Dominant chlorophylls and carotenoids in macroalgae of the Baltic Sea (Baltic proper): Their use as potential biomarkers

Abstract. Long-term oxygen and nutrient transports in the Baltic Sea are reconstructed using the Swedish Coastal and Ocean Biogeochemical model (SCOBI) coupled to the Rossby Centre Ocean model (RCO). Two simulations with and without data assimilation covering the period 1970–1999 are carried out. Here, the weakly coupled scheme with the Ensemble Optimal Interpolation (EnOI) method is adopted to assimilate observed profiles in the reanalysis system. The reanalysis shows considerable improvement in the simulation of both oxygen and nutrient concentrations relative to the free run. Further, the results suggest that the assimilation of biogeochemical observations has a significant effect on the simulation of the oxygen-dependent dynamics of biogeochemical cycles. From the reanalysis, nutrient transports between sub-basins, between the coastal zone and the open sea, and across latitudinal and longitudinal cross sections are calculated. Further, the spatial distributions of regions with nutrient import or export are examined. Our results emphasize the important role of the Baltic proper for the entire Baltic Sea, with large net transport (export minus import) of nutrients from the Baltic proper into the surrounding sub-basins (except the net phosphorus import from the Gulf of Riga and the net nitrogen import from the Gulf of Riga and Danish Straits). In agreement with previous studies, we found that the Bothnian Sea imports large amounts of phosphorus from the Baltic proper that are retained in this sub-basin. For the calculation of sub-basin budgets, the location of the lateral borders of the sub-basins is crucial, because net transports may change sign with the location of the border. Although the overall transport patterns resemble the results of previous studies, our calculated estimates differ in detail considerably.

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The first large-scale assessment of three-spined stickleback (Gasterosteus aculeatus) biomass and spatial distribution in the Baltic Sea

ICES Journal of Marine Science ◽

10.1093/icesjms/fsz078 ◽

2019 ◽

Vol 76 (6) ◽

pp. 1653-1665 ◽

Cited By ~ 7

Author(s):

Jens Olsson ◽

Eglė Jakubavičiūtė ◽

Olavi Kaljuste ◽

Niklas Larsson ◽

Ulf Bergström ◽

...

Keyword(s):

Spatial Distribution ◽

Baltic Sea ◽

Gasterosteus Aculeatus ◽

Population Characteristics ◽

Alternative Methods ◽

The Baltic Sea ◽

Baltic Proper ◽

The Baltic ◽

The Impact ◽

Bothnian Sea

Abstract Declines in predatory fish in combination with the impact of climate change and eutrophication have caused planktivores, including three-spined stickleback (Gasterosteus aculeatus), to increase dramatically in parts of the Baltic Sea. Resulting impacts of stickleback on coastal and offshore foodwebs have been observed, highlighting the need for increased knowledge on its population characteristics. In this article, we quantify abundance, biomass, size structure, and spatial distribution of stickleback using data from the Swedish and Finnish parts of the Baltic International Acoustic Survey (BIAS) during 2001–2014. Two alternative methods for biomass estimation suggest an increase in biomass of stickleback in the Baltic Proper, stable or increasing mean size over time, and larger individuals toward the north. The highest abundance was found in the central parts of the Baltic Proper and Bothnian Sea. The proportion of stickleback biomass in the total planktivore biomass increased from 4 to 10% in the Baltic Proper and averaged 6% of the total planktivore biomass in the Bothnian Sea. In some years, however, stickleback biomass has ranged from half to almost twice that of sprat (Sprattus sprattus) in both basins. Given the recent population expansion of stickleback and its potential role in the ecosystem, we recommend that stickleback should be considered in future monitoring programmes and in fisheries and environmental management of the Baltic Sea.

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Geoelectric Monitoring of Wind-Driven Barotropic Transports in the Baltic Sea

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech2068.1 ◽

2007 ◽

Vol 24 (9) ◽

pp. 1655-1664 ◽

Cited By ~ 5

Author(s):

Jenny A. U. Nilsson ◽

Peter Sigray ◽

Robert H. Tyler

Keyword(s):

Baltic Sea ◽

Circulation Model ◽

Correlation Study ◽

The Baltic Sea ◽

Barotropic Flow ◽

Spatial Coverage ◽

Baltic Proper ◽

The Baltic ◽

Scale Motion ◽

Geoelectric Monitoring

Abstract The possibility of using data from a cable-based observational system for long-term monitoring of barotropic flow in the Baltic Sea was investigated. Measurements were made of the induced potential differences between Visby on the island of Gotland and Västervik on the Swedish mainland and a yearlong period was studied in order to ensure the presence of seasonal fluctuations. The predictions from a 2D electric-potential model, forced by velocity fields from a shallow-water circulation model, proved to be well correlated with the observations. A winter and a summer period were selected for a thorough analysis, the results of which indicated a stronger correlation during winter. This implies that the relative importance of the barotropic forcing tends to weaken during summer. The spatial coverage of the induced potential differences for the cable region was found to encompass a considerable part of the Baltic proper. The correlation study indicated that the winter circulation in the Baltic proper showed “broad-scale” motion, whereas summer conditions were characterized by a barotropic gyre. An overall result of the investigation is that geoelectric monitoring is capable of providing useful data for oceanographic purposes.

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The significance of wave–current interaction on modelled wave fields in the Baltic Sea

10.5194/egusphere-egu2020-15900 ◽

2020 ◽

Author(s):

Hedi Kanarik ◽

Laura Tuomi ◽

Jan-Victor Björkqvist ◽

Tuomas Kärnä ◽

Antti Westerlund

Keyword(s):

Baltic Sea ◽

Wave Spectrum ◽

Hydrodynamical Model ◽

Gulf Of Finland ◽

Surface Currents ◽

The Baltic Sea ◽

Notable Effect ◽

Baltic Proper ◽

The Baltic ◽

The Gulf Of Finland

Currents in the Baltic Sea are relatively weak and are thus often expected to have a negligible effect on sea surface waves. To evaluate the magnitude of wave&#8211;current interactions in the Baltic Sea, we ran the third generation wave model WAM with and without surface currents from the 3D hydrodynamical model Nemo4. The results showed that the currents have a notable effect on wave field only on rare occasions and that the effects are largest in coastal areas of the Baltic Proper, most notably in the western Gotland Basin, and the Gulf of Finland. The simulations showed that the currents in the Baltic Sea can cause differences of significant wave height up to tens of centimeters. More notable effect was the change in the peak of the wave spectrum from swell to wind driven waves and vice versa in some occasions. In our study we mostly focus on the events of strong wave&#8211;current interactions in the northern Baltic Proper and Gulf of Finland as we have measured wave spectra available from these locations. From the comparison with wave buoy measurements we see that implementing surface currents slightly improves the modelled peak period in the Gulf of Finland. The Gulf of Finland is of special interest also because a group of ADCP&#8217;s were installed close to the wave buoy. The current measurements from these devices can therefore be used to evaluate the accuracy of the currents in the hydrodynamical model.

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Bathymetric Properties of the Baltic Sea

10.5194/os-2019-18 ◽

2019 ◽

Cited By ~ 1

Author(s):

Martin Jakobsson ◽

Christian Stranne ◽

Matt O'Regan ◽

Sarah L. Greenwood ◽

Bo Gustafsson ◽

...

Keyword(s):

High Resolution ◽

Baltic Sea ◽

Ocean Circulation ◽

Deep Water ◽

Water Exchange ◽

The Baltic Sea ◽

Resolution Mapping ◽

Baltic Proper ◽

Southern Side ◽

The Baltic

Abstract. Marine science and engineering commonly require reliable information about seafloor depth (bathymetry), e.g. for studies of ocean circulation, bottom habitats, fishing resources, sediment transport, geohazards and site selection for platforms and cables. Baltic Sea bathymetric properties are analysed here using the using the newly released Digital Bathymetric Model (DBM) by the European Marine Observation and Data Network (EMODnet). The analyses include hypsometry, volume, descriptive depth statistics, and km-scale seafloor ruggedness, i.e. terrain heterogeneity, for the Baltic Sea as a whole as well as for 17 sub-basins defined by the Baltic Marine Environment Protection Commission (HELCOM). We compare the new EMODnet DBM with IOWTOPO, the previously most widely used DBM of the Baltic Sea which has served as the primary gridded bathymetric resource in physical and environmental studies for nearly two decades. The area of deep water exchange between the Bothnian Sea and the Northern Baltic Proper across the Åland Sea is specifically analysed in terms of depths and locations of critical bathymetric sills. The EMODnet DBM provides a bathymetric sill depth of 88 m at the northern side of the Åland Sea and 60 m at the southern side, differing from previously identified sill depths of 100 and 70 m respectively. High-resolution multibeam bathymetry acquired from this deep water exchange path, where vigorous bottom currents interacted with the seafloor, allows us to assess what we are missing in presently available DBMs in terms of physical characterisation and our ability to then interpret seafloor processes and highlights the need for continued work towards complete high-resolution mapping of the Baltic Sea seafloor.

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Nutrient cycling in the Baltic Sea – results from a 30-year physical-biogeochemical reanalysis

10.5194/bg-2016-301 ◽

2016 ◽

Author(s):

Ye Liu ◽

H. E. Markus Meier ◽

Kari Eilola

Keyword(s):

Baltic Sea ◽

Ocean Model ◽

Optimal Interpolation ◽

Nutrient Concentrations ◽

Biogeochemical Model ◽

Phosphorus Transport ◽

The Baltic Sea ◽

Gulf Of Riga ◽

Baltic Proper ◽

The Baltic

Abstract. The long-term oxygen and nutrient cycles in the Baltic Sea are reconstructed using the Swedish Coastal and Ocean Biogeochemical model (SCOBI) coupled to the Rossby Centre Ocean model (RCO). Two simulations covering the period 1970–1999 are carried out with and without data assimilation, respectively. Here, the "weakly coupled" scheme with the Ensemble Optimal Interpolation (EnOI) method is adopted to assimilate the observed profiles in the reanalysis system. The simulation results show considerable improvements in both oxygen and nutrient concentrations in the reanalysis relative to the free run. Further, the results suggest that the assimilation of biogeochemical observations has a significant effect on the simulation of the oxygen dependent dynamics of biogeochemical cycles. From the reanalysis, nutrient transports between subbasins, between the coastal zone and the open sea, and across latitudinal and longitudinal cross sections, are calculated. Further, bottom areas of nutrient import or export are examined. Our results emphasize the important role of the Baltic proper for the entire Baltic Sea, with large net exports of nutrients into the surrounding subbasins (except the phosphorus transport into the Gulf of Riga and the nitrogen transports into the Gulf of Riga and Danish Straits). In agreement with previous studies, we found that the Bothnian Sea imports large amounts of phosphorus from the Baltic proper that are buried in this subbasin. For the calculation of subbasin budgets, it is crucial where the lateral borders of the subbasins are located, because net transports may change sign with the location of the border. Although the overall transport patterns resemble the results of previous studies, our calculated estimates differ in detail considerably.

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A Regime Shift Toward a More Anoxic Environment in a Eutrophic Sea in Northern Europe

Frontiers in Marine Science ◽

10.3389/fmars.2021.799936 ◽

2021 ◽

Vol 8 ◽

Author(s):

Elin Almroth-Rosell ◽

Iréne Wåhlström ◽

Martin Hansson ◽

Germo Väli ◽

Kari Eilola ◽

...

Keyword(s):

Baltic Sea ◽

High Pressures ◽

Sea Water ◽

Northern Europe ◽

Data Series ◽

Vertical Profiles ◽

The Baltic Sea ◽

Worst Case ◽

Baltic Proper ◽

The Baltic

Dissolved oxygen in the sea is essential for marine fauna and biogeochemical processes. Decline in the sea water oxygen concentration is considered to be an effect of eutrophication, also exacerbated by climate change. The Baltic Sea is one of the most eutrophic seas in the world and is located in northern Europe. It is a vulnerable, brackish, semi-enclosed sea, suffering from high pressures from human activity. This leads to increased hypoxic and anoxic areas, which can be used as a measure of the environmental state. In the present study the extent of anoxic (O2 < 0 ml l–1) and hypoxic (O2 < 2 ml l–1) areas were estimated for the autumns in 1960–2019 using vertical profiles of observed oxygen concentrations in the Baltic proper and four sub-areas of the Baltic proper: the Bornholm Basin, the western, northern and eastern Gotland basins. From vertical profiles of observed salinity, the annual average of the halocline depths in the four sub-basins were estimated. The results imply regime shifts toward increased anoxic area extents in the Gotland basins around the turn of the 20th century. In autumn 2018, the extent of anoxic bottom areas in the Baltic Sea was record high since the start of the data series. During the later part of the studied period the depths of the halocline coincide with the depth of the hypoxia in the Gotland basins. This implies that in these basins a worst-case scenario for the extent of hypoxic areas seems to be reached.

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Baltic Sea sediments record anthropogenic loads of Cd, Pb, and Zn

Environmental Science and Pollution Research ◽

10.1007/s11356-020-10735-x ◽

2020 ◽

Author(s):

Sina Shahabi-Ghahfarokhi ◽

Sarah Josefsson ◽

Anna Apler ◽

Karsten Kalbitz ◽

Mats Åström ◽

...

Keyword(s):

Baltic Sea ◽

Environmental Governance ◽

Heavy Metal Contamination ◽

The Baltic Sea ◽

The West ◽

Large Spatial Scale ◽

Bottom Waters ◽

Baltic Proper ◽

The Baltic ◽

Bothnian Bay

Abstract The unsustainable settlement and high industrialization around the catchment of the Baltic Sea has left records of anthropogenic heavy metal contamination in Baltic Sea sediments. Here, we show that sediments record post-industrial and anthropogenic loads of Cd, Zn, and Pb over a large spatial scale in the Baltic Sea. We also demonstrate that there is a control on the accumulation of these metals in relation to oxic/anoxic conditions of bottom waters. The total concentrations of Cd, Zn, and Pb were obtained with the near-total digestion method in thirteen cores collected from the Bothnian Bay, the Bothnian Sea, and the west and central Baltic Proper. The lowest average concentrations of Cd, Zn, and Pb were observed in Bothnian Bay (0.4, 125, 40.2 mg kg−1 DW, respectively). In contrast, the highest concentrations were observed in the west Baltic Proper (5.5, 435, and 56.6 mg kg−1 DW, respectively). The results indicate an increasing trend for Cd, Zn, and Pb from the early nineteenth century until the 1970s, followed by a decrease until 2000–2008. However, surface sediments still have concentrations above the pre-industrial values suggested by the Swedish EPA (Cd is 0.2, Zn is 85, and Pb is 31 mg kg−1 DW). The results also show that the pre-industrial Cd, Zn, and Pb concentrations obtained from 3 cores with ages < 1500 B.C. were 1.8, 1.7, and 1.2 times higher, respectively, than the pre-industrial values suggested by the Swedish EPA. To conclude, accumulations of metals in the Baltic Sea are governed by anthropogenic load and the redox conditions of the environment. The significance of correct environmental governance (measures) can be illustrated with the reduction in the pollution of Pb, Zn, and Cd within the Baltic Sea since the 1980s.

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Brief communication: Characteristic properties of extreme wave events in the Baltic Sea

10.5194/nhess-2017-117 ◽

2017 ◽

Author(s):

Jan-Victor Björkqvist ◽

Laura Tuomi ◽

Niko Tollman ◽

Antti Kangas ◽

Heidi Pettersson ◽

...

Keyword(s):

Baltic Sea ◽

Wave Height ◽

Significant Wave Height ◽

Wave Steepness ◽

Extreme Wave ◽

The Baltic Sea ◽

Baltic Proper ◽

Wave Conditions ◽

The Baltic ◽

Proper Wave

Abstract. A significant wave height of 7 m has been measured five times by the northern Baltic Proper wave buoy in the Baltic Sea, exceeding 8 m twice (2004 & 2017). We classified these storms into two groups by duration and wave steepness. Interestingly, the two highest events exhibited opposite properties, with the 2017 event being the longest storm on record. This storm is also the first where the harshest wave conditions were modelled to occur in the western part of the Baltic Proper. The metrics quantifying the storm's duration and steepness might aid in issuing warnings for extreme wave conditions.

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Bathymetric properties of the Baltic Sea

Ocean Science ◽

10.5194/os-15-905-2019 ◽

2019 ◽

Vol 15 (4) ◽

pp. 905-924 ◽

Cited By ~ 2

Author(s):

Martin Jakobsson ◽

Christian Stranne ◽

Matt O'Regan ◽

Sarah L. Greenwood ◽

Bo Gustafsson ◽

...

Keyword(s):

High Resolution ◽

Baltic Sea ◽

Deep Water ◽

Water Exchange ◽

The Baltic Sea ◽

Resolution Mapping ◽

Baltic Proper ◽

Southern Side ◽

Northern Side ◽

The Baltic

Abstract. Baltic Sea bathymetric properties are analysed here using the newly released digital bathymetric model (DBM) by the European Marine Observation and Data Network (EMODnet). The analyses include hypsometry, volume, descriptive depth statistics, and kilometre-scale seafloor ruggedness, i.e. terrain heterogeneity, for the Baltic Sea as a whole as well as for 17 sub-basins defined by the Baltic Marine Environment Protection Commission (HELCOM). We compare the new EMODnet DBM with IOWTOPO the previously most widely used DBM of the Baltic Se aproduced by the Leibniz-Institut für Ostseeforschung Warnemünde (IOW), which has served as the primary gridded bathymetric resource in physical and environmental studies for nearly two decades. The area of deep water exchange between the Bothnian Sea and the Northern Baltic Proper across the Åland Sea is specifically analysed in terms of depths and locations of critical bathymetric sills. The EMODnet DBM provides a bathymetric sill depth of 88 m at the northern side of the Åland Sea and 60 m at the southern side, differing from previously identified sill depths of 100 and 70 m, respectively. High-resolution multibeam bathymetry acquired from this deep water exchange path, where vigorous bottom currents interacted with the seafloor, allows us to assess what presently available DBMs are missing in terms of physical characterization of the seafloor. Our study highlights the need for continued work towards complete high-resolution mapping of the Baltic Sea seafloor.

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