Chlorophyll (alpha) -normalized photosynthetic parameters, e.g. the photosynthetic efficiency ((alpha) ^B), and the maximum photosynthetic rate (P^B_m), for natural phytoplankton communities exhibit extreme ranges of variation. Part of this variation is related to the species composition of the communities, another part has methodological causes, and a large part has physiological causes, i.e. manifestations of adaptational responses to variations in environmental factors. To exemplify species differences in Chl(alpha) -normalized photosynthetic parameters, the high parameter values for prymnesiophytes in contrast to diatoms are discussed. These are primarily due to the lower chlorophyll (alpha) :carbon (Chl(alpha) :C) ratios in prymnesiophytes and therefore do not indicate that prymnesiophytes are superior to diatoms in the harvesting of light.

Fluorescence profiles were measured together with water samples taken in three expeditions to Norwegian Sea between 1988 and 1991. Chlorophyll concentration values obtained for the samples with a spectrophotometric method were used to recalibrate the fluorescence profiles to chlorophyll units.

The onset of the phytoplankton spring bloom in the Barents Sea usually takes place in April/May, at a time when the daily total irradiance and the `critical' depth increase fast. The onset of the spring bloom is normally assumed to be counteracted by water column vertical turbulence. During field investigations in the Barents Sea we observed that the blooms took place in vertically homogeneous water columns. By model simulations it is shown that entraiment of phytoplankton cells from the bottom sediments may be an important factor regulating the onset of spring blooms, and that if such processes exists, a vertically mixed water column may be beneficial for blooms. A new hypothesis is also presented where daylight is important, not through physiological processes enhancing photosynthesis, but by triggering the germination of phytoplankton spores.

Vertical profiles of optical parameters in stratified sea water are known to demonstrate the presence of thin (units of meters) layers characterized by enhanced backscattering. Such layers may be formed by high concentration of large (tens of microns in diameter) suspended particles, alga cells (diatoms,m etc.) in particular. The intensity of light backscattered from within the layers makes it possible to identify them by the shape of lidar signals. On the base of developed theory of lidar echo-signal formation the analysis is presented of the scattering layers discriminability (Sakitt's D-index) and recommendations for lidar parameters optimization are formulated. The optimal characteristics of lidar system for subsurface layers detection are shown to differ significantly from such characteristics for traditional bathymetrical airborne lidars.

In this study, Coastal Zone Color Scanner data have been used to study the distribution of Chlorophyll-(alpha) in Norwegian Coastal Waters. The images have been processed, and an atmospheric correction algorithm has been evaluated with in situ measurements of chlorophyll-(alpha) . In order to do the evaluation, it was necessary to calculate the total amount of Chlorophyll- (alpha) in the water-column. These calculations were partly based on in situ measurements. Attempts have also been made to recognize various physical phenomena in the Norwegian Coastal Waters. Documented in situ upwelling could not be seen, neither could eddy features, associated with the Norwegian Coastal Current. Fronts off the western coast of Norway and higher pigment signal in the North Sea, due to continental runoff and bottom entrainment, appear in the CZCS images.

The effect of ozone depletion on penetration of UVB radiation through the atmosphere and into an aquatic system is investigated with the use of a newly developed radiation model pertinent for the coupled atmosphere-ocean system. The atmosphere and underlying water are each divided into a sufficient number of horizontal layers to resolve the changes in model accounts for all orders of multiple scattering and the change in index of refraction across the air- water interface. The penetration of UVB radiation into the aquatic system is examined by assuming `normal' ozone abundance, taken to be 350 DU, and about 30% reduction from normal (250 DU), at 70 degree(s) N. The effect of ozone depletion on the UVB penetration into the water is more pronounced in early spring than in summer. The UVB enhancements are up to 36% at the earth surface and 33% 10 meters below the sea surface on April 1 at 70 degree(s) N as a consequence of ozone depletion from normal level to 250 DU.

The light attenuation coefficient c((lambda) ) is a key parameter which gives information about basic optical properties of marine environment. A set of measurements of c((lambda) ) together with suspension concentration (m_s), Secchi disc (z_(sigma )) and CTD were done during cruises in 1988 - 1992 in Spitsbergen fiords and Franz Josef Land. Mutual relationships between measured parameters were examined. The layer of horizontal suspension transport was estimated based on vertical profiles of m_s and CTD.

Now there are well known maps of vertical attenuation coefficient distribution over the World Ocean, which describe the upper 10 meters layer. For calculations the values of Kd from such maps are extrapolated usually to deep layers. But while the ocean is stratified optical characteristics may vary significantly in depth. So such approximation is not quite correct and calculation results, particularly for large depth, may have significant errors. For the last years with the use of a new device `Alfamer', a representative experimental array of data on vertical stratification of Kd was collected. The stratification data may improve an accuracy of E(Z) estimation. In this article Kd(Z) data are analyzed and generalized.

A central problem in optical oceanography is to specify the submarine irradiance field as a function of depth and wavelength. For many applications, however, it is sufficient to know the average optical properties of a layer of arbitrary thickness. Among such properties is the diffuse extinction coefficient, which is strongly dependent on the local concentration of photosynthetic pigments. In general, vertical pigment profiles in the ocean can be represented by shifted gaussians that may be parameterized through field observations. We have found analytical results for the average extinction coefficients in arbitrary segments of such profiles. The results can be applied to the calculation of primary production through the evaluation of integrals of spectral irradiance weighted by the photosynthetic action spectrum.

A theoretical approach for the problem of lidar signal formation is developed which accounts for the anisotropy of light scattering in the back hemisphere. The results explain the shape of observed return signal anomalies in airborne lidar experiments. An interpretation is proposed for the effect of signal `retardation' (i.e. the time delay between maxima of pulse of sea-water response and surface-reflected pulse), as well as for the anomalously high level of lidar signals from within distinct layers of sea water.

A new methodic for estimation the water quality parameters such as chlorophyll `a' concentration, absorption of `yellow substance' at 390 nm and Vsp--volume concentration of small particles from spectral vertical attenuation coefficient Kd((lambda) ), and spectral radiance was developed. These problems were solved by nonlinear programming methods with adaptive strategy. Adaptive strategy permits results with higher precision than the usual nonlinear methods and provides stability of solution in comparison to the least square roots method.

A method is proposed to estimate the accuracy of parameters retrieval from the spectral sea reflectance based on certain assumptions about errors distribution in the input data. Maximum likelihood method has been used to estimate the error of the retrieval stemmed from the random errors of experimental data. The method has been applied to the retrieval of chlorophyll-a concentration, coefficient of scattering in the backward direction of non-chlorophylous particles and absorption of yellow substance in the waters of north-east part of the Black sea. The retrieved chlorophyll concentrations are consistent with in situ measurements. The modeled values of scattering coefficient check well with measurements of extinction coefficient. Proposed accuracy estimates proved to be close to direct ones. The proposed method is general enough to be applicable to the accuracy estimation in various inverse problems of remote sensing of the ocean and atmosphere.

Light attenuation coefficient (LAC) of crude oil/sea water emulsion was investigated. It was measured using a spectrometer and calculated based on the Mie scattering theory. The emulsion was prepared in laboratory conditions: in two different temperatures (6.7 degree(s)C and 19.3 degree(s)C) and in two different light conditions (in the dark and exposed to light of intensity L equals 500 W/m²). Then the emulsion was stored in temperature T equals 1.3 degree(s)C or in T equals 15.4 degree(s)C and in the dark or exposed to light for 28 days. LAC obtained from model (LAC-M) and LAC obtained from specord (LAC-S) are compatible for fresh emulsion, stored no longer than 3 days. The difference between LAC-M and LAC-S, mainly in the short waves range, increase in time quicker for emulsion stored in a higher temperature than in a lower one or exposed to light than for emulsion stored in the dark.

A deeper understanding of radiative transfer in the ocean will require accurate measurements of inherent optical properties (IOPs) and apparent optical properties (AOPs) simultaneously or near simultaneously in the same water. Toward this goal, we have instrumented a remotely operated vehicle (ROV) with state-of-the-art instruments that measure the beam attenuation, volume absorption, backscattering coefficients, vector and scalar irradiances, temperature, salinity, and undisturbed particle-size distributions and concentrations. The ROV and its instruments are described and data are presented from deployments at Lake Pend Oreille, Idaho; Tongue-of-the-Ocean, Bahamas; and Monterey Bay, California.

Since 1988 a newly designed transmissometer (OPTISENS) has been used along the southern Norwegian coast to monitor phytoplankton blooms. The instrument has been suspended on a buoy equipped with an ARGOS PTT for satellite transmission of data. The OPTISENS is a light beam transmissometer with 3 different colors of the light, i.e. red, green and blue with peak wavelengths at 650 nm, 555 nm and 470 nm, respectively. Long-term measurements in the sea and laboratory experiments of in vivo absorption- and fluorescence excitation spectra, have demonstrated that it not only can distinguish between different particles but also identify of different groups of bloom-forming phytoplankton, some of which are toxic. The attenuation coefficient ratios between the colors blue, green, yellow and red will be discussed for different phytoplankton groups.

Nowadays it becomes more and more necessary to identify suspended matter in oceans in order to increase knowledge about primary productivity as well as the transfer of contaminants or to discriminate toxic phytoplanctonic species. It has been demonstrated for many years that fluorescence can be a well suited method to obtain specific signatures of organic matter in the sea. The paper presented here describes an interesting design of instrumentation based on optical fiber use and multiwavelength analysis which will offer wide possibilities for in situ monitoring of algae. Combining the flexibility of optical fibers and video as data carrier, results show great promise for new oceanographic equipment. In addition to technical descriptions, responses of some different grown species like dinoflagelates or diatoms families will be presented and discussed.

An underwater spectral radiometer has been designed and field tested to measure the in situ apparent optical properties of ocean waters from 400 nm to 800 nm. Light from scalar and vector collectors sensitive to upwelling and downwelling irradiance in the marine light field is relayed locally by fiber optic cables to the slit position of a sealed spectrometer. By simultaneously measuring the upwelling and downwelling scalar and vector irradiances at two depths the system becomes impervious to changing ambient light levels and requires relative rather than absolute calibration of its collector/sensor sensitivities. Capable of descending to 100 meters, the spectrometer images up to ten spectra from the marine environment with 5 nm spectral resolution simultaneously.

We have investigated the effects of a phytoplankton model of an area in the Barents Sea subject to different ways of specifying the light field. Three different schemes is used to calculate the light available for photosynthesis, (1) non-spectral attenuation of light in the water column, (2) spectral attenuation, and (3) calculating the photosynthetic usable radiation from the spectral scheme. This study also investigates the effects of changes in the spectral distribution under a cloudy sky with an increase in the shortwave radiation and a decrease in radiation at longer wavelengths.

During the international SPASIBA expedition (August - September 1991) optical measurements in Laptev Sea were made at few sections from Lena River delta to open sea (42 stations). Mainly vertical profiles of beam attenuation coefficient C(z) were measured using beam transmissometer. Statistical analysis showed that beam attenuation coefficient closely correlated with suspended matter concentration (r equals 0.96). So results of optical measurements can be interpreted in terms of suspended matter concentration.

Use of Landsat-5 Thematic Mapper data has been difficult due to uncertainty about the calibration constants. In order to establish a correct relation between the satellite signal and surface temperature, it has been necessary to use a high number of in-situ data for each new satellite scene. In the period 1984 - 1992 we used Landsat 5 TM data for mapping Sea surface temperatures at 20 occasions. We have been able to derive a linear correlation between pixel values in system corrected digital TM data and in situ measured temperatures.

The laboratory measurements of spectrum of light attenuation on phytoplankton particles i.e. monoculture of unicellural green algae Chlorella vulgaris are presented. The measurements were carried out for alive culture and the cultures subjected to chemical (NaOH) or physical (ultrasounds) modification. The distinct changes in the light attenuation spectrum were a result of modification of the internal cell structures.