The Black Sea—The Past, Present, and Future Status

Chapter 21

The Black Sea—The Past, Present, and Future Status Abdulaziz Güneroğlu⁎, Osman Samsun†, Muzaffer Feyzioğlu‡, Mustafa Dihkan§ ⁎

Department of Marine Ecology, Faculty of Marine Sciences, Karadeniz Technical University, Çamburnu, Trabzon, †Faculty of Fisheries, Sinop University, Sinop, Turkey, ‡Department of Marine Science and Technology, Faculty of Marine Sciences, Karadeniz Technical University, Çamburnu, Trabzon, §Department of Geomatics, Faculty of Engineering, Karadeniz Technical University, Çamburnu, Trabzon

1 INTRODUCTION The Black Sea is an internal semienclosed basin characterized by brackish and high productivity waters surrounded by six different countries (Turkey, Russian Federation, Ukraine, Romania, Bulgaria, and Georgia). The Black Sea has suffered from unwanted ecological and environmental problems for the last 50 years. Despite an awareness of the issues among bordering countries, there is no satisfactory steps put forward for making positive future projections of this unique ecosystem (O’Higgins et al., 2014). The remedy depends on the synchronization level across the countries bordering the sea and their efforts to overcome the problems. This is because each country has its own regulations and systems and it is difficult to bring them together. The European Union (EU) membership of Romania and Bulgaria is promising. Turkey is also candidate member, which means EU regulations can be applied at least to some extent. It is widely accepted that negative impacts of global climate change on world ecological settings are now observed in many geographic regions such as in the Black Sea ecosystem. One of the most important and measurable effect on world seas and oceans is the elevated trends of mean sea surface temperatures (SSTs). Moreover, changing flood and plume patterns of the rivers, strong stratification of water masses, changing water salinities, and limited vertical exchange of nutrients or oxygen are some other negative impacts mentioned in the literature (Miladinova et al., 2016). Expected ecosystem-related problems of the Black Sea for the next 50 years can be summarized as unregulated fishing and overfishing, partially mitigated eutrophication, global climate change-related rising mean SSTs, coastal urbanization, and dense housing, solid waste discharges including micro and macroplastics and a high risk from maritime oil transportation. Among all of them, even though related to human-induced activities, eutrophication and high SSTs are demanding and complex problems that cannot be resolved in short time spans and furthermore appropriate solutions for such problems can be considerably expensive. On the other hand, coastal urbanization, solid waste disposal, and overfishing are relatively easy problems to respond to by effective regulations and the application of necessary engineering solutions. Environmental issues of the Black Sea are very well documented in the literature for the last 50–60 years. The regime shifts observed in the ecological state of the sea were generally attributed to anthropogenic interference. There are mainly two approaches explaining the rationale behind the shifts. The first one is overfishing (especially the top predators) causing the trophic cascade in a top-down ecosystem hierarchy by interrupting the prey-predator relations and the second one is the eutrophication resulted by the massive intrusion of the nutrients into the system and characterized by very intense blooming events and high production rates. However, the double effect of these two approaches is more likely to be responsible for the regime shifts of the Black Sea. However, the impact of the natural climate oscillations in the mitigation of the problem witnessed in the last 20 years has to be explained in more detail in order to be prepared for the next 50 years. The hot agenda of ecosystem-related problems in the Black Sea will probably be an issue of high priority in upcoming decades as a result of persistent anthropogenic activities. The philosophy to follow as a potential solution can be based on the root causes and attempts to formulate the solutions by bringing together science and society. This can only be achieved by consensus among the bordering countries by starting international cooperation that is applicable and legally binding for each nation. Unfortunately, a full recovery of the ecosystem can be more difficult and demanding than expected.

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364  SECTION |D  Enclosed, Semi-enclosed, and Open Coasts

2  GEOGRAPHIC SETTING AND COASTAL GEOMORPHOLOGY The Black Sea is the world’s largest anoxic sedimentary basin surrounded by a 4400-km long coastline with a relief of approximately 398-m mean elevation. The basin is inhabited by approximately 140 million human population and covers approximately 460,000 km2 of sea surface. The geomorphologic character of the region is represented by low-relief areas on the western side and steep high-relief zones on the eastern and southeastern parts (Ludwig et al., 2009; Allenbach et al., 2015). The Black Sea has a diverse geomorphology such as plains, mountains, highlands, and forests as a result of its unique geographic location. Boreal climatology dominates the northern sections whereas the southern regions have subtropical character. Generally, the Black Sea faces weather masses from Atlantic, Mid-European, and Siberian origins. Saharan-originated weather systems can also be observed especially during the mid-seasons. The area is the sedimentary basin of Alpin-Himalayan orogeny and situated between the Caucasian, Crimean, and Balkan mountains. However, the northwestern side of the region is under the influence of the Eastern European platform. This explains the roughness and geomorphologic movements of the region as the Black Sea basin is in the middle of two colliding plates with different tectonic formations (Drozdov et al., 1992). The Caucasian and Crimean mountains are located on the northern and northeastern sections while Balkanid-Pontid Mountains extend along the western and northwestern sides (Antonidze, 2010; Kosyan and Velikova, 2016). The compaction of Arabian and South European plaques is considered as the reason for the formation of the sedimentary basin millions of years ago. The sediment accumulation in the middle of the basin proves that the area geologically was possibly a part of ocean or inner sea. The area is an enclosed region formed by two subbasins, one on the west and the other on the east (BSC (Black Sea Commission), 2008). Lakes, islands, and swamps of the Danube delta characterize the geomorphological setting of the west part. The delta was possibly a bay of the Black Sea 6500 years ago before the transportation of excessive sediment by rivers that shaped the current deltaic formation. The delta moves toward the sea approximately 30 m each year. In the region, the Dobruja plateau exhibits moderate roughness with small rock formations. Beginning from the Istanbul strait, steep and harsh mountain formations extend toward eastern side along the coastal periphery. The southern coast of the sea is fed by many rivers such as the Sakarya, Yesilirmak, Kizilirmak, and Coruh. Associated areas are fertile agricultural lands. Many other small streams are in the form of unregulated creeks transporting waters and nutrients as open drainage to the sea (Zaitsev et al., 2002). Sediment grain sizes transported by rivers differ according to its origin, geomorphological shape, and place. The sediments transported from southern and southeastern sides have generally large grain sizes whereas the northwestern sediment type consists of fine grains due to relatively low slopes. Undoubtedly, the Danube River is the most influential factor in shaping the northwestern deltaic environment (Panin and Jipa, 1998). The western shelves including the Istanbul strait are characterized by very productive waters. This area covers almost 127,000 km2, that is, around 30% of the total Black Sea surface area and comprises 94% of the total continental shelf of the whole basin (Panin and Jipa, 2002). The Black Sea has been attributed different characters throughout the history. Sometimes it was regarded as having “unhospitable or dangerous” waters, and sometimes it was given positive attributes. The region has attracted many nations due to its unique geographic locations (Kosyan and Velikova, 2016). The bordering countries of the Black Sea have a remarkable history and the center of many civilizations. It is known that coastal utilization is a common for all countries, as they need the coast for various activities such as transport, settlement, and recreation (Antonidze, 2010). Until the beginning of the 20th century, the Black Sea was a relatively natural and pristine basin with limited human impact. Nevertheless, in recent decades, the situation changed and intense anthropogenic processes caused a degradation of the basin (Kosyan and Velikova, 2016). Linear littoral settlement types appear to be a problem in areas dominated by coastal mountains with limited hinterland. The geomorphological setting and inadequate planning strategies are the major causes of the coastal urbanization in the region (Guneroglu et al., 2013). The vulnerability to inundation and flood risk are some other problems linked to very dense coastal urbanization. The most recent urbanization level around the coastal strips of the Black Sea is shown in Fig. 1. Many landslides and flooding incidences are experienced each year that result in a loss of life and properties. Furthermore, near coastal and exclusive economic zone (EEZ) areas of the total sea surface there are problems due to the overexploitation of resources and sectoral competition such as tourism and fisheries. Therefore, coastal and open sea interactions, which are vital for the basin, are limited as a result of unregulated usage and degradation. Additional ecological problems associated with institutional and application issues emanate from the mismanagement of coastal resources (Guneroglu et al., 2014). Another human-induced problem related to geomorphology is the coastline change observed along the coastal periphery of the Black Sea. Coastline changes can occur as the result of both natural and anthropogenic factors. Recently, most of the changes reported on the coastal zone of the Black Sea are mainly the result of human activities such as urbanization and inappropriate engineering solutions (Guneroglu, 2015). The importance of coastline change is strongly linked to the economic value of the coastal area. Coastal lands are valuable as they offer productive places for activities such as transport,



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FIG.  1  Landsat 8-LDCM classified mosaic image of the Black Sea basin showing coastal impervious surfaces, vegetation, and bathymetric variability.

tourism, and recreation. Therefore, dynamic changes of the coastline are the expected results of both natural and humaninduced causes (Guneroglu, 2015; Kuleli et al., 2011; Karsli et al., 2011). Living very close to the coastline creates some risks and dangers to our daily lives such as storm surges, huge waves, and rising sea levels. Although sea level rise (SLR) is not a big problem today for the Black Sea, if the global climate change continues in its current level for the next decades, it can become a major coastal issue in the near future. Moreover, the populations living on coastal zone of the Black Sea have not yet experienced SLR as the sea is not affected by tides. Therefore, in order to avoid unwanted consequences, a strategic plan about the sea should include a section on SLR. It is reported that the seawaters of Turkey have risen approximately 2.5– 2.8 mm/year for the last 85 years. Similarly, on the northern coasts of the Black Sea, the figures reach up to 3.5–4.5 mm/year (Alpar, 2009). Avsar et al. (2015) reported almost the same rates (3.16 ± 0.77 mm/year) for the Black Sea based on data between 1993 and 2014. For example, a project carried out by Stănică and Panin (2009) on the northwestern shelf of the sea revealed that by 2030 the SLR can reach up to 13–14 cm which is very dangerous as it may causes seawater to retreat toward the land by approximately 35–50 m. This can cause a massive destruction in areas especially with narrow coasts in the southern and southeastern parts of the sea. As the most of the investments and urbanization occur on these narrow strips, Kuleli (2010) emphasized that a possible rise by 10 m in Turkish coast can cover 7319 km2 of the total coastal land of the country. Undoubtedly, Turkish coasts are vulnerable to SLR risk if the necessary precautions are not taken and put into action in the near future. The IPCC climate scenarios must be seriously taken into account and evaluated to avoid possible negative results of SLR in the Black Sea basin. Regarding the coastal beaches of the Black Sea, there are in total 1228 available beaches of the basin, 2042 km long and occupying an area of 224 km2. Interestingly, the width of 61% of the beaches is less than 50 m and 47% of them are protected by engineering structures (Allenbach et al., 2015). The adverse effect of SLR may also couple with man-made structures such as building dams in the region. Although dams are necessary for water storage and usage and electricity production, they can limit the sediment supply to the coastal zone and degrade its vulnerability against coastal erosion. A basin-wide action plan can help to mitigate these negative impacts of anthropogenic pressure on the coastal zone of the Black Sea (Tsereteli et al., 2011). The geomorphological setting is also related to land-use type in the region. Most of the coastal regions in the Black Sea are used as agricultural lands especially in places with moderate roughness such as deltaic environments. Agriculture is an important tool for creating revenues as the total population approximates to 140 million in the basin (Ludwig et al., 2009). However, agricultural practices affect both the aquatic and terrestrial ecological formation

366  SECTION |D  Enclosed, Semi-enclosed, and Open Coasts

of the basin. Intense use of fertilizers causes a suite of eutrophication problems in coastal waters leading to a distortion and complex interactions in aquatic food webs. Moreover, the irrigation infrastructure planned to meet the necessary water demand for agriculture alters the terrestrial ecology around the dams or the inland water resources. In accordance with the MSFD and WFD, the bordering countries, as agreed in 1992 Bucharest Convention, are required to stop point or nonpoint (diffuse) nutrient discharges to the aquatic environment by carrying out specific regional projects and monitoring. Engineering solutions for protecting the coastal zone may also alter the coastal morphology. It is highly recommended that soft engineering techniques should be used in defending the coast instead of hard engineering constructions. Firstly, soft engineering designs are best suited to the natural environment compared to hard structures, they are cheaper than hard solutions, and they can be used to preserve sediment load as well as supply habitats to the aquatic biota. Hard engineering solutions could be used in places where soft engineering techniques tend to fail in defending the coastal zone.

3  ECOLOGICAL STATE AND HEALTH OF THE SEA The Black Sea, despite various definitions in the literature, is regarded as a semienclosed subbasin of Mediterranean Sea as there are many similarities in terms of biological, geographical, and ecological aspects. Connecting European and Asian continents, the ecology of the Black Sea is determined by geological activities of the region (Zaitsev, 2001). The coastal deep formation is mainly covered by sand dunes and shallow banks on northwestern shelf, whereas rocks and mud banks are found in the northern and southern sections of the coast. The well-known cyclonic (clockwise) circulation pattern of the rim current is also affected by the coastal bathymetry and morphology. The main circulation pattern of the Black Sea can be depicted by two subgyres—one in the west and the other is on the east. The formation of the cyclonic gyres is attributed to a positive freshwater budget and the outflow of many rivers, which creates a quasipermanent buoyancy of surface waters with low salinity above the more saline water masses. Meanders and quasipermanent anticyclonic gyres are formed between the coastal waters and the main circulation pattern and they are very important for triggering mixing and intrusion of the coastal waters to the inner basin. The exchange of these two water masses is quite important for the productivity of the continental shelf. Ekman upwelling zones can be observed in the inner basin as a result of the wind stress curl and frictional convergence effect, which creates a depression zone on the coastal waters. The result is anticyclonic eddies formed by a coupled impact of the wind dynamics and sea topography (Miladinova et al., 2016). The divergence of water masses in the inner basin is balanced by convergence areas formed in the coastal section. A strong vertical and horizontal mixing of water can reach its maxima in the winter season. Some other seasonal upwelling regions can be observed in very near coastal areas of the Black Sea (Daskalov, 1999). A cold intermediate layer (CIL) formation is a characteristic oceanographic process of the Black Sea, which enhances vertical mixing, and nutrient transport. The depth and thickness of the CIL could be changed through heating and cooling mechanisms but it is generally observed between 30 and 100 m depth and most aquatic life activity occurs in the first 50 m depth of the sea that is rich in oxygen, light, and adequate nutrients. Moreover, continental shelves on both narrow and wide coastal margins are responsible for the most productive fisheries of the Black Sea (Miladinova et al., 2016). The other vertical water mass of the sea that begins just below the CIL is the permanent pycnocline. The pycnocline layer limits the water mixing between haline Mediterranean anoxic layer and the CIL. It is well known that most of the aquatic systems are fragile against the excessive anthropogenic nutrient supply. An increasing population and demand for agricultural products triggered usage of fertilizers on coastal lands that can lead to high production rates and algal blooms in the marine environment. The process could even end with eutrophication and very high rates of carbon production, which then consumes the available oxygen in the water column and on the seabed during decomposition (Friedrich et al., 2014). Annual peak values of bloom dynamics of the Black Sea are typically observed in autumn and winter seasons inside the rim current region and reach its lowest values in summers (Yunev et al., 2002; McQuatters-Gollop et al., 2008). Bloom dynamics and chl-a concentrations show different characteristics in coastal and open waters (BSC (Black Sea Commission), 2008). For instance, high chl-a concentrations can be observed in outflows of Bosporus in summer season. In winter when the prevailing winds are very strong, rim currents limit the exchange of coastal waters with inner regions but under low wind stress, high chl-a concentrations and phytoplankton spread to the entire waters of the basin (BSC (Black Sea Commission), 2008). The Black Sea is distinguished from the Mediterranean Sea in terms of the phytoplankton and zooplankton assemblages, primary production, and nutrient supply (Zaitsev et al., 2001). Diatoms and dinoflagellates dominate the Black Sea phytoplankton groups. Despite the low plankton diversity, the sea is highly productive with a high abundance of cells per volume. The major taxa observed are Bacillariophyceae, Dinophyceae, Prymneciophyceae, and small flagellates (Moncheva et al., 2012). Some important species of note are Emiliania huxleyi, Pseudonitzschia pseudodelicatissima, Pseudosolenia calcar-avis, Prorocentrum cordatum, Thalassionema nitzschioides, Ceratium fusus, and Gymnodinium sp.

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(Eker-Develi and Kideys, 2003). Furthermore, microflagellates are also remarkably abundant in the Black Sea. A total of 54 classes and 267 genera of dinoflagellates were reported for the basin. Some important species are Protoperidinium sp., Ceratium sp., Dinophysis sp., Peridinium sp. ve Gymnodinium sp. (Gómez and Boicenco, 2004). Diatoms that are widely reported in the region are Cerataulina pelagica, Chaetoceros curvisaetus, Chaetoceros socialis, Cylindrotheca closterium, and Skeletonema costatum (Moncheva et al., 2001). The Black Sea phytoplankton structure is strongly linked to environmental conditions and climatic variability. Therefore, the dominant phytoplankton group at any given time that can be observed are diatoms and sometimes switch to dinoflagellates. The causal factors behind this phenomenon are assumed to be the shift of the system toward a small cell community structure during the high primary production periods to make the better use of available sunlight. Some percentage rates of major systematic groups observed before and after 2000 and 2002 are illustrated in Table 1. The major nanaplankton contributor to total production of the sea is Emiliania huxleyi and the first bloom of this species was first reported in 1951 for the Black Sea (Mikaelyan et al., 2005, 2011). Recently, the bloom of this coccolithophorid has been widely observed in coastal waters of the Black Sea with increasing frequency (Mikaelyan et al., 2015). There are different explanations for the primary production mechanism whether it is limited by phosphorus or nitrogen and whether silicate is available in sea column during the photosynthesis. For example, the spring bloom is limited by nitrogen whereas summer bloom is governed by both nitrogen and phosphorus. Moreover, the imbalance between the major nutrients can lead to a domination by bacteria or microzooplankton in the first levels of the food web (Mee et al., 2005). For example, Moncheva et al. (2001) reported that the northwestern shelf was diatom-dominated based on data collected for the period 1999 and 2000. Furthermore, the availability and abundance of different nutrients may enhance the ambient conditions for establishing diatom- or dinoflagellate-dominated ecosystems. Bloom timing and intensity are not only governed by environmental parameters but also they are influenced by sinking, grazing, and a trophic state control mechanism. The Black Sea trophic structure has been greatly changed during the last 50 years. Considering the primary production and bloom timing between May and October, this period can be partitioned into three sections according to major shifts observed. Preeutrophication (prior to 1980), eutrophication (~1980–90), and posteutrophication (after 2000s) periods are important time spans shaping the Black Sea productivity. The trophic system of the sea evolved in accordance with changing environmental conditions. For instance, one of the most important picoplankton species (Synechococcus spp.) abundance has greatly increased in 10 years and reached up to 10-fold compared to rates prior to 2000 (Uysal, 2000, 2001; Feyzioglu et al., 2004, 2015; Kopuz et al., 2012). One of the most severe consequences of Black Sea eutrophication is red tide blooms. Red tides can be initiated by different species in the Black Sea such as dinoflagellates, euglena, or diatoms (Feyzioğlu and Öğüt, 2006). Recently, red tides of Noctiluca scintillans have been widely observed by bloom rates reaching up to 6.81 × 109 cells m−3 in 2011 on the southeastern coastal waters (Kopuz et al., 2014). Ecological peculiarities of the Black Sea have shown a unique community structure of the zooplankton assemblage, which then shapes the base of the food web and is responsible for the healthy flow of the energy. Being the key components of the ecosystem, zooplankton are also important in terms of water quality as they are filter-feeding organisms. Oceanographic regular sampling of zooplankton in the Black Sea dates from 1950. Black Sea zooplankton structure is mainly composed of mesozooplankton groups such as Copepods, Cladocera, Chaetognatha, and Oikopleuridae. Advancements in new sampling gears and technologies promoted in situ sampling campaigns by enhancing the scientific quality and assurance of collected data. A micro (<0.5 mm), mesozoo (0.5–10 mm), and macro (>10 mm) classification scheme was applied using these technological gears on board a research vessel (Kovalev et al., 1999). The planktonic assemblage of the Black Sea is affected by the salinity of seawater. Zooplankton structure can ecogeographically be characterized as three origins: Mediterranean,

TABLE 1  The Rates of Some Microplanktonic Groups Observed in the Region in Different Periods Systematic Groups

Before 2000 (%)

After 2002 (%)

Bacillariophyceae

52.88

44.12

Dinophyceae

33.65

41.18

Euglenophyceae

5.77

5.88

Chloprophyceae

2.88

1.47

Crysophyceae

3.85

5.88

Primnesiophyceae

0.96

1.47

368  SECTION |D  Enclosed, Semi-enclosed, and Open Coasts

pontic, and fresh water groups. Although they are low in number, those of Mediterranean origins are dominant in the Black Sea. Approximately 50 functional Mediterranean origin species were adapted to Black Sea ecological conditions (Kovalev et al., 1999). The most abundant mesozooplankton species observed are Copepoda, Cladocera, Chaetognatha, Oikopleuridae groups, and some ichthyoplankton such as eggs and larvae. In daylight conditions, some species such as Calanus euxinus, Pseudocalanus elongatus, and Sagitta setosa remain just above the anoxic layer at approximately 60 m depth. The percentage of Acartia clausii in the total zooplankton assemblage has greatly increased from 17% to 75% between 1980 and 1990 (Kovalev et al., 1999). The decreasing trend in biomass of C. euxinus at the end of 1990 is followed by the observation of Oithona similin and Oithona nana in some in situ sampling studies carried out in the Black Sea but more recently Oithona davisae, an indo-pacific origin invasive species transported by ballast waters, was observed even in southeastern waters of the sea. It seems that Oithona davisae has established within an ecological niche to integrate with the available food web (Kovalev et al., 1999; Gubanova and Altukhov, 2007; Yıldız et al., 2017). Similar fluctuations in the biomass of pelagic fishes and mesozooplankton structure reported in the Black Sea were also observed in the North and the Baltic sea (Niermann et al., 1998). The phenomenon observed in the three seas may have some connections with climatic oscillations (Oguz et al., 2006). Zooplankton biomass intensity was generally observed in the first 50 m depth in coastal waters of the Black Sea. The zooplankton as secondary producers tend to follow the areas with high primary production such as the northwestern shelf, plume areas of important rivers and some near coastal waters of Turkey. A hypoxia problem occurred in northwestern shelf waters in 1973 causing greater eutrophic conditions and leading to long-lasting impacts on the marine ecosystem (Mee et al., 2005). Normally, ecological systems are known for their slow adaptation to changing environmental conditions. This rule is valid for systems with a good and healthy inner ecological balance. If the inner balance of the system is disturbed or broken, then it becomes vulnerable to any environmental stressors and may change very rapidly. This type of sudden deviation from the equilibrium state is a regime shift (Oguz and Gilbert, 2007). A typically changing state continuing for more than a decade is to be regarded as a regime shift in marine ecology. In the Black Sea the period started in 1960 and lasted till 1990. In 1970, the ecological system has evolved from predator fishes to planktivorous pelagic fish groups, which triggered grazing on zooplanktons and caused a high eutrophication state (Daskalov et al., 2007; Pershing et al., 2015). This also coincides with an extreme cooling period of the Black Sea. The cooling period was followed by 20-year warming conditions and experienced a gelatinous carnivorous intrusion at the beginning of 1980 (Oguz and Gilbert, 2007). A gelatinous carnivore Mnemiopsis leidyi holds an important place in the zooplankton assemblage of the Black Sea. It was first introduced to the ecosystem in 1980, reached its maximum populations in 1990, and slowly lost its place in the ecosystem after 1994 by biological control from another comb jelly, Beroe ovata (Akoglu et al., 2014). The zooplankton community structure and abundance are also influenced by anthropogenic factors such as pollution and overfishing. A similar degradation was also observed in the benthic ecosystem of the Black Sea when the Rapana whelk, an East Asian originating-carnivore, was introduced into the system in 1940 (Mee et al., 2005; Oguz et al., 2012). Another benthic indicator affected by the eutrophic state is the red alga “Phyllophora.” Until the beginning of the 1960s, the biomass of these red algae was abundant in northwestern shelf waters. Due to eutrophic conditions related to hypoxia and limited light problems, this indicator algae disappeared from the system until recent studies that reported sightings of it in field surveys (Minicheva, 2007; Langmead et al., 2009; Capet et al., 2013). Such catastrophic impacts of eutrophication have greatly altered the ecological aquatic life and food chain of the sea. However, there are some signs of recovery of the Black Sea ecosystem and a move to changing the conditions back to the preeutrophication period, which was known as meso-trophic state before 1970. From 1970 to 1980, very high primary and secondary production rates created hypoxic conditions and led to a very large deterioration of benthic life (Akoglu et al., 2014). It seems that precautions and regulations of anthropogenic factors such as agriculture and pollution have been effective at least to some extent in the recovery of the ecological system of the Black Sea. Chl-a satellite images showing the mean annual concentrations from different satellites are depicted in Fig. 2. The causes of the regime shift encountered in the Black Sea can possibly be attributed to overfishing and the intrusion of M. leidyi to the system and new ecological conditions had altered the trophic state from bottom-up to top-down by creating a trophic cascade effect (Akoglu et al., 2014). A trophic cascade is generally observed in benthic life or coastal margins with some exceptions reported in large marine ecosystems (Daskalov et al., 2007). A trophic cascade can occur in both top-down and bottom-up directions in aquatic systems—if the consumers are dominant then the system is top-down, but if primary producers are abundant with high biomass then the system is bottom-up controlled. The ratio between consumers and producers should approach unity for the ecosystems working in balanced conditions (Daskalov, 2002; Daskalov et al., 2007). Top-down systems are generally found in terrestrial ecology and are rarely observed in coastal or freshwater ecosystems (Daskalov, 2002). It should be emphasized that ecological shifts witnessed in the Black Sea are not only caused by anthropogenic factors but also influenced by large-scale climatic oscillations such as the North Atlantic Oscillation (NAO). There are also some known effects of global warming on rising mean SST, which reached up to 4–5°C in the Black Sea and



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FIG. 2  Annual mean composite chl-a images of different periods.

370  SECTION |D  Enclosed, Semi-enclosed, and Open Coasts

approximately 0.3°C in the global oceans according to measurements started in 1950. Increasing trends of SST anomalies are well correlated with the NAO (Oguz et al., 2003). This physical impact has important interactions with oceanographic mixing process of the water column. The CIL formation is directly affected by increasing SST trends. The depth of the CIL is limited to lower values which causes less vertical mixing and inadequate production rates. Moreover, due to a limited nutrient input to the photic zone, the system shifts toward small cell phytoplankton groups for a more efficient use of available light and nutrients in ambient conditions (Oguz et al., 2003).

4 FISHERIES Fisheries are one of the most important revenue-generating activities in the Black Sea. Although it is not significant in terms of the basin economy, fisheries is a part of the cultural history in the region and dates back several thousand years. Today, industrial, semiindustrial, and small-scale fishing types are widely practiced in the basin. There are approximately 11,000 fishing boats of different sizes and with different gears. The number of the purse seiners totals approximately 455 (FAO, 2016). The largest fishing fleet belongs to Turkey with maximum annual fish yield in the basin. Considering the entire basin fishing effort of all the surrounding countries, registered fishing boat numbers are as follow: Turkey (16,448), Ukraine (135), Russian Federation (33), Georgia (47), Romania (158), and Bulgaria (704). Although the registered boat number is very high in Turkey compared to other countries, approximately 15,000 of total registered boats are less than 12 m in length (FAO, 2016). According to data for 2013, the total catch reported is approximately 1250 kt in the basin. Moreover, 68% of total landings is reported from Turkey. The number of economically important species is less today than it was during the preeutrophication period. Fishes that comprise the greatest part of the total landings are as follows: European anchovy (Engraulis encrasicolus), sprat (Sprattus sprattus), Mediterranean horse mackerel (Trachurus mediterraneus), Atlantic bonito (Sarda sarda), and bluefish (Pomatomus saltatrix), turbot (Psetta maxima), whiting (Merlangius merlangus), picked dogfish (Squalus acanthias), striped and red mullets (Mullus barbatus, M. surmuletus), and four species from the Mugilidae family (European Parliament, 2010). In paralleling the increasing trends of the world population, the Black Sea coastal population has been also increasing in recent decades. Therefore, aquatic resources of the basin fail to meet the necessary high demands of the bordering countries. There are some issues of high priority regarding the fishing regulations in the basin and problems related to fishing must be handled by consensus among all neighboring countries. These problems can be summarized as follows: overfishing problem undoubtedly is the first of all as it is clearly seen in decreasing trends of total catch year by year in the Black Sea. This is governed by stock size, which is related to the recruitment rate of fish stocks (Daskalov, 1999) as well as available food for larvae and eggs in ambient conditions. Nutrient supply by fresh water sources of the basin can also play an important role in developing healthy fish stocks as it is necessary for primary producers. The decreasing trend of anchovy stock size is critically reported to have started in 2005 and linked to enlarged fishing fleet with a too large and unsustainable fishing effort pressure on natural stocks as well as illegal fishing (Raykov et al., 2011). It is well known that overfishing can also alter the food chain and energy flow in the marine environment. Palkovacs (2011) reported that the body size of the same fish captured in the same biogeographic region 100 years later can show a 43% difference in weight and a 69% difference in length. Fish length, weight, and age can be extremely adversely affected by overfishing. An important threshold showing the success of the fisheries management in the Black Sea could be in achieving Good Environmental Status (GeNS), for the EU Marine Strategy Framework Directive, by taking into account the maximum sustainable yield (MSY) as an indicator. The biggest problem preventing Black Sea fisheries to achieve MSY is the synchronization problem of different institutional arrangements and international environmental policies (Goulding et  al., 2014). However, there are also good examples of consensus on environmental policies among bordering countries such as the Bucharest Convention signed in 1992 after recommendations of 1972 Stockholm Conference on environment and development. Following the Bucharest Convention, Black Sea Environmental Program (BSEP) was established with the aim of restoring the Black Sea ecosystem and carrying out specific monitoring programs with financial budgets supported by UNEP, UNDP, and GEF (BSEP (Black Sea Environmental Programme), 1997). Solution to some other important problems involved in Black Sea fisheries can be summarized as shortening the total length of fishing boats to limit their fishing capacity, switching from industrial type to artisanal and small-scale fishing, controlling by-catch, delineating no-take zones, and imposing necessary fishing quotas. These are necessary and urgent issues that should be handled precisely in order to achieve GeNS and restoring the natural stocks in the basin. Turkey is the first country on the list influenced by the problems stated above. For instance, total anchovy landings in Turkey was around 500 kt in 1960 and decreased to 150 kt within a 30-year period (Akoglu et al., 2014). According to official statistics, the total anchovy catch of Turkey was around 100 kt for 2016 (www.tuik.gov.tr). Recently, the migration behavior of

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TABLE 2  Some Fishing Information of Black Sea Countries Country

Coast Line (km)

Area of EEZ (km2)

Total Fishing Vessel (#)

Average Landings (2000–13) (kt)

Turkey

1400

210.565

5973

307

Russia

475

69.038

33

32

Romania

225

31.108

158

1.26

Ukraine

1628

138.362

135

68.9

Bulgaria

300

34.288

704

7.72

Georgia

310

18.612

47

12.6

(Data from: European Parliament: Directorate general for internal policies, policy department B: structural and cohesion policies, Irina Popescu, 2010, Fisheries in the Black Sea, pp. 1–69; FAO, 2016. The state of Mediterranean and Black Sea fisheries. General fisheries Commission for the Mediterranean, Italy, Rome ; www.tuik.gov.tr; Landings and total fishing vessel information of Turkey represent the average total numbers for Black Sea.)

anchovy has also changed in Southern Black Sea waters. The root causes of the new migration pattern of anchovy must be investigated in detail to determine whether the natural or anthropogenic factors are involved in the problem. The length and mesh size of fishing nets are some additional problems causing depletion of the anchovy and other pelagic fish stocks in the Black Sea. Black Sea fisheries management must be based on scientific monitoring tools and approaches that account for related environmental and ecosystem indicators (Caddy, 2009). The Black Sea fishing figures by bordering countries are summarized in Table 2. As inferred from Table  2, Turkey is ranked first in terms of fishing activity in the basin. Therefore, any fisheriesrelated problem can directly influence the socioeconomic well-being of the families living on the Turkish coastal zone. Synchronization with EU fisheries policy could be the best action to be followed by Turkey in order to achieve MSY and GeNS in the region. Necessary regulations and precautions should be implemented without any delay. The power of fishing boat engines, technological fishing gears used on board, fish net length, and mesh size are also the controls that can be used to regulate fishing strategy. Recently, Turkey has also implemented fishing licence revocation for approximately 150 registered fishing boats (purse seiners) by paying a legal compensation amount to reduce fishing pressure on natural stocks.

5  POLLUTION (MARINE LITTER) Marine litter is one of the most important environmental problems of the Black Sea basin. They can be found in the water column, on the seabed, on the coast, or as floating wastes transported from land. Marine litter could be in the form of nano, micro, or macro-size in marine environment and can accumulate in tissues of aquatic organisms as plastic residuals or cause entanglements of marine fishes. The main pollution source of the Black Sea is land-based solid wastes transported by rivers (Tuncer et al., 1998). Marine litter can be described as all types of solid waste that disturbs the marine environment by creating pollution defined as the damage to the ecology. Apart from their sizes and types, these toxic substances threaten the aquatic living resources and marine environment. The nano and microform of marine litter can be ingested by demersal and pelagic fishes or filter feeding organisms by contaminating their natural diets (UNEP and GRID-Arendal, 2016). Marine litter has been reported from the world seas since 1970 and by an accelerated and alarming increase in 1990s (Corcoran et al., 2009). This might be attributed to a consumption economy and high purchasing power of the people in the developed countries. The problem of marine litter is increasing and more complex in the oceans. Moreover, small gyres of litter are now easily detected by remote sensing satellites around mid-regions of all oceans, especially, the Pacific Ocean (Pichel et al., 2007). The sources of marine litter pollution in the Black Sea are mainly rivers or creeks distributed all around the coastal periphery of the basin (Guneroglu, 2010; Aytan et al., 2016). A very small part of the total volume might be generated by commercial vessels or fishing boats. In the frame of MSFD to achieve GES in marine environment, 11 descriptors were defined and explained in Annex 1 of the Decision 2010/477/EU by the EU Commission. Descriptor 10 is allocated for marine litter and explained by four subindicators (Galgani et al., 2013). The primary concern of marine litter in the Black Sea was originally started with aesthetic considerations but evolved in course of time and became a problem with high priority. The solution to the problem must be searched for by all bordering countries, as it is a general environmental issue. Increasing public awareness, education, and solid waste management policies can be used for controlling and mitigating the problems.

372  SECTION |D  Enclosed, Semi-enclosed, and Open Coasts

The best solution can be in stopping the solid waste at its source before reaching the marine environment. Therefore, the initiative by local managers and decision-makers plays a crucial role in recovering the unique Black Sea ecosystem.

6  RECOMMENDATIONS AND CONCLUSIONS The Black Sea basin is a valuable area with its natural, historical, and ecological assets. Preservation and usage balance have deteriorated because of various factors in the last 50 years. However, setting the successful management of this ecosystem for the next 50 years depends on handling current problems with cautions by using scientific tools and approaches. The essential step in the conservation of the Black Sea ecosystems must focus on sustainability of the basin by tuning usage and protection principles. Considering decreasing the nutrient input to ecosystem, there are some clear signs of recovery of the basin reported in different scientific studies, which should be evaluated precisely before accepting this as a total recovery. Lower algal concentrations and less-frequent bloom events observed in northwestern shelf were also complemented by a decrease in abundance of gelatinous species (McQuatters-Gollop et al., 2008; Shiganova et al., 2008; Oguz and Velikova, 2010). Regular monitoring of the ecosystem is a prerequisite for its ecological protection. In this course, satellite remote sensing and data processing techniques have reached a great potential for the fast and accurate modeling and simulation of the area under investigation. Some basic environmental parameters such as available light, temperature, chlorophyll, and salinity are very easy to obtain and use information such as from satellite images with global coverage. Therefore, almost real-time observation of algal blooms or eutrophication events can be easily carried out by using remote sensing tools. For instance, SST and chl-a data can be embedded into ecosystem models for estimating the ecological state for the next 30 years. The SST data is especially important as it is related to global warming and CIL formation in the Black Sea. Stratification and vertical mixing need to be regularly monitored as they are linked to trophic state of the ecosystem. Although remarkable progress has been achieved in limiting nutrient inputs to the Black Sea environment, scientific projects must be financed to determine point and diffuse sources of current nutrient supply as well as monitoring the state of the coastal productive regions. Another issue regarding anthropogenic nutrient state is the very dense coastal population especially on the northwestern and southern sections of the sea. The correlation between nutrient levels and coastal population settlements can be carried out to determine the hotspots on the coastal environment. There is also a risk of nutrient deficiency in the long term at least at some local coastal regions due to accelerated efforts of dam construction for producing electricity. Sediments with high nutrient content are trapped and deposited in deep layers behind the constructed dams, which limits nutrient concentrations per volume of fresh waters flowing in to the basin. The final aim in the Black Sea environmental protection must focus on reaching GES as explained in MSFD and WFD documentation. This is also necessary to solve the problems related to fisheries. The state of Black Sea fisheries is definitely alarming and getting worse day by day. Overfishing and inadequate controls of fishing fleet are the main problems. Necessary quotas, fishing area allocation zones, and times must be redefined by consensus of all bordering countries. This can be also be supported by establishing a new Black Sea fisheries coordination body that can make recommendations and suggestions following EU regulations on the fisheries. In this case, Turkey must lead other countries as the country being the highest beneficiary of the Black Sea fisheries. Issuing new fishing licences must be strictly controlled and preferably no new licences of purse seiners should be offered. Engine power and onboard technological gears can be limited to reduce fishing pressure on natural stocks. Solid waste pollution in the basin is largely due to a mismanaged municipal service that fails in collecting garbage containers on regular schedules. The lack of the service in southern regions of the basin is partly because of scattered settlement patterns. Therefore, unmanaged solid wastes finally reach the sea environment in different shapes and forms. They can float, sink, or suspend in water column as marine litter and enter into food cycle with different pathways. An effective municipal service and monitoring is necessary to stop the marine litter problem in the Black Sea. New policies and regulations are required for designing garbage collection and management at their site of origin. Limiting plastic covers and packaging materials could greatly contribute to reduce marine litter problem. Furthermore, some kind of country marker can be designed to be used in packing materials for determining and controlling marine litter transport. Specially designed solid waste collectors can be also used on predefined sections of rivers or creeks. The oil and gas industry also has a wide application area in the Black Sea. Oil products transported by large tanker ships create environmental pollution risks in the Black Sea and Bosporus. Alternative routes and an efficient vessel traffic system must be designed in order to avoid any collision or grounding accidents. The environmental pollution risk of maritime transport in the Black Sea cannot be limited with oil spill occurrence, grounding, or collision, as the basin experiences invasive alien species transported by ballast waters and in turn cause catastrophic impacts on the marine food web. The impact of the ctenophore M. leidyi on the Black Sea marine ecosystem is such an effect that cannot be overlooked or forgotten. However, more than 100 MT oil was carried via the Bosporus strait each year. Moreover, oil transport pipelines from the Caucasus



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to European regions traverse the Black Sea deep layers with potential threats to the marine ecosystem. There also some recent initiatives seeking new energy resources in the basin carried out by bordering countries on their EEZs. Therefore, environmental regulations in addition to MARPOL and SOLAS, new alternative solutions and routes such as may help to reduce environmental pollution risk in the southwestern Black Sea and Bosporus regions. Despite many mitigation policies, it is clear that global warming will continue to be a problem posed by humanity at least for the coming decades. Regarding the coastal environment, SLR could be the most destructive result of the global warming effect in the Black Sea. An expected 10–15 cm rise of seawater could cause billions of dollars of flood or storm surge effects in the region. It is suggested that, starting now, no built-up zones on very near coastal areas have to be defined and planned by responsible decision-makers. Finally, the future of the Black Sea is in the hands of the countries surrounding the basin and their international cooperation level to achieve a better proposed environmental status for a better and sustainable natural heritage to leave for the next generations. After taking all necessary preventive measures and following internationally recognized environmental arrangements, the Black Sea also needs an element of good luck for totally recovering and reaching the preeutrophication stage as mentioned above in the text. This is because global warming and global climate change impacts are hard to predict nonlinear phenomena.

ACKNOWLEDGMENTS The authors are grateful to EMODnet Bathymetry Consortium (2016): EMODnet Digital Bathymetry (DTM) for bathymetric data and Global Land Cover Facility GLCF for providing the Landsat satellite data. The CZCS, SeaWiFS and MODIS satellite images were made available by NASA OB.DAAC archives.

REFERENCES Akoglu, E., Salihoglu, B., Libralato, S., Oguz, T., Solidoro, C., 2014. An indicator-based evaluation of Black Sea food web dynamics during 1960–2000. J. Mar. Syst. 134, 113–125. Allenbach, K., Garonna, I., Herold, C., Monioudi, I., Giuliani, G., Lehmann, A., Velegrakis, A.F., 2015. Black Sea beaches vulnerability to sea level rise. Environ. Sci. Policy 46, 95–109. Alpar, B., 2009. Vulnerability of Turkish coasts to accelerated sea-level rise. Geomorphology 107 (1), 58–63. Antonidze, E., 2010. ICZM in the Black Sea region: experience and perspectives. J. Coast. Conserv. 14 (4), 265–272. Avsar, N.B., Kutoglu, S.H., Jin, S., Erol, B., 2015. Investigation of sea level change along the Black Sea coast from tide gauge and satellite altimetry. Int. Arch. Photogramm. Remote Sens. Spat. Inf. Sci. 40 (1), 67. Aytan, U., Valente, A., Senturk, Y., Usta, R., Sahin, F.B.E., Mazlum, R.E., Agirbas, E., 2016. First evaluation of neustonic microplastics in Black Sea waters. Mar. Environ. Res. 119, 22–30. BSC (Black Sea Commission), 2008. Statee of the environment of the Black Sea (2001–2006/7). Publications of the Commission on the Protection of the Black Sea against Pollution (BSC), 3. BSEP (Black Sea Environmental Programme) RER/92/G31—RER/93/G31—RER/94/G41—RER/96/006, Final Report, 1997. Caddy, J.F., 2009. Practical issues in choosing a framework for resource assessment and management of Mediterranean and Black Sea fisheries. Mediterr. Mar. Sci. 10 (1), 83–119. Capet, A., Beckers, J.M., Grégoire, M., 2013. Drivers, mechanisms and long-term variability of seasonal hypoxia on the Black Sea northwestern shelf-is there any recovery after eutrophication? Biogeosciences 10 (6), 3943. Corcoran, P.L., Biesinger, M.C., Grifi, M., 2009. Plastics and beaches: a degrading relationship. Mar. Pollut. Bull. 58 (1), 80–84. Daskalov, G., 1999. Relating fish recruitment to stock biomass and physical environment in the Black Sea using generalized additive models. Fish. Res. 41 (1), 1–23. Daskalov, G.M., 2002. Overfishing drives a trophic cascade in the Black Sea. Mar. Ecol. Prog. Ser. 225, 53–63. Daskalov, G.M., Grishin, A.N., Rodionov, S., Mihneva, V., 2007. Trophic cascades triggered by overfishing reveal possible mechanisms of ecosystem regime shifts. Proc. Natl. Acad. Sci. 104 (25), 10518–10523. Drozdov, V.A., Glezer, O.B., Nefedova, T.G., Shabdurasulov, I.V., 1992. Ecological and geographical characteristics of the coastal zone of the Black Sea. GeoJournal 27 (2), 169–178. Eker-Develi, E., Kideys, A.E., 2003. Distribution of phytoplankton in the southern Black Sea in summer 1996, spring and autumn 1998. J. Mar. Syst. 39 (3), 203–211. European Parliament, 2010. Directorate General for Internal Policies, Policy Department B: Structural and Cohesion Policies. Fisheries in the Black Sea, Irina Popescu, pp. 1–69. FAO, 2016. The State of Mediterranean and Black Sea Fisheries. General Fisheries Commission for the Mediterranean. Rome, Italy. Feyzioğlu, A.M., Eruz, C., Yıldız, İ., 2015. Geographic variation of Picocyanobacteria Synechococcus spp. along the Anatolian Coast of the Black Sea during the late Autumn of 2013. Turk. J. Fish. Aquat. Sci. 15 (4), 471–475.

374  SECTION |D  Enclosed, Semi-enclosed, and Open Coasts

Feyzioglu, A.M., Kurt, I., Boran, M., Sivri, N., 2004. Abundance and Distribution of Synechococcus spp in the South-Eastern Black Sea During 2001 Summer. Indian J. Marine Sci. 33 (4), 365–368. Feyzioğlu, A.M., Öğüt, H., 2006. Red tide observations along the eastern Black Sea coast of Turkey. Turk. J. Bot. 30 (5), 375–379. Friedrich, J., Janssen, F., Aleynik, D., Bange, H.W., Boltacheva, N., Çagatay, M.N., Dale, A.W., Etiope, G., Erdem, Z., Geraga, M., Gilli, A., 2014. Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon. Biogeosciences 11, 1215–1259. Galgani, F., Hanke, G., Werner, S.D.V.L., De Vrees, L., 2013. Marine litter within the European marine strategy framework directive. ICES J. Mar. Sci. 70 (6), 1055–1064. Gómez, F., Boicenco, L., 2004. An annotated checklist of dinoflagellates in the Black Sea. Hydrobiologia 517 (1–3), 43–59. Goulding, I., Stobberup, K., O’Higgins, T., 2014. Potential economic impacts of achieving good environmental status in Black Sea fisheries. Ecol. Soc. 19 (3), 1–11. Gubanova, A.D., Altukhov, D.A., 2007. Establishment of Oithona brevicornis Giesbrecht, 1892 (Copepoda: Cyclopoida) in the Black Sea. Aquat. Invas. 2 (4), 407–410. Guneroglu, A., 2010. Marine litter transportation and composition in the Coastal Southern Black Sea Region. Sci. Res. Essays 5 (3), 296–303. Guneroglu, A., 2015. Coastal changes and land use alteration on Northeastern part of Turkey. Ocean Coast. Manag. 118, 225–233. Guneroglu, A., Karsli, F., Dihkan, M., 2014. Dynamic management of the coasts: marine spatial planning. Proc. Inst. Civil Eng.-Maritime Eng. 167 (3), 144–153. Guneroglu, N., Acar, C., Dihkan, M., Karsli, F., Guneroglu, A., 2013. Green corridors and fragmentation in South Eastern Black Sea coastal landscape. Ocean Coast. Manag. 83, 67–74. Karsli, F., Guneroglu, A., Dihkan, M., 2011. Spatio-temporal shoreline changes along the southern Black Sea coastal zone. J. Appl. Remote. Sens. 5 (1), 053545. Kopuz, U., Feyzioglu, A.M., Agirbas, E., 2012. Picoplankton dynamics during late spring 2010 in the south-eastern Black Sea. Turk. J. Fish. Aquat. Sci. 12 (5), 397–405. Kopuz, U., Feyzioglu, A.M., Valente, A., 2014. An unusual red-tide event of Noctiluca scintillans (Macartney) in the Southeastern Black Sea. Turk. J. Fish. Aquat. Sci. 14 (1), 261–269. Kosyan, R.D., Velikova, V.N., 2016. Coastal zone–Terra (and aqua) incognita–Integrated Coastal Zone Management in the Black Sea. Estuar. Coast. Shelf Sci. 169, A1–A16. Kovalev, A.V., Skryabin, V.A., Zagorodnyaya, Y.A., Bingel, F., Kıdeyş, A.E., Niermann, U., Uysal, Z., 1999. The Black Sea zooplankton: composition, spatial/temporal distribution and history of investigations. Turk. J. Zool. 23 (2), 195–210. Kuleli, T., 2010. City-based risk assessment of sea level rise using topographic and census data for the Turkish coastal zone. Estuar. Coasts 33 (3), 640–651. Kuleli, T., Guneroglu, A., Karsli, F., Dihkan, M., 2011. Automatic detection of shoreline change on coastal Ramsar wetlands of Turkey. Ocean Eng. 38 (10), 1141–1149. Langmead, O., McQuatters-Gollop, A., Mee, L.D., Friedrich, J., Gilbert, A.J., Gomoiu, M.T., Jackson, E.L., Knudsen, S., Minicheva, G., Todorova, V., 2009. Recovery or decline of the northwestern Black Sea: a societal choice revealed by socio-ecological modelling. Ecol. Model. 220 (21), 2927–2939. Ludwig, W., Dumont, E., Meybeck, M., Heussner, S., 2009. River discharges of water and nutrients to the Mediterranean and Black Sea: major drivers for ecosystem changes during past and future decades? Prog. Oceanogr. 80 (3), 199–217. McQuatters-Gollop, A., Mee, L.D., Raitsos, D.E., Shapiro, G.I., 2008. Non-linearities, regime shifts and recovery: the recent influence of climate on Black Sea chlorophyll. J. Mar. Syst. 74 (1), 649–658. Mee, L.D., Friedrich, J., Gomoiu, M.T., 2005. Restoring the Black Sea in times of uncertainty. Oceanography 18 (2), 32–43. Mikaelyan, A.S., Pautova, L.A., Chasovnikov, V.K., Mosharov, S.A., Silkin, V.A., 2015. Alternation of diatoms and coccolithophores in the north-eastern Black Sea: a response to nutrient changes. Hydrobiologia 755 (1), 89–105. Mikaelyan, A.S., Pautova, L.A., Pogosyan, S.I., Sukhanova, I.N., 2005. Summer Bloom of Coccolithophorids in the Northeastern Black Sea. Oceanology 45 (Suppl. 1), 127–138. Mikaelyan, A.S., Silkin, V.A., Pautova, L.A., 2011. Coccolithophorids in the Black Sea: their interannual and long-term changes. Oceanology 51 (1), 39–48. Miladinova, S., Stips, A., Garcia-Gorriz, E., Moy, D.M., 2016. Changes in the Black Sea physical properties and their effect on the ecosystem. In: Tech. Rep. EUR 28060 EN, Publications Office of the European Union, Luxembourg. https://doi.org/10.2788/69832. Minicheva, G.G., 2007. Contemporary morpho-functional transformation of seaweed communities of the Zernov phyllophora field (Black Sea). Int. J. Algae 9 (1), 1–21. Moncheva, S., Gotsis-Skretas, O., Pagou, K., Krastev, A., 2001. Phytoplankton blooms in Black Sea and Mediterranean coastal ecosystems subjected to anthropogenic eutrophication: similarities and differences. Estuar. Coast. Shelf Sci. 53 (3), 281–295. Moncheva, S., Pantazi, M., Pautova, L., Boicenco, L., Vasiliu, D., Mantzosh, L., 2012. Black Sea Phytoplankton data quality–problems and progress. Turk. J. Fish. Aquat. Sci. 12 (5), 417–422. Niermann, U., Binge, F., Ergün, G., 1998. Fluctuation of dominant mesozooplankton species in the Black Sea, North Sea and the Baltic Sea: is a general trend recognisable? Turk. J. Zool. 22 (1), 63–82. Oguz, T., Akoglu, E., Salihoglu, B., 2012. Current state of overfishing and its regional differences in the Black Sea. Ocean Coast. Manag. 58, 47–56. Oguz, T., Cokacar, T., Malanotte-Rizzoli, P., Ducklow, H.W., 2003. Climatic warming and accompanying changes in the ecological regime of the Black Sea during 1990s. Global Biogeochem. Cycles 17 (3), 1–14.



The Black Sea—The Past, Present, and Future Status Chapter | 21  375

Oguz, T., Dippner, J.W., Kaymaz, Z., 2006. Climatic regulation of the Black Sea hydro-meteorological and ecological properties at interannual-to-decadal time scales. J. Mar. Syst. 60 (3), 235–254. Oguz, T., Gilbert, D., 2007. Abrupt transitions of the top-down controlled Black Sea pelagic ecosystem during 1960–2000: evidence for regime-shifts under strong fishery exploitation and nutrient enrichment modulated by climate-induced variations. Deep-Sea Res. I Oceanogr. Res. Pap. 54 (2), 220–242. Oguz, T., Velikova, V., 2010. Abrupt transition of the northwestern Black Sea shelf ecosystem from a eutrophic to an alternative pristine state. Mar. Ecol. Prog. Ser. 405, 231–242. O’Higgins, T., Farmer, A., Daskalov, G., Knudsen, S., Mee, L., 2014. Achieving good environmental status in the Black Sea: scale mismatches in environmental management. Ecol. Soc. 19 (3), 1–9. Palkovacs, E.P., 2011. The overfishing debate: an eco-evolutionary perspective. Trends Ecol. Evol. 26 (12), 616–617. Panin, N., Jipa, D., 1998. Danube river sediment input and its interaction with the north-western BlackSea: results of EROS-2000 and EROS-21 projects. Geo-Eco-Marina 3, 23–35. Panin, N., Jipa, D., 2002. Danube River sediment input and its interaction with the north-western Black Sea. Estuar. Coast. Shelf Sci. 54 (3), 551–562. Pershing, A.J., Mills, K.E., Record, N.R., Stamieszkin, K., Wurtzell, K.V., Byron, C.J., Fitzpatrick, D., Golet, W.J., Koob, E., 2015. Evaluating trophic cascades as drivers of regime shifts in different ocean ecosystems. Philos. Trans. R. Soc. Lond. B Biol. Sci. 370 (1659), 20130265. Pichel, W.G., Churnside, J.H., Veenstra, T.S., Foley, D.G., Friedman, K.S., Brainard, R.E., Nicoll, J.B., Zheng, Q., Clemente-Colon, P., 2007. Marine debris collects within the North Pacific subtropical convergence zone. Mar. Pollut. Bull. 54 (8), 1207–1211. Raykov, V., Velikova, V., Lisichkov, K., Kuvendziev, S., 2011. Review of main fisheries indicators in the Black Sea by using diagnostic analysis. Natura Montenegriana. Podgorica 10 (3), 309–312. Shiganova, T., Musaeva, E., Araskievich, E., Kamburska, L., Stefanova, K., Michneva, V., Polishchuk, L., Timofte, F., Ustun, F., Oguz, T., Khalvashi, M., 2008. The state of zooplankton. In: State of the Environment of the Black Sea (2001–2006/7). 3. pp. 201–246. Stănică, A., Panin, N., 2009. Present evolution and future predictions for the deltaic coastal zone between the Sulina and Sf. Gheorghe Danube river mouths (Romania). Geomorphology 107 (1), 41–46. Tsereteli, E., Gobejishvili, R., Bolashvili, N., Geladze, V., Gaprindashvili, G., 2011. Crisis intensification of geoecological situation of the Caucasus Black Sea coast and the strategy of risk reduction. Procedia. Soc. Behav. Sci. 19, 709–715. Tuncer, G., Karakas, T., Balkas, T.I., Gökçay, C.F., Aygnn, S., Yurteri, C., Tuncel, G., 1998. Land-based sources of pollution along the Black Sea coast of Turkey: concentrations and annual loads to the Black Sea. Mar. Pollut. Bull. 36 (6), 409–423. UNEP and GRID-Arendal, 2016. Marine Litter Vital Graphics. United Nations Environment Programme and GRID-Arendal, Nairobi and Arendal. Uysal, Z., 2000. Pigments, size and distribution of Synechococcus spp. in the Black Sea. J. Mar. Syst. 24 (3), 313–326. Uysal, Z., 2001. Chroococcoid cyanobacteria Synechococcus spp. in the Black Sea: pigments, size, distribution, growth and diurnal variability. J. Plankton Res. 23 (2), 175–190. Yıldız, İ., Feyzioglu, A.M., Besiktepe, S., 2017. First observation and seasonal dynamics of the new invasive planktonic copepod Oithona davisae Ferrari and Orsi, 1984 along the southern Black Sea (Anatolian Coast). J. Nat. Hist. 51 (3–4), 127–139. Yunev, O.A., Vedernikov, V.I., Basturk, O., Yilmaz, A., Kideys, A.E., Moncheva, S., Konovalov, S.K., 2002. Long-term variations of surface chlorophyll a and primary production in the open Black Sea. Mar. Ecol. Prog. Ser. 230, 11–28. Zaitsev, Y., 2001. An introduction to Black Sea Ecology, European Research Offıce London (Great Britain) Army Engineer Research And Development Center. 174. Defense Technical Information Center. Zaitsev, Y., Alexandrov, B.G., Berlinsky, N.A., Zenetos, A., 2001. Europe’s biodiversity–biogeographical regions and seas, European Environmental Agency (Report). ZooBoTech HB, Sweden. Zaitsev, Y.P., Alexandrov, B.G., Berlinsky, N.A., Zenetos, A., 2002. Europe’s Biodiversity–Biogeographical Regions and Seas: The Black Sea an OxygenPoor Sea. EEA (European Environment Agency), Copenhagen.