ICES CM 2007/C:15 Dynamics of biodiversity in the eastern Gulf of Finland (Baltic Sea): the role of climatic and anthropogenic factors Sergey Golubkov Baltic Sea Regional Project (BSRP), Lead Laboratory on Biodiversity ABSTRACT: Assessment of biological diversity of the Neva Estuary (eastern Gulf of Finland), which is one of the largest Baltic estuaries affected by very high human activity, has been conducted applying BSRP SGEH indicators. They include macrophytobenthos, macrozoobenthos, alien species, ichthyofauna, marine aviafauna, mammals as well as implementation of biodiversity protection measures in the area. Poor biodiversity status was estimated for the upper freshwater Neva Bay, and moderate biodiversity status – for lower brackish part of the estuary. Alien species and eutrophication are the most important threats to biodiversity of the Neva Estuary. At present, alien species contribute about 8 per cent of species richness and 60 - 90 per cent of biomass of the bottom animal communities. Climatic mediated fluctuations in near bottom oxygen conditions are the main natural factor responsible for the dynamics of benthic communities in the open waters of the estuary. These fluctuations also lead to decline of aboriginal and prosperity of invasive species. Filamentous algae blooms and macroalgal floating mats affect biodiversity dynamics in shallow coastal zone. Decline of bottom natural communities mostly dominated by crustacean leads to impairment of food conditions for fish and contributes greatly to sharp reduction of their populations, which in turn may be partly responsible for population decline of ringed seals. Large-scale digging and dumping of bottom sediments connected with constructions of new lands, ports and oil terminals are the main factor affected fish and submerged macrophyte communities in the Neva Bay. Most of fish spawning grounds in the shallow Neva Bay were lost during the last decades. Construction of 22 km long flood protection dam in the lower part of the Neva Bay led to expansion of reeds and prosperity of waterfowl. New protected areas are supposed to be established in the reed zones and on the islands of the eastern Gulf of Finland. Long-term forecasts and measures for conservation and improving biological diversity should take into account the periodicity of climate changes and planned development of the region. Sergey Golubkov, Zoological Institute RAS, Universitetskaya emb. 1, 199034, St. Petersburg, Russia [tel: +7 812 328 0711, fax: +7 812 328 2941, e-mail: [email protected]]. Created with novaPDF Printer (www.novaPDF.com) 1. Introduction The eastern Gulf of Finland as well as the Gulf of Gdansk have been selected by the Baltic Sea Regional Project - BSRP (ICES, 2006; ICES, 2007) as a demonstration areas for the upcoming assessments of biological diversity in the Baltic Sea (HELCOM BSAP, 2006).The reasons for these selections are concerned with long-term research of different biodiversity patterns in these regions and importance of their goods and services which have been seriously affected by the diverse anthropogenic impacts. These impacts resulted mainly from large Baltic rivers and large megapolis: River Neva and St. Petersburg City in case of the eastern Gulf of Finland and River Vistula and Tri- city (Gdansk-Sopot-Gdynia) in case of the Gulf of Gdansk. The assessment of biological diversity of the eastern Gulf of Finland is based on historical and recent data published in scientific literature since the beginning of the last centaury and on a limited number of biodiversity indicators, proposed by the ICES/BSRP Study Group on Baltic Ecosystem Health (SGEH) as priority indicators (ICES, 2006; ICES, 2007). They include macrophytobenthos, macrozoobenthos, alien species, ichthyofauna, marine aviafauna, mammals as well as implementation of biodiversity protection measures in the area. The evaluation of biodiversity status has been done in five quality grades (high – score 5, good – score 4, moderate – score 3, poor – score 2 and bad – score 1, in accordance with recommendations of EU WFD (2000). Environmental quality and biological diversity existing in the eastern Gulf of Finland in the first half of 20th centaury has been chosen as reference conditions. Percent of reference value 0 to 10 % attributed to bad (score 1), 11 to 25 % to poor (score 2), 26 to 50 % to moderate (score 3), 51 to 75 % to good (score 4), and over 75 % considered as very good (score 5). 2. Identification and description of hydro-geo-morphological units Russian part of the eastern Gulf of Finland practically coincides with the boundaries of the Neva Estuary: the largest Baltic estuary with surface area 3600 km2 (Fig. 1). The Neva Estuary receives water from the Neva River, a major contributor of fresh water to the Baltic Sea. The catchment area of the Neva River exceeds 280 000 km2, and its water discharge averages 2490 m3 s-1, (78.6 km3 yr-1). The Neva Estuary consists of two parts: the upper freshwater - Neva Bay and lower brackish-water part of the estuary. 2.1. Neva Bay: the upper freshwater part of the Neva Estuary Surface area of the Neva Bay (Fig. 1) is about 400 km2, salinity – 0.07-0.02 ‰, with the exception of short-term intrusions of brackish water from the lower part of the estuary during surge Created with novaPDF Printer (www.novaPDF.com) events when brackish waters from the lower part of the Neva Estuary come to the Neva Bay and mix there with fresh waters; the depth of the bay is 3.5 – 4 m. In the middle of 1980’s Neva Bay had been separated from lower part of the estuary by a storm-surge barrier (Dam), which is still under construction. The storm-surge barrier has several water leaking gates in its northern part and a broad ship gate in the southern part. 2.2. Lower brackish-water part of the Neva Estuary Salinity in the lower brackish part of the Neva Estuary (Fig. 1) ranges from 1.5-3 ‰ in the eastern part to 3-8 ‰ in the western part, depth from 12 – 14 m at the east to 40 – 50 m at the west. Several large bays are located in this part of the estuary, e.g., Luga Bay at the south and the Gulf of Vyborg at the north, with desalinated water in their inner parts. There are a lot of islands in different parts of the estuary. The largest ones are Kotlin Island, which is located at the boundary between Neva Bay and the lower brackish part of the Neva Estuary, Beryozovyye islands at the north, Moschniy Island and Gogland Island in the middle-western part the estuary. The Neva River is among the most important sources of pollution for the Gulf of Finland, because it provides about 60-80 per cent of the nutrient loads to the Gulf (Kondratyev et al. 1997, Pitkanen et al. 1997). Considerable part of pollution comes from St. Petersburg, which is one of the largest megapolises in the world with 4.5 millions of citizens and well developed industry. This leads to intensive eutrophication of the eastern Gulf of Finland (Golubkov et al., 2003a, 2003b). The coastal zone of the estuary has been intensively used for recreation (especially in the Resort District of St. Petersburg situated along the northern coast of the Gulf), sport and commercial fishery, and different industries, including a nuclear power station, and shipping (Fig. 1). Intensity of ship traffic has increased greatly during the last decade. There is almost fivefold increase in oil transportation in the eastern Gulf of Finland since 1987. Two large oil terminals were constructed in its north-western part and cargo port in the Luga Bay in early 2000’s (Fig. 1). High anthropogenic impact comes from intensive dredging activity connecting with creations of new building lots and passenger terminal in the Neva Delta. Considerable amounts of bottom sediments and sand drag from the bottom in the eastern part of the Neva Bay, part of them suspends in the water decreasing its transparency and pass to the western part of the bay and even in the lower brackish part of the Neva Estuary. Created with novaPDF Printer (www.novaPDF.com) Fig. 1. Neva Estuary at the eastern Gulf of Finland. 3. Descriptive assessment of the status of biological diversity 3.1. Macrophytobenthos Indicator: Phytobenthos: area distribution of submerged vascular plants and macroalgae beds First evaluations of composition and distribution of macrophytobenthos in the Neva Estuary were conducted at the end of 19th centaury and in the first half of 20th centaury (Gobi, 1874, 1877; Rozanova, Golubeva, 1921; Derjugin, 1947). The investigations were continued in the second half of XX centaury mostly in connection with eutrophication processes in the estuary (e.g., Belavskaya, 1987; Korelyjkova, 1997; Golubkov et al., 2003b). Macrophytobenthos is a good indicator of environmental changes and anthropogenic impacts in the Neva Estuary, especially in a case of eutrophication. At the beginning of 20th centaury submerged vascular plant and macroalgae meadows were widely distributed in coastal zone of Neva Bay. Reeds were mostly distributed along the southern and north-eastern coasts (Rozanova, Golubeva, 1921; Derjugin, 1947). In 1980’s most of submerged plant meadows (probably 80-90 %) were lost. More then 20 species of submerged macrophytes, e.g., Isoetes lacustris, I. echinospora, Zannichelia palustris, disappeared (Zhakova, 2007). Submerged plant Created with novaPDF Printer (www.novaPDF.com) meadows were replaced by reed beds, which widely expanded along the northern coast (Belavskaya, 1987). The reason for deterioration of submerged vegetation was intensive dredging activity in summer time connecting with creations of new building lots of St. Petersburg along the eastern cost of the Neva Bay and construction of the storm-surge protecting Dam in 1980’s. This activity decreased water transparency to 0.1 – 0.3 m in summer time.