Satellite Monitoring of the Black Sea Ecological Risk Areas

Results of multiyear monitoring of zones of persistent ecological risk in the Black Sea are presented. These ones are most affected by oil pollution, raised concentration of suspended particulate matter and harmful algae bloom. Studies are based on satellite remote sensing data obtained over the Black Sea from 2000 to 2017 from radar sensors ERS-2 SAR, Envisat ASAR, Sentinel -1A, -B, Radarsat 2, TerraSAR-X; visible and infrared data from Envisat MERIS, Landsat-5 TM, Landsat-7 ETM+, Landsat-8 OLI, MSI Sentinel-2A and Terra/Aqua Modis. An analysis of radar data indicated areas most affected by ship spills of bilge waters. Greatest polluted area were found along the main ship routes, near biggest ports and at sites of anchor positions. It is necessary to separate anthropogenic oil pollution and oil-containing slicks caused by natural hydrocarbon seeps including mud volcanoes, natural gas and oil outflows from the sea bottom, and gas hydrates. The geographical distribution of these slicks is defined by their permanent locations that well correlate with locations of natural hydrocarbon seeps from the sea bottom in this region. Areas characterized by increased concentration of suspended particulate matter were revealed at maps compiled from Envisat MERIS, MSI Sentinel-2A data and Landsat colour composites. Among the most notable ones are river plume zones, first of all, those of the Danube River and mountain rivers of Georgia. Results of satellite data processing were used for detecting impacts of various natural factors, such as precipitation, rivers flows, wind-driven water circulation and vortex activity, on suspended matter proliferation. Mapping of zones of maximum propagation of suspended solids in different seasons was performed for the examined areas. Eutrophication has recently become a very important problem worldwide. It is true also for the Black Sea, especially for its western part.


Introduction
The ecological state of the marginal and inland seas causes reasonable concerns of specialists.This is due to many reasons: an increase in oil pollution due to the expansion of the oil and gas industry and the intensity of shipping; increasing the concentration of suspended matter in water, which leads to an increase in the turbidity of water and a decrease in bioproductivity; anomalous algal bloom in water, which every year covers an increasing area, becomes more prolonged and occurs in those areas where it was not previously observed.At the present stage, the study of the World Ocean is impossible without the use of information obtained with the help of remote sensing devices installed on various satellites specialized in remote sensing of the Earth.Recently, a large number of satellites with scientific equipment on board operating in different ranges of the electromagnetic spectrum have been launched all over the world.The accuracy and resolving capabilities of these sensors is constantly growing, and a set of parameters characterizing the state of the oceans and seas that can be measured from the space is expanding.
Satellite environmental monitoring of the sea surface includes not only the identification of oil, anthropogenic and biogenic pollution, but also the forecast of their spread.Moreover, the forecast for the spread of pollution is possible only on the basis of detailed knowledge of the entire set of hydrodynamic processes characteristic for the monitoring area.
Our long experience in satellite observations of various regions of the World Ocean and the seas of Russia shows (Lavrova andMityagina, 2013, Mityagina et al 2015), the task of identifying marine pollution and studying the dynamic processes is necessary to solve in close interrelation.The diversity of hydrophysical and meteorological conditions in the real ocean, the influence of a huge number of factors, both atmospheric and oceanic, with great complexity and cost of full-scale measurements, create a certain fragmentation in the description of real processes occurring in specific water areas.Many practical problems require more detailed information about the actual spatio-temporal distribution of meso-and sub-mesoscale processes (vortices, vortex dipoles, jets, internal waves and fronts) in different regions, close to real time.Complex structures of currents accompanying these phenomena appear on the sea surface and can be detected from space by modern means of remote sensing.
The development of scientific foundations and methodology for quantitative assessment of the ecological state of marine areas and the solution of the problem of determining the parameters of pollution and dynamic characteristics of the aquatic environment on the basis of a comprehensive analysis of satellite information both in the inland and marginal seas is today extremely urgent.These seas are most susceptible to oil pollution due to the large-scale development of oil and gas reserves on the sea shelf, accompanied by the construction and operation of offshore oil and gas platforms, onshore terminals, hydrocarbon storage facilities, submarine pipeline laying, seismic and drilling operations.
First of all, we are talking about the oil pollution of the sea surface, as well as the content of suspended matter and biogenic organic impurities associated with both the process of photosynthesis in phytoplankton and anthropogenically provoked increase in the biological productivity of algae.Based on the data of satellite remote sensing in different spectral ranges, integral estimates of the ecological state of the investigated water areas can be obtained.One of the most important tasks of satellite monitoring of the ecological state of marine areas is to study the influence of dynamic and circulating processes and natural factors (meandering of currents, vortex activity, sea level fluctuations, surges and upwelling, temperature and wind regimes, precipitation, river runoff) on temporal and spatial variability and intensity of marine pollution.
Based on the results of our long-term satellite monitoring of the Black Sea and on the basis of a comprehensive analysis of all the aggregate information on sources of pollution and the mechanisms for their distribution, permanent zones of environmental risk were identified, i.e., areas most prone to oil pollution, "harmful" algal blooms and increased concentrations of suspended matter.

Material and Methods
Identification and mapping of pollution (of various origins) of the marine environment of the Black Sea was carried out on the basis of the integrated use of satellite information obtained by various sensors installed on various specialized remote sensing satellites: data from multichannel optical sensors TM Landsat-5, ETM + Landsat-7, OLI Landsat-8; MSI Sentinel-2, ASAR Envisat synthetic aperture radar (SAR) data (until 2012) and Sentinel-1A, B (from October 2014 and September 2016, respectively).
The heterogeneous satellite data is systematized and integrated into the distributed information system "See the Sea" (STS), developed and functioning in Space Research Institute of Russian Academy of Sciences (IKI RAS, Moscow).The functionality of the STS is described in details in (Mityagina et al., 2014).STS provides researchers with tools for integrated analysis of various processes and phenomena in the world's oceans, qualitative and quantitative estimates of their properties, identifying their temporal and spatial variations, revealing conditions of their origination and evolution.STS has the capability of describing various processes and phenomena in seas and oceans and keeping long-term databases of such descriptions.Database tools allow storing and visualization of graphical and attributive information, hierarchical classification of observed processes, and search by spatial, time and typological criteria.
To build pollution maps of the sea surface, a cartographic interface integrated into the STS system was used.The interface provides access to various cartographic layers, such as isolines of depths, coastlines, villages, cities and ports, rivers in the coastal zone, state borders, navigable routes, and places of oil extraction on the shelf.

Results
Oil pollution as a result of ship discharges.For the economy of the Black Sea countries, the transport importance of the Black Sea is great.The international transport corridor TRACECA (Transport Corridor Europe -Caucasus -Asia) goes through the Black Sea.The Black Sea ports are also the end points of a number of pan-European transport corridors.A significant volume of sea transportation is made up by tankers that export oil and oil products from the ports of Russia (primarily from Novorossiysk and Tuapse) and Georgian ports.
Satellite monitoring is an effective method of controlling the marine environment and allows daily monitoring of the occurrence of oil pollution on a vast water area simultaneously, including the territorial waters of neighboring countries, which is especially important in the case of transboundary transport of pollution by currents.The overwhelming majority of anthropogenic marine pollution detected during the satellite monitoring of the Black Sea are leaks and discharges from ships of waters containing oil products.As an illustration, Figure 1 shows the SAR image received by the ASAR Envisat sensor over the western part of the Black Sea on March 17, 2010.One satellite image identifies at least six cases of marine contamination with oily films caused by discharges from vessels moving along the route.The enlarged fragments representing the identified contaminations are taken out by arrows in circles and ovals and are marked with numbers.Depending on the location, the oil pollution identified in the Black Sea from the analysis of satellite data is divided into three main types: 1) pollution in straits and areas of the water area near the entrance to the straits; 2) pollution at anchorages; 3) pollution along the main navigable routes in the open sea.Each of these types of pollution has its own characteristics.
Oil pollution in the straits and water areas near the entrance to the straits.By the degree of isolation from the ocean, the Black Sea is second only to the Sea of Azov.In the south-west it communicates with the Sea of Marmara through the Bosporus Strait, which, in fact, is a narrow canal 31 km long, 3.7 to 0.7 km wide, with a minimum depth of 50 m.In the north, the Black Sea is connected to the Sea of Azov by narrow and shallow Kerch Strait, which has a length of about 45 km, a width varying from 4.5 to 15 km, and a depth of 7-18 m.
For example, in 2015 (see Bosphorus Strait News, 2015) a total of 43,544 ships crossed the Bosporus.Of the total number 5,836 vessels were oil tankers, that is, every day about 16 large-tonnage tankers passed through the central part of Istanbul, which has a population of 14 million people.The Bosporus Strait is overloaded, and, despite the fact that the traffic control system in it is considered to be one of the most perfect in the world, for a passage the ships have to wait several days for their turn at the anchorage.It is quite clear that an increased attention should be given to satellite observations of the part of the Black Sea adjacent to the Bosporus Strait as a zone with an increased likelihood of environmental risks.It should be noted that the fact of the detection of oil pollution in the area of the Bosporus Strait on satellite images is, fortunately, a relatively rare event.Oil pollution of the sea surface in this region is due mainly to the discharge of oily waters from stationary vessels waiting to be queued at anchorage.The overwhelming majority of the spots of surface oil-containing films detected are relatively small, not exceeding 1 km 2 .However, sometimes under the influence of wind and waves, the oil film spreads and covers a large area.Most likely, such a relatively favorable situation is a consequence of the increased control of international organizations of the countries of the Black Sea region over the ecological state of the strait.An example of identification of oily contaminants in the sea surface near the entrance to the Bosporus Strait is shown in Figure 2(left).The Kerch Strait is also a large transport artery.Several large port complexes operate on its shores.Because of the shallow water of the strait, it is impossible to use ships with a large draft, therefore, mainly "river-sea" vessels are conducted along the strait.At the anchorage near the Black Sea mouth the cargo is loaded into large-capacity vessels.In the open sea in the roads, oil is pumped and bulk cargo is transferred from one ship to another, and transshipment is often carried out to the storage vessel simultaneously from two river vessels to both sides, although this is prohibited by the rules.According to our observations, navigation in the strait is sometimes accompanied by unauthorized discharges of dirty ballast water containing oil products.On satellite radar images of the Kerch Strait and the part of the Black Sea adjacent to it, dark spots of reduced scattering are regularly detected, due to the presence of oily film contaminations on the sea surface.A typical example is shown in Figure 2(right).The spot marked with the letter "A" is located on the navigable route in the center of the strait and is due to the discharge of water polluted by oil products from the passing vessel.Apparently, the spill of 0.8 km 2 occurred a few hours before the radar survey and is spread under the influence of wind and waves.Spot, marked with the letter "B" with an area of 0.12 km 2 was detected in the water area of the Port of Taman, in the immediate vicinity of the terminal for reloading oil and fat raw materials.This is a pollution of the sea surface caused by the spillage of organic oils during loading and unloading operations.
Contamination at the anchorage.While at anchorage, vessels await approach to the berth, and also perform loading and unloading operations, take fuel, water, and sometimes are repaired.Practice shows that in the course of improper execution of rules during these operations, as well as in cases when the conditions for the discharge of oily bilge waters are not met, pollution with oil products occurs in the area of anchorage.Figure 3(left) shows the ASAR Envisat fragment received on September 2, 2011 over the northwestern part of the Black Sea.There is a cluster of bright dots on it, corresponding to the ships at the anchorage of the Port of Odessa.In the zone of ships concentration, a contamination with oil-containing films, originally of a rounded shape, gradually spreading in the west direction, is well distinguished.The spot area is 2.3 km 2 .To the west of this pollution, also in the anchorage area, one more spot is detected at the radar image, but a bit smaller (0.3 km 2 ).Oil pollution as a result of natural hydrocarbon seeps from the seabed.The increased level of pollution of the marine environment is determined not only by anthropogenic but also by natural pollution, including natural releases (seeps) of hydrocarbons from the seabed.Fig. 5 shows characteristic examples of contaminations detected on radar images of the sea surface obtained over the continental slope in the Poti-Batumi area.
All the above images clearly display large oil slicks of characteristic shapes.It is easy to see that in all the examples given, slicks have a fixed starting point.The same pattern is manifested for all satellite images obtained by us over this region.Comparing the localization of slicks detected on satellite images and the location of methane seeps localized in the course of field research (Klaucke et al., 2006, Reitz et al, 2011), we came to the conclusion that the slick structures correspond to the natural manifestations of hydrocarbons from two closely located methane seeps, namely, "Colkheti Seep" and "Pechori Mound" on the seabed.On the sea surface above them, we regularly observe emissions of relatively small amounts of oil.The greatest thickness of the oil film is observed near the point of ascent.Surface slicks are formed under the influence of wind and currents.Depending on the formation conditions, the surface film either extends along the direction of the near-surface wind, or is involved in the vortex movements of water.The map of oil pollution of the Black Sea surface in the region of the continental slope near the coast of Georgia, allowed to estimate the probability of contamination of the sea surface in this area (Fig. 5).The area with a high probability of contamination by oil is about 850 km 2 .In some cases, oil films under the influence of wind and currents spread over distances up to 45 km from the point of exit to the sea surface.Based on the results of satellite observations, the eastern part of the Black Sea in the area of the continental slope near the coast of Georgia should be referred to areas of environmental risk.Distribution of suspended matter carried by rivers to the eastern part of the Black Sea.The Black Sea is one of the most studied sea basins on the planet.However, some processes require additional research.These include the spread of suspended matter in the coastal zone.The situation has changed in recent years not for the better, due to the increase in the level of marine pollution, which is not the least due to the runoff of water and sediment from the adjacent land.
The flux of suspended and dissolved terrigenous substances to the sea, their distribution in the coastal zone is a complex and multifaceted process, in the study of which many factors must be taken into account.Many scientific articles have been devoted to this problem, almost all of them consider certain regional features related to the influence of specific river, estuarine and marine factors, as well as geographic features of the coastal zone (Teodoro & Almeida, 2011;Lina et al., 2015;Zavialov et al., 2014).The primary role in such studies is played by numerical modeling of the processes of removal and spread of suspended matter in the coastal zone (Zhurbas et al., 2011;Osadchiev & Zavialov, 2013;Lina et al., 2015).However, any simulation requires verification of its results.The development of satellite facilities and the availability of remote sensing data from space for more than thirty years allow us to study the influence of various factors on the spatial distribution of suspended matter over large areas in different periods of observation.The main factors affecting the distribution of suspended matter carried by rivers are river runoff, tidal and coastal currents, bottom topography and wind impact.Since the Black Sea can be considered as a non-tidal one, the tidal currents do not affect the spread of the suspended matter.
The total number of rivers flowing into the Black Sea is about 1,000 and they differ greatly in water content and in size of the basins.The vast majority of them are small rivers and only about 500 have a length of more than 10 km.The category of large (with a catchment area of more than 10,000 km 2 ) include only 10 rivers.In the eastern part of the sea, more than 100 rivers flow into it, and the runoff is incomparably higher than, for example, from the territory of Russia.The total annual flow of river water to the Black Sea from the territory of Georgia (including small rivers) is 46.0 km 3 .Of this quantity, almost three-quarters of the sea falls on large rivers: Bzyb -3.79 km 3 ; Kodori -4.17 km 3 ; the Erisskali Canal, to which the Inguri drain has been transferred after regulation -3.15 km 3 ; Rioni -13.37 km 3 and Chorokh -8.71 km 3 .When developing methods for assessing the influence of various factors on the distribution of suspended matter carried by rivers to the eastern part of the Black Sea, we limited ourselves to studying the outflow of the Rioni and Chorokh rivers.
Bottom topography of the eastern Black Sea is characterized by a narrow offshore shoal that shrinks north to south.In the north, a 50 m isobath is located 7 km off the coastline.Another peculiarity of the bottom topography is a large number of canyons.They play an important role in sediment distribution, over 2000 thousand m 3 of coarse-grained sediments are trapped by the canyons and transported to great depths.
The analysis of the whole set of satellite information showed that the plumes of the rivers Rioni, Khobi and Supsa are observed in all images of the visible range, regardless of the season.This is explained by the mixed feeding of these rivers: rain and glacial.Rains are intensifying in the summer-autumn period.The seasonal difference is observed in the amount of suspended matter in the water area immediately adjacent to the river mouth.The average value of the suspended matter concentration, estimated on the basis of the MERIS Envisat data, was 40 g/m 3 , in July and October it increased to 60 g/m 3 .
The plume of the Chorokh River has a pronounced seasonal character.During the snowmelt period in the mountains from March to June, riverine water has a high content of suspended matter, reaching 35-40 g/m 3 .A repeated increase in its concentration is observed in November and December, which is associated with increased precipitation.In the remaining months, the plume of the Chorokh River either does not appear at all on satellite images, or has an area with a suspended matter content not exceeding 8-10 g/m 3 .
Distribution of plumes in the coastal zone of the Black Sea occurs in most cases to the right of the mouth, along the coastline, parallel to the isobaths, which corresponds to the direction to the north.This fully corresponds to model descriptions (Garvin, 1982(Garvin, , 1987;;Zhurbas et al., 2011).The spread of plumes in the form of long-shore jets is observed at the western winds, which are prevailing in this region.At a strong east wind, jets with a high content of suspended matter propagate perpendicular to the shore, suspended matter is carried far into the sea for a distance of 30 to 50 km (Figure 6 upper).
Our studies of the influence of various factors on the distribution of suspended matter carried by rivers to the eastern part of the Black Sea showed that for a given area the amount of runoff of highly turbid mountain rivers is of decisive importance.The shape of the outflow (river plume) also depends on its intensity (for example, a plume in the form of a vortex dipole near the Chorokh River) and the size of the plume.A strong east wind can somewhat change the configuration of the plume, promote the formation of jets.With the west wind, the plume spreads along the shore to the right of the mouth.Intensive jets often form internal waves, which can spread both to and from the shore (Figure 6 upper).
One of the most important tasks is mapping the distribution areas of suspended matter and determining the areas with the greatest concentration.This task was solved on the basis of maps obtained during the classification for rivers flowing into the eastern part of the Black Sea (from Rioni to Chorokh).The maximum area of the region closest to the mouth, with a maximum suspended matter concentration was 175 km 2 .Such dimensions are typical for March-April and are encountered in November, i.e. when the sediment flux of all rivers is maximal.The maximum total area covered by the suspended matter reaches 2200 km 2 in April-May (Figure 6 bottom).
Our studies have shown the effectiveness of satellite monitoring for the study of river plumes (Lavrova et al, 2015(Lavrova et al, , 2016)).A joint analysis of satellite information and hydrometeorological data made it possible to evaluate the influence of various factors, primarily wind, on the spread of suspended matter carried by rivers to the eastern part of the Black Sea.Investigation of the influence of coastal currents on the spread of anthropogenic pollution.One of the most striking examples of the effect of vortex structures on the spread of pollution was studied by us during the measurements in October 2011 (Lavrova et al., 2013).The heavy rainfall that took place on October 5, 2011, when 33 mm of precipitation fell, not only led to an increase in the flow of muddy river waters, but also, apparently, overflowing the reservoirs of the Gelendzhik treatment plant at Tolstyi Cape, and emergency discharge of sewage in the sea.It should be noted that accidental wastewater discharges at obsolete treatment facilities in Gelendzhik are not a rare phenomenon, and their effects are regularly observed on satellite images (Lavrova et al., 2011).The sharp increase in the concentration of suspended solids in the Tolstyi Cape area was also confirmed by data obtained from space, for example, on a map of the suspended matter concentration, based on the MERIS Envisat sensor data on October 7, 2011, the concentrations exceed 6 g/m 3 (Fig. 7 upper left).Pollution is spread over the distance from the discharge site by more than 35 km.The Tolstyi Cape area, where the pipe leaves the treatment facilities in the sea, is one of the permanent places of our satellite and field monitoring.According to technical norms, the discharge of sewage should be made by a deep-water outlet, the head of which should be more than 2 km from the shore at a depth of about 30 m. Due to pipe failure and emergency discharges, untreated or poorly purified water enters the sea right near the shore.Given the nature of the coastal currents, one can expect the spread of pollution both along the coast and into the Gelendzhik Bay itself -one of the largest recreational centers on the Black Sea.
The second example relates to our field measurements in 2013.During the standard measurements from the small boat on October 11, 2013, an oily spot was found on the surface of the water (Figure 7 upper right).Going around the perimeter of the contamination area and determining its boundaries with GPS, it was determined that the contaminated area was about 10 km 2 (Figure 7 bottom).Measurements of the currents parameters carried out with the help of ADCP showed that on October 11 an anticyclonic vortex was observed in the area of our research.Based on the results of ADCP measurements and on the shape of the spot, it was concluded that the source of pollution was the discharge from the vessel of contaminated water.Judging by the nature of the spread of the oil slick, the tanker "Vigna" carrying the crude oil was the culprit of the pollution.Our visual observations were confirmed by AIS data.

Discussion
The results of our long-term satellite monitoring of the Black Sea have made it possible to identify the main sources of pollution and the mechanisms for their distribution.For the Black Sea, sustainable zones of environmental risk are (Figure 8): • Major shipping routes along which unauthorized discharge of water containing oil products regularly occurs.These include the shipping routes: Istanbul -Varna, Istanbul -Constanta, Istanbul -Odessa, Istanbul -Kerch Strait, Istanbul -Novorossiysk, Istanbul -Tuapse, shipping routes leading to the ports of Georgia (Figure 8, areas 1-5).
• The Danube Delta region: increased suspended matter, contamination along navigable waterways near the shore (Figure 8, area 6).
• North-western shelf: the shallowest part of the Black Sea is most affected by river flow (80% of the total flow to the Black Sea): the Danube, the Dniester, the Southern Bug, the Dnieper, Ingul; intensive phytoplankton bloom, oil pollution near the ports (Figure 8, area 7).
• Port water areas, especially where oil terminals operate: large ports of Bulgaria, Turkey, Romania and Ukraine.In the Russian part of the Black Sea, the ports of Sevastopol, Novorossiysk (Tsemesskaya Bay) and Tuapse are the most polluted (Figure 8,areas 8,10,12).
• The Kerch Strait, where an elevated concentration of suspended matter is regularly observed, caused by the construction of the Crimean Bridge; numerous film contaminations at the remote piers of the Taman transshipment complex, related to carrying out technological operations for pumping oil, oil products and synthetic oils (Figure 8, area 9).
• Areas of anchorages near major ports and in the vicinity of the Kerch Strait, where cargo is transshipped from one type of vessel to another (Figure 8, areas 9 and 10).
• Gelendzhik Bay: the water area near a large tourist center with infrastructure that does not match the increased tourist flow; discharge of sewer practically right into the sea; the presence at Tolstyi Cape of an out-of-date deep-water sewage outlet.A weak water exchange in a semi-enclosed bay does not contribute to its self-purification (Figure 8, area 11).
• Greater Sochi area: a huge recreational load, the largest Russian resort on the Black Sea.One of the sources of pollution is also numerous industrial enterprises located along the rivers Mzymta and Sochi.During the flood period, the concentration of suspended matter in the area of the outflow of the Pshada, Vulan, Tuapse, Bitcha, Sochi, Kudepsta, Mzymta rivers increases sharply (Figure 8, area 13).
• Area of natural hydrocarbon seeps from the bottom in the southeastern part of the Black Sea.The area, which has a high probability of contamination with oil films as a result of natural oil manifestations, is about 850 km 2 .In addition, the seabed and the lower layers of the water column in the vicinity of natural sources are susceptible to hydrocarbon contamination (Figure 8, area 14).
• Eastern part of the Black Sea: oil pollution of both anthropogenic and natural origin, especially near the ports of Batumi and Poti.An increase in the suspended matter content associated with the runoff of numerous rivers, primarily Rioni and Chorokh (Figure 8, area 15).

Figure 2 .
Figure 2. Oil pollution near the straits.Left: Oil pollution at the entrance to the Bosphorus; ASAR Envisat on 02.10.2011, 08:11 UTC.The area of the spot is 3.2 km 2 .Right: Oil pollution in the Kerch Strait.SAR Sentinel-1A from 07.09.2016, 03:40 UTC.

Figure 3 .
Figure 3. Manifestation of oil contamination at the SAR images.Left: Oil pollution at the anchorage of the Port of Odessa.ASAR Envisat on 02.09.2011, 08:10 UTC; Right: Oil pollution on the navigable route, directed towards Sevastopol.ASAR Envisat on 17.07.2011,19:50 UTC.

Figure 4 .
Figure 4. Summary map of oil-containing ship discharges in the Black Sea, detected as a result of satellite radar data analysis in 2009-2012.

Figure 5 .
Figure 5. Natural oil slicks in the southeastern Black Sea.Upper left: Envisat ASAR, 27.10.2010,07:32 UTC; Upper right: Sentinel-1A SAR, 18.07.2016,03:16 UTC; Bottom: a generalized scheme of oil pollution of the sea surface over the region of natural hydrocarbon seeps from the bottom in the southeastern part of the Black Sea.

Figure 6 .
Figure 6.Upper: Fragment of a true color image of the eastern part of the Black Sea acquired by OLI Landsat-8 on 08.03.2016 shows up to 50 km long jet-like plumes, eddy and internal waves.White arrow marks internal wave train; Bottom: areas of the maximum spread of suspended matter; green curve marks the boundary of the greatest spread of suspended matter; red curve -the boundary of a region with a maximum suspended matter concentration.

Figure 7 .
Figure 7. Distribution of polluted waters under the influence of anticyclonic vortices in the coastal zone of the Black Sea.The upper left: suspended matter concentration from Envisat MERIS data obtained on 07.10.2011;The upper right: pollution on the sea surface on 10.11.2013 (photo from shipboard); Bottom: the scheme of spread of pollution on 10.11.2013.

Figure 8 .
Figure 8. Areas of environmental risk in the Black Sea, identified on the basis of satellite remote sensing data: 1 -Istanbul-Varna shipping route; 2 -Istanbul-Constanta shipping route; 3 -Istanbul-Odessa shipping route; 4 -Istanbul -Kerch Strait and Istanbul -Novorossiysk shipping routes; 5 -shipping routes leading to the ports of Georgia; 6 -water area near the Danube Delta; 7 -area of intense algal bloom on the northwestern shelf; 8 -Sevastopol Bay; 9 -Kerch Strait; 10 -Tsemesskaya Bay; 11 -Gelendzhik Bay; 12 -the Port of Tuapse; 13 -water area near Sochi; 14 -area of intensive methane seeps; 15 -coastal zone of the extreme eastern part of the Black Sea.