Oceanologia No. 48 (S) / 06

Contents

Papers

Papers


What we know about the Baltic Sea: a summary of BSSC 2005
Oceanologia 2006, 48(S), 3-19

Jan Piechura1, Janusz Pempkowiak1, Teresa Radziejewska2, Szymon Uścinowicz3
1Institute of Oceanology, Polish Academy of Sciences,
Powstańcow Warszawy 55, PL-81-712 Sopot, Poland;
e-mail: piechura@iopan.gda.pl
2Department of Palaeoceanology, University of Szczecin,
Wąska 13, PL-71-415 Szczecin, Poland
3Polish Geological Institute,
Kościerska 5, PL-80-328 Gdańsk, Poland

Keywords: BSSC, Baltic Sea

Received 28 November 2005, revised 16 January 2006, accepted 26 June 2006.
Introduction
    The Baltic Sea, an internal sea of the European Community, is one of the largest brackish water bodies in the world. It is quite unique in many respects, particularly in its natural features and in the cultural, political and socio-economic patterns of the countries bordering it.
     After nearly 40 years, during which Baltic marine physicists, chemists, biologists and geologists had been holding separate scientific meetings, it was decided the time was ripe to arrange joint scientific conferences with the purpose of getting together to discuss general and specific aspects of the Baltic Sea, to exchange information, to integrate efforts, and to get to know and understand each other better. The Sopot 2005 Congress, preceded by the Baltic Sea Science Congresses in Rønne (1997), Warnemünde (1999), Stockholm (2001) and Helsinki (2003), was the fifth joint meeting of the Conference of Baltic Oceanographers (CBO), Baltic Marine Biologists (BMB) and Baltic Sea Geologists (BSG). Like all the previous congresses, the one held in Sopot bore witness to the idea that we all, members of CBO, BMB and BSG, should continue to work together even more closely.
     The meeting in Sopot instigated discussion on a broad spectrum of problems, from large-scale climate change-related processes to local, small-scale specific Baltic Sea features. Further subjects for deliberation included modelling as a research tool and as a way of providing services and forecasting certain phenomena, operational oceanography, and man's impact on the Baltic Sea environment and its resources.
     We are indebted to our Scientific Committee for their work during the past months to sort out and select interesting contributions to all the oral and poster sessions, and thus for making the Congress an attractive and quality event. We also thank the Polish Academy of Sciences and the City of Sopot for their financial support.
     We hope that the joint Congress and fruitful scientific discussions it sparked will promote new contacts and pave the way to even closer cooperation between scientists involved in Baltic research.
     Altogether, 274 abstracts were submitted for presentation. The International Scientific Committee selected 30 to be presented orally at the plenary sessions and 85 at thematic sessions; 151 contributions were presented as posters. There were 8 invited lectures, which dealt with broad questions such as climate change, the world's fisheries and ecosystem changes.
     The Congress also organised five workshops on the following topics:
full, complete article (PDF - compatibile with Acrobat 4.0), 157 KB

Unusual Baltic inflow activity in 2002-2003 and varying deep-water properties
Oceanologia 2006, 48(S), 21-35

Rainer Feistel, Günther Nausch, Eberhard Hagen
Leibniz Institute for Baltic Sea Research,
Seestrasse 15, D-18119 Rostock-Warnemünde, Germany;
e-mail: rainer.feistel@io-warnemuende.de

Keywords: inflow, deep water renewal, salinity trend, residence time, Baltic Sea

Received 26 October 2005, revised 28 March 2006, accepted 10 April 2006.

This paper was presented at the Baltic Sea Science Congress in Sopot, Poland, 2005(BSSC). It references several related BSSC presentations as "unpublished". Some of those may be published in the BSSC proceedings, yet unknown to these authors at the time this paper was completed.
Abstract
The unusual sequence of inflow events into the Baltic Sea that occurred in 2002 and 2003 includes the first ever important baroclinic inflow to be described (August 2002), the Major Baltic Inflow (January 2003), which gave rise to the highest oxygen levels in the Gotland Deep since the 1930s, and the baroclinic inflow (August 2003) that elevated the Gotland Basin deep water salinity to values last observed in 1977, and caused the surface salinity to rise again. From these trend changes, salt residence times were estimated at about 20 years in the deep waters and 30 years above the pycnocline. Ventilation of the remote Karlsö Deep took until 2005, two years after the inflow event responsible, at a time when the Bornholm and Eastern Gotland Basins were already returning to stagnation.
full, complete article (PDF - compatibile with Acrobat 4.0), 777 KB

Distinctive features of water exchange across the Słupsk Sill (a full-scale experiment)
Oceanologia 2006, 48(S), 37-54

Vadim Paka, Nikolay Golenko, Andrey Korzh
Atlantic Branch of the Shirshov Institute of Oceanology,
Prospect Mira 1, 236000 Kaliningrad, Russia;
e-mail: paka@ioran.baltnet.ru

Keywords: thermohaline structure, high-resolution transects, stagnation conditions, inflow waters, water exchange across the sill

Received 13 December 2005, revised 22 February 2006, accepted 1 March 2006.

Part of this study was supported by RFBR, grant No 04-05-65145.
Abstract
The flows of brackish waters in the upper layer and saline waters in the lower layer meet above the Słupsk Sill, which makes this one of the most significant features of the Baltic Sea, controlling as it does the ventilation of the deep basins in its central region. Earlier high-resolution measurements using towed scanning probes conducted here for more than ten years had revealed the complexity and variability of the water dynamics in this area.
     Mapping surveys repeated in quick succession are needed to study the water exchange in such an area. A survey of this kind was attempted in October 2003 during the 57th cruise of the r/v "Professor Shtokman". Three surveys were carried out in the areas of the Słupsk Sill, the eastern Bornholm Basin, and the western Słupsk Furrow by means of a scanning probe towed along closely-spaced transects. The water structure around the sill was different each time, despite the rather short time gaps between the surveys. As follows from the data analysis, during the first survey, the saline Bornholm waters flowed over the sill as an axially symmetrical jet and entrained the adjacent freshened cold waters of the intermediate layer. In ten days, this joint flow displaced to the southern flank of the sill and propagated in the Słupsk Furrow along its southern border, with the dense core of saline waters gradually moving over the bottom to the northern border. Concurrently, the contrary flow of the main volume of cold freshened waters, originating from northern areas and leaving the Baltic Sea, was pushed away from the southern wall of the furrow and blocked at a significant distance from the sill. In three days, the blocked waters forced their way through towards its northern flank. Just below these waters, waters of elevated salinity were found above the eastern slope of the sill at the depth of its ridge, while waters of a similar salinity occurred below the depth of the ridge above the western slope of the sill. There were no indications of intensive overflow in the central and southern areas of the sill. Accordingly, the return flow of Bornholm waters across the sill became possible.
full, complete article (PDF - compatibile with Acrobat 4.0), 1234 KB

Modelling of the circulation, water exchange and water age properties of the Gulf of Bothnia
Oceanologia 2006, 48(S), 55-74

Kai Myrberg*, Oleg Andrejev
Finnish Institute of Marine Research,
Dynamicum, Erik Palménin aukio 1,
PO Box 2, FIN-00561 Helsinki, Finland;
e-mail: Kai.Myrberg@fimr.fi
*corresponding author

Keywords: mean circulation, water age, water exchange

Received 28 November 2005, revised 30 March 2006, accepted 12 April 2006.
Abstract
To estimate the mean circulation, water exchange and water age in the Gulf of Bothnia a ten-year simulation using a three-dimensional numerical model was carried out. The results confirmed the early findings by Witting (1912) and Palmén (1930) that a mean cyclonic circulation takes place both in the Bothnian Sea and in the Bothnian Bay. However, the modelling results showed clearly that there exist meso-scale circulation features including coastal "jets", not reported in the Witting-Palmén results. The simulated mean currents were also higher than those found earlier, while the persistency of this circulation is typically between 20 and 60%, which is similar to the earlier results. There is a large difference between the various model-based water-exchange estimates: these are strictly dependent on the time-averaging used. Water age proved to reflect properties of the mean circulation system, and the highest water age (of around 7.4 years) was found in the central part of the Bothnian Bay. The water age was found to be rather high also in the entire Gulf of Bothnia, which provides evidence of the rather slow water exchange between the Gulf and the Baltic Sea. This leads to the conclusion that, from the physical point of view, the Gulf of Bothnia is vulnerable to eutrophication.
full, complete article (PDF - compatibile with Acrobat 4.0), 1744 KB

Periodic variability of currents induced by topographically trapped waves in the coastal zone in the Gulf of Finland
Oceanologia 2006, 48(S), 75-90

Lembit Talpsepp
Marine Systems Institute, Department of Marine Physics,
Tallinn University of Technology,
Akadeemia tee 21, EE-12618 Tallinn, Estonia;
e-mail: talpsepp@phys.sea.ee

Keywords: water exchange, topographic waves, trapped waves, currents, Gulf of Finland, Pakri Bay

Received 30 November 2005, revised 4 May 2006, accepted 9 May 2006.

This paper was partly supported by Estonian Science Foundation, grant No 5869.
Abstract
The aim of this paper is to examine the water exchange regime between the bays of northern Estonia (Pakri Bay, Ihasalu Bay and Muuga Bay) and the open part of the Gulf of Finland. To this end, the current measurements and CTD-castings performed at the border of the bays and the open part of the Gulf of Finland in summer 1994, 1995-96 and 1997 are analysed. All the current measurements displayed one feature in common: the existence of periodic variability with a current amplitude of between 5 and 25 cm s-1 and a variability period of 3-4 days (68 hours in Pakri Bay, 72 hours in Muuga Bay and 78 hours in Ihasalu Bay). The amplitudes of this variability differed during different time periods of the experiment and in different parts of the southern Gulf of Finland. The hypothesis was propounded that this variability is the result of bottom-trapped waves, as had been found in many other regions of the Baltic Sea (Aitsam & Talpsepp 1982, Talpsepp 1983). To interpret the results of the measurements, a model of bottom-trapped waves for this region was used. This was the short-wave version of Huthnance's (1978) numerical model of coastal-trapped waves, according to which the wave parameters for the experimental regions were calculated. Comparison of the model and the measurements implies that coastal-trapped waves do exist off the southern coast of the Gulf of Finland.
full, complete article (PDF - compatibile with Acrobat 4.0), 689 KB

Large halocline variations in the Northern Baltic Proper and associated meso- and basin-scale processes
Oceanologia 2006, 48(S), 91-117

Jüri Elken1, Pentti Mälkki2, Pekka Alenius2, Tapani Stipa2
1Marine Systems Institute, Tallinn University of Technology,
Akadeemia tee 21, EE-12618 Tallinn, Estonia;
e-mail: elken@phys.sea.ee
2Finnish Institute of Marine Research,
Dynamicum, Erik Palménin aukio 1,
PO Box 2, FIN-00561 Helsinki, Finland

Keywords: Baltic Sea, Gulf of Finland, halocline, currents, mesoscale eddies

Received 5 December 2005, revised 12 May 2006, accepted 15 May 2006.

This study has been partly supported by grants Nos 2194 and 5868 from the Estonian Science Foundation.
Abstract
The Northern Baltic Proper is a splitting area of the Baltic Sea saline water route towards the two terminal basins - the Gulf of Finland and the Western Gotland Basin. Large halocline variations (vertical isopycnal displacements of more than 20 m, intra-halocline current speeds above 20 cm s-1 appear during and following SW wind events, which rapidly increase the water storage in the Gulf of Finland and reverse the standard estuarine transport, causing an outflow in the lower layers. In the channel of variable topography, basin-scale barotropic flow pulses are converted into baroclinic mesoscale motions such as jet currents, sub-surface eddies and low-frequency waves. The associated dynamics is analysed by the results from a special mesoscale experiment, routine observations and numerical modelling.
full, complete article (PDF - compatibile with Acrobat 4.0), 1806 KB

Sea surface temperature development of the Baltic Sea in the period 1990-2004
Oceanologia 2006, 48(S), 119-131

Herbert Siegel1, Monika Gerth1, Gisela Tschersich2
1Leibniz Institute for Baltic Sea Research,
Seestrasse 15, D-18119 Rostock-Warnemünde, Germany;
e-mail: herbert.siegel@io-warnemuende.de
2German Federal Maritime and Hydrographic Agency,
Postfach 30 12 20, D-20305 Hamburg

Keywords: NOAA-SST; Baltic Sea; trends; regional, seasonal, inter-annual variations

Received 28 November 2005, revised 15 May 2006, accepted 23 May 2006.
Abstract
Sea Surface Temperature (SST) maps derived from NOAA weather satellites for the period 1990-2004 were used to investigate seasonal and inter-annual variations in the Baltic Sea. A comparison between monthly mean SST and in situ measurements at the MARNET station "Arkona Sea" showed good agreement with differences in July and August. Monthly means reflect strong seasonal and inter-annual variations. The yearly means show a slight positive trend with an increase of 0.8 K in 15 years. In particular, summer and autumn months contribute to this positive trend, with stronger trends in the northern than in the southern Baltic. The winters are characterised by a slightly negative trend. The winter minimum SST in the Arkona Sea correlates best with the WIBIX climate index derived for the Baltic region.
full, complete article (PDF - compatibile with Acrobat 4.0), 380 KB

Ventilation of the Baltic Sea deep water: A brief review of present knowledge from observations and models
Oceanologia 2006, 48(S), 133-164

H. E. Markus Meier1,*, Rainer Feistel2, Jan Piechura3, Lars Arneborg4, Hans Burchard2, Volker Fiekas5, Nikolay Golenko6, Natalia Kuzmina7, Volker Mohrholz2, Christian Nohr4, Vadim T. Paka6, Jüurgen Sellschopp5, Adolf Stips8, Victor Zhurbas7
1Swedish Meteorological and Hydrological Institute,
Rossby Centre, Folkborgsvägen 1, SE-60176 Norrköping, Sweden;
e-mail: markus.meier@smhi.se
* corresponding author
2Leibniz Institute for Baltic Sea Research,
Seestrasse 15, D-18119 Rostock-Warnemünde, Germany
3Institute of Oceanology, Polish Academy of Sciences,
Powstańców Warszawy 55, PL-81-712 Sopot, Poland
4Department of Oceanography, Göteborg University,
Box 460, SE-40530 Göteborg, Sweden
5Forschungsanstalt der Bundeswehr für Wasserschall und Geophysik,
Klausdorfer Weg 2-24, D-24148 Kiel, Germany
6Atlantic Branch of the Shirshov Institute of Oceanology,
Prospect Mira 1, 236000 Kaliningrad, Russia
7Shirshov Institute of Oceanology,
Nakhimovsky Prospect 36, 117851 Moscow, Russia
8CEC Joint Research Centre, Inland and Marine Waters Unit,
Via E. Fermi 1, I-21020 Ispra (VA), Italy

Keywords: Baltic Sea, salt water inflows, deep water, ventilation, entrainment, turbulent mixing

Received 16 December 2005, revised 27 April 2006, accepted 4 May 2006.
Abstract
The ventilation of the Baltic Sea deep water is driven by either gale-forced barotropic or baroclinic salt water inflows. During the past two decades, the frequency of large barotropic inflows (mainly in winter) has decreased and the frequency of medium-intensity baroclinic inflows (observed in summer) has increased. As a result of entrainment of ambient oxygen-rich water, summer inflows are also important for the deep water ventilation. Recent process studies of salt water plumes suggest that the entrainment rates are generally smaller than those predicted by earlier entrainment models. In addition to the entrance area, the Słupsk Sill and the Słupsk Furrow are important locations for the transformation of water masses. Passing the Słupsk Furrow, both gravity-driven dense bottom flows and sub-surface cyclonic eddies, which are eroded laterally by thermohaline intrusions, ventilate the deep water of the eastern Gotland Basin. A recent study of the energy transfer from barotropic to baroclinic wave motion using a two-dimensional shallow water model suggests that about 30% of the energy needed below the halocline for deep water mixing is explained by the breaking of internal waves. In the deep water decade-long stagnation periods with decreasing oxygen and increasing hydrogen sulphide concentrations might be caused by anomalously large freshwater inflows and anomalously high mean zonal wind speeds. In different studies the typical response time scale of average salinity was estimated to be between approximately 20 and 30 years. The review summarizes recent research results and ends with a list of open questions and recommendations.
full, complete article (PDF - compatibile with Acrobat 4.0), 1657 KB

Trends and extremes of wave fields in the north-eastern part of the Baltic Proper
Oceanologia 2006, 48(S), 165-184

Barry Broman1, Thomas Hammarklint2, Kalev Rannat3, Tarmo Soomere3,*, Ain Valdmann4
 1Swedish Meteorological and Hydrological Institute, Rossby Centre,
Folkborgsvägen 1, SE-60176 Norrköping, Sweden
2Swedish Meteorological and Hydrological Institute, Observation Unit,
Folkborgsvägen 1, SE-60176 Norrköping, Sweden
3Centre for Non-linear Studies, Institute of Cybernetics,
Tallinn University of Technology,
Akadeemia tee 21, EE-12618 Tallinn, Estonia;
e-mail: soomere@cs.ioc.ee
*corresponding author
4Municipal Engineering Services Department, City of Tallinn,
Mündi 2, EE-15197 Tallinn, Estonia

Keywords: wind waves, Baltic Sea, wave climate, wave measurements

Received 31 November 2005, revised 12 June 2006, accepted 16 June 2006.

This work was supported by the Estonian Science Foundation (grant No 5762). The study was partially carried out when one of the authors (TS) was visiting the Centre of Mathematics for Applications, University of Oslo, within the framework of the Marie Curie Transfer of Knowledge project CENS-CMA.
Abstract
The paper analyses one of the longest contemporary wave measurements in the northern Baltic Sea, performed at Almagrundet 1978-2003. This record contains the roughest instrumentally measured wave conditions (significant wave height = c. 7.8 m) in the northern Baltic Proper until December 2004. The data for the years 1979-95, the period for which the data are the most reliable, show a linear rising trend of 1.8% per annum in the average wave height. The seasonal variation in wave activity follows the variation in wind speed. The monthly mean significant wave height varies from 0.5 m in May-July to 1.3-1.4 m in December-January. No corrections have been made in the analysis to compensate for missing values, for their uneven distribution, or for ice cover.
full, complete article (PDF - compatibile with Acrobat 4.0), 4162 KB

Nonlinear ship wake waves as a model of rogue waves and a source of danger to the coastal environment: a review
Oceanologia 2006, 48(S), 185-202

Tarmo Soomere
Centre for Non-linear Studies, Institute of Cybernetics,
Tallinn University of Technology, Akadeemia tee 21, EE-12618 Tallinn, Estonia;
e-mail: soomere@cs.ioc.ee

Keywords: nonlinear ship waves, high-speed ships, shallow water waves, extreme waves, solitons, soliton interaction

Received 5 December 2005, revised 12 May 2006, accepted 15 May 2006.

This work was supported by the Estonian Science Foundation (grant No 5762). The study was partially carried out when the author was visiting the Institute of Coastal Research, GKSS Forschungszentrum, with the financial support of the Alexander von Humboldt Foundation.
Abstract
A substantial part of the energy of wake waves from high-speed ships sailing in shallow water is concentrated in nonlinear components which at times have a solitonic nature. Recent results of investigations into solitonic wave interactions within the framework of the Kadomtsev-Petviashvili equation and their implications for rogue wave theory are reviewed. A surface elevation four times as high as the counterparts occurs if the properties of the interacting waves are specifically balanced. The slope of the water surface may increase eightfold. The resulting structure may persist for a long time. Nonlinear wake components may exert a considerable influence on the marine ecosystem in coastal areas
full, complete article (PDF - compatibile with Acrobat 4.0), 325 KB

Variability in the optical properties of a crude oil - seawater emulsion
Oceanologia 2006, 48(S), 203-211

Tadeusz Król, Adam Stelmaszewski, Włodzimierz Freda
Gdynia Maritime University, Department of Physics,
Morska 81-87, PL-81-225 Gdynia, Poland;
e-mail: krol@am.gdynia.pl

Keywords: Baltic, petroleum, emulsion, light scattering

Received 30 November 2005, revised 7 February 2006, accepted 4 May 2006.
Abstract
The paper analyses the optical properties of a crude oil - seawater emulsion, which is a form of petroleum pollution of the sea. These properties depend on the spillage concentration, the optical characteristics of the seawater and oil in question, and on the size distribution of the oil droplets. They may be described by the attenuation specific cross-sections and absorption specific cross-sections. Specific cross-sections and other optical parameters for droplets of a Baltic crude oil - Baltic seawater emulsion were calculated using Mie's solution. These characteristics were computed for fresh and weathered petroleum.
full, complete article (PDF - compatibile with Acrobat 4.0), 477 KB

A simple tool for the early prediction of the cyanobacteria Nodularia spumigena bloom biomass in the Gulf of Finland
Oceanologia 2006, 48(S), 213-229

Madis-Jaak Lilover1,2,*, Jaan Laanemets1
1Marine Systems Institute, Tallinn University of Technology,
Akadeemia tee 21, EE-12618 Tallinn, Estonia
e-mail: madis.lilover@jrc.it
2European Commission - DG Joint Research Centre,
Institute for Environment and Sustainability, Global Environment Monitoring Unit,
Via E. Fermi 1 (TP 272), I-21020 Ispra (VA), Italy
*corresponding author

Keywords: harmful algal blooms, Nodularia spumigena, fuzzy logic model, Gulf of Finland

Received 12 December 2005, revised 12 May 2006, accepted 18 May 2006.

This study was partly supported by EC project HABES (contract No EVK2-CT-2000-00092).
Abstract
A fuzzy logic model for predicting the maximum biomass of the toxic cyanobacteria Nodularia spumigena bloom in the Gulf of Finland is suggested. The model bloom biomass depends on the phosphate conditions up to 15 June, including the excess phosphate left over after the spring bloom and on the phosphate inputs parameterised by wind mixing and upwelling from 1 May to 15 June. The surface layer temperature, set to vary from 14 to 23ºC, is regarded as a bloom regulating parameter. The model simulations showed that the predicted N. spumigena biomasses differ markedly from year to year and clearly depend on phosphate conditions up to 15 June.
full, complete article (PDF - compatibile with Acrobat 4.0), 229 KB

Tolerance of Paramysis lacustris and Limnomysis benedeni (Crustacea, Mysida) to sudden salinity changes: implications for ballast water treatment
Oceanologia 2006, 48(S), 231-242

Irina Ovčarenko1, Asta Audzijonytė2, Zita Rasuolė Gasiūnaitė1
1Coastal Research and Planning Institute, Klaipėda University,
H. Manto 84, LT-92294, Klaipėda, Lithuania;
e-mail: irinaovcarenko@yahoo.com
*corresponding author
2Finnish Museum of Natural History, University of Helsinki,
PO Box 26, FIN-0014, Finland

Keywords: experiment, Curonian Lagoon, invasive species, Ponto-Caspian, salinity tolerance

Received 30 November 2005, revised 6 April 2006, accepted 14 April 2006.

This study was supported by the EU FW6 IP 506675 ALARM (Assessing Large Scale Environmental Risks with Tested Methods) project and the Walter and Andrée de Nottbeck Foundation.
Abstract
In order to draw implications for ballast water management, we tested the tolerance of two Ponto-Caspian mysid species Paramysis lacustris and Limnomysis benedeni to sudden salinity changes. The naturally stenohaline P. lacustris was more susceptible to higher salinities; its mortality rate at 19 PSU was 60%, whereas exposure to 23 PSU was 100% lethal. The euryhaline L. benedeni survived in salinities of up to 19 PSU, but experienced 100% mortality at 34 PSU. The return of both mysid species to fresh water after the 24 h exposure to higher salinities did not prevent further mortality. Considering the rather high short-term salinity tolerance of both species, a salinity of at least 30 PSU should be used as an appropriate biocide.
full, complete article (PDF - compatibile with Acrobat 4.0), 184 KB

Distribution, population structure and ecosystem effects of the invader Cercopagis pengoi (Polyphemoidea, Cladocera) in the Gulf of Finland and the open Baltic Sea:
Oceanologia 2006, 48(S), 243-257

Larissa F. Litvinchuk, Irena V. Telesh
Zoological Institute, Russian Academy of Sciences,
Universitetskaya nab. 1, 199034 St. Petersburg, Russia;
e-mail: llitvinchuk@yahoo.com

Keywords: invasions, Baltic Sea, Gulf of Finland, Cercopagis pengoi, population structure, ecosystem impact

Received 30 December 2005, revised 8 May 2006, accepted 9 May 2006

This study was partly supported by the Russian Foundation for Basic Research (projects Nos 04-04-49207, 05-04-90588, and 05-04-49703), grant for Leading Scientific School on Production Hydrobiology from the Russian Ministry of Education and Science (NSH-1634.2003.4, NSH-5577.2006.4), and the Russian Academy of Sciences' programs "Biological Resources" and "Biodiversity".
Abstract
Spatial distribution, density, biomass, population structure, predation effects, and the influence of abiotic environmental characteristics (salinity, water temperature, transparency, and depth) on a population of the Ponto-Caspian invasive cladoceran Cercopagis pengoi (Ostroumov, 1891) were studied in the Gulf of Finland and the open Baltic Sea (August 1999 and 2004). In our study in 1999, this species was first recorded in plankton of open south-eastern Baltic waters. The age and sexual structure of the C. pengoi population were interrelated with population density. The strongest impact of C. pengoi predation on the pelagic community in the Gulf of Finland was registered at the stations where the percentage of C. pengoi in the total zooplankton biomass was the highest. The calculated impact values of C. pengoi exceeded those registered a decade ago, during the first years after Cercopagis had invaded the eastern Gulf of Finland.
full, complete article (PDF - compatibile with Acrobat 4.0), 2121 KB

A home away from home: a meiobenthic assemblage in a ship's ballast water tank sediment
Oceanologia 2006, 48(S), 259-265

Teresa Radziejewska1, Piotr Gruszka2, Joanna Rokicka-Praxmajer3
1Department of Palaeoceanology, University of Szczecin,
Wąska 13, PL-71-415 Szczecin, Poland;
e-mail: tera@univ.szczecin.pl
2Department of Marine Ecology and Environmental Protection, Agricultural University of Szczecin,
Kazimierza Królewicza 4, PL-71-550 Szczecin, Poland

Keywords: ballast tank sediment, dispersal, meiobenthos

Received 12 December 2005, revised 14 April 2006, accepted 4 May 2006.
Abstract
The world-wide research on ship-aided dispersal of marine organisms and invasions of non-indigenous species focuses primarily on the plankters, which show the greatest potential for invading new areas and establishing viable populations in them, either in the water column (holoplankton) or on the bottom (meroplanktonic larvae of benthic species settling on the sea floor). As meiobenthic animals usually lack a pelagic larval stage in their life cycle, no biological invasion study has, to our knowledge, ever specifically targeted marine transport as a means of meiofaunal dispersal.
     Here we present a set of data showing that the sediment deposited in a ship's ballast water tank does support a viable meiobenthic assemblage. We examined 0.015-dm3 aliquots of a 1 dm3 sample from a c. 1.5-cm thick layer of sediment residue in the ballast tank of MS Donnington, brought to the "Gryfia" Repair Shipyard in Szczecin (Poland). The samples were found to contain representatives of calcareous Foraminifera, hydrozoans, nematodes, turbellarians, harpacticoid copepods and their nauplii, and cladocerans, as well as meiobenthic-sized bivalves and gastropods. Nematodes proved to be the most constant and most numerous component of the assemblage. The sediment portions examined revealed the presence of 1-11 individuals representing 11 marine nematode genera. The viability of the meiobenthic assemblage was evidenced by the presence of ovigerous females of both nematodes and harpacticoids.
     Survival of the meiobenthos in shipborne ballast tank sediment residues may provide at least a partial explanation for the cosmopolitan distribution of meiobenthic taxa and may underlie the successful colonisation of new habitats by invasive meiofaunal species.
full, complete article (PDF - compatibile with Acrobat 4.0), 156 KB

Effects of physical disturbance, isolation and key macrozoobenthic species on community development, recolonisation and sedimentation processes
Oceanologia 2006, 48(S), 267-282

Kristjan Herkül1,2, Jonne Kotta1, Ilmar Kotta1, Helen Orav-Kotta1
1Estonian Marine Institute, University of Tartu,
Mäealuse 10a, EE-12618 Tallinn, Estonia;
e-mail: kristjan.herkyl@sea.ee
2Institute of Zoology and Hydrobiology,
University of Tartu, Vanemuise 46, EE-51014 Tartu, Estonia

Keywords: Baltic Sea, ecosystem functioning, field experiment, functional diversity, physical disturbance

Received 5 December 2005, revised 12 May 2006, accepted 15 May 2006

The study was carried out within the framework of the Estonian Target Financing Programme No 0182578s03, Estonian Science Foundation grants Nos 6015 and 6016.
Abstract
The relative effect of physical disturbance, isolation and key macrozoobenthic species on community development and sedimentation processes were studied in an in situ factorial field mesocosm experiment in the northern Baltic Sea. Differences in abundance and biomass structure of recolonising invertebrates were due to exposure and isolation. The initial invertebrate communities had a negligible effect on the final communities. However, the organic matter content of the sediment in isolated cages increased with the initial number of invertebrate species. The main conclusion of the study: physically driven fluxes override the effects of biological interactions in shallow water systems of the northern Baltic Sea.
full, complete article (PDF - compatibile with Acrobat 4.0), 194 KB

The impact of fast ferry traffic on underwater optics and sediment resuspension
Oceanologia 2006, 48(S), 283-301

Ants Erm, Tarmo Soomere
Marine Systems Institute, Institute of Cybernetics,
Tallinn University of Technology,
Akadeemia tee 21, EE-12618 Tallinn, Estonia;
e-mail: ants@phys.sea.ee; e-mail: soomere@cs.ioc.ee

Keywords: marine optics, fast ferry wakes, wave measurements

Received 5 December 2005, revised 12 May 2006, accepted 15 May 2006.

This work was supported by the Estonian Science Foundation (grants 5762 and 6159).
Abstract
Wake waves produced by fast ferries bring about significant changes in the optical parameters of sea water in the c. 1 m thick near-bottom layer of the coastal areas of Tallinn Bay. The greatest of these changes occur at relatively small depths, but the duration of the influence increases with increasing depth. Rough quantitative estimates suggest that the overall influence of fast ferry traffic in Tallinn Bay may result in an annual loss of the order of several hundred litres of fine sediments from each metre of the coastline.
full, complete article (PDF - compatibile with Acrobat 4.0), 653 KB