porthole into the seawater; then, after having been reflected 

 from an outboard spherical mirror, it returns. Such a returning 

 beam, attenuated by the seawater, is directed to a 

 photomultiplier where it is compared with a reference beam, 

 passing inside the instrument. Originally, this reference beam 

 has the intensity equal to that of the probing beam. The 

 required spectral range is discriminated with the aid of a 

 suitable light filter, which is installed in front of the 

 photomultiplier. A different signal is transmitted over the 

 cable-line to the board block and registered there as a function 

 of the depth probed. The instrument measurement base is 0.5 

 m; maximum depth of immersion, 250 ni (Kumeisha & 

 Vinokurov, 1984). 



The assessment of measurement errors is a very difficult 

 problem because of the lack of "clear water" reference. Usually 

 verification is carried out with the aid of samples that are 

 standardized neutral filters and thin glasses and whose 

 coefficients of transmissivity (orrellection) are measured on a 

 standard spectrophotometric equipment or can readily be 

 calculated. Modeling has shown that the absolute error of 

 measurements made to detemiine the attenuation index of clear 

 {£ < 0.15 m ') waters is not in excess of 0.01%; in less clear 

 waters the relative error is nearly 5%. 



A bathometer is an attachment to the "Kvant-3"" 

 transmittance meter which allows an assessment, on the basis 

 of visual analysis, of a profile of the attenuation index. The 

 bathometer valves are tested for reliable functioning by 

 measuring the transmittance of an assay selected, making use 

 of a special cell in the "Kvant-3" instrument (intended for 

 onboard analysis), and then comparing transmittance values 

 with those measured //( situ on the horizons of probing. All tests 

 showed satisfactory results. 



A board indicatrix meter is constructed as a cylindrical cell 

 with an attached illuminator and scanning device with a 

 photodetector. The illuminator emits a collimated beam of 

 light, which, via portholes in the cell, transilluminates water 

 samples (cell volume is 3 ml). The scanning device receives 

 radiation scattered from the zone at angles from 0.5° to 165° 

 relative to the direction of its propagation. The illuminator and 

 receiver embody aperture and field diaphragms pemiitting 

 alteration of angular divergence of light fiuxes and their cross- 

 sections. The volume, subjected to photometry analysis, is 

 5- 10 ml. Hence, one can safely neglect the contribution of this 

 factor to the scattering of zooplankton. 



Received light is directed to the photomultiplier through a 

 glass light filter; an electric signal, proportional to the light 

 flux, is then amplified, filtered, and applied to a digital 

 recorder. 



In order to obtain absolute values of scattering indices, the 

 intensity of light that has passed through the instrument is 

 measured (Gabrilovich, 1976). The instrument was verified 

 with the aid of monodisperse polystyrene latex solution. 

 Comparing the results of measurements and calculations, the 

 relative error of angular measurements of light scattering has 

 been found to be 10%. 



Results 



All primary hydrooptic characteristics were measured at 

 wavelength X = 530 mm. The obtained vertical profiles of 

 attenuation index were tabulated through 1 m in shallow parts 

 of the seas and through 5 m at depth H = 100-250 m. Since, in 

 biology, they often operate with average characteristics ( related 

 to water layer or water column), we also calculated average 

 index of attenuation in layer 0-H: 



j e(H')dH' 



<e>H = 



H 



Absolute values o{y) within 0.5-165°, full index of 

 scattering and integral characteristics of indices (k, cos y and 

 R [ Y„ = 2° 1 ) were calculated from angular relationships of light 

 scattering. Volume concentrations V^ and V, (in cmVm') of 

 coarse (particles having radii in excess of 1 urn) biological and 

 fine mineral (less than 1 |im) fractions of suspended matter 

 were assessed following Kopelevich (1981). Such calculations 

 are possible using a physical model of scattering. Ocean water 

 particulates is divided into two independent fractions in terms 

 of size and index of refraction. Angles of y < 2° for coarse 

 particles, and y> 45° for fine, can be calculated; however, the 

 numbers are weakly correlated. 



This is, of course, an idealized model of ocean water 

 particulates; yet, on the whole, it allows interpretation of 

 material that has been collected earlier. Its advantage lies in the 

 fact that it permits assessing the content of fine fraction 

 particulates (including submicron particles), which is beyond 

 the capacities of conventional geological methods. It should be 

 noted, however, that the model has not been tried by the author 

 ( Kopelevich, 1 98 1 ) to describe indicatrices of highly productive 

 waters where variation of content of coarse and fine particulates 

 differs from that in open ocean. Fine suspended particles may 

 predominantly be of organic matter. Applicability of generally 

 accepted concepts becomes doubtful when suspended minerals 

 dominate in coarse fraction. This is why the assessments of 

 particulates content, presented in this report, should be regarded 

 only as preliminary, subject to verification through direct 

 biological observations and through appropriate model-based 

 calculations. 



Volume content of fine and coarse fractions (V, and VJ 

 was inferred from the following relations: 



V, = 10.2o,4, ,-1-4x1 0-*o,,., -0.002, 

 V, = 2.2xl0^o„.,-1.2a,45.„ 



(11) 

 (12) 



where o,, ,and 0,43, are indices ofdirected scattering at l°and 

 45° angles. 



The optical type of water, assessed from measured values 

 of 0,4;; I and o, , ,, will also be helpful when added to the above- 

 mentioned parameters. Since according to ( 1 1 ) and (12) such 



137 



