Oceanologia No. 41 (3) / 99

Special issue on the Pomeranian Bay

Contents

Preface

Papers

Preface


The papers in this volume make up part of the outcome of studies conducted within the framework of the project 'The impact of Odra river waters on the ecosystem of the Pomeranian Bay'. Some publications have been or will be placed in other journals.
The project was carried out in 1996-1998 and was co-funded by the Foundation for Polish-German Co-operation in Warsaw.
The following scientific institutions took part in the project: The Pomeranian Bay is an element of the River Odra (Oder) estuary. The oceanographic conditions in the estuary are, to a great extent, formed by seasonal variability in the outflow of riverine waters. The Odra is one of the largest rivers discharging its waters and pollutants into the Baltic Sea. The drainage area of the river covers part of the areas of three countries: Poland, Germany and the Czech Republic. Before the Odra waters enter the Pomeranian Bay they flow through the Szczecin Lagoon (Zalew Szczecinski, Oderhaff) and the Swina, Dziwna and Peene (Piana) rivers which together play a significant buffering role. Bereft of topographical barriers, the Pomeranian Bay is exposed to permanent, intensive water exchange between itself and the neighbouring Arkona and Bornholm Basins; the Bay is the scene of intensive mixing of riverine and seawaters.
The main aim of the project was to study the pathways of anthropogenic substances in the Pomeranian Bay and to determine their impact on the Bay's ecosystem.
The work packages in physics, chemistry and biology covered the following aspects of the ecosystem: As the Pomeranian Bay straddles the border between Poland and Germany, the two countries worked out a detailed joint programme to fulfil the expectations of both partners and provide good co-ordination of the fieldwork. The project was carried out in close co-operation with the Institute for Baltic Research in Warnemünde. The German Institute had conducted the complementary TRUMP research project ('Transport and Turnover in the Pomeranian Bay') in 1994-1996.
The main phase of that project had been preceded by Polish-German pilot studies in September/October 1993, the aim of which was to acquire knowledge providing a platform for the formulation of detailed research objectives in the main studies.
The main phase of the present studies was conducted in 1996 and 1997 on board r/v 'Baltica', 'Oceania' and the motorboat 'Stynka', each vessel having different objectives. This approach was reflected in the cruise schedules, the distribution of measuring stations and the measurement and sampling strategy. The task of the 'Stynka' included hydrological measurements and the sampling of water for the determination of chemical parameters in the Swina outlet from January 1996 to January 1998.

Jan Warzocha
Project co-ordinator

Aacknowledgements

We gratefully acknowledge the financial support provided by the Foundation for Polish-German Co-operation in Warsaw (grant 1567/94/LN). We would also like to thank all the scientists from the Institute for Baltic Research in Warnemünde involved for their assistance at every stage of this study. We would like to express our appreciation and gratitude to the Environmental Protection Inspectorate in Szczecin for collecting and providing the data on water outflow and material discharges measured at the river monitoring stations. Our thanks also go to all those who reviewed the manuscripts in this volume.

Papers


Transport of the Odra river waters and circulation patterns in the Pomeranian Bay
Oceanologia 1999, no 41 (3), pp. 279-308

Agnieszka Beszczyńska-Möller
Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, 81–712 Sopot, Poland; abesz@iopan.gda.pl

Keywords: Pomeranian Bay, River Odra, riverine water transport circulation, river plume

Manuscript received 30 March 1999, reviewed 20 April 1999, accepted 2 June 1999.
Abstract
During several cruises of r/v 'Oceania' in different seasons of 1993-1997 detailed investigations of the Pomeranian Bay were carried out with particular attention to the vicinity of the Odra river mouth. On the basis of CTD soundings as well as quasi-continuous profiling by means of a towed CTD probe, the thermohaline fields were analysed in order to determine the pattern of riverine water transport. The characteristic flow paths under different meteorological conditions were identified, Ekman transport of freshened waters being found to prevail along the coasts of the Pomeranian Bay. Physical phenomena such as the pulsating outflow of the river Odra and the formation of isolated plumes of freshened water were observed. The vertical and horizontal extents as well as the lifetime and speed of movement of the plume-like structures were estimated. A typical plume was a few km in diameter and there were steep horizontal and vertical salinity gradients at the boundaries. As the plume moved away from the mouth, it was transformed and finally vanished. There was strong wind mixing and entrainment into underlying, more saline water at some distance from the channel mouth. Hydrological fronts between riverine and ambient waters frequently formed. Numerous intrusions were found in the temperature and salinity profiles in the frontal zones. The freshwater fraction in the entire volume of the bay waters was estimated for different hydrological situations, the highest values being obtained for the period following the flood event of summer 1997. Under favourable wind conditions, dense, saline waters flowing in from the Arkona and Bornholm Deeps were present in the near-bottom layer at the edges of the bay. Anomalously, waters of higher salinity were found in the Pomeranian Bay in November 1997 as a result of a minor inflow from the Danish Straits.
full, complete article (PDF)

Seasonal changes in selected optical parameters in the Pomeranian Bay in 1996-1997
Oceanologia 1999, no 41 (3), pp. 309-334

Piotr Kowalczuk, Sławomir Sagan, Jerzy Olszewski, Mirosław Darecki, Ryszard Hapter
Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, 81-712 Sopot, Poland; piotr@iopan.gda.pl

Keywords: optical properties, seasonal changes, Pomeranian Bay

Manuscript received 12 April 1999, reviewed 24 May 1999, accepted 16 June 1999.
Abstract
The main task of the Joint Polish-German Pomeranian Bay Project was to achieve a better understanding of the impact of freshwater discharge on this environment. The freshwater from the River Odra enters the Pomeranian Bay through four outlets. The most important of these is the River Swina, as it carries the largest volume of water exchange between the bay and the Szczecin Lagoon. This freshwater carries a large load of optically active substances: dissolved organic materials, mineral and organic sediments, as well as nutrients, which boost phytoplankton growth. The effect of riverine discharge can be traced with the use of optical methods. The elevated level of optically active components can significantly reduce the light required for photosynthesis. The Institute of Oceanology carried out a survey of selected inherent and apparent optical properties in the Pomeranian Bay in three seasons in 1996 and 1997. The results are presented and discussed, as are the relations between the various optical parameters and salinity.
full, complete article (PDF)

Near-bottom fluxes and composition of suspended matter in the Pomeranian Bay
Oceanologia 1999, no 41 (3), pp. 335–353

Mario Jose Laima
Department of Earth Sciences, Aarhus University, Ny Munkegade, Building 520, 8000 Aarhus C, Denmark; geomario@aau.dk

Lars Chresten Lund-Hansen
Marine Ecology, Biological Institute, Aarhus University, Finlandsgade 14, 8200 Aarhus N, Denmark;

Ksenia Pazdro
Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, 81-712 Sopot, Poland;

Christian Christiansen
Institute of Geography, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark;

Kay-Christian Emeis
Baltic Sea Research Institute Warnemünde, Seestrasse 15, 18111 Warnemünde, Germany.

Keywords: suspended matter, sedimentation fluxes, organic matter, fatty acids, River Odra

Manuscript received 19 January 1999, reviewed 23 February 1999, accepted 26 March 1999.
Abstract
The quality and composition of suspended organic matter in near-bottom fluxes was determined at a mooring station (Odas Tonne) 20 km north-north-west of the Odra river mouth from June to December 1997. Salinity data and high concentrations of suspended matter near the bottom showed that the material entering the Pomeranian Bay from the Odra flood was recognisable for about three weeks. Vertical sediment fluxes, however, were low ~ 40 g m-2 d-1 compared to those measured later in the year ~ 60 g m-2 d-1. On the other hand, average molar CNP ratios in sediment trap material decreased from June to December 1997. These results may have been a combined effect of dilution and material transport in a layer close to the sediment surface. Fluff layers sampled at Odas Tonne in August 1997 contained a very high proportion of branched fatty acids of bacterial origin, indicating high rates of bacterial degradation. Long-chain fatty acids indicated an origin from higher terrestrial plants. The saturated fatty acid content was high in the surface sediment and the traps, increasing towards the top trap. The percentage composition of fatty acids indicated that the lowest trap was fed mainly by material from the underlying sediment. Low salinities, variability in molar ratios for major elements, higher than usual bacterial activities and detection of fatty acids characteristic of land plants during the June-August deployment show a relationship with the Odra flood of summer 1997.
full, complete article (PDF)

Photosynthetic light curves in the Pomeranian Bay
Oceanologia 1999, no 41 (3), pp. 355-371

Henryk Renk, Stanisław Ochocki, Henryk Chmielowski, Sławomira Gromisz, Jan Nakonieczny, Marianna Pastuszak, Mariusz Zalewski
Department of Oceanography, Sea Fisheries Institute, H.Kollataja 1, 81-332 Gdynia, Poland; sochocki@miryb.gdynia.pl

Keywords: photosynthetic rate, assimilation number, photosynthetic light curves, Pomeranian Bay

Manuscript received 18 January 1999, reviewed 8 March 1999, accepted 8 April 1999.
Abstract
Photosynthetic light curves at selected stations in the Pomeranian Bay were determined during four cruises undertaken in March and July 1996, and in May and October 1997. The mean assimilation numbers measured in particular seasons were as follows: spring - 2.46 mgC mgChl-1 h-1, summer - 3.99 mgC mgChl-1 h-1, autumn - 3.24 mgC mgChl-1 h-1 and winter - 2.17 mgC mgChl-1 h-1. A significant correlation was found between the assimilation number and water temperature over the entire period of study. In some seasons a dependence between the assimilation number and nutrient concentrations was also noted. Assimilation numbers in the areas adjacent to the Odra river months were higher than in the offshore zone.
full, complete article (PDF)

The impact of Odra river waters on the seasonal and spatial distribution of primary production and chlorophyll a concentrations in the Pomeranian Bay in 1996-1997
Oceanologia 1999, no 41 (3), pp. 373-388

Stanisław Ochocki, Henryk Chmielowski, Jan Nakonieczny, Mariusz Zalewski
Department of Oceanography, Sea Fisheries Institute H. Kollataja 1, 81-332 Gdynia, Poland; sochocki@miryb.gdynia.pl

Keywords: primary production, chlorophyll a, Pomeranian Bay

Manuscript received 10 May 1999, reviewed 7 June 1999, accepted 15 June 1999.
Abstract
Primary production and chlorophyll a concentrations were measured in March and May 1996, July and October 1997. The study was carried out in the coastal zone adjacent to the mouths of the Swina and Dziwna, which together drain over 80% of the waters carried by the river Odra, and in the open Pomeranian Bay.
Chlorophyll a concentrations in the entire Pomeranian Bay varied between 0.8 and 16.5 mg m-3. The minimal daily in situ primary production measured in March was 19.3 mgC m-2 d-1, the July maximum was 1238.6 mgC m-2 d-1. The potential primary production ranged from 1.5 to 59.2 mgC m-3 h-1. The rate of photosynthesis expressed as the assimilation number (AN) varied from 0.3 to 6.6 mgC mgchl-1 h-1.
The waters of the river Odra reinforce eutrophication in the coastal zone of the Pomeranian Bay. The photosynthetic rate there is usually higher than in open bay waters.
full, complete article (PDF)

The abundance, biomass and production of bacterioplankton in the Pomeranian Bay
Oceanologia 1999, no 41 (3), pp. 389-401

Anetta Ameryk, Zbigniew Mudryk, Beata Podgórska
Marine Biology Centre, Polish Academy of Sciences, Sw. Wojciecha 5, 81-347 Gdynia, Poland;ameryk@cbmpan.gdynia.pl

Keywords: Pomeranian Bay, bacterioplankton, abundance, biomass, production

Manuscript received 18 January 1999, reviewed 22 February 1999, accepted 17 March 1999.
Abstract
A microbiological investigation was carried out in the Pomeranian Bay in 1996-1997 to determine the spatial and seasonal changes in the numbers, biomass and productivity of bacterioplankton. Substantial differences in the spatial distribution of bacterioplankton populations were found. At the stations in the coastal zone of the Pomeranian Bay numbers, biomass and production of bacteria were high, with maximum values noted at the mouth of the river Swina. This is indicative of the significant impact of riverine waters on the bacterioplankton in the Pomeranian Bay.
Seasonal fluctuations and bacterial microflora activity were recorded. The dynamics of the changes showed that most of the bacteriological parameters examined reached their maximum in summer while minimum values were noted in winter.
full, complete article (PDF)

The impact of the River Odra on the phytoplankton composition and biomass in the Pomeranian Bay
Oceanologia 1999, no 41 (3), pp. 403-427

Sławomira Gromisz, Zbigniew Witek, Tomasz Mackiewicz
Department of Oceanography, Sea Fisheries Institute, H. Kołłątaja 1, 81-332 Gdynia, Poland; grosz@miryb.gdynia.pl

Keywords: phytoplankton, Baltic Sea, estuary, assemblages, diversity

Manuscript received 30 April 1999, reviewed 14 June 1999, accepted 6 July 1999.
Abstract
The article is based on the analysis of phytoplankton samples collected in the Pomeranian Bay during five cruises in the years 1993, 1996 and 1997.
In each season a number of phytoplankton assemblages were formed under the impact of the hydrological and hydrochemical conditions gradually changing along an axis from the outlets of the Szczecin Lagoon towards the open sea. The most distinct assemblages could be described as 'river-mouth', 'open-Bay' and 'open-sea' assemblages.
The highest phytoplankton biomass was noted near the mouth of the Swina Strait in the 'river-mouth' assemblages, where the concentration of chlorophyll a was 4 to 5 five times higher in comparison with the 'open-sea' values. The phytoplankton biomass in the 'open-Bay' assemblages was roughly twice as high as that in the 'open-sea' assemblages.
Because of the high N:P ratio in the Odra waters, phosphorus was very probably the factor limiting phytoplankton primary production in the Pomeranian Bay during periods of intensified inflow of riverine waters.
The species dominating the phytoplankton of the Pomeranian Bay during the present study were found to be the same as those recorded in this region 40 years earlier.
full, complete article (PDF)

Transformations and release of phosphorus forms at the sediment-water interface in the Pomeranian Bay (southern Baltic)
Oceanologia 1999, no 41 (3), pp. 429-444

Leszek Frankowski, Jerzy Bolałek
Institute of Oceanography, Gdańsk University, al. Marszałka Piłsudskiego 46, 81-378 Gdynia, Poland; frank@pasat.ocean.univ.gda.pl

Keywords: organic matter deposition and transformations, phosphorus release, sediments, principal component analysis, Pomeranian Bay

Manuscript received 19 February 1999, reviewed 23 March 1999, accepted 9 June 1999.
Abstract
A laboratory chamber experiment was carried out to estimate the release of phosphate from sediments to water. The phosphate thus released originated almost exclusively from the mineralisation of organic matter. Since the release took place between the fifth and the tenth day of the experiment, the compounds undergoing mineralisation were most probably proteins, aminoacids or lipids, whose decomposition times are of the order of several days to several weeks.
Principal component analysis (PCA) was applied to determine the similarities and differences in the chemical composition of the surface sediments of the Pomeranian Bay. The study area can be divided into three subregions based on PCA. The first is the estuarine region A with a distinct station located next to the Swina River estuary; the second is the central Pomeranian Bay (region B), and the third is the deep region C, with a distinct subregion in the vicinity of the Sassnitz Deep.
The phosphorus flux from sediments to water was estimated at 14 x 103 t per year, but was balanced by the deposition flux of organic matter. Phosphorus deposition and release at the sediment-water interface in the Pomeranian Bay therefore play a crucial role in qualitative transformations of the phosphorus compounds, although Pomeranian Bay sediments may not be important as a source or sink of phosphorus compounds.
full, complete article (PDF)

Temporal variability in the chemical composition of bottom sediments in the Pomeranian Bay (southern Baltic)
Oceanologia 1999, no 41 (3), pp. 445-459

Dorota Burska, Leszek Frankowski, Jerzy Bolałek
Institute of Oceanography, Gdańsk University, al. Marszałka Piłsudskiego 46, 81-378 Gdynia, Poland; burak@pasat.ocean.univ.gda.pl

Keywords: Pomeranian Bay, sediments, organic carbon, organic nitrogen, C ratio, total phosphorus, organic phosphorus
Manuscript received 4 March 1999, reviewed 9 April 1999, accepted 15 June 1999.
Abstract
Seasonal changes in the chemical composition of sediments from four stations located in the Pomeranian Bay were analysed. The investigations were carried out in four periods (March and July 1996, and May and October 1997). The following parameters were investigated: organic carbon and nitrogen, total phosphorus and organic phosphorus, loss on ignition and redox potential.
On the basis of these results the influence of the following processes and phenomena was noted: the early spring phytoplankton bloom dominated by diatoms (March 1996); the intense inflow of allochthonous matter brought into the Bay with the waters of the Swina (May 1997); the summer bloom of blue-green algae and dinoflagellates (July 1996); the consequences of the summer 1997 flood which occurred in southern Poland (October 1997).
full, complete article (PDF)

In-water remote sensing algorithms for the detection of chlorophyll and yellow substances in the Pomeranian Bay
Oceanologia 1999, no 41 (3), pp. 461-474

Jerzy Olszewski, Piotr Kowalczuk, Mirosław Darecki
Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, 81-712 Sopot, Poland; olszewsk@iopan.gda.pl

Keywords: marine optics, remote sensing, local algorithms

Manuscript received 12 March 1999, reviewed 12 May 1999, accepted 24 May 1999.
Abstract
In-water remote sensing algorithms for estimating chlorophyll concentration and the absorption of light (400 nm) by yellow substances valid for the surface layer of the Pomeranian Bay are described. The accuracy of the algorithms has been estimated at 20-60%. The statistical analysis of data collected during a two-year experiment in 1996-1997 enable algorithms to be constructed which use a linear combination of spectral reflectances at selected wavelengths, all of them in the log-log form. The wavelengths in nm are 510, 550, 589 or 510, 625 in the 'chlorophyll' case, and 589, 665 or 490, 665 in the 'yellow substances' case. The correlation coefficient between the log-transformed reflectance ratios and the chlorophyll concentration is around 0.9. The correlation coefficient between the log-transformed reflectance ratios and the yellow substance absorption coefficient at λ = 400 nm is around 0.6.
full, complete article (PDF)

Acoustic properties of the Pomeranian Bay bottom sediments
Oceanologia 1999, no 41 (3), pp. 475-487

Jarosław Tęgowski, Zygmunt Klusek
Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, 81-712 Sopot, Poland; tegowski@iopan.gda.pl

Keywords: marine acoustics, bottom backscattering, Baltic Sea

Manuscript received 17 March 1999, reviewed 12 May 1999, accepted 30 June 1999.
Abstract
The properties of bottom backscattered signals in the Pomeranian Bay have been investigated using a one-frequency single beam echosounder working at a central frequency of 30 kHz. The backscattering strength, time of reverberation and attenuation coefficient in sediments were estimated and mapped for the whole area. The other purpose of the investigations was to verify the acoustic one-frequency multiparametric method in order to determine the sediment-type distribution in the Pomeranian Bay. This method was found as useful tool for sediment identification in the study area.
full, complete article (PDF)