CONTENTS & ABSTRACTS
In English. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Volume 52 No. 3 September 2003
Special issue on the changing state of the Gulf of Finland ecosystem
The Changing State of the Gulf of Finland Ecosystem – a trilateral Estonian–Finnish–Russian symposium held in Tallinn, 28–30 October 2002; 171–172
Jüri Elken and Harry Liiv
Benthic release of phosphorus and its relation to environmental conditions in the estuarial Gulf of Finland, Baltic Sea, in the early 2000s; 173–192
Heikki Pitkänen, Jouni Lehtoranta, Heikki Peltonen, Ari Laine, Jonne Kotta, Ilmar Kotta, Pavel Moskalenko, Anita Mäkinen, Pentti Kangas, Matti Perttilä, and Mikko Kiirikki
Abstract. After the mid-1990s the phosphorus concentrations and budget of the Gulf of Finland have been strongly affected by the enhanced benthic P input caused by reduced conditions at the sediment–water interface. Especially in late summers and autumns of 1996 and 2001 the total areas of reduced bottom sediments were large enough to affect the P concentrations of the whole gulf. The total benthic release of phosphate-P, on an annual level, can be several times higher than the bioavailable P load from the catchment of the gulf. The area of reduced surface sediments varies considerably both spatially and from year to year, especially in the relatively shallow eastern gulf. The intensity of the internal P loading is greatly controlled by vertical stratification, bottom topography, organic matter content of the sediment surface layer, and the abundance of benthic fauna. Evidently the sediment efflux can strongly affect the annual P balance and dynamics of the Gulf of Finland and counteract the decreases in the external P loading. This is verified both by inter-annual concentration changes and experimental results. The only way to reduce the benthic release of nutrients is to decrease primary production and the succeeding sedimentation of organic matter via further cutting external nutrient inputs both directly to the Gulf of Finland and to the Baltic Proper, which is an important source of nutrients for the gulf.
Key words: sediment efflux, phosphorus, nitrogen, benthic fauna, Baltic Sea.
Late summer vertical nutrient fluxes estimated from direct turbulence measurements: a Gulf of Finland case study; 193–204
Madis-Jaak Lilover, Jaan Laanemets, Tiit Kullas, Adolf Stips, and Kaisa Kononen
Abstract. Profiles of nutrient concentrations, current velocity, density, and microstructure were obtained at the entrance to the Gulf of Finland in July 1998. The averaged vertical eddy diffusivity, Kρ, had high values (2–8 ´ 10–3 m2 s–1) for three microstructure measurement series in different wind forcing regimes in the upper mixed layer (UML) and remained scattered between 10–6 and 10–4 m2 s–1 below the seasonal pycnocline. The amount of nutrients transported from below the pycnocline into the UML is calculated by a simplified diffusion equation using profiles of Kρ and phosphate and nitrate concentrations. The estimated nutrient input carried a clear excess of phosphate due to a large spacing between the phosphocline and the nitracline.
Key words: eddy diffusivity, turbulent fluxes, cyanobacterial bloom, Gulf of Finland.
Does excessive phosphorus necessarily cause increasing biomass of diazotrophic cyanobacteria?; 205–217
Andres Jaanus and Katja Pellikka
Abstract. The influence of increasing phoshporus (PO4-P) on the biomass and composition of diazotrophic (N2-fixing) cyanobacteria was evaluated on the ground of 6-year (1997–2002) intensive monitoring data, collected from the ship route between Tallinn and Helsinki (central Gulf of Finland). Phytoplankton biomass estimations were performed weekly from 15 June to 31 July to obtain the magnitude of cyanobacterial dominance, and the results were related to inorganic nutrient residual concentrations left from spring bloom. We could not find any strong relationships between cyanobacterial biomass and pre-bloom PO4-P concentrations or the N : P ratio. In 1997 and 2002, the years of exceptional summer blooms, the mass development of Aphanizomenon flos-aquae was likely a response to short-time nutrient pulses accompanied with upwelling and/or other hydrodynamical forcing. Nodularia spumigena formed only local short-time blooms in 1999 and 2001, when the phosphorus concentration was at its lowest (< 0.1 µM). It is the favourable nutrient conditions preceding the most intensive development of cyanobacterial bloom that determine the magnitude of biomass growth rather than the situation after the spring bloom decline.
Key words: Gulf of Finland, nutrients, cyanobacterial blooms.
Effects of eutrophication and invasion of Dreissena polymorpha in the coastal zone of the eastern Gulf of Finland; 218–235
Sergey M. Golubkov, Saara Bäck, Vera N. Nikulina, Marina I. Orlova, Lydia E. Anokhina, and Ludmila P. Umnova
Abstract. Ecosystem studies in the littoral zone of the Neva estuary have shown that eutrophication is a serious environmental problem for the coastal zone of the eastern part of the Gulf of Finland. It brings about an intensive development of filamentous algae Cladophora glomerata and periodical blue-green blooms. Wave action detaches Cladophora mats from substrates and causes an intensive secondary pollution of the beaches in the St. Petersburg Resort District. The zoobenthos community is dominated by caddis fly larvae in the shallow littoral. The alien species Dreissena polymorpha in deeper littoral is facilitating filamentous algae growth, clearing the water and recycling nutrients. An important recovery measure in the ecosystem management in the coastal zone is removal of hard substrates from shallow waters to curb the development of filamentous algae. Another important measure is nutrients reduction and control of the P : N ratio in the coastal zone of the Gulf of Finland.
Key words: Gulf of Finland, estuary, littoral, eutrophication, filamentous algae, Dreissena.
Benthic communities of four selected habitat types in the sea area of Lahemaa National Park, southern Gulf of Finland; 236–253
Jonne Kotta, Georg Martin, and Kaire Torn
Abstract. Benthic communities of Lahemaa National Park, Estonia, were mapped in August 2001 in connection with the establishment of Natura 2000 marine areas. Underwater mapping was performed using SCUBA diving. Four bays with a total surface area of 220 km2 were investigated. The spatial distribution of four habitat types of EU habitat Directive Annex I was estimated. The prevailing habitat type was “sandbanks covered with sea water”, which made up 26% of the study area. “Mudflats and sandflats not covered by seawater at low tide” and “reefs” were found in 3% and 2% of the cases, respectively. “Higher plant beds” accounted for less than 1% of the study area. A total of 5 species of Rhodophyta, 7 species of Phaeophyta, 2 species of Chlorophyta, 4 species of Charophyta, 7 species of phanerogams, and 8 species of benthic invertebrates were found in the study area. The differences in geomorphology described the major variability of the benthic communities. Based on the results the studied area is considered as a suitable Natura 2000 site.
Key words: habitat types, macrophytobenthos, macrozoobenthos, sediment.
Alien species introductions in the eastern Gulf of Finland: current state and possible management options; 254–267
Vadim E. Panov, Dmitry E. Bychenkov, Nadya A. Berezina, and
Alexey A. Maximov
Abstract. Recent studies showed that the eastern Gulf of Finland should be considered as a “hot spot” in the Baltic Sea area, taking into account the high rate of alien species introductions, the negative environmental impacts of established alien species, and rapidly increasing export-oriented shipping. At minimum, 14 new species have established in the eastern Gulf of Finland during the last two decades, including several invasive species. Alien species are playing an important role in the structural and functional organization of communities, specifically in the littoral zone, but this role has not been fully evaluated yet. Rapid development of new ports in the eastern Gulf of Finland will result in manifold increase in the volumes of discharged ballast waters, as well as in associated risk of new invasions of harmful aquatic species in the near future. Development of effective management options to control established nuisance species and to prevent or minimize the risk of new invasions is urgently needed.
Key words: Gulf of Finland, biological invasions, alien species, environmental effects, ballast water management.
How are the zebra mussels doing in the Gulf of Finland?; 268–283
Alexander E. Antsulevich, Pentti Välipakka, and Juhani Vaittinen
Abstract. The zebra mussel (Dreissena polymorpha) was first found in the Gulf of Finland only in 1990. Its distribution, abundance, ecology, and growth rate were studied in this area using SCUBA diving. The growth rate of juveniles and adults was studied by direct observations in the nature on artificial substrates and by reconstructing the linear growth from annual rings. Growth rate analysis was performed for five local populations dispersed widely in both the Finnish and Russian parts of the Gulf of Finland. It was found that the dispersal of zebra mussels to the west of the gulf is limited by the average salinity level of 5 PSU. During the last decade, the abundance of the mussels increased from one to two orders of magnitude. The growth rate of the zebra mussels in the Gulf of Finland is probably the lowest worldwide.
Key words: zebra mussel, Dreissena polymorpha, Gulf of Finland, growth rate, ecology.
Establishment of new gammarid species in the eastern Gulf of Finland (Baltic Sea) and their effects on littoral communities; 284–304
Nadya A. Berezina and Vadim E. Panov
Abstract. During the last ten years two new species of gammarids, Gmelinoides fasciatus (Stebb.) and Pontogammarus robustoides (Sars), invaded the Gulf of Finland. We studied the distribution and abundance of these species and their effects on littoral communities in the Neva estuary in 1998–2002. The study was performed in three types of habitats: Phragmites australis beds, exposed stone littoral, and Cladophora glomerata mats on stones. Feeding rates of the gammarids consuming filamentous algae and benthic invertebrates were estimated experimentally. Intensive consumption of plant food (Cladophora, roots and debris of Phragmites) by gammarids resulted in the production of faeces that increases organic matter availability for benthic detritivores. At the same time, gammarid predation resulted in a decrease of benthic invertebrates. The magnitude of the effects depended on the density of the established species and the type of habitat. In addition, an experimental study of interactions between G. fasciatus and P. robustoides revealed the existence of intraguild predation, which was the strongest in the case of P. robustoides.
Key words: bioinvasions, gammarids, Gmelinoides fasciatus, Pontogammarus robustoides, salinity tolerance, feeding, predation.
Concentrations of mercury and cadmium in some coastal fishes from the Finnish and Estonian parts of the Gulf of Finland; 305–318
Abstract. Concentrations of mercury and cadmium were analysed from Clupea harengus membras L., Sprattus sprattus sprattus L., Osmerus eperlanus L., Zoarces viviparus L., Gasterosteus aculeatus L., Myoxocephalus quadricornis L., M. scorpius L., Cyclopterus lumpus L., Perca fluviatilis L., Platichthys flesus L., and Psetta maxima L. sampled from coastal waters of the Finnish and Estonian parts of the Gulf of Finland: the Tvärminne Archipelago at Hanko-Hangö and the Helsinki region in Finland, and from the bays of Muuga, Käsmu, and Kunda in Estonia. The concentrations of Hg in muscle tissue, liver, and gonads were the highest in predatory species, e.g. M. scorpius, P. fluviatilis, and P. maxima regardless of the sampling area, and for most species, except C. harengus membras and C. lumpus, the concentrations were higher in muscle tissue than in liver. A statistically significant negative correlation between the condition factor (K) and the concentration of Hg in muscle tissue was found for O. eperlanus and P. flesus from Tvärminne. The highest concentrations of Cd were recorded from the liver of P. flesus, C. harengus membras, and P. fluviatilis from Tvärminne, and Z. viviparus from Muuga and Kunda. The results show a weak, although not statistically significant, decrease of Hg in muscle tissue, but a pronounced decrease of Cd in liver by the present time compared to the 1970s–80s. Except Hg in the muscle tissue of P. fluviatilis from the Helsinki area and in two individuals of M. scorpius from Tvärminne, the concentrations of both metals studied did not exceed either the Finnish (Hg = 0.5 mg kg–1, Cd = 0.1 mg kg–1 f.wt) or the Estonian (Hg = 0.5, Cd 0.2 mg kg–1 f.wt) maximum permissible levels for fish for human consumption.
Key words: mercury, cadmium, coastal fishes, Gulf of Finland, Baltic Sea.
A specific impact of waves of fast ferries on sediment transport processes in Tallinn Bay; 319–331
Tarmo Soomere and Jüri Kask
Abstract. Tallinn Bay is a semi-enclosed basin in the Gulf of Finland with a mild wave regime and an exceptionally heavy density of high speed ship traffic. Several implications resulting from the difference between the periods of wind waves (typically 3–4 s, maximum 7–8 s in extreme storms) and waves excited by fast ferries (10–15 s) are described. It is shown that ship-generated waves may play a decisive role in certain coastal processes. They cause unusually high near-bottom velocities at depths of 5–25 m. The influence of ship waves may trigger an additional sediment transport mechanism and cause considerable changes in the existing balance of sediment transport processes.
Key words: fast ferry wakes, ship-generated waves, sediment transport, Gulf of Finland, coastal processes.
The modelling of ecosystem processes in the Gulf of Finland; 332–345
Rein Tamsalu, Vladimir Zalesny, Peeter Ennet, and Harri Kuosa
Abstract. The aim of this work was to introduce the last version of the hydrodynamic–ecosystem model FinEst and to supplement this model to enable its easy application for local areas. Complications in the case of local areas appear in the treatment of initial and open boundary conditions. This paper demonstrates how to handle the open boundaries and the initial data using a multi-step scheme of calculations in the Baltic Sea. First the model was applied for the entire Baltic Sea. Then the results of these calculations were used for the Gulf of Finland (GOF). Finally, calculations for some local areas in the GOF were made using the initial and open boundary conditions from the results of the GOF calculations.
Key words: ecosystem, modelling, plankton.
A simulation of the Gulf of Finland ecosystem with a 3D model; 346–359
Ivan A. Neelov, Tatyana R. Eremina, Alexey V. Isaev, Vladimir A. Ryabchenko, Oleg P. Savchuk, and Roman E. Vankevich
Abstract. Comparison of simulations with a 3D eutrophication model with observation data for the Gulf of Finland showed that the model reproduced satisfactorily typical features of seasonal variability in the Gulf of Finland system, especially in the surface layers. However, as the model is driven by real atmospheric forcing for 1995–2000 and by climatically average river runoff and nutrient loads, it was unable to simulate the exact succession of events occurring in the deep layers of the gulf during this period. More time-specific data are needed both for prescription of boundary conditions and as validation criteria in order to further calibrate the model and test its performance.
Key words: eutrophication, 3D modelling, hydrodynamics, biogeochemical cycles, validation, Baltic Sea, Gulf of Finland.
Instructions to authors; 360–362