The ecological status of the Black Sea has varied greatly in the last 40 years, from a quasi-pristine environment in the 1960s, to a highly degraded situation in the 1980s, and more recently a situation of recovery. The following section briefly describes the status of the Black Sea ecosystem in terms of its biodiversity, habitats, alien species, protected areas and fisheries.

The Black Sea biota reflects the general historical processes that have influenced the ecosystem of the sea.

Black Sea coastal waters and the continental shelf are predominantly eutrophic (rich in nutrients), the central part is mesotrophic (medium level of nutrients) in character, and significant parts are hypertrophic (high level of nutrients). The largest hypertrophic areas are located in the north-western part of the Black Sea in the zone influenced by inflow from the Danube, Dniester and Dnieper rivers which have high levels of chlorophyll. Phytoplankton reacts to anthropogenic impacts by alterations in species composition and abundance and the timing and duration of blooming events. The status of phytoplankton and zooplankton can be assessed using a range of indicators including abundance, biomass and community composition The sections below outline briefly their current status.

Phytoplankton abundance and biomass   Phytoplankton abundance and biomass have shown considerable inter-annual variability over the last two decades (Fig. 3.15). In 2001, when a temporary return of hypoxic conditions was observed an increase in abundance occurred equivalent to that observed in the 1980s. However, when longer-term averages are considered, an emerging pattern of reducing phytoplankton biomass can be seen. A similar pattern of decreasing phytoplankton biomass is shown throughout the Black Sea as a whole (1997-2005) by remote sensing imagery of chlorophyll-like substances (http://marine.jrc.cec.eu.int/frames/archive_seawifs.htm). Figure 3.16 Phytoplankton cell density and biomass (average annual data) offshore of Constanta, Romania (1983-2005) Phytoplankton community composition   Plankton community composition also indicates that recovery is starting to taking place. Unfortunately, taxonomic data are not available from the 1960s reference period, but it is clear that in terms of the contribution of major taxonomic groups to total phytoplankton biomass, at least, the status in recent years has returned to a situation resembling that in the 1980s. Post-2000, the situation with regard to cell counts has been rather less straightforward, since a temporary return of eutrophic conditions in 2001 was reflected very strongly in phytoplankton communıty composıtıon results (Anon, 2006). Zooplankton abundance   Phytoplankton-eating microzooplankton in the Black Sea are dominated by Cladocera and Copepoda, long-term data for which present an interesting reflection of the biological changes that have occurred since the 1960s. Fig. 3.16 shows a clear long-term trend of declining abundance, with extrapolation of the long-term linear regression line suggesting that by 2006, zooplankton abundance would have been a full order of magnitude lower than that in 1967. However, there is a great deal of inter-annual variability in the figures, and when only more recent data are considered (1997-2005), these suggest that zooplankton abundance has actually levelled off or increased over the last decade. This huge depression (and possible start of recovery) in the zooplankton community can be related to many different factors – mass development of inedible phytoplankton species, Mnemiopsis (Fig. 3.17) outbursts, increase in small pelagic fish population, etc. (Prodanov et al, 1997). Of particulat interest is the correspondingly huge increase in Noctiluca abundance and biomass. Noctiluca scintilans is a large heterotrophic dinoflagellate (and therefore technically a member of the phytoplankton community), which because of its large size is monitored as part of the zooplankton community. The growth of thsi organism is stimulated by organic enrichment, as well increased nutrient levels. During blooms Noctiluca can account for well in excess of 90% of zooplankton biomass in coastal areas of the NW Shelf. The first positive sign in the 1990s was a reduction in the summer biomass of phytoplankton (Mee, 1999).   Figure 3.16 Long-term summer abundance of Cladocera and Copepoda three nautical miles offshore of Cape Galata, Bulgaria (1967-2005) Mnemiopsis, a highly reproductive and fast-growing comb jelly which feeds on zooplankton and fish larvae, was first identified ın the Black Sea during the early 1980s. By the mid 1990s, there was estimated to be approaching one billion tonnes of this organism in the Black and Azov seas, responsible (in part at least) for a huge decline in fish stocks and fish yields from the Sea. However, in 1997 another invasive comb jelly, Beroe ovata (Fig. 3.17), which feeds almost exclusively on Mnemiopsis, was identified in the Black Sea. Since this time, it appears that the trend of decreasing numbers of phytoplankton-eating zooplankton has begun to reverse (Fig. 3.16), possibly as a consequence of Beroe’s appearence, but the data are so variable that this is not possible to say with any certainty. The highly seasonal reproductive pattern of Beroe ovata means that long-term Mnemiopsis eradication due to the introduction of Beroe ovata is unlikely. Assessment of the comb jelly situation over the past decade is also complicated by the natural 3-4 year cycle of Mnemiopsis abundance/biomass, which occurs in both the NE Atlantic (from where Mnemiopsis originates) and the Black Sea. (A) (B) Figure 3.17 A tale of two jellies: (A) Mnemiopsis leidyi and (B) Beroe ovata Whether Mnemiopsis still constitutes a threat to fishery productivity is a moot point (Mnemiopsis competes with zooplankton-eating fish for food and also preys directly on fish larvae). However, Mnemiopsis abundance values in NW Shelf waters were high during summer 2006, and conversations with Turkish fishermen suggest that the 2007 anchovy season was of a shorter duration than usual, resulting in reduced catches (albeit unquantified at this time). Since anchovy makes a far greater contribution to total fish catch statistics than any other species, 2007 total catch statistics could be low, reversing the trend of recent years (Fig. 4.5).

There are a number of identified benthic habitats of transboundary importance. These include: Mytilus galloprovincialis habitats; Cystoseira habitats; Zostera beds; and sublittoral sands.

During the last two decades, the areas covered by eelgrass (Zostera) have decreased tenfold in shallow waters. The typical 'Zernov's Phyllophora field', in the centre of the north-west shelf, at 20-50 m depth, is an example of a habitat destruction due to human activity. The red algae Phyllophora was not only an important generator of oxygen and the nucleus of a benthic community, which included 118 species of invertebrates and 47 species of fish, but was also commercially harvested for the extraction of gelatine used as an ingredient for microbiological cultures, medicine, food industry and other purposes. Phyllophora dominated an area of the north-west shelf with the combined size of Belgium and the Netherlands. During the 1970s and 1980s, the north-west shelf ecosystem collapsed suddenly and catastrophically due to eutrophication, silting and other factors.Eutrophication has led to an increase of some algae such as the link frond (Enteromorpha) and red algae (Ceramium).

The Black Sea macrozoobenthos is represented by approximately 800 species, the status of which can be assessed using a range of indicators including abundance, biomass, number of species present and biological indices. The information presented below is a summary of the results from the Phase I BSERP research cruises of 2003 and 2006.

Zoobenthos abundance and biomass   Although the coastal area is free of hydrogen sulphide, concentrations increase rapidly under the thermocline due to the restricted ventilation of deeper shelf water. Consequently, the number of macrobenthic species decreases rapidly with increasing depth - only the polychaete worm Notomastus profundus is found below about 120 m. Abundance/biomass increases in front of the Danube delta and Constanta (Romania), with decreased abundance in front of Odessa (Ukraine), possibly due to contamination by pesticides, and at more southerly Bulgarian sites. Offshore, abundance/biomass clearly decreases due to the reduced influence of major rivers (the Danube and Dniester) which provide an import source of nutrients and organic carbon which are cycled through the food chain. Zoobenthos species diversity   Higher species richness in shallower waters is associated with good dissolved oxygen conditions whilst in deeper areas there is lower diversity due to natural oxygen depletion with increasing depth in the Black Sea. In the shallow Danube delta and Odessa areas low benthic diversity is preconditioned by the content of silt/clay fraction in sediments and aggravated by decreased oxygen concentrations associated with anthropogenic eutrophication. The effect of toxic substances may also play a role in the Odessa area. Figure 3.18 ıllustrates the change in zoobenthos status between 1988 and 2003 with a 1960s reference. Since the mid-1990s, the number of species has doubled although the number is still somewhat lower than the “reference” situation of the1960s.   Figure 3.18 Number of macrozoobenthos species near Constanta, Romania (1960s- 2003) Zoobenthos indices   The Bulgarian coastal area is distinguished by good, occasionally high zoobenthic status. The Danube plume area is characterised by moderate to poor zoobenthic status, although improving status is evident in more southerly Romanian wasters (with increasing distance from the Danube). The Dniester area coastal stations are moderately disturbed with an improving situation offshore. The zoobenthos status in the Odessa area contradicts those of other zoobenthic indicators (lowest abundance of crustaceans, lowest species richness, absence of adult molluscs, etc.). Deep area stations are generally considered to be undisturbed.

Fish and shellfish

Birds

Mammals

Economic globalisation provided unprecedented opportunities for species to overcome geographic barriers and establish in new habitats. Enclosed or semi enclosed ecosystems, as the Black Sea, seem particularly sensitive to biological invasions. With the increased shipping traffic, aquaculture and trade the Black Sea has become a major recipient of alien species. The shared marine environment contributes to the spread of alien species from one national sector to the others. Alien species can cause irreversible environmental impact at the genetic, species and ecosystem levels in ways that cause significant damage to the goods and services provided by ecosystems and thus to human interests. For this reason, they are now recognized as one of the great biological threats to the environment and economic welfare globally.

An inventory of the aquatic and semi-aquatic alien species recorded in the Black Sea marine and coastal habitats is given in Annex 6. The number of registered alien species at the regional level amounts to 217 (parasites and mycelium excluded). Nearly half of them (102) are permanently established, a quarter - highly or moderately invasive (20 and 35 species respectively). This high ratio of invasive aliens suggests serious impact on the Black Sea native biological diversity and negative consequences for human activities and economic interests.

Figure 3.19 Number of new recorded alien species (Black Sea and coastal aquatic habitats) per decade

Extinction is perhaps the most fundamental form of biodiversity loss that has resonance with the public and decision makers, and which has clear relevance to ecological processes and ecosystem function. Within the last 100 years, the Black Sea biota has undergone dramatic change. Since the beginning of the 20th century, species started declining and local/regional extinctions occurred as early as the 1960s. As an example, at this time (which is now considered to be the reference period for the Black Sea), commercially important bivalve molluscs like Ostrea edulis and Solen marginatus and highly prized fish like tuna and swordfish were already extinct in Romania and Bulgaria.

The Black Sea community has a global responsibility to preserve the character of its varied ecosystems and landscapes, and to conserve the migratory species that cross the region and the threatened species that it hosts. Measures taken to conserve or restore habitats and species in the Black Sea entail the establishment of protected areas as a major approach of in situ biodiversity conservation.

The total surface of Black Sea marine and coastal protected areas by country is given in Table 3.6. The statistics show that the largest marine protected areas (MPAs) are designated by Ukraine, while protected wetlands and coastal terrestrial areas are the largest in Romania. Romania leads in terms of protected marine area per unit shoreline, followed by Ukraine and Georgia. In Bulgaria and Russia  the coverage of MPAs appears insufficient. Turkey has no designated MPAs, and a low coverage of coastal protected areas when compared with other Black Sea countries (see footnote below regarding Russian coastal wetlands). However, Turkish authorities are keen to state that the identification and future designation of MPAs is an on-going process. Harvesting of all marine products is prohibited by the Turkish Ministry of the Environment and Forestryare in areas of 500 m. radius towards to sea from the centre of river mouths. However, this only amounts to 39 ha/river; a small area compared to the values presented in Table 3.6).

The majority of protected marine and coastal areas (93%) were declared during the 1990s, which is indicative of significant recent progress in in situ conservation of biodiversity in the Black Sea region. Romania ranks first (56%) regarding surface of protected areas designated during the 1990s, followed by Ukraine (22%) Bulgaria (10%) and Georgia (4%), while Turkey did not declare any protected areas during this period. The dates of designation of Russian sites are not known, so are excluded from these calculations.

Table 3.6 Total surface of Black Sea marine and coastal protected areas by country and marine protected areas (MPA) per unit shoreline

* Russia contains 173,000 ha of coastal wetlands MPA (Ramsar sites) bordering the Sea of Azov, but has no Black Sea coastal wetlands

Fisheries and aquaculture provide a vital source of food, employment, recreation and trade which supports the Black Sea region communities. Both fisheries and aquaculture are critical to the social and economic health of the region. After 50 years of rapid geographical expansion of the fishing areas, together with advances in fishing technology, increases in catches and shifts in fish populations, in combination with the impacts of invasive species, the greater Black Sea fisheries are at a critical point.

Due to over-fishing in the early 1970s-1980s, the structure of catches shifted significantly. Declining stocks of predatory species such as bonito (Sarda sarda), horse mackerel (Trachurus trachurus), bluefish (Pomatomus saltatrix) and others resulted in an increase in non-predatory species such as anchovy (Engraulis encrasicolus) and sprat (Sprattus sprattus). Consequently, fishing fleets have increasingly targeted these species.

During this period, the number of commercially (valuable) exploited fish species declined from twenty to only five. Extensive expansion of fishing fleet capacity, especially of purse seine and trawlers in the mid 1980s, led to catch rates of between 800,000-900,000 tonnes per year. Catches have increased since the mid-1990s, but are still only about half of this amount (Fig. 4.5).

The combined factors of over fishing and invasive species led to a near complete collapse of the Black Sea fisheries in the 1990’s. The previous Black Sea SAP sought to address this issue through the revitalization of marine living resources. Since this time there has been a slow but continuous process of improvement in many ecosystem components of the Black Sea. The rehabilitation of marine living resources has been also noted, but it has not been symmetrical in terms of either geography or species structure.

Since the mid-1990s the number of large fishing vessels in the Black Sea has increased (Fig. 3.20). High value species, such as sturgeon (Acipenseridae), turbot (Psetta maxima) and spiny dogfish (Squalus acanthias) continue to be threatened by over fishing. Recognizing that sturgeon stocks in the BlackSea/lower Danube River have been seriously depleted, Bulgaria, Romania and Ukraine (and Serbia) have requested zero CITES quotas for these fish in 2007.

Figure 3.20 Total fish landings from and total number of fishing vessels >12 m length in the Black Sea, 1991-2005

Fish consumption within the region continues to increase and, as market demand increases, it is expected that this will result in increased pressure on fish (populations) stocks in the Black Sea. Despite these challenges, the economic importance of Black Sea fisheries remains high, contributing to employment both directly and in supporting sectors in communities around the Black Sea coast.

Recently, new “ecosystem-based fisheries management” approaches have been advocated, but these must also address issues influencing fisheries such as land based pollution, habitat deterioration, nutrient loading and eutrophication, as well as the impact of industrial fishing techniques. In addition, consideration related to biodiversity shifts, and climate change will have impacts on the health of fisheries in the Black Sea.