Environmental Conditions and the Fish Stocks Situation in the Black Sea, between Climate Change, War, and Pollution
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water
Article
Environmental Conditions and the Fish Stocks Situation in the
Black Sea, between Climate Change, War, and Pollution
Victorita Radulescu
Hydraulics, Hydraulic Machinery and Environmental Engineering Department, University Politehnica of
Bucharest, Splaiul Independentei 313, 060042 Bucharest, Romania; vradul4@gmail.com; Tel.: +40-745076494
Abstract: Climate change, pollution, capture, invasive species, and the war from Ukraine have
a significant impact on the environment and fish populations in the Black Sea. In June last year,
on the Romanian and Bulgarian seashore, large amounts of algae, dead fish, and jellyfish were
discovered. The ongoing depletion of fish stocks necessitates extensive research, concerning their
living conditions, reproduction, population, and migration. This paper starts by presenting the
environmental conditions for air, sediment, and water up to 60 m, based on direct monitoring and
measurements realized between 2014 and 2020. The recent war has affected the environmental
conditions of the sea, especially near Snake Island and Crimea Peninsula, well known for fish
reproduction. A dedicated paragraph presents the sources of water pollution, with direct effects on
eutrophication, fish reproduction, and their populations. The appearance and development of some
invasive species, which influence the local fish populations, are also illustrated. All these new factors
associated with the capture quotas are responsible for decreasing the number of fish species and their
populations in the Black Sea. Finally, some discussions are mentioned, which are necessary to be
followed in order to restore the fish stocks.
Keywords: biodiversity; environmental monitoring; marine biodiversity; marine pollution;
water monitoring
Citation: Radulescu, V. 1. Introduction
Environmental Conditions and the
With an area of 461,000 km2 and a volume of 540,000 km3 , the Black Sea is considered
Fish Stocks Situation in the Black Sea,
deep, with a maximum depth of 2212 m. Its characteristics make it unique in Europe [1],
between Climate Change, War, and
being practically a closed sea, communicating only with the Sea of Azov in the north
Pollution. Water 2023, 15, 1012.
https://doi.org/10.3390/w15061012
through the Kerch Strait, and with the Mediterranean Sea to the southwest via the Bospho-
rus and Dardanelles Straits [2]. Compared with other seas, the Black Sea has distinct
Academic Editors: Jun Yang and natural conditions, with a stratified structure of water composition. Unlike anoxic deep
Adriano Sfriso water, surface water is rich in oxygen and nutrients. There is practically no exchange of
Received: 10 January 2023 substances between these two layers, affecting the diversity of living organisms, being
Revised: 22 February 2023 lower in species and number than in the Mediterranean Sea [3,4]. The shallow surface layer
Accepted: 2 March 2023 has medium–high salinity. It has decreased significantly in recent decades due to a large
Published: 7 March 2023 influx of fresh water from large rivers such as the Danube, Dnieper, Dniester, and Don.
The Black Sea has strategic and political influence, representing the east border of the
EU (European Union) and NATO (North Atlantic Treaty Organization Alliance). Bounded
to the west by two EU member states, Romania and Bulgaria, and in the rest by four non-EU
Copyright: © 2023 by the author.
states, Ukraine, Russia, Georgia, and Turkey, the Black Sea became a conflict zone due to the
Licensee MDPI, Basel, Switzerland.
Russia–Ukraine war. Three of these countries are also NATO members: Turkey, Bulgaria,
This article is an open access article
and Romania [5,6]. The Black Sea is important for Russia because it represents a direct
distributed under the terms and
connection with the Mediterranean Sea and, further, with the Atlantic Ocean. It ensures
conditions of the Creative Commons
the transport of goods from Russia to the rest of the world throughout the year. The war
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
affects life in the Black Sea. The pipeline Turck Stream, with the protocol signed in 2016,
4.0/).
started its first deliveries through Turkey to Bulgaria in 2020, and the Blue Stream pipelines
Water 2023, 15, 1012. https://doi.org/10.3390/w15061012 https://www.mdpi.com/journal/water
Water 2023, 15, 1012 2 of 22
(protocol signed in 2002), with its first deliveries achieved in 2003 to Turkey, connect Russia
with other countries through the Black Sea [7,8]. These pipelines, due to their recorded
accidents, have affected the environment in these areas.
To maintain the environment and the living conditions of the Black Sea, all states
surrounding the Black Sea must respect the signed protocols for good neighborliness. The
actual Convention consists of four protocols: the Protocol on the Protection of the Black
Sea Marine Environment Against Pollution from Land-Based Sources (LBS Protocol), the
Protocol on the Protection of the Black Sea Marine Environment Against Pollution by
Dumping, the Protocol on Cooperation in Combating Pollution of the Black Sea Marine
Environment by Oil and Other Harmful Substances in Emergency Situations, and The Black
Sea Biodiversity and Landscape Conservation Protocol (CBD Protocol) [9–11].
Unfortunately, the Black Sea is nowadays the most polluted sea in Europe. Among the
principal causes, a few are be mentioned below:
- Uncontrolled spills of oil and residual substances from shipyards and ports;
- Nitrite and nitrate compounds transported by rivers from agricultural lands;
- Bottles and plastic bags, deposited garbage near the seashore;
- Effects induced by war over various environmental aspects: the air, sediments,
and water;
- Different substances are discharged, due to the improper functioning of sewage
treatment plants placed near the maritime coasts [12–15].
This paper analyzes the principal sources of pollution and their effects on the ecosys-
tem, and fish development and distribution in the medium and long term. Up to 10–15 years
ago, the sea was teeming with life, including birds, specific vegetation, shell and mussel,
fish, and mammals, such as dolphins and seals. This marine ecosystem is more complex
than other seas due to its specific structure. Its protection is more difficult for scien-
tists [16,17]. The salty waters, from the Bosphorus Strait, go to the bottom of the sea, while
fresh water from the main rivers, containing agricultural fertilizer and sewage runoff,
remains at the surface.
In the warm season, these substances cause a rapid and excessive bloom. They affect
the oxygen concentration in the water, with a high impact on the entire ecosystem. The
lack of mixing between these two layers of water, of which nearly 90% is oxygen-depleted,
limits the number of marine species that live in the Black Sea. Bacteria consume the organic
matter from this oxygen-free environment (dead plants or fish), producing hydrogen
sulfide—H2 S [18,19]. The Black Sea is nowadays the largest H2 S reserve in the world,
necessitating permanent monitoring. The implemented environmental regulations are
inefficient without constant surveillance.
Other problems refer to the current economic and political conditions in the area. The
large sturgeon populations in the beginning of the 20th century put black roe on the tables
of each fisherman working in the Black Sea.
Nowadays, excessive fishing and increased maritime transport have produced the
extinction of four of the seven species of sturgeon found once in the Black Sea. The
cliffs from the Crimea Peninsula provided, not long ago, a safe refuge for fish, birds,
and marine mammals. After the fights of 2014 and due to the mine explosions from last
year, associated with the increased transport of commercial ships, many fish and marine
mammals retreated to the rock habitats in Bulgaria and Turkey [20]. However, another
issue has appeared. The intense development of tourist resorts in both countries in these
areas has reduced these habitats even more. Anchovy stocks, once the main catch in the sea,
have been massively reduced in the last two decades [21]. Recent hostilities from Ukraine
have stopped previous efforts to repopulate some species. Currently, around the Crimean
peninsula, 20 km offshore, are Russian waters, where no one knows if the international rules
regarding environmental protection, marine life conditions, and fish quotas are respected.
The increased Russian and NATO naval exercises have restricted some areas of the Black
Sea to civil traffic, including the scientific teams that conduct environmental monitoring
Water 2023, 15, 1012 3 of 22
and surveillance of marine life. Under these conditions, the most recent data recorded and
used in this paper were recorded at the end of 2020.
As tensions rose, the military ships’ utilization of sonar harmed fish migrations the
most. Many species have changed their traditional spawning route, especially near the
Ukrainian ports of Odessa and Mykolaiv. Military equipment affects fish life, causing
them to leave their usual nesting or foraging areas. Because they can no longer locate the
proper places, they have difficulty securing their food and habitat. Last year, many of these
animals died near the shore. The worst part is that the environmental monitoring of water
quality and living conditions can no longer be realized in many areas.
The paper analyzes, in the beginning, the principal causes that have affected the Black
Sea ecosystem in the last years, based on the systematic measurements and monitoring
realized between 2014 and 2020. The explosive growths of algae in the northern part of the
Black Sea, and invasive species of marine fauna, affect the local fish stocks. A few causes
affecting endangered fish species are illustrated, based on the recorded measurements
for the sediment structure and composition, water quality, and fish captures. A special
paragraph is dedicated to some threatened species currently on the verge of extinction if
urgent measures to protect them or their living and reproduction zones are not taken.
Some measures are proposed for protecting the environment, based on these ob-
servations and measurements, as well as the surveillance of fishing quotas, for saving
endangered species, and for the restoration of the fish stock, at least in those areas without
military exercises that affect wildlife living conditions.
The presented results were mostly obtained through direct measurements collected
from 2014 to 2020. In 2020, I was part of a research team that collected samples of sedi-
ments, water, and biological structure, from the Black Sea. The rest of the data present,
by comparison from the previous period 2014–2020, other recorded values, used in order
to analyze the evolution of these significant parameters. Some data are reported by other
countries, to the Black Sea Commission—BSC.
2. Materials and Methods
The Romanian Black Sea coastline is 245 km long, from Musura Bay, with the border
with Ukraine in the north and the Bulgarian border to the south. Two commercial ports,
Tulcea and Constanta, and two shipyards, Mangalia and Navodari, are in this area. The
ports are well-known for maritime traffic, due to the Danube–Black Sea channel, which
allows the quick transport of different merchandise. These ports were overcrowded last
year due to the high volume of ships carrying cereals, oil, and other products from Ukraine
to the rest of Europe. The shipyards, also known for the production of commercial ships
and their repair, were in great demand last year.
A special observation should be made for this area. Many small earthquakes have
been recorded recently near the border with Bulgaria. The most recent and significant was
in April 2020, with a magnitude of 4.3 on the Richter scale. After that, some small deep
currents of fresh water appeared, with a small flow rate but a continuous one. In time, they
modified the seashore, causing coastal erosion, with collapsed cliffs.
Besides these natural factors, new problems have arisen due to industrial development.
Commercial transport, much more intensive in the last year, affects the environmental
conditions. Some invasive species from the Mediterranean Sea have colonized the Black
Sea and affect the local fauna. Water eutrophication, associated with massive fish catches,
mainly by the Turkish, Georgian, and Russian vessels, influences the fish population, which
has decreased significantly in the last few years. In addition, the war also perturbs marine
life and the environment.
Some responsible factors will be next investigated. The main, specific fish characteris-
tics of the Black Sea that have been affected by these new conditions will also be presented.
icant risks not only for the health of coastal residents but also for the entire environment.
To assure good living conditions for people and the marine ecosystem, we must first an‐
alyze each responsible factor, starting with air quality, sediment characteristics, and espe‐
cially the water parameters. The principal sources of pollution, including effects induced
by massive nutrient discharge, ports’ activities, municipal waste production, and inten‐
Water 2023, 15, 1012
sive maritime transport, are all responsible for the actual situation in the Black Sea.4 All of 22
these factors impact the biological diversity, trophic chains, appearance and development
of non‐indigenous species, and finally, endemic fish and crustacean stocks. A brief presen‐
2.1. Main
tation Causes
of the mainoffishthe species
Environmental
is also Degradation
illustrated. Many of them are nowadays on the red
list asClimate
endangered species.
change and human activity have a major impact on the marine ecosystem.
The large-scale eutrophication of water due to nutrients brought by rivers, the infiltration of
2.1.1. The Air and
oil residues, Quality
waste from human or industrial activities, has produced microbiological
and Based
chemicalon contamination
the Black Sea in the water, sediments,
Collaboration Agreement andimplementation,
even air. They create significant
riparian states
risks not only for the health of coastal residents but also for the entire
constantly monitor air and water quality. Figure 1a,b illustrates the number of monitoringenvironment. To
assure good living conditions for people and the marine ecosystem, we must
vessels and the measuring points by country, according to the last report of the Black Sea first analyze
each responsible
Commission [22]. factor, starting with air quality, sediment characteristics, and especially
the water parameters.
Air pollution Theby
is caused principal
natural,sources of pollution,
industrial, or different including effects
local factors, suchinduced
as: by
massive nutrient discharge, ports’ activities, municipal waste production, and intensive
‐ Natural sources: volcanic eruptions, earthquakes, rock erosion, pollen scattering;
maritime transport, are all responsible for the actual situation in the Black Sea. All these
‐ Anthropogenic sources, such as industrial activities, thermoelectric power plants, or
factors impact the biological diversity, trophic chains, appearance and development of non-
car traffic;
indigenous species, and finally, endemic fish and crustacean stocks. A brief presentation
‐ Recently, other factors were associated, such as bomb explosions, the presence of
of the main fish species is also illustrated. Many of them are nowadays on the red list as
many battle vessels, bomb explosions, etc.
endangered species.
Generally, dust, industrial gases, or the unpleasant odors of rotting products or waste
2.1.1.
are theThe Air Quality
primary causes of air pollution. Sizes of the dust particles or residual gas elements
from economic
Based on the Blackare
activities also
Sea important parameters.
Collaboration AgreementMainly, the concentrations
implementation, riparianofstates
SO2
and NO2 in monitor
constantly port areas air determine air pollution.
and water quality. FigureThe
1a,bdust concentration
illustrates the numberin cities refers to
of monitoring
the suspended
vessels and theparticles
measuring PMpoints
10 (Particulate
by country,matter 10 μm)toand
according the PM
last 2.5. Excessive
report concen‐
of the Black Sea
trations have an
Commission impact on the environment.
[22].
(a) (b)
Figure
Figure1.1.Surveillance
Surveillanceininthe
theBlack
BlackSea:
Sea:(a)
(a)Number
Numberofofmonitoring
monitoringvessels;
vessels;(b)
(b)The
Themeasurement
measurement
points from the western part.
points from the western part.
Air pollution is caused by natural, industrial, or different local factors, such as:
- Natural sources: volcanic eruptions, earthquakes, rock erosion, pollen scattering;
- Anthropogenic sources, such as industrial activities, thermoelectric power plants, or
car traffic;
- Recently, other factors were associated, such as bomb explosions, the presence of many
battle vessels, bomb explosions, etc.
Generally, dust, industrial gases, or the unpleasant odors of rotting products or waste
are the primary causes of air pollution. Sizes of the dust particles or residual gas elements
from economic activities are also important parameters. Mainly, the concentrations of SO2
and NO2 in port areas determine air pollution. The dust concentration in cities refers to the
suspended particles PM 10 (Particulate matter 10 µm) and PM 2.5. Excessive concentrations
have an impact on the environment.
Sulfur dioxide (SO2 ), carbon dioxide, NOx (nitrogen oxides), solid lead, benzene,
carbon monoxide, ozone, arsenic, Cd, Hg, and Ni are the main monitoring parameters
of air quality. On the Romanian coast, five fixed stations monitor air parameters, such as
Water 2023, 15, 1012 5 of 22
CO, benzene, PM 10, SO2 , NOx , As, PM 2.5, Cd, NO2 , and Ni levels in the areas of Tulcea,
Navodari, Mamaia, Constanta, and Mangalia. The direction and intensity of the wind, air
temperature, and precipitation play important roles in the transmission of particles that can
pollute the Black Sea. The recorded values are used to create databases that are registered
hourly, and reported daily or monthly. Based on them, the risk areas are determined.
In the chapter Results, the month of May 2020 is mentioned, as an example of the
measured values for wind direction, air temperature, and amount of precipitation. Heavy
metal particles (HM), Persistent Organic Pollutants (POP), Cd, Pb, Hg, and benzopyrene-
B(a)P levels were measured during 2015–2020. For the year 2021, no more centralized
databases have been created. In the Results chapter, some obtained results obtained up
to 2020, which are associated with some remarks based on the performed measurements,
are illustrated.
2.1.2. Pollutants in the Bottom Sediments
The Black Sea’s unique characteristics make it vulnerable to environmental conditions.
The almost complete absence of tides prevents the dilution of contaminants, favoring the
natural phenomenon of sedimentation. The movement of water masses between the Black
Sea’s two main layers is almost absent. European legislation establishes environmental
quality standards only for contaminants in seawater and biota. There are no established
threshold values for sediments. On the Romanian coast, systematic measurements are
realized at different depths and locations to prevent sediment pollution. Each sample is
measured and analyzed optically, physically, and chemically.
Content of PAH—Polycyclic Aromatic Hydrocarbon
In recent decades, there has been a focus on the content of PAHs and heavy metals.
According to the Black Sea Commission (BSC) analysis, seabed sediments can be classified
into three categories based on the Total PAH-TPAH content:
- Slightly polluted: TPAH < 250 g/kg;
- Polluted: TPAH = 250–500 g/kg;
- Highly polluted: TPAH > 500 g/kg.
The degree is calculated as the ratio of “technical-Fl ” PAH from industrial and hu-
man activities and “natural-Fy ” PAH. The PAH analysis from Romania, 2020, reveals the
presence of 11 dangerous organic contaminants in marine sediments: naphthalene, ace-
naphthylene, fluorene, acenaphthene, phenanthrene, anthracene, fluoranthene, pyrene,
benzo(a)anthracene, and chrysene. The Results chapter also illustrates the reported values
for 2020, from Romania, Turkey, Bulgaria, and Ukraine, at three time intervals: May, June,
and July. For the Romanian coast, the total content of the 11 PAHs (µg/kg) found in
sediments is also mentioned.
According to the BSC regulations, the following sources of emissions in the environ-
ment are estimated:
- If the ratio Fl /(Fl + Fy ) < 0.4, pollution is of petroleum origin;
- Values 0.4–0.5, pollution caused by combustion products of liquid fuel or oil;
- Values > 0.5 indicate pollution caused by the combustion of coal or wood.
Sediment samples were processed according to internal standards. An accelerated sol-
vent was used on the pressure extraction unit (PLE) with a mixture of hexane/dichloromethane/
methanol (60%/20%/20%) in the chemistry laboratory of the University Politehnica of
Bucharest. In the laboratory in Bulgaria, hexane: acetone in a ratio of 1:1 v/v was used in
the microwave. Sulfur was removed with activated copper. The extraction was followed
by purification, which was performed on the florisil segment when using organochlorine
pesticides (OCP); polychlorinated biphenyls (PCB) were utilized in the silica/alumina
segment for polyaromatic hydrocarbons (PAH). The concentration of components was
achieved using the Kuderna-Denish concentrator in Romania, a rotary evaporator with
Water 2023, 15, 1012 6 of 22
nitrogen flow. In Bulgaria, using a silica gel structure, the concentration was achieved in a
turbo-evaporator with nitrogen flow.
Persistent organic pollutants were analyzed by gas chromatography (GC). In Romania,
the electron capture detection method (GC-ECD) was used for OCPs and PCB, and the gas
chromatography–mass spectrometry (GC-MS) method was used for PAH.
Content of Heavy Metal (HM)
Sediments with finer organic content tend to accumulate higher concentrations of
HM than coarse sediments. The accumulation of fine and polluting particles is facilitated
in deep marine areas, whereas coarse-grained particles dominate in coastal zones. The
spatial distribution of HM concentrations in sediments revealed an increasing gradient
for some elements in the western part of the Black Sea, with the exceptions of Pb and
Ni. The chapter, dedicated to the obtained results, presents a comparison between the
values recorded for HM in 2014 with those from 2020. The strong correlation between these
elements, particularly for Cu, Cr, and Al, confirms the influence of the mineralogical and
granulometric properties of the sediments.
Except for Ni, the concentrations of Cd, Pb, Ni, and Cr measured in the sediments of
the Romanian coast were below the sediment quality standards. Higher concentrations
were found near the Danube delta and the ports of Constanta and Mangalia. HM concen-
trations are low in the central and southern tourist areas. Based on the last report of BSC,
in Georgia, the average concentration of Fe decreases by 7.5–4% in the south but remains
constant in the rest of the country, at 14.5–8.3%. The Mn is evenly distributed at 0.25–0.35%
values. The Chorokhi River brings in sediments polluted with mining minerals, causing
an accumulation of Cu, Zn, Ni, Cr, and As near Batumi and Gonio. There are no regula-
tions in Ukraine for bottom sediments. The estimates were developed using EU-funded
programs. In 2017, for Georgia, the highest concentrations were found: Zn—10 µg/g, and
Cr—78 µg/g.
In 2017, the absolute concentrations of heavy metals decreased in the following order:
Zn > Cr > Cu > Ni > Pb > Co > As > Cd > Hg; for 2020, there was the following order:
Zn > Cr > Cu > Ar > Ni > Co > Pb > Cd > Hg. Any value measured in 2020 for Cd and Zn
exceeded the allowed values of 1.2 µg/g for Cd and 150 µg/g for Zn. The percentage of
samples with concentrations higher than the accepted thresholds ranged from 6% for Pb
and Hg to 16% for Cr, 56% for Cu, and 90% for Ni. Compared with the 2015 measurements,
the Ni level frequently exceeds the value of 20.9 µg/g. The BSC admits that the natural
level of Ni in Black Sea sediments is higher than the values admitted for other seas.
2.2. Sources of Seawater Pollution
The Black Sea receives freshwater from main rivers such as the Danube, Dnieper, and
Dniester from the northwestern area. Because 87% of seawater is anoxic, it is vulnerable to
anthropogenic impacts, due to its large catchment area and limited connections to other
seas. Each year, roughly one-third of the continental runoff freshwater, about 350 km3 /year,
flows into the Black Sea. The changes in its ecosystem clearly show it is vulnerable to
anthropogenic effects. Some issues must be studied:
- Biodiversity losses due to pollution, invasive species, and habitat destruction;
- Pollution from land and discharged wastewater;
- Overexploitation of marine resources, with a direct impact in the extinction of some
fish species or with a massive decrease of their stocks. Overfishing, coastal industrial
and tourist development, and heavy maritime traffic have all contributed to the marine
resources decline.
The main causes of the Black Sea pollution are derived from the land, or are brought
about by rivers, air or sediment pollution, and waste discharge. Based on an interna-
tional program ongoing since 2002 in the Black Sea, 37 monitoring boats are present, with
11 permanently active in five-day cycles, and the rest participating in seasonal programs of
monitoring and measurements. Water parameters are monitored for depths up to 1000 m;
Water 2023, 15, 1012 7 of 22
some can explore even up to 1500 m. Based on the measurements from 2020, the Results
illustrate some of the principal causes of seawater pollution. Until now, researchers have
not considered the effects of war; these will be estimated in time.
2.2.1. Nutritive Loads
Agriculture is the primary source of nutrients that reach the seawater. The Danube
provides about 50% of nutrients in the Black Sea; the rest is supplied by the Ukrainian
rivers Dnieper, Dniester, and Bug, the Turkish rivers, atmospheric nitrogen, and municipal
and industrial discharges. In recent decades, EU member countries have implemented
a new policy of reducing the quantities of fertilizer from agriculture, determined by the
nitrogen/phosphorus (N/P) ratios. Unfortunately, due to the widespread use of fertilizers
in Ukraine and Russia, the western coastal waters remain high in dissolved inorganic and
organic nitrogen, without any improvement. DIN (internationally recognized standard)
mentioned that P-PO4 concentrations, on the other Black Sea coasts (S, NE, and N), are
approximately three to four times lower than on the western coast. Nutrient inputs from
sediments can contribute to progressive eutrophication. In the Results chapter, the nutrients
discharged, based on the measurements from 2020, will be mentioned, with their effects on
eutrophication. In 2019, 453 monitoring stations were installed in the Black Sea, with the
majority in the western part.
The phosphate concentration in water reveals the role of phosphorus in the increased
biological activity during the warm season. The phosphorus concentration is average at
depths of 10–40 m; below, up to 50 m, it decreases, regardless of the season. Silicates are
horizontally distributed. Their present average concentrations are lower than reported in
the 1960s. Nitrate concentrations are lower than the 1990s average, but with high variability
in the northwest region, due to the river input. Compared with other inorganic components,
the nitrites have small spatial and seasonal variations. The trends from 2009 to 2019 showed
an average increase, followed by a steady decrease until 2020. Ammonium levels are the
highest in spring, and decrease when the flow rates of rivers increase, as well as during
algal blooms. Except for phosphates, the nutrient concentrations in the Black Sea surface
waters decreased between 2014 and 2020.
2.2.2. The Hydrological Balance in Seawater
The primary element affecting seawater quality is the hydrological balance. Annual
and seasonal fluctuations of the water balance determine its physical–chemical characteris-
tics. Water balance may be expressed as:
( Q R + Q P + Q M + Q A ) − ( Q E + Q LM + Q LA ) = ∆V/T (1)
where QR —is the total rivers flow rate, QP —the amount of precipitation, QM —the flow
rate that enters into the Black Sea through the Bosphorus Strait from the Sea of Marmara,
QA —the flow rate from the Sea of Azov through the Kerchi Strait, QE —the flow rate lost due
to the evaporation, QLM —the flow rate lost due to surface currents in the Seas of Marmara
and Azov, and ∆V—changes in sea volume in time T (year or season). Equation (1) may be
condensed to:
F + Q B + QK = ∆V/T (2)
Here, F = Q R + Q P − Q E represents the freshwater balance, QB = QM − QLM is the
resultant water flow through the Bosporus Strait and QK = QA − QLA is the result of the
water flow through the Kerch Strait.
The precision of measurements affects the accuracy of the water volume estimation.
211 rivers flow into the Black Sea directly or via lagoons, according to the BSC Report.
Geographically speaking, the flow rate of rivers from Romania, Crimea, Caucasus, Turkey,
and Bulgaria represents the majority of tributary flow from rivers. A total of 58.5% of
the Black Sea tributary flows arrive from the Danube, Dniester, and other rivers from the
Water 2023, 15, 1012 8 of 22
northwest. According to the previous measurements, it was observed that the average
annual flow rate varies between 287–480 km3 /year.
Unfortunately, there is no information on the river flow rates from Georgia and Turkey.
The error in estimating the annual average of the tributary flow rates of rivers in the Black
Sea is between 9.5–10% and about 3035 km3 /year. The information about the tributary
flow rates from Turkey and Caucasus, estimated as 355.6 km3 /year, was received only for
2017–2019. The average annual water consumption is 29.6–39.6 km3 /year or 8–11% of the
average long-term runoff.
An important factor in the hydrological balance of the Black Sea is represented by
atmospheric precipitation. Its volume is comparable to the tributary flows from the rivers.
The results are obtained by measurements of seasonal and multi-annual precipitation,
taken at coastal stations and in the open Black Sea. The minimum precipitation in the
open sea area is in summer, when convective precipitation prevails, and the maximum
is in autumn and at the beginning of winter, due to the increase of cyclonic activity and
the intensification of the vertical convective air currents. The measurements show that
regardless of the season, the southern part, the Anatolian coast, and the Caucasus region
receive most of the precipitation. The average annual precipitation varies between 119 and
662 km3 /year.
The hydrological balance must consider also the evaporation of the water. It is influ-
enced by air humidity and water vapor pressure as a function of temperature, salinity, and
wind speed. The total amount of evaporation was calculated by adding the losses from
different locations. Unfortunately, there are not many stations for measuring wind speed,
water temperature, surface water salinity, air temperature, and humidity in the north and
east part of the Black Sea. The measurements recorded in 2020 show that the evaporation
varies between 232 and 441 km3 /year. The NW and NE regions of the Black Sea have the
highest rates of evaporation.
As a result, river discharges and the amount of precipitation minus evaporation
are mainly used to determine the water balance. From 2007, researchers observed the
effects of climate change in the Black sea area. The balance of freshwater decreased by
67 km3 /year, mainly due to a lack of precipitation. With little precipitation, the average
annual evaporation rate increased in 2020 to 417 km3 /year, varying by 38 km3 /year
compared with the previously recorded annual average rate.
2.2.3. Effects of Port Operations and Municipal Sewage Treatment Plants
Maritime Transport
The Black Sea has recorded a steady increase in maritime transport over the last ten
years. The increased number and dimensions of ships produce increased pollution and
perturb the environment. Figure 2a illustrates the travels through the Bosphorus Strait to
the Mediterranean Sea in July 2017. Figure 2b,c illustrate, by comparison, the situation in
the western part of the Black Sea, of the fishing and transport vessels in July 2018 and 2021.
In 2021, they almost doubled. The meaning of the colors in each image is mentioned.
Starting in May 2022, the Romanian ports of Constanta, Mangalia, and Sulina have
been over-congested. This is due to the war and the increased necessity of transporting
cereals from Ukraine to the rest of Europe. After the bombing of the ports of Odessa and
Mikolayv, the number of ships from Ukraine drastically decreased. Instead, the Kerch Strait
was occupied by ships traveling from Russia to Turkey. Despite being in the most dangerous
area of the Black Sea, last year, from Ukraine to Romania and Bulgaria, authorities recorded
about 25,000 ship calls. The ecosystem and environment of the Black Sea are undoubtedly
impacted by this intense maritime transport.
x FOR PEER REVIEW
Water 2023, 15, 1012 9 9of
of 23
22
(a) (b) (c)
Figure
Figure 2.
2. The
The situation
situation of
of maritime
maritime transport
transport in
in the
the Black
Black Sea:
Sea: (a)
(a) 2017;
2017; (b)
(b) 2018;
2018; (c)
(c) 2021.
2021.
Starting
Municipal in May
Sewage 2022, thePlants
Treatment Romanian ports of Constanta, Mangalia, and Sulina have
been The
over-congested. This is due
wastewater released by municipal to the warsewageand thetreatment
increasedfacilities,
necessityindustrial
of transporting
activi-
cereals from Ukraine
ties, shipyards, to the rest of
and commercial Europe.
ports After the
represents bombing
another factor ofcontributing
the ports of Odessa and
to seawater
Mikolayv,
pollution. the number of ships(HCB),
Hexachlorobenzene from Ukraine
lindane drastically decreased.aldrin,
(HCH), heptachlor, Instead, the Kerch
dieldrin, and
Strait was occupied by ships traveling from Russia to Turkey.
polychlorinated (PCB) 28, PCB 52, and PCB 101 are the chemical compounds found in Despite being in the most
dangerous
wastewater.area of the Black Sea,
Concentrations of theselast contaminants
year, from Ukraine to Romania
frequently exceed and Bulgaria,
the limits of a author-
healthy
ities recordedMeasurements
ecosystem. about 25,000 ship calls. The ecosystem
in seawater must be made and environment
at three different of the depths:
Black Sea0are m,
undoubtedly
5 m, and 20 m. impacted by thisstarting
In Romania, intense with maritime2018,transport.
the total amount of hydrocarbons was
82–503 mg/L, values accepted by the BSC against pollution. This is a consequence of the
Municipal
rehabilitation Sewage
of twoTreatment
major sewage Plants stations. Some other chlorinated pesticides, such as
heptachlor, cyclodiene pesticides
The wastewater released by municipal (aldrin, dieldrin,
sewageendrin), andfacilities,
treatment the HCHindustrial
groups were, in
activi-
Romania,
ties, underand
shipyards, the commercial
recommended ports values. The concentrations
represents another factorfor HCH = 0.0–7.18
contributing ng/L,
to seawater
the cyclodiene
pollution. group 0–2.4 ng/L,
Hexachlorobenzene (HCB), and heptachlor
lindane (HCH), 0.0–6.07 ng/L varied
heptachlor, in the
aldrin, northwest
dieldrin, and
part of the Black(PCB)
polychlorinated Sea in28,2019.
PCBThese 52, and values
PCBare 101lower
are thethan those recorded
chemical compounds in 2009–2012,
found in
before the rehabilitation
wastewater. Concentrations of theofsewagethese stations.
contaminantsThe previously
frequentlyrecorded
exceed values were,offor
the limits a
the cyclodiene group, 0.0–63.95 ng/L, for heptachlor, 0.0–63
healthy ecosystem. Measurements in seawater must be made at three different depths: 0ng/L, and for HCH (lindane),
0.0–129
m, 5 m, ng/L.
and 20 m. In Romania, starting with 2018, the total amount of hydrocarbons was
82–503 mg/L, values accepted by the BSC against pollution. This is a consequence of the
2.2.4. Oil Pollution
rehabilitation of two major sewage stations. Some other chlorinated pesticides, such as
The ongoing
heptachlor, growth
cyclodiene in oil and(aldrin,
pesticides gas production
dieldrin, around
endrin),theand Caspian
the HCH Seagroups
has determined
were, in
increased oil transportation in the Black Sea. When
Romania, under the recommended values. The concentrations for HCH = 0.0–7.18the war is finished, this trend would
ng/L,
probably
the increase
cyclodiene again.
group Oil ng/L,
0–2.4 pollution andoccurs when0.0–6.07
heptachlor crude oilng/L
and varied
petroleum products
in the northwestleak
from tankers, offshore platforms, drilling rigs, wells, and pipelines
part of the Black Sea in 2019. These values are lower than those recorded in 2009–2012, or when ships such as
ferries, tourist, military, or fishing ships discharge bunker fuel,
before the rehabilitation of the sewage stations. The previously recorded values were, for waste oil, or bilge water.
In these cases, the spills are mostly concentrated near the major ports or along the major
the cyclodiene group, 0.0–63.95 ng/L, for heptachlor, 0.0–63 ng/L, and for HCH (lindane),
shipping routes.
0.0–129 ng/L.
The worst oil pollution occurs when there are accidents with oil tankers, as was the
case in 2005 and 2009, with two Turkish ships were damaged and partially sunk in their
2.2.4. Oil Pollution
territorial waters. Unfortunately, in such accidents, the effects are felt across large surfaces
The ongoing
and often for a quite growth in oil and
long period. Thegas production
ability around the
to track accidents in Caspian
real timeSea has has deter-
increased,
mined
due to the information received from satellites and drones. Between 2014 and 2016, oiltrend
increased oil transportation in the Black Sea. When the war is finished, this spills
would probably
were visible increase
in about 50%again.
of theOil pollution
radar images, occurs
and when crudetooil
from 2017 andthey
2020, petroleum prod-
were visible
ucts
in 64%leakoffrom
cases.tankers,
Nowadays,offshore theplatforms,
Black Seadrilling
surfacerigs, wells, and pipelines
is permanently or when
air-monitored, ships
mainly
such as ferries, tourist, military, 2 or fishing ships discharge bunker
due to the war. About 800 km surrounding the significant seeps is estimated as being fuel, waste oil, or bilge
water.
completely exposed to the oil contamination. The effect of this poses a serious threat to the
In these cases, the spills are mostly concentrated near the major ports or along the
major shippingOil
environment. routes.
spills can travel up to 40–80 km when the wind blows. They endanger
marineTheresources,
worst oil contaminating
pollution occurs thewhen
waterthere are beaches,
and the accidentsand withcan oillast
tankers, as was the
for months.
case in 2005 and 2009, with two Turkish ships were damaged and partially sunk in their
territorial waters. Unfortunately, in such accidents, the effects are felt across large surfaces
and often for a quite long period. The ability to track accidents in real time has increased,
Water 2023, 15, 1012 10 of 22
2.3. Current Situation of Fish Stocks in the Black Sea
The International Day of Action for the Black Sea is celebrated annually on 31 October.
On this occasion, some actions are required for the entire area, including beach cleaning,
and measurements concerning the air, water, and sediment quality. New major goals are set
for better conditions for the locals, environment, and biosphere. Last year, the meeting was
postponed until 2023 because of the war. The most recent scheduled objectives were related
to measures aiming to reduce eutrophication, restore fish reproduction areas, improve
compliance with fish catches, and survey invasive species.
The last international expedition was conducted in 2020, by an international team of
scientists from Romania, Bulgaria, and Turkey, in the western part of the Black Sea.
As a member of the research team, we also collected 21 biological samples. The Black
Sea sprat prefers colder waters and migrates irregularly. The variations in temperature
produced by global warming have affected its population. Due to the war and heavy
maritime traffic, it could not migrate in 2022 to the northeastern region, its preferred
spawning area. A significant reduction in the migration distance was noticed via satellite
monitoring. The Mediterranean Sea and the Black Sea host a large population of whiting,
a gregarious and demersal species. In spring, when the temperature reaches 7–8 ◦ C, it
approaches the shore, helped by the cold currents. When the water is 10–15 ◦ C in summer,
it prefers deep waters. Unfortunately, the whiting population suffered significantly in 2022
due to the heavy maritime traffic. In all areas of the Black Sea, the mullet can be found in
coastal waters, at depths of 30–100 m, in areas with stony, sandy, or muddy bottoms. The
war had a small impact on his development.
In the Black Sea, there are 198 species of fish, either native, invasive, or newly intro-
duced. To analyze their dynamics, the next indicators were considered: catches, population
structure, length and size at maturity, age, class structure, sex ratio, fecundity rates, survival
or mortality rates, reproductive stocks, and genetic structure [22,23]. The most common
species found in the Black Sea are next illustrated.
Pontic shad can be found in open sea and coastal areas, up to depths of 100 m. One of the
most significant fish families in the world is the Clupeidae. The largest catches are reported
in Sozopol, Cape Emin, and Varna. The Fauna Habitats Directive lists the most well-known
anadromous fish species that are at being in danger of extinction. Alosa species are extremely
vulnerable to anthropogenic changes, especially related to the access and quality of their
breeding areas. Industrial and domestic pollution, water acidification, drainage, land use
changes, river barriers, overfishing, the introduction of new species, and, recently, the
conflict in the Crimean region are threats to these species. Overfishing during the migration
period still remains the main threat. Based on the last BSC report from 2021, less than
1400 km2 comprises the space of the breeding areas. A preponderance of groups measuring
13.5–14 cm was observed, starting in 2014. It means that the majority are still young and
sexually immature. This criterion estimates their status to be “unfavorable–unsatisfactory”.
The pelagic fish Engraulis encasicolus ponticus and Engraulis encasicolus maeoticus are
the two most well-known anchovy species from the Black Sea. The migration of anchovies
from the Mediterranean Sea through the Bosphorus Strait aids in maintaining differences
between them. The Black Sea anchovy is longer and has a lower percentage of body fat.
Less than 3% of the Black Sea’s anchovy population reaches the sexual maturity of one year,
which is the age at which they begin to spawn. A steady annual harvest rate of roughly
60% of the total anchovy biomass is noted. In the last five years, fifteen scientific studies
have been done to study their behavior, spawning grounds, migration, and wintering.
Fortunately, their fish eggs are laid in the southern Black Sea, where they can survive
amid ongoing conflict. There is not a well-known annual route for the migration of
anchovies. Depending on the velocity of the water currents, water temperature, or the
maritime vessels’ routes, this can be modified. Last year, the anchovies’ route changed
due to the increased maritime traffic through the Bosphorus. They passed Turkey and
traveled directly to Georgia. As a result, Turkey’s anchovy catches were lower than usual.Water 2023, 15, 1012 11 of 22
Anchovies 1–3 years old have lengths of 9–13.5 cm. Their dimensional structure and spatial
distribution are currently considered to be in a “favorable” state.
The sprat, Sprattus sprattus, number in the Black Sea has risen quickly. The sprat
biological mass was estimated in 2017 as being 277,720 t. Previously, in 2010 and 2011, the
catches were generally low, but starting in 2012, they permanently increased. The length
of young fish, of 0–4 years, varies between 4 and 12 cm. The dimensional structure and
spatial distribution are currently estimated to be in a “favorable” state.
Scad, Trachurus mediterraneus ponticus, is a migratory species found throughout the
entire Black Sea. Black horse mackerel is a subspecies of the mackerel from the Mediter-
ranean Sea. They migrate in spring, unfortunately, to the conflict zones, for breeding and
feeding. In autumn they go to the coasts of Anatolia and the Caucasus. They winter at
depths of 20–90 m off the Crimean Peninsula and at 20–60 m in the Caucasus region. Horse
mackerels range from 8 to 19 cm, but catches are generally between 12 and 16 cm. It is
uniformly distributed in September and October, spending the day 7–12 m deep and 1–3 m
above the bottom, and during the night it is located in the middle layer, at 5–10 m deep. Its
current situation is considered to be “favorable”.
The Black Sea contains a large population of Atlantic Bonito, Sarda sarda, at depths of
80–200 m. For its proper living conditions, the water salinity must be 14–39% (g/L), and
the temperature must be 12–27 ◦ C. One of the top predators in the Black Sea, tuna fish has
a significant economic impact, particularly on Turkish fisheries. The bonito population
benefits from the average water temperature increase due to global warming. Compared
with the period before 2000, nowadays, the spawning period is longer. It spends more time
in the sea than it did before the year 2000, migrating in early spring and feeding on small
pelagic fish, such as anchovies, horse mackerel, and sprat. Unfortunately, its number has
decreased in the last period, mainly caused by the NW Black Sea pollution, the problems
with the migration routes due to the commercial vessels, and intensive fishing from Georgia
and Russia. Few mature individuals and almost no fish longer than 50 cm are recorded
now in catches. It indicates that adults are not nowadays present in the Black Sea. Between
0 and 3 years it grows quickly, but its status is still “unfavorable”.
The turbot, Psetta maxima, lives at depths up to 100–140 m, can be found all over the
Black Sea, and has a long lifespan. This species has decreased in numbers in the last years,
being frequently caught by accident. Only 26 turbot specimens were caught in Bulgarian
waters in the 2018 campaign. Their age was 2–7 years, with lengths of 26–70 cm. Its current
status is “unfavorable unsatisfactory”.
Red mullet, Mullus barbatus, lives near Crimea and Caucasus. There are two types
of mullets: migratory and colonized. The migratory mullet crosses the Kerch Strait into
the Sea of Azov in spring, for breeding and spawning, and for winter it returns along the
Crimean coast. The last year’s war perturbed his migration. The migrant form dominates
the catches in Ukraine. The two subspecies, red mullet (Mullus barbatus) and striped mullet
(Mullus surmuletus) have recently been the subject of some debates. Finally, these two
subspecies were classified together. Generally, it stays at depths of 20–60 m, but its current
status is still “unsatisfactory”.
Whiting is one of the most prevalent demersal fish in the Black Sea. Without extensive
migrations, they spawn in its habitat during the colder months. The young whiting spends
about a year in water up to 10 m deep. The adults prefer temperatures between 6 and
10 ◦ C, from deep waters of 60–120 m. Fish under six years predominate, representing
the commercial concentrations. The whiting is a by-catch, being rarely the target species
for fishing. For ages up to 6 years, its length varies between 5.2 and 24.3 cm. Since its
assessment is merely indicative, whiting catches cannot be estimated. Its state now is
considered to be “favorable”.
The thornback ray, Raja clavata, known as the Black Sea Fox, is now in danger of
extinction. It lives at the bottom of the sea, at about 300 m deep, but also it may be seen
in shallower waters of 10–70 m. Water temperature and pollution are the main factorsWater 2023, 15, 1012 12 of 22
affecting its distribution. Catches are aged between 1 and 12 years. The adult males are
56–77 cm long and females about 62.3–79 cm. Unfortunately, its condition is still “critical”.
The spotted dogfish, Squalus acanthias, lives throughout the Black Sea, where the
temperatures are 6.5–15 ◦ C. It migrates in autumn to Caucasus, Crimea, and Anatolia,
where there are abundant anchovies and black horse mackerel. It is a viviparous species
that mainly breeds in Ukrainian waters, in the Karkinitsky Bay, Kerch Strait, and Feodosia
Bay. It swims up to the coastal zone at depths of 10–30 m to give birth to the cubs, with an
average of eight per female. The majority of specimens ranging from 1 to 14 years were
7–8 years, and of both sexes. Males and females are 82–88 cm in length at maturity. The
reproductive biomass has significantly decreased in the last decades. Its current condition
is “unsatisfactory”.
3. Results
Starting in 2014, some international expeditions were systematically organized, in
order to monitor environmental parameters, water quality, and biological mass. In 2020,
the last expedition was organized in the western part of the Black Sea, with researchers
from Romania, Bulgaria, and Turkey. Being part of this expedition, I could observe the
methods of collecting physical, chemical, and biological samples. There were observed the
medium-term effects of water pollution and the introduction of invasive species of jellyfish
and aquatic plants. In the following, some results obtained from these measurements will
be presented, and are also compared to the previous years of monitoring.
3.1. Air Monitoring and Air Pollution
The results obtained from the monitoring of the Romanian coast are mainly presented.
Where I have the opportunity, I present also the results of measurements, or the data
reported by other riparian states from this interval. Figure 3 illustrates such measurements
for some environmental parameters. Such an example is illustrated, for March 2020, for the
Romanian seashore, the wind direction, daily temperatures, and average precipitation. In
Figure 3b, the maximum, minimum and average values of temperatures T (◦ C) are marked
in red, and the relative humidity (RH) (%) is in blue. In Figure 3c, the values of the fallen
precipitation (L/m2 ) and the amount of water lost through evaporation are represented.
The remaining positive value of water, which will be accumulated in the sea, is marked
in blue, and the one lost through evaporation is marked in gray. There are days when the
Water 2023, 15, x FOR PEER REVIEW 13 of 24
entire amount of water falling (from dew, condensation, waves) is lost through evaporation,
and this appears only in the columns marked with gray.
(a) (b) (c)
Figure 3.
Figure 3. Air
Air parameters
parameters for
for March
March 2020:
2020: (a)
(a) Wind direction; (b)
Wind direction; (b) Air
Air temperature;
temperature; (c)
(c) Precipitations.
Precipitations.
The
The heavy
heavyMetals
Metals(HM)(HM) and
andPOP particles,
POP such
particles, as Cd,
such as Pb,
Cd,Hg,
Pb, and
Hg,benzopyrene- B(a)P,
and benzopyrene‐
were
B(a)P,measured in the atmosphere
were measured in the atmospherefrom 2015
fromto2015
2020,
to based on emissions
2020, based from Romania
on emissions from Ro‐
and
manianeighboring countries.
and neighboring They were
countries. Theyassociated with precipitation,
were associated wind intensity,
with precipitation, and
wind inten‐
direction. The increase
sity, and direction. Thein averageintemperature
increase and concentration
average temperature of atmospheric
and concentration reactants
of atmospheric
produced an increaseanofincrease
reactants produced B(a)P, recorded
of B(a)P,inrecorded
the 2020 in
measurements. Cadmium deposition
the 2020 measurements. Cadmium
reached its peak in 2017. Figure 4 illustrates the recorded values.
deposition reached its peak in 2017. Figure 4 illustrates the recorded values. Larger concentrations of
Larger con‐
HM have been discovered in the western part of the Black Sea. The first
centrations of HM have been discovered in the western part of the Black Sea. The first figure presents the
recorded values for
figure presents theCd, Hg, and
recorded BaP (µg/g).
values for Cd,For
Hg,Pb,and
theBaPmeasured
(μg/g).values
For Pb,arethe
multiplied
measuredby
100, as to
values arebemultiplied
representedbyon theassame
100, to begraph. The second
represented on the graph
sameshows
graph.theThevalues recorded
second graph
shows the values recorded in 2015–2020 as a percentage, compared to 2009, considered to
be the reference year for measurements in the Black Sea. Then, systematic and automatic
measurements began for most of the monitored parameters.Water 2023, 15, 1012 13 of 22
Water 2023, 15, x FOR PEER REVIEW 14 of 24
in 2015–2020 as a percentage, compared to 2009, considered to be the reference year for
measurements in the Black Sea. Then, systematic and automatic measurements began for
most of the monitored parameters.
(a) (b)
Figure 4. Air
Figure deposits
4. Air depositsfor
forHM
HM and POPparticles:
and POP particles:(a)(a) Values
Values recorded;
recorded; (b) Comparison
(b) Comparison with 2009.
with 2009.
3.2. Characteristics of the Sediments
3.2. Characteristics of the Sediments
Table 1 displays the average recorded values of PAHs in the sediment measurements,
Table 1indisplays
realized the average
2020, in Romania, recorded
Turkey, values
Bulgaria, of PAHs
and Ukraine, forin the sediment
three-time measurements
intervals: May,
realized
June, in 2020,
and July.inAs
Romania, Turkey,
part of the Bulgaria,
research and2 Ukraine,
team, Table illustratesfor
thethree‐time
total content intervals:
of the May
11 and
June, PAHsJuly.
(µg/kg) foundofinthe
As part sediments of the
research Romanian
team, Tablecoast in July 2020.
2 illustrates theTable
total3content
illustratesof the 11
PAHsa comparison between
(μg/kg) found the recordedof
in sediments values in 2014 andcoast
the Romanian 2020, in
inorder to see the
July 2020. appeared
Table 3 illustrates a
modifications. The strong correlation between Cu, Cr, and Al confirms their influence on
comparison between the recorded values in 2014 and 2020, in order to see the appeared
the mineralogical and granulometric properties of the sediments.
modifications. The strong correlation between Cu, Cr, and Al confirms their influence on
the Table
mineralogical and granulometric
1. Average recorded properties
values of PAHs in 2020. of the sediments.
Romania Turkey Bulgaria Ukraine
PAH PAH PAH PAH PAH PAH PAH PAH
Sample Sample Sample Sample
[g/kg] [%] [g/kg] [%] [g/kg] [%] [g/kg] [%]
Constanta 2230 7 1 810 46 1 974 6 1 340 45
Costinesti 321 3 2 1093 47 2 221 3 2 423 46
Eforie 1593 11 3 1078 46 3 2022 7 3 579 49
Mamaia 563 7 4 790 41 4 341 5 4 1001 39
Mangalia 2038 19 5 352 38 5 207 7 5 884 43
Portita 782 23 6 464 40 6 1654 15 6 940 44
Sulina 2891 32 7 341 40 7 394 32 7 763 42
Vama Veche 3045 24 8 558 43 8 2298 11 8 712 40
3.3. Seawater Pollution, Characteristics, Nutrients, and Eutrophication
The samples from the depth were collected in 5 L Teflon Niskin bottles, attached
to a Rosette System equipped with in situ fluorometer. We observed the distance from
the surface, temperature, salinity, fluorescence, and the presence of deep-sea chlorophyll,
as well as at 1 m above the depth of sample collection. In 2020, several monitoring
campaigns were carried out. Three of them targeted the western Black Sea. Table 4 lists
the principal sources of water pollution in all riparian countries based on previous and
2020 measurements. Regarding the content of nutrients that reach the water, agriculture is
the principal source. As I presented in Section 2.2.1, unfortunately, the Danube provides
approximately 50% of the nutrient content, the rest being supplied by the rest of the
rivers, and by urban and industrial discharges. Although measures have been taken to
reduce nitrates and phosphates in agriculture, Ukraine and Russia still maintain highWater 2023, 15, 1012 14 of 22
concentrations, reflected in the seawater content. Table 5 illustrates the intakes of nutrients
discharged into seawater by all riparian countries, where P-PO4—phosphate, TP—total
phosphorus, and TN—total nitrates, N-NO3, or total nitrites, N-NO2 .
Table 2. Dangerous organic contaminants recorded in the Romanian sediments.
Compound Number Samples Min [µg/kg] Max [µg/kg]
Naphthalene 61 1.2 634.7
Acenaphthylene 54 0.8 78.9
Fluorene 61 1.6 976
Acenaphthene 54 2.2 292.2
Phenanthrene 58 4.8 409.7
Anthracene 60 0.3 294.5
Fluoranthene 56 1 272.8
Pyrene 58 1 325.8
Benzo(a)anthracene 52 0.4 279.8
Chrysene 56 0.2 85.8
Fluorane(b)benzo(b) 56 0.1 255.1
Table 3. Variation of the HM concentrations in sediments.
Heavy Metal 2014 2020
(µg/g) Samples Min Max Samples Min Max
Cu 14 13.76 50.31 18 8.81 55.07
Cd 14 0.057 0.386 21 0.024 0.61
Pb 14 9.21 45.18 20 5.37 57.74
Ni 14 15.7 57.8 19 9.23 70.42
Cr 16 7.67 97.88 19 38 88.1
Zn 19 26.1 85.6 15 28.2 123.1
Mn 24 349 1425.3 17 257 1637
V 22 5.3 91.2 21 7.2 55.14
Co 21 4.37 12.82 19 0.43 14.28
As 21 8.3 9.5 20 9.7 14.3
Hg 24 2.8 3.29 19 3.42 5.88
Table 4. Principal sources of the seawater pollution.
Sources of Pollution
Stationary
Run-Offs from Coastal Diffuse Air and Ships and Marine
Types Land-Based
Rivers 2 Sources 3 Sediments 4 Platforms 5
Outfalls 1
Chemicals: + + +
Persistent organic + + + + +
Oil and petroleum + + + + +
Nutrients + + + + +
Trace elements + + + + +
Radioactive + +
Marine litter + + + +
Biologic + + + + +
Microbial + + + +
Exotic species of fish + + + +
Note(s): 1 Liquid industrial waste, oil spills, insufficiently treated sewage from coastal cities and settlements;
2 Nutritive inputs from agriculture, industry, mining, and municipal sewage; 3 Inputs of organic materials from
agriculture, animal husbandry, and unmanaged tourism, mainly through land runoff (coastal rainwater and
groundwater); 4 Air pollution as smoke, dust, and exhaust gases, regardless of the place of origin; 5 Discharge
of solid waste, from explosions and dredged materials, lost fishing nets, or from the introduction of foreign
marine organisms.You can also read
