Danube Delta

Before reaching Black Sea, the Danube river forms a delta covering a surface of 5,165 km² shared between Romania (86%) and Ukraine (14%). The Danube Delta is the second largest in Europe, after that of the Volga River. The geomorphology of the area formed by the dynamics of the river arms, low altitudes and the presence of the sea, creates a complex landscape made by freshwater ecosystems (canals, shallow lakes, and wetlands), flood plains, alluvial forests, reed-beds, lagoons and coastal area (Fig. 1).

Due to its diversity, both biological and cultural, the area has a triple international conservation designation: UNESCO World Heritage Sites, Biosphere Reserve since 1990 and Ramsar site due to its importance for migratory birds. At EU level the Danube Delta is recognized as part of Natura 2000 network for the great diversity of birds listed on the Bird directive, as well as for the habitats and species listed on the annexes of Habitat directive. The following Natura 2000 sites are overlapping the area: ROSPA0031 Danube Delta and Razelm – Sinoie Lagoon System, ROSPA0076 Black Sea, ROSCI0065 Danube Delta, and ROSCI0066 Danube Delta – marine area. There are also 18 strictly protected areas that are covering 509 km² (Fig. 2).

The natural habitats formed here offer very good living conditions for a large number of plants and animals. Among these, reed forms one of the largest compact areas in the world covering 2400 km². Also, Letea and Caraorman forests represent the northern limit for two rare species of oak that are more frequently found in the south of the Italian and Balkan peninsulas.

Together with the great number of aquatic and terrestrial plants, there are also many important colonies of pelicans and cormorants, which are characteristic of the Danube Delta, as well as a variety of other water birds which are residents or in passage/visit in the delta for breeding or wintering. About half the world’s white pelicans and over 60 percent of the world’s pygmy cormorants breed within the Danube Delta. Worth to mention that nearly all of the world’s red-breasted geese are wintering here.

The large number of fish species is also notable, with both high economic and ecological value. Among them, the most famous are sturgeons that are crossing the Danube Delta in their way to spawning places on the river.

Fauna comprises terrestrial and aquatic species: 3272 species of invertebrates (2219 of which insects), 84 species of fish, 10 amphibian species, 11 species of reptiles, 315 birds species and 41 species of mammals. Flora from the Danube Delta it is formed by 955 species and 64 subspecies which means one third of the total known number of species from the whole Romanian flora. Also, 34 habitat types listed on the Habitat directive annex can be found here, seven of which are EU priority ones (Table 1). These habitats are listed in the standard data forms of the three sites of community importance ROSCI0065 Danube Delta, ROSCI0066 Danube Delta – marine area, and ROSCI0237 – Methanogen submarine structures St. George (all sites were designated in 2007).

Table 1. Habitat types within the Natura 2000 sites of community importance in the Danube Delta

Except for seven bird species, the rest are covered by international protection conventions, despite the fact that some are not endangered in the Danube Delta. Among rare bird species there are the pelicans (Pelecanus onocrolaturs and P. crispus), the cormorants (Phalacrocorax carbo sinensis and P. pygmeus), the egrets (Egretta alba and E. garzetta), the spoon bill, the big owl, the white tail eagle etc.

Endangered mammals that can be found here are: the otter (Lutra lutra), the European mink (Mustela lutreola), the ermine (Mustela erminea) and species came through dispersal - the enot dog (Nycterentes procyonoides) and the jackal (Canis aureus).

The ichtyofauna, the second in richness after reed, comprises species of fish specific to Danube Delta spreading channels (starlet - Acipenser ruthenus, bleak - Alburnus alburnus, rapacious carp - Aspius aspius, Elymus pycnattum deltaicus etc.), at which are added a series of anadromous species (beluga - Huso huso , sturgeon - Acipenser gueldenstaedtii, sevruga - A. stellatus, Danube mackerel etc.) and of marsh (carp - Cyprinus carpio, pike - Esox lucius, crucian - Carassius auratus gibelio, tench - Tinca tinca etc.). 26 of these species are protected by Berna Convention.

Ecosystem services provided by the Danube Delta are quite divers due to the highly heterogeneity and dynamics of the ecological systems in the area.

Ecosystem integrity/support services: are by far the most important services for which the area was gaining its protection status. These services are measured through highly biodiversity of the area, diversity of ecosystem types etc.

Provisioning services: consists mainly of fish captures (fresh- and sea- water), water (for drinking), reed harvesting as fodder, row materials (reed, wood, sand), honey, hunting (as wild food), forestry (especially willow and poplar), agriculture (mainly eco and bio certified production) etc..

Regulation and maintenance services: are the most important ones and is worth to mention few of them as following mechanical filtration done by plants, filtration done by mussels, biogeochemical cycles occurring in aquatic ecosystems, dilution in lakes, rivers, sea and sediments, transport and storage of sediment by Danube river and delta's lakes and wetlands, pollination by insects; seed dispersal by insects, birds and other animals, important reproduction area for fish and bird populations, gas emissions as result of decomposition processes, carbon sequestration etc.

Cultural services: leisure and ecotourism, spiritual value (different religious beliefs), human ethno-cultural diversity, bird watching, boating, sport fishing/hunting, research and monitoring activities.

Restoration activities inside Danube Delta are aimed at re-flooding areas that were drained for agricultural purposes and closing of some artificial canals to restore the natural water circulation (Driga 2008). Also, activities regarding potential for restoration at catchment level were done both from scientific (Hein 2016) and political viewpoint.

Ecological reconstruction in the Danube Delta started in 1994 with two polders Babina (2220 Ha) and Cernovca (1580 Ha) that were hydrologically reconnected with the Danube river. Currently two other projects aimed at ecological restoration are in advanced stage of implementation: one in Zaghen polder (in the south of Tulcea city) and another in Carasuhat polder in front of Mahmudia city on the left side of St George arm.

Modeling activities in the Danube Delta are mainly focused on hydrology and sediment transportation (Bajo et al. 2014; Giosan et al. 2013; Popescu et al. 2015; Stanica, Ungureanu, and Gheorghe 2007), reconstructing historical geomorphological conditions (Romanescu 2013) or different events such as algal blooms (Cioaca et al. 2009). For these activities there were used processed based modes such as one-dimensional model DELFT Sobek (Stanica et al. 2007), the more recent Delft3D (Popescu et al. 2015) and Shallow water HYdrodynamic Finite Element Model (SHYFEM) (Bajo et al. 2014).

Optical sensors used for remote sensing in the Danube Delta are: aerial photography (starting from 1950), Aster, Landsat (TM, ETM+), IRS LISS III, Spot 4, MODIS, for land cover mapping, sediment transport, assessing vegetation type etc. (Constantin, Doxaran, and Constantinescu 2016; Güttler, Niculescu, and Gohin 2013), also Lidar aimed at Digital Surface Models (Marian et al. 2015).
Satellite Aperture Radar products were also used to determine the variations of water levels (Poncos et al. 2013).

Due to its high biodiversity and unique landscapes, many institutions (University of Bucharest, Danube Delta National Institute for Research and Development, Romanian Academy – Institute of Biology, NIRD GeoEcoMar, Romanian Waters etc.) as well as NGO’s (ex. Ornithological Romanian Society, Milvus group, WWF Romania etc.) carried out research or monitoring programs in the Danube Delta from a long time period with an increasing frequency after political changes occurred at the beginning of 90s.

Unfortunately, many research or monitoring data were lost due to poor data management. Recently, Danube Delta National Institute for Research and Development made its first attempt to publish its metadata (Hanganu et al. 2015) available at http://data.freshwaterbiodiversity.eu/fmj/. Also, because the Danube Delta is part of European Long-Term Socio-Ecological Research Network, summary of data products are available on the Repository for Research Sites and Datasets (https://data.lter-europe.net/deims/).

The Danube Delta Biosphere reserve has the great advantage of having its own administration (www.ddbra.ro) lead by a governor. The role of this administration is to implement the management plan, keeping in contacts with stakeholders, assure a sustainable development of the area and taking care of public awareness campaigns.

Our expectation from ECOPOTENTIAL project is the development of an integrated approach aimed at a better assessment of the ecosystem integrity/support services as they are the foundation for the other ecosystem services. Such a common approach would be useful for designation of new protected areas.

Bajo, Marco, Christian Ferrarin, Irina Dinu, Georg Umgiesser, and Adrian Stanica. 2014. “The Water Circulation near the Danube Delta and the Romanian Coast Modelled with Finite Elements.” Continental Shelf Research 78:62–74. Retrieved (http://dx.doi.org/10.1016/j.csr.2014.02.006).

Cioaca, E., F. E. Linnebank, B. Bredeweg, and P. Salles. 2009. “A Qualitative Reasoning Model of Algal Bloom in the Danube Delta Biosphere Reserve (DDBR).” Ecological Informatics 4(5-6):282–98. Retrieved (http://dx.doi.org/10.1016/j.ecoinf.2009.09.010).

Bajo, Marco, Christian Ferrarin, Irina Dinu, Georg Umgiesser, and Adrian Stanica. 2014. “The Water Circulation near the Danube Delta and the Romanian Coast Modelled with Finite Elements.” Continental Shelf Research 78:62–74. Retrieved (http://dx.doi.org/10.1016/j.csr.2014.02.006).

Cioaca, E., F. E. Linnebank, B. Bredeweg, and P. Salles. 2009. “A Qualitative Reasoning Model of Algal Bloom in the Danube Delta Biosphere Reserve (DDBR).” Ecological Informatics 4(5-6):282–98. Retrieved (http://dx.doi.org/10.1016/j.ecoinf.2009.09.010).

Constantin, Sorin, David Doxaran, and Ștefan Constantinescu. 2016. “Estimation of Water Turbidity and Analysis of Its Spatio-Temporal Variability in the Danube River Plume (Black Sea) Using MODIS Satellite Data.” Continental Shelf Research 112:14–30. Retrieved (http://www.sciencedirect.com/science/article/pii/S0278434315301047).

Driga, Basarab Victor. 2008. “The Hidrological Relationship Between Danube Arms and Lake Complexis in the Danube Delta.” Lakes, reservoirs and ponds 1-2(December):61–71.

Giosan, Liviu, Stefan Constantinescu, Florin Filip, and Bing Deng. 2013. “Maintenance of Large Deltas through Channelization: Nature vs. Humans in the Danube Delta.” Anthropocene 1:35–45. Retrieved (http://dx.doi.org/10.1016/j.ancene.2013.09.001).

Güttler, Fabio N., Simona Niculescu, and Francis Gohin. 2013. “Remote Sensing of Environment Turbidity Retrieval and Monitoring of Danube Delta Waters Using Multi-Sensor Optical Remote Sensing Data : An Integrated View from the Delta Plain Lakes to the Western – Northwestern Black Sea Coastal Zone.” Remote Sensing of Environment 132:86–101. Retrieved (http://dx.doi.org/10.1016/j.rse.2013.01.009).

Hanganu, Jenica et al. 2015. “Introduction of the Danube Delta Database.” Freshwater Metadata Journal (November):1–11. Retrieved (http://data.freshwaterbiodiversity.eu/metadb/showfmjarticle.php?dbcode=MARS_12).

Marian, Mierla, Gheorghe Romanescu, Iulian Nichersu, and Ion Grigoras. 2015. “Hydrological Risk Map for the Danube Delta-a Case Study of Floods within the Fluvial Delta.” IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 8(1):98–104.

Poncos, Valentin, Delia Teleaga, Constantin Bondar, and Gheorghe Oaie. 2013. “A New Insight on the Water Level Dynamics of the Danube Delta Using a High Spatial Density of SAR Measurements.” Journal of Hydrology 482:79–91.

Popescu, Ioana, Eugenia Cioaca, Quan Pan, Andreja Jonoski, and Jenica Hanganu. 2015. “Use of Hydrodynamic Models for the Management of the Danube Delta Wetlands: The Case Study of Sontea-Fortuna Ecosystem.” Environmental Science and Policy 46:48–56. Retrieved (http://dx.doi.org/10.1016/j.envsci.2014.01.012).

Romanescu, Gheorghe. 2013. “Geoarchaeology of the Ancient and Medieval Danube Delta: Modeling Environmental and Historical Changes. A Review.” Quaternary International 293:231–44. Retrieved (http://dx.doi.org/10.1016/j.quaint.2012.07.008).

Stanica, A., S. Ungureanu, and V. Gheorghe. 2007. “Coastal Changes at the Sulina Mouth of the Danube River as a Result of Human Activities.” Marine Pollution Bulletin 55(10-12):555–63.

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