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1

Variability of chlorophyll a concentration in surface waters of the open Baltic Sea

Stramska Małgorzata, Jakacki Jaromir

Oceanologia

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2024

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Vol. 66 (2)

365--380

EN

In situ, satellite and reanalysis data from numerical models were used to study the characteristic features of Chl variability in the Baltic Sea. The analysis is focused on the years 2003–2020 when regular observations of ocean color with the MODIS AQUA are available. In the Baltic Sea, there is a pronounced annual cycle in physical conditions in the water column, driven by seasonal cycles in atmospheric forcing. The seasonal cycle of Chl concentration does not conform to the picture known from classical models, with low phytoplankton concentration when nutrients are low. In contrast, in the Baltic Sea, the concentration of Chl is high even during the summer months when nutrients are depleted. This can be explained by a continuous supply of nutrients by runoff from land, as well as by a significant contribution to primary production by phytoplankton able to survive in environment poor in dissolved nutrients. There is also a considerable interannual variability in Chl. There are many possible cause/effect interactions involved, but the data series are still too short to make clear which of them are the most important. The most striking event was a spring bloom in 2008.

2

The use of Argo floats as virtual moorings for monitoring the South Baltic Sea

Merchel Małgorzata, Walczowski Waldemar, Rak Daniel, Wieczorek Piotr

Oceanologia

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2024

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Vol. 66 (1)

99-110

EN

The Argo float measurement network is increasingly effectively covering internal seas and shelf areas. In this paper, a specific approach to using Argo floats as ‘virtual moorings’ within the conditions of the Baltic Sea is presented. Following a series of successful deployments with standard configurations, it was decided that the settings forcing the float to stay at the bottom between profiles should be tested. This significantly reduced the drift of the float and allowed measurements to be made in a limited water area for a longer time. The data obtained from Argo floats used as virtual mooring can be a valuable source for monitoring and analysing the hydrology of individual basins of the Baltic Sea. The results show that the temporal and spatial variability of the observed fields of temperature, salinity, and other properties of seawater is very high. More data are needed to correctly determine the mean properties of the basins and their temporal variability. Therefore, Argo floats can be a source of efficient and inexpensive hydrographic data for shallow seas such as the Baltic.

3

Submesoscale processes in the surface layer of the central Baltic Sea: A high-resolution modelling study

Väli Germo, Meier H.E. Markus, Liblik Taavi, Radtke Hagen, Klingbeil Knut, Gräwe Ulf, Lips Urmas

Oceanologia

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2024

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Vol. 66 (1)

78--90

EN

A high-resolution model with a horizontal resolution of 250 m was used to analyze the surface eddy fields and the distribution of kinetic energy in the Baltic Sea. The results indicate a close relationship between the wind speed and the kinetic energy at the surface and the vertically averaged kinetic energy in the sea, and a lagged correlation between the kinetic energy at the surface and the eddy field. The spatial patterns of kinetic energy indicate more energetic currents in the western and southern parts of the Baltic Sea. The distribution of vorticity is inhomogeneous and differs significantly between sea areas. Submesoscale features are also inhomogeneously distributed and occur more frequently in the Gdańsk Basin, the Gulf of Finland, and the western part of the northern Baltic proper.

4

Spatiotemporal variability of wave climate in the Gulf of Riga

Najafzadeh Fatemeh, Jankowski Mikolaj Z., Giudici Andrea, Männikus Rain, Suursaar Ülo, Viška Maija, Soomere Tarmo

Oceanologia

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2024

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Vol. 66 (1)

56--77

EN

Basic properties of wind wave climate in the Gulf of Riga, the Baltic Sea, are evaluated based on modelled wave fields, instrumentally measured and historical visually observed wave properties. Third-generation spectral wave model SWAN is applied to the entire Baltic Sea for 1990–2021 with a spatial resolution of 3 nautical miles (nmi, about 5.5 km) forced by the wind field of ERA5, to the Gulf of Riga and its entrance area with a resolution of 1 nmi (about 1.85 km), and to nearshore areas of this gulf with a resolution of 0.32 nmi (about 600 m). The calculations are performed for an idealised ice-free climate. Wave properties are represented by 36 directional and 32 frequency bins. The simulations are complemented by five sessions of instrumental measurements in the 2000s and two sets of historical visual wave observations from the island of Ruhnu and the Sõrve Peninsula for 1954–2011. Predominantly representing fetch-limited windseas, the wave climate in the gulf is milder and more intermittent than in the open Baltic Sea. The average significant wave height is mostly in the range of 0.6–0.8 m and peaks at 0.82 m inside the gulf. Typical wave periods are shorter than in the Baltic proper. The spatial pattern of wave heights, with higher wave intensity in the northern and eastern parts of the basin, follows anisotropy in wind conditions. Interannual variations are highly synchronised in different parts of the gulf. Their magnitude is less than 10% of the long-term average wave height. No long-term trend has been found in significant wave height and no distinct decadal variation exists inside the gulf.

5

Soft postglacial cliffs in Poland under climate change

Różyński Grzegorz, Cerkowniak Grzegorz

Oceanologia

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2024

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Vol. 66 (2)

319--333

EN

The paper presents the results of the simulations of soft cliff erosion in Poland under future sea level rise. Two locations were investigated: one situated on the Wolin island, and the second near the town of Ustka. The cliffs will be suffering enhanced erosion for a number of reasons. First, the adopted sea level rise of 0.7 m results in a direct attack on cliff foot, leading to enhanced erosion with rates being roughly twice as high as that occurring without the rise. A high rate of erosion can persist because the cliff cannot reconfigure itself by moving landward and will permanently remain exposed to wave attack even under milder regimes. Second, the wave climates in the Baltic Sea release most energy in close shoreline proximity. Third, longer storm event durations can lead to ‘erosion saturation’, but this result requires further investigations, which will include alongshore effects induced by local bathymetry and longshore currents, ignored in 1-D simulations. Finally, the granulometry was found less important; finer grains offer less resistance to depletion, leading to greater erosion. The results demonstrate the need for vast follow-up research: (1) detailed mapping of the bathymetry near cliffs in order to properly reproduce alongshore redistribution of sediment during storms and achieve better estimates of cliff erosion, (2) detailed mapping of cliff lithology in order to properly reproduce their sediment composition and thus achieve better estimates of built-in susceptibility to erosion, (3) preparation of 2-D modeling suites for improved assessment of the rates of erosion of cliffs subjected to sea level rise.

6

Phytoplankton pigments in the Baltic Sea : mathematical description of chlorophylls and carotenoids content in different seasons and regions

Stoń-Egiert Joanna, Ostrowska Mirosława, Stoń-Egiert Joanna

Oceanologia

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2024

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Vol. 66 (2)

405--423

EN

This study aimed to trace the spatial and seasonal changes in pigment composition and to develop mathematical formulas to quantitatively describe their composition in different seasons in two regions: the open Baltic Sea region and the Gulf of Gdańsk. The analyses were carried out based on a 20-year database of empirical data from 1999 to 2018 obtained using the HPLC method. The proportion of chlorophyll a in the total content of pigments was stable irrespective of the season and region (62% ± 5%). In summer and autumn, a higher total amount of photoprotective carotenoids (about 15–17% in total pigment content) than photosynthetic ones was recorded. The concentrations of marker pigments are related to periodic increases in the corresponding algal classes. The spring bloom dominated by diatoms and dinoflagellates results in 40% of fucoxanthin and 70% of peridinin in relation to their total content throughout all seasons. The highest percentage of chlorophyll b (up to 10% in open waters) and other pigments specific to green algae (neoxanthin, violaxanthin, lutein) were observed during summer and autumn. The 30% percentage of fucoxanthin confirms the occurrence of diatoms in autumn. The concentrations of groups and individual pigments have been determined as a function of chlorophyll a concentration. The best approximation results were obtained for the seasonal dependence of marker pigments for specific classes of algae. In summer and autumn – for chlorophyll b concentrations – zeaxanthin, fucoxanthin, alloxanthin and peridinin standard error factor ranges between 1.56 and 1.84.

7

Environmental impact of water exchange blocking in a strait – a multidisciplinary study in the Baltic Sea

Liblik Taavi, Buschmann Fred, Siht Enriko, Kuprijanov Ivan, Väli Germo, Lipp Maarja, Erm Ants, Laanemets Jaan, Eschbaum Redik, Verliin Aare, Saks Lauri, Zekker Ivar

Oceanologia

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2024

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Vol. 66 (1)

9--25

EN

In this study, we report the environmental impact of water exchange blocking by a 3 km road dam built in 1896 in the shallow Väike Strait, north-eastern Baltic Sea. Using a multidisciplinary measurement campaign and numerical simulations, we show ecological conditions in the strait have considerably altered; the previously free-flowing strait now comprises two bays with separate circulation systems. Water exchange in the area close to the dam has decreased 10–12-fold. Since advection is weakened, exchange with the atmosphere and sediments has a relatively greater role in shaping water characteristics. Consequently, occasional very high sea surface temperature, salinity, and total nitrogen, and strong diurnal cycles in water temperature (>4°C) and dissolved oxygen (>4 mg l−1) were observed near the dam in summer. Oxygen levels are continuously below saturation in winter and concentration occasionally drops to hypoxic levels with ice cover. Nitrogen content in sediments near the dam is 3–4 times higher than in neighboring areas. The dam also modifies sea level, wind wave and suspended matter patterns in the strait. Sediments near the dam show elevated content of hazardous substances likely associated with traffic on the dam road. The phytobenthos community near the dam is dominated by annual green algae, which massively decompose during winter. The dam likely impedes fish migration between suitable feeding and spawning areas, also there have been fish kills caused by rapid fluctuations in sea levels, amplified by dam. The construction of new openings would alleviate negative impacts of the dam.

8

Coverage estimation of benthic habitat features by semantic segmentation of underwater imagery from South-eastern Baltic reefs using deep learning models

Šiaulys Andrius, Vaičiukynas Evaldas, Medelytė Saulė, Buškus Kazimieras

Oceanologia

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2024

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Vol. 66 (2)

286--298

EN

Underwater imagery (UI) is an important and sometimes the only tool for mapping hard-bottom habitats. With the development of new camera systems, from hand-held or simple “drop-down” cameras to ROV/AUV-mounted video systems, video data collection has increased considerably. However, the processing and analysing of vast amounts of imagery can become very labour-intensive, thus making it ineffective both time-wise and financially. This task could be simplified if the processes or their intermediate steps could be done automatically. Luckily, the rise of AI applications for automatic image analysis tasks in the last decade has empowered researchers with robust and effective tools. In this study, two ways to make UI analysis more efficient were tested with eight dominant visual features of the Southeastern Baltic reefs: 1) the simplification of video processing and expert annotation efforts by skipping the video mosaicking step and reducing the number of frames analysed; 2) the application of semantic segmentation of UI using deep learning models. The results showed that the annotation of individual frames provides similar results compared to 2D mosaics; moreover, the reduction of frames by 2–3 times resulted in only minor differences from the baseline. Semantic segmentation using the PSPNet model as the deep learning architecture was extensively evaluated, applying three variants of validation. The accuracy of segmentation, as measured by the intersection-over-union, was mediocre; however, estimates of visual coverage percentages were fair: the difference between the expert annotations and model-predicted segmentation was less than 6–8%, which could be considered an encouraging result.

9

Continuing long-term expansion of low-oxygen conditions in the Eastern Gulf of Finland

Stoicescu Stella-Theresa, Hoikkala Laura, Fleming Vivi, Lips Urmas

Oceanologia

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2024

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Vol. 66 (1)

139--152

EN

o develop an oxygen indicator for the eastern part of the Gulf of Finland (EGOF), a dataset covering 1900–2021 was compiled. The analysis revealed a long-term declining trend in dissolved oxygen concentrations in the EGOF deep layer of 0.022 mg L–1 a–1 and multi-decadal variations associated with the observed changes in hydrographic conditions. About 27% of the decline in oxygen concentrations for 1900–2021 and 40% for 1990–2021 can be explained by the decrease in solubility due to the temperature increase and changes in hydrographic conditions. The water volume and bottom area under low oxygen conditions in 2016–2021, characterized by dissolved oxygen concentrations <= 6 mg L–1, have increased, compared to the selected reference period with almost no human impact in the 1920s–1950s, from 9.8 km3 to 78.0 km3 (from 2.6% to 20.9% of the EGOF total volume) and from 1190 km2 to 4950 km2 (from 13.4% to 56.0% of the EGOF total area), respectively. The environmental status of the EGOF was assessed as not good based on the introduced oxygen indicator. We conclude that, in the long-term, low oxygen conditions have expanded mostly due to the excess load and accumulation of nutrients in the system and temperature-related changes in biogeochemical processes and fluxes. However, on a decadal scale, changes in hydrographic conditions, i.e. stratification and mixing, can significantly impact the sub-surface oxygen conditions in the EGOF and similar estuarine basins.

10

Changes in cloudiness contribute to changing seasonality in the Baltic Sea region

Post Piia, Aun Margit

Oceanologia

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2024

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Vol. 66 (1)

91--98

EN

In the Baltic Sea region, a significant increase in solar radiation has been detected during the past half-century. Changes in shortwave irradiance are associated with atmospheric transparency and cloudiness parameters like cloud fraction and albedo. One of the most important reasons for day-to-day changes in cloudiness is the synoptic-scale atmospheric circulation; thus, we look for reasons for solar radiation trends due to changes in atmospheric circulation. We analysed regional time series and trends from satellite-based cloud climate data record CLARA-A2 for the Baltic Sea region in 1982–2018. As the rise in solar radiation depends on the seasonally averaged values of total fractional cloud cover (CFC), surface incoming shortwave radiation (SIS) and occurrences of circulation types were analysed. We show that the shift in seasonality connected to the earlier accumulated sums of SIS is at least partly explained by the changes in synoptic-scale atmospheric circulation.

11

Assessing the effect of coastal upwelling on the air temperature at the south-eastern coast of the Baltic Sea

Dabulevičienė Toma, Nesteckytė Laura, Kelpšaitė-Rimkienė Loreta

Oceanologia

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2024

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Vol. 66 (2)

394--404

EN

Coastal upwelling along the SE Baltic Sea coast is a common feature, especially during the warm season. It significantly lowers sea surface temperature (SST) in the coastal areas, and, therefore, may be responsible for modifying meteorological conditions in those coastal areas, where upwelling is most frequently observed. This study aims to assess the effect of coastal upwelling on the air temperature at the south-eastern coast of the Baltic Sea based on long-term period observations (2002–2021) from coastal hydrometeorological stations and satellite data. Overall, our study revealed that due to its high frequency and spatial extent, upwelling is responsible for lowering the mean summer season SST of the SE Baltic Sea coast by about 1°C. And even though upwelling is a short-term event, upwelling-induced SST drop results in cooling air temperatures in the coastal areas, i.e., the mean air temperatures during upwelling are typically 2−4°C lower than before. It was also observed that upwelling is favouring the development of advective fog. Thus, sudden changes in meteorological parameters during upwelling can have versatile effects on various socio-economic activities. The results of this study contribute to the understanding of upwelling feedback onto the lower atmosphere and, therefore, are important for advancing the accuracy of weather forecasts that are needed for coastal communities, including marine and coastal industries.

12

Morskie farmy wiatrowe w Polsce

Parfianowicz Kamil

Inżynier Budownictwa

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2024

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nr 5

80--85

13

Tombak M. L., Tapaninen U., Palu R.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2023

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Vol. 17 No. 4

973--980

EN

Baltic Sea maritime transport makes up about 15% of all cargo globally transported via sea, which makes it one of the busiest maritime areas all over the world [1]. At the same time shipping operations create environmental pressures to the air, discharges of oil, sewage from passenger ships as well as invasion of alien organisms from ships’ ballast water or hulls [2]. In order to move from assessment of discharges from one ship to a certain area, it is necessary to combine the discharge factors to the activity patterns [3]. In this study the shipping activities that have environmental impact in the Estonian sea area will be analysed. In addition, the activities will be related with their source of pollution (e.g., manoeuvring, anchoring, loading/unloading cargo) and the impact or consequences are analysed (e.g., emission to air (CO2, SOx, NOx) discharge to water (antifouling paints, scrubber water, ballast water, bilge water, black water), physical discharge (underwater noise) etc). Finally, we assess the relative importance of the environmental effect of shipping in Estonian waters.

14

Open-loop scrubbers and restricted waterways: A aase study investigation of travemünde port and increased sulphur emissions immediately after the scrubbers are turned off

Altarriba E., Rahiala S., Tanhuanpää T.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2023

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Vol. 17 No. 2

465--471

EN

Open-loop sulphur scrubbers must be switched off, and the fuel must be changed to low-sulphur fuel before entering German inland waters. Immediately after the scrubbers are turned off, warm exhaust gases cause the residue left in the scrubber to vaporise, leading to the increased sulphur content of the exhaust gas. The momentary increase in sulphur emissions immediately after the open-loop scrubbers are turned off has received little attention in research. This paper presents the onboard measurement results of exhaust gases and examines the effects of sulphur compounds released into the air. In this case, the observed sulphur emission peak is problematic due to the geographical location. The ship sails to the river port, passing the coastal town of Travemünde, where the exhaust gases are released. Due to this, the emissions are more harmful when compared to emissions generated in the open seas.

15

Using the Coastal Clean Index to assess the impact of anthropogenic pressure on sandy beaches in Ustka, Poland

Bigus Katarzyna, Jarosiewicz Anna

Studia Quaternaria

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2023

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Vol. 40, Nr 2

67--76

EN

The article summarizes results of the studies of the Coastal Clean Index (CCI) on selected Polish beaches. In 2022, an attempt was made to estimate the amount of litter on the beach in Ustka. Debris on the beach was collected during a peak season in July and August. An attempt was also made to estimate the daily increase in garbage on the beach. The main part of the research was based on the quality and quantity of litter in beach sediments to the east and west of Ustka. Litter was divided according to a type of material, use, size and origin. The collected material was dominated by a plastic waste. The largest amount of marine litter was collected on the beach, on the eastern side of the Słupia River.

16

Preliminary approach to modelling eutrophication - anthropopressure impact on sea water quality

Bogalecka Magdalena

Safety and Reliability of Systems and Processes

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2023

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Summer Safety and Reliability Seminar 2023

19--31

EN

The chapter is devoted to the problem of eutrophication. Methods and parameters for its assessment are described. Furthermore, the eutrophication of the Baltic Sea is discussed in detailed. Finally, the semi-Markov model of the eutrophication process is proposed, and its characteristics are determined.

17

Kartografia 4D w strefie brzegowej południowego Bałtyku : zadanie państwowej służby geologicznej

Uścinowicz Grzegorz

Przegląd Geologiczny

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2023

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Vol. 71, nr 3

138--144

EN

The research task Geological integrated coastal zone mapping concerns the recognition and visualization of the geological structure of the Polish coastal zone, enriched with the modelling of erosion-accumulation processes, including prediction of changes in the position of the shoreline and identification of geohazards. It has been running since 2012 and implements multi-instrumental research methods. To date, a total length of about 155 km of the Polish coastal zone has been studied in an area of about 621 km 2 . The main results of the work are presented in the form of maps (e.g., lithogenetic, hydrogeological, geohazard), models (e.g., morpho-geological, hydrodynamic, predictive) and specialized analyses (e.g., morphodynamical, slope stability). In general, the work carried out is done for a utilitarian purpose, i.e. aimed at the practical use of environmental information. According to the standards of the Polish Geological Survey, most of the geological data acquired can be geoprocessed.

18

Potencjał południowego Bałtyku jako miejsca lokalizacji elektrowni falowych

Jakusik Ewa, Sapiega Patryk

Przegląd Budowlany

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2023

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R. 94, nr 11-12

96--101

PL

Wyczerpywanie się surowców nieodnawialnych oraz ich możliwy negatywny wpływ na środowisko i klimat skłania do wyszukiwania alternatywnych metod wytwarzania energii elektrycznej. W pracy przedstawiono analizę możliwości pozyskiwania energii z falowania w południowej części Morza Bałtyckiego w oparciu o reanalizę i pomiary falowania, zlokalizowanymi w dwóch różnych strefach głębokościowych. Maksymalna możliwa energia do wygenerowania mieści się w przedziale 5,7-7,2 kW/m grzbietu fali. Na podstawie danych pomiarowych falowania oraz danych producenta elektrowni pływakowej oszacowano, iż 71-88 km modułów pływakowych mogłoby zaopatrzyć w energię elektryczną aglomerację trójmiejską, a średnia wartość wytworzonej energii plasowałaby się w przedziale 100-169 kW. Przeprowadzona analiza wskazuje na przeciętny potencjał Bałtyku Południowego, związany z krótkookresowymi, wysokimi stanami hydrodynamicznymi morza.

EN

Depletion of non-renewable resources keep us for searching of new alternative methods of generating electricity. There were possibilities in the paper that two of the undulations that are consistent with the experience of the Baltic Sea based on reanalysis and wave measurements, operating based on different depth zones. The maximum power this system can generate is within 5,7-7,2 kW per meter of a wave rigde. Based on the waving mesurments and manufactures data of this kind wave plant, the length 71-88 km of modules could be supply Tri-city agglomeration consumption. Average power of installation would be range 100-169 kW. The conducted analysis access to the average potential of the South Baltic Sea, research with short-term, fast hydrodynamic states of the sea.

19

Variations of temperature, salinity and oxygen of the Baltic Sea for the period 1950 to 2020

Stockmayer Vera, Lehmann Andreas

Oceanologia

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2023

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Vol. 65 (3)

466--483

EN

Variations of temperature, salinity and oxygen of the Baltic Sea on interannual to decadal timescales were studied for the period from 1950 to 2020. Both observational data and the output of a numerical circulation model of the Baltic Sea were analyzed. In addition, we investigated the influence of atmospheric parameters and river runoff on the observed hydrographic variations. Variability of sea surface temperature (SST) closely follows that of air temperature in the Baltic on all timescales examined. Interannual variations of SST are significantly correlated with the North Atlantic Oscillation in most parts of the sea in winter. The entire water column of the Baltic Sea has warmed over the period 1950 to 2020. The trend is strongest in the surface layer, which has warmed by 0.3–0.4°C decade−1, noticeably stronger since the mid-1980s. In the remaining water column, characterized by permanent salinity stratification in the Baltic Sea, warming trends are slightly weaker. A decadal variability is striking in surface salinity, which is highly correlated with river runoff into the Baltic Sea. Long-term trends over the period 1950–2020 show a noticeable freshening of the upper layer in the whole Baltic Sea and a significant salinity increase below the halocline in some regions. A decadal variability was also identified in the deep layer of the Baltic Sea. This can be associated with variations in saltwater import from the North Sea, which in turn are influenced by river runoff: fewer strong saltwater inflows were observed in periods of enhanced river runoff. Furthermore, our results suggest that changes in wind speed have an impact on water exchange with the North Sea. Interannual variations of surface oxygen are strongly anti-correlated with those of SST. Likewise, the positive SST trends are accompanied by a decrease in surface oxygen. In greater depths of the Baltic Sea, oxygen decrease is stronger, which is partly related to the observed increase of the vertical salinity gradient.

20

Seasonal variation in size structure and production of autotrophic plankton community in eutrophied, low-light environment: A focus on Mesodinium rubrum

Labucis Atis, Labuce Astra, Jurgensone Iveta, Barda Ieva, Andersone Ingrida, Ikauniece Anda

Oceanologia

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2023

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Vol. 65 (2)

398--409

EN

Temporal variations in the primary production of the size-fractionated autotrophic plankton community were studied in coastal-estuarine waters of the eutrophic Gulf of Riga, Baltic Sea. The community was net-autotrophic during spring and summer and net-heterotrophic during autumn. The results of the present study clearly demonstrate strong covariation between net primary production (NPP) and <56 µm fractionated community biomass, particularly small-sized (16–33 µm) Mesodinium rubrum, implying that the majority of NPP stems from the lower end of the size spectrum. A pronounced size distribution shift was observed within the M. rubrum population. Large-sized (length ≥34 µm) M. rubrum was the most abundant in the first half of the productive season (until week 24), whereas small-sized M. rubrum dominated during the stratified period.