Institute Of Oceanology
Vol. 2 Varna 1998
Bulgarian Academy of Sciences



Phase of the wind waves in the coastal zone
Zhivelina Cherneva, Albena Velcheva

Wind waves propagating in the coastal zone have usually investigated by traditional spectral and statistical characteristics like wave heights, power spectrum and various probability density functions. But in this case there isn't a valuable information about wave group structure.
In this work by Hilbert transformation technique the amplitude and phase modulation is investigated. Sea surface elevation has been measured at eleven fixed points in the coastal zone with a depths from 18 to 1 m. Wave amplitudes, wave phases and their derivatives are computed from these data. It is concluded that these characteristics are rather suitable for studing the wind wave groups.

Determination of diffusion turbulent coefficient in wave flow
Vesselin D. Peichev

On the basis of natural observation on the vertical distribution of suspended sediment concentrations diffusion coefficient is calculated. Experimental diffusion turbulent coefficient and theoretical diffusion coefficient for average wave are compared. The best results is received when operating on wave characteristics corresponding to 13% spectral density.


Alexander V. Rozhdestvenskiy

The paper presents an examination of principal Black Sea bottom silts components input with the river inflow, dust and rains. Quantitative data are deduced. The conclusion, that the principal inorganic components input last years decreases and organic sediments increase.

Galina P. Shtereva

The content of total suspended matter, particulate organic carbon and organic phosphorus in the thin surface microlayer and surface waters are studied and compared.
The results are based on tree transects samples of 12 stations in front of the Bulgarian Black sea coast.
The established higher concentrations in the thin surface layer of the sea-atmosphere boundary shows accumulation of organic suspended matter there.

Alexander V. Rozhdestvenskiy

Mandra - lake is the southern of the tree Burgas - lakes. At first it was open to sea, with the great seasonal movements of salinity ( 0,18 - 33,01 ‰ in our investigations 1948 -1962). In 1962 the greater part of lake was turn into reservoir. Became a change of chemical composition of water in dammed and open parts of lake (1962 -1965). In this paper are the results of investigations during 1966 - 1985.

Alexander V. Rozhdestvenskiy

In 1991 was continued the hydrochemical monitoring in Varna-gulf. The results showed extraordinarily of movement of middle chemical datas and their quantities.

Galina Shtereva, Alexander Dimitrov

This paper describes the distribution of the organic carbon, proteins and nucleic acids in water and surface layer of bottom sediments in the Varna lake and Beloslav lake. The results are based on samples of 22 stations.
The organic components in the surface and near bottom water are compared. A tendency is established of decrease in the organic content of the Varna Bay water and sediments.
The proteins and organic carbon in the sediments of Varna lake are higher in comparison with Beloslav lake.

Alexander S. Stoyanov, Lidia D. Mihova, Ilia I. Shtirkov

In order to find out the connection between the increasing eutrofication of the Blask sea basin and the changes that had taken place in the biogeochemical cycle of the organic matter representative researches by RV " Academic " and the diving inhabitable apparatus PC-8 were done in 1990. The sampling were taken using constructed by us special system for precise sampling the needed horizons during the diving of the apparatus. Besides the visual watches at the structure of the "planctonic snow" and the species of the macrozooplancton, the dinamic of the suspended matter by the vertical direction and two of its main organic components C and P, were studied.
The results show that in connection wich the increasing eutrophication the structure of the suspended matter in the Bulgarian shelf area has changed significantly. The cause is in the general increasing of its organical part, which is basic element of the sedimental flow. This shows an increasing of the called "planctonic snow" with the prior of the zooplanctonic content. Its level of dispersity in the vertical direction is being by season changes in the thermohalinic structure of the water. In this order the processes of coagoalation and agregation, which intensity is higher in the summer, are from great significance. The corelation between the content of the suspended matter, the suspended Corg and the dissolved phosphorus shows that depth the thermocline during the both biologically active seasons - spring and summer is not enough as a bar to the process of sedimentation and cannot assure the possibility for transformation and destruction yet in the water. Common law for the both seasons is that in the layer from 20 to 25 m above the bottom, the level of dispersity decreases. Its high agregate stability and low level of dispersity are the main factors determining the increased sedimental flow, which causes involving a great number of phosphorus and carbon in the sediments.

Iliya At. Shterev

One of the most perspective methods for water-supply of marine vessels and coastal settlements is desalination of sea water through membrane reverse osmosis plants. The quality of desalinated water appears as a major problem for the effectiveness of the process and the duration of membrane life. Contemporary methods for assessment of the processed water qualities are discussed in the paper. Data from investigations of Silt Density Index at different Black Sea regions is presented. Recommendations are made for implementation of the membrane desalination equipment under proper conditions ensuring normal and continued work.

Galina P. Shtereva, Iliya A. Shterev

The study was based on monthly monitoring at two stations on Balchik Bay of the following parameters: dissolved oxygen, nutrients, organic, carbon, surface active substances and heavy metals. The seasonal dynamic of the main parameters in the different regions were compared. The impact of anthropogenic factors on the hydrochemistry of Balchik Bay was established. The influence of Batova river on the hydrochemical regime of the South part of the area was estimated.
The phosphorus, carbon and metals in the surface sediments were investigated.


Seabed Pockmark in the Southern Bulgarian Black Sea Zone
Lyobomir Dimitrov, Valentina Dontcheva

In 1988, pockmarks were discovered for the first time in the SE of the Bulgarian Black Sea zone. The echo - 'sounder and shallow seismic data analyses of investigations conducted before and after 1988, allow primary pockmark area to be enlarged and detailized.Total of 305 pockmark have been localized, within an area more than 100 km2 (2 - 5 km wide and 41 km long). The bottom of the area is covered with Holocene soft silty clay. The following tendencies are defined from northern part of pockmarks area to southern one: - increasing of the seabed sediments thickness from 2.5 m to more than 3.2m and decreasing of the mean grain sizes; - increasing of the water depths from 160 - 300 to 230 - 340 m at the places where the pockmarks occur; - increasing of the average visible size of the pockmarks from 86 to 132 m in diameter and from 2 m to 4 m in depth; - decreasing of the extrapolated density of the pockmarks from 8 - 9 pm/km2 to 3 - 4 pm/km2. Similar tendency is observed seaward and the pockmark profile shape is changed from smooth U - shaped to sharp V - shaped form, and their walls slope angle reaches more than 10°. A variety of acoustic anomalies such as acoustic turbidity, bright spots, enhanced reflections etc., are registred in many places within the pockmarks area, which is an indication for gas presence in the sediments. Water column anomalies have also been registered. The paper discusses the origin of the gas (most likely to be a mixture of thermogenic and biogenic gas), and time of pockmarks formation as well.

Slides in the upper part of the continental slope and plow structures in the peripheral shelf terrace in the Black Sea SE of Cape Kaliakra
Lyobomir Dimitrov

A variety of gravity structures caused by slope slumping processes are observed in geophysical profiles from the peripheral shelf terrace and upper part of the continental slope in the Black sea southeast cape Kaliacra. On the upper slope a series of rotational-transitional slides are developed on areas of 5 - 6" to 10" gradient. Two circular rotational slides are localized too. It is given a brief description of the slide's divisions. The data suggest that they are geologically recent - Upper Pleistocene. The most probable triggering mechanisms are sea level change, earthquakes or sediment instability. A system of plow structures and slide grooves is developed along a tensional faults landward the slide crowns on the peripheral shelf terrace. Their profiles on the echo-sounder and shallow seismic sections are V or U cone shaped depressions, similar to pockmark and it can made an incorrect interpretation, especially if there are evidences for shallow gas as it is in this case.

New Indications of Detemination of Transgressive and Regressive Sediments in the Shelf of the Rezovo Strucural Zone
Orlin Dimitrov

The ways of passing of the seismic waves through media of different physical properties are shown in this study as well as the ways of their reflection and drawing upon the seismograms. Sedimental processes in the formation of transgressive and regressive sediments are viewed as well as mechanic coercions as slipping masses, sea waves and additional local tectonic changes.
Respective conclusions about texture structure of the settling sediments and their physical properties are done. As a result the author does conclusions about the ways of reflection upon the seismograms of the different seismic facies units.

Velocity Model of Oligocene and Eocene Sediments from Dolna Kamchiya Depression
Orlin Dimitrov

The problem of the velocity of the seismic waves in the rocks is of an exclusive importance. The discussed parameter is necessary for figuring depth of the geologic sections, structural maps and thichness of the seismic facies units.
In this work, using different dependances between the physical properties of the rocks density and porosity, from one side and depth of the rocks and their stratigraphic and litologic belonging, from another, we determine the velocity of the seismic waves in the separate stratigraphic intervals. After that the results are compared to each other and the mean velocity of the seismic waves in the rocks is determined.

Tectonic Disturbances and the Genesis of the Sources of Hydrocarbonic Gas in the Shallow Area of the Bulgarian Shelf
Ivan D. Genov

The article considers the faults of the gulf of the Baltchik and the adjacent area according to their permeability. Depth, crust-reflected and epistructural disturbances have been selected, presuming that the two kinds of faults are structure-generating.
The existence of gas-seepages is related to the submeridional disturbances, having broken the Oligocene sedimentations and subject to a specific geodynamic extension. Under such conditions these faults represent opening structures and serve as conductors for the hydrocarbonic fluids.

Veliko Dachev, Radko Genov

The fast progress of marine construction activities in Bulgaria during the last decades shows that human interaction in the coastal processes often yields consequences which can hardly be foreseen. Some of them affect both functional efficiency of structures and ecosystems' equilibrium, and may occur either during construction or after that.
The paper discusses the main accompanying effects with reference to the natural conditions, physical factors, intensity and duration of their impact.
A classification diagram comprising the most characteristic of the Bulgarian construction works' concomitant side effects is proposed. The latter could be used by designers of marine structures and the respective managers for prognoses and environmental impact assessment.

Palaeooceanological reconstruction in the West Black sea part during the Quaternary
P.S.Dimitrov, E.S.Michova, V.D.Peichev

On the basis of the data presented it is established that the eustatic sea level fluctuations have been a controlling factor for the formations of the West Black sea part relief during the Quaternary. Tectonics impact is exhibited in regional scope.
The regressive coastal complexes of the Early Chaudinian, Post-Karangatian and Early. New-Euxinian basins are traced in the peripheral shelf zone. Uzunlarian, Karangatian and Holocenian transgressive coastal formations and sediments are found along the coast and in the inner and central shelf zone.
Sea level fluctuations are characteristic feature of the Holocene.


The structure of the zooplankton in the Black Sea in front the Bulgarian coast, formeted in the summer 1990
Daniela P.Georgieva

The thesys focus on a detailed characteristics of zooplankton species diversity, vertical and horizontal distribution, seasonal periodicity, trophic structure and the consequences of the introduction of species of high ecological valency under the conditions of increased eutrophication of Black Sea ecosystem along the Bulgarian Black Sea coast during 1990 - 1991 .
A trend of decrease in zooplankton biomass from North to South has been established typical for all seasons. Regarding the zooplankton structure the main trend is an increase in the biomass of the species A.clausi, P.polyphemoides, 0. dioica, and a decrease in the biomass of the species C.kroyeri, E.tergestina, E.spinifera, P.avirostris.
The preceding of P.avirostris from coastal to open sea and the significant increase in the abundance of P.polyphemoides and Noctiluca scintillans in the coastal area may be used as an indication of the trophic pottential of the coastal zone.

Zooplankton in the lake Pomoriysko-composition, dynamics, trophic interactions and secondary assimilation
Vassil P. Vassilev, Assen S. Konsulov

Investigations of quantitative and qualitative composition of the zooplankton in the Lake Pomoriysko and their dynamics were generalized. An attempt was made to analyze the trophic relations and to calculate the secondary assimilation of that important ecologic category of aquatic organisms. Samples for analyses were collected monthly or every second month from February 1986 to September 1987 from the whole water column in 6 points by means of an especially constructed plankton set. The zooplankton taxonomic composition was quite scant due to extreme environmental conditions. Nearly 1/3 from the biomass (average about 400 mg.m'2) and from the secondary assimilation (less than 1 g C/ m2. year) belonged to Copepoda, Rotatoria and meroplanktonic larvae of benthic organisms.
A typical spring maximum and a slight autumn maximum were registered in the development of zooplankton. Deficient in quantity, the zooplankton limited the fish productivity in the lake. That was a result of the relatively low phytoplankton biomass and production. The restricting influence could be avoided by cultivating ,,living food" for the fry spending the winter in farming thanks and used for the stoking the lake in the spring.

Size-age and sexual composition of Bulgarian catches of Trachurus capenses during February-July 1988
Kamen B. Prodanov

The length composition of Cape horse mackerel varies significantly during the months. It depends on the intensity of reproduction and the migrations connected with it. Because of this the length composition of the catches depends on a great extend from the depths where the trawlers do operations. The mean length of the fishes in the coastal zone is considerably lower than those from the depths 350 - 450 m.
The population of Cape horse mackerel was spawning all the time during the investigated period with two clearly expressed maximums:February and May. During the period under consideration the number of male fishes with gonads in IV-VI stages of fecundity was higher than those of females. Because of this, during the spawning period, the male fishes (in numbers) dominant on the females nevertheless their lower abundance as a hole. This is probably an adjusting gear ensuring better reproduction possibilities for the Cape horse mackerel.
The great importance for the successful reproduction of Cape horse mackerel has the total abundance of 4-8 year old fishes. The last one in 1988 was with 10% lower than its mean value during the period 1973-1987.

On the diel dynamic of chlorophyll a content in Sceletonema costatum (Grev .) CL. as s function of light and temperature variation
Snejana P. Moncheva, Stephan M. Krastev

Изследвано е влиянието на температурата и светлината върху динамиката на съ- държанието на хлорофил а на клетка в денонощен аспект при морската диатомея Sceletопета соstatuт (Grev.) СL. (ав-тохтонен черноморски изолат) в лабораторни условия. Установено е, че с увеличаване на температурата нараства и съдържанието на хлорофил а, като максимумът му е при температура 22-24° С. Основният тренд в денонощната промяна под влияние на експерименталните условия е увеличение през светлинната фаза и намаляване през тъмнинната фаза. Денонощната динамика е по-ясно изразена при съвместното въздействие на висока температура (22-24°С) и ниска осветеност (2000 1х). Дискутирано е значението на тази физиологична особеност на Sceletопета соstatuт за проявата на два цъфтежни максимума на вида (зимно-пролетен и летен) в естествени условия.

Vasil P. Vassilev, Snezhana P. Moncheva, Detelina S. Moneva

The paper presents the results of a study of the composition, dynamics, and spatial distribution of phytoplankton in the Lake Pomoriysko during 1985 - 1987. In the planktonic microalgal flora were listed 39 species belonging to 5 classes: 17 species of Dinophyceae, 15 of Bacillariophyceae, 5 of Cyanophyceae, 1 of Chlorophyceae, and 1 of Cryptophyceae.
Two main maxima characterized the seasonal dynamics of the phytoplankton community in the lake: the spring maximum was dominated by Chlorophyceae and Cryptophycea species, and the summer maximum by Dinophyceae. There was a ,,clear water" period between them. No typical autumn maximum was observed. Strong storms in the autumn spread out great amounts of the decaying seaweeds accumulated along the west shore over the whole lake, and thus enriched the water body with nutrients. As a result of this short-term but intensive dinoflagellate blooms (Gymnodinium splendens) occurred.
The horizontal distribution of phytoplankton was relatively homogenuous during the main part of the year. A blooming zone covering 20 to 30% of the total area was observed in summer and at the beginning of autumn along the stripe of decaying seaweeds by the western shore and in the narrow northern part of the lake. The basin can be classified as a- to 6-eutrophic according to the annual average phytoplankton biomass of 5.25 - 2.14 g/m3.

Catches of the Black Sea Sprat (Sprattus sprattus L.) with Bulgarian Ocean Fishing Trawlers
Ljudia St. Ivanov, Galina N. Ivanova

It is the first time that the results of the fishing of sprat with Bulgarian ocean trawlers for the period of 1980 - 1986, which until recently were confidential, are published. Besides the general, the effort catches classified according to months and regions of fishing for 1980 - 1983 are announced. The alterations in th e general and effort catches are studied against the background of the changes of the general and exploitation stocks, and also in comparison with the catches and the fishing efforts with small (Black Sea) ships and stationary traps. It has been found out, that with the reduction of the stocks in 1983, caused by the scanty generations of 1981 and 1982, the effort catch of the ocean ships has fallen dawn relatively to a greater extent than of the Black Sea trawlers. Estimated according to their volume, the ocean ship catches were many times lower than the general catches made with the rest fishing devices. That's why the mortality rate, caused by the ocean ships has been over and over again lower than the total fishing mortality, which has been considerably below the accepted admissible limit. The ocean trawlers however have strongly disrupted the bottom biocenoses. The conclusion is that the ocean trawler fishing has been an episode, which probably will not occur in the future. The estimation is that fishing in the Black Sea with large and heavy ships is ecologically harmful and economically unsubstantiated.

Ecological Determination of the New Ctenophore (Вегое оvаtа) Invasion in the Black Sea
Asen S. Konsulov, Lyudmila T. Kamburska

През последните двадесет години в резултат на повишената еутрофикация и антропогенно въздействие Черноморският басейн се явява благоприятен за трайното установяване на много пришълци. Масовото развитие на някои от тях води до драстични промени в биоразнообразието на планктонната фауна. Това се отнася изключително за представителите от клас Сtenophora. За черноморската планктонна фауна до 1997 г. са известни два представителя на този клас-Pleurobrachia pileus и Mnemiopsis leidyi. Според редица автори масовото развитие на M. leidyi след 1986 г. доведе до намаляване на експлоатационния запас на рибите и биоразнообразието на зоопланктона. GESAMP изработва стратегия за ограничаване развитието й в Черно море. Едно от предложенията е за биологичен контрол чрез интродуциране на неин хищник от род Веrое, а именно Веrое ovata, което има както предимства, така и недостатъци. През октомври 1997 г. в района на Шабла бе открит нов представител на клас Сtenophora, принадлежащ към род Веrое и идентифициран от нас като Веrое ovata. Този хищник не е съобщаван досега за фауната на басейна. Естественото навлизане на Веrое ovata в Черно море направи излишна намесата на човека. Настоящата публикация представя основната причина за навлизането на новата за Черно море ктенофора Веrое ovata, а именно високата численост на M. leidyi, която е основна храна на новия вид. Това ни дава основание да приемем, че естественото навлизане на новия вид в Черно море е трофично обусловено. Но ако новата ктенофора се развие масово, елиминирайки една от причините за повишена еутрофност- Mnemiopsis leidyi, това би могло да доведе до нови драстични промени в черноморската екосистема, тъй като масовото развитие на ктенофорите видоизменя структурата дори на стабилни биологични съоб-щества. Остава открит въпросът дали Веrое ovata ще се установи трайно, кой ще бъде нейният хищник и кога ще се появи?


Anchor dampher for oceanographic buoys
Trayan K. Trayanov

The perennial investigations on anchor devices for oceanographic and navigation buoys reveal that under extreme dynamic loading, chain links that are nearer the anchor change informant after certain time break.
To increase the reliability of oceanographic and navigation buoys, anchor damphers are used based on old aircraft tyres.
The papers present results for energy-deformation characteristics of dampher, which reveal what part of the energy has changed irreversibly into heat.

A microwave doppler measurer of the sea wave parameters
Lybomir H. MIadenov, Andrey K. Savchenko, Hristo D. Slabakov

The block-diagrams of an experimental setup of a microwave Doppler radar have been shown.
A comprasion is made between the heights and the periods of the "sea waves measured with a microwave Doppler radar and with a string type wave recorder.
Their frequency spectra have been analized too. The results obtained by synchronized measurements with both measurers have shown a very good coincidence.
It has been proved that the microwave Doppler radar can be used for remote determination of the sea waves parameters ( mean height, period, spectrum, etc. )

Method for modelling of acoustic channel with passive R, L and C elements
Atanas Al. Atanasov

A technique for modelling of acoustic channel with passive R, L and C elements is described. The transformed electrically equivalent scheme which has been obtained allows experimental determination of the transmitting function of the electroacoustical circle.

Experimental study on the relationship between phyto- and zooplankton biomass and sound velocity in sea water
A. Palazov, Ch. Slabakov, S. Moncheva, A. Konsulov, T. Trayanov

The specific pattern of distribution of phyto- and zooplankton biomass under eutrophication results in alteration in water masses acoustic properties. It has been suggested that the variability in the sound velocity through the water column could be used as an indicator of the pattern of plankton biomass distribution. The experimental test reveal that, in the renge of explored concentrations, the sound velocity in sea water is more sensitive to the variability of temperature and salinity that to the variability of plankton biomass.

Programmable marine proton magnetometer
Veselka M. Marinova, Assen N. Krastev

The article describes a programmable marin e proton magnetometer PMPM 001 designed at the Institute of Oceanology -Bulgarian Academy of Sciences for measuring of magnetic anomalies in the Black See region. A block scheme and a Time-diagrams of the magnetometer are shown. The nuclear-precessional measuring method lying at the basis of operation of the magnetometer is explained. Experimental results from tests during research expeditions are applied.