spruce of Vermont and the Norway spruce of Baden-Wuerttemberg; the similarity suggests a common source of damage. Spectra of both species include a 5-nm blueshifting of the red-edge inflection point, while pigment data for both species indicate a loss of total chlorophylls. The blue shift of the chlorophyll absorption maximum, as well as the increased red radiance and decreased near-IR radiance of the damaged spruce, may be used to delineate and map damage areas.
Characteristics of temporal variability in the California Current system are analyzed using a 30-month time series of CZCS imagery. About 20-25 percent of the variance is produced by a periodic annual cycle with peak values in winter. Analysis of ship-based chlorophyll measurements indicates that the winter peak is only characteristic of the upper portion of the euphotic zone and that total water column chlorophyll peaks during the spring upwelling season. Satellite studies of intraannual variability are modulated by strong 5- to 6-day oscillation in the availability of usable imagery, resulting from a combination of satellite orbital dynamics, which produces images of the study area roughly 4 out of every 6 days, and an oscillation in cloud cover, which controls the availability of clear imagery. The cloud cover oscillation, which is also present in coastal winds, undoubtedly affects the ocean surface and biases the data obtained by satellites. Analysis of data using a 5-day time step indicates that the predominant mode of nonseasonal variability is characterized by in-phase fluctuations throughout the southern and central California coastal region.