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Environmental changes in the central Baltic Sea during the past 1000 years: inferences from sedimentary records, hydrography and climate

Leipe T., Dippner J.W., Hille S., Voss M., Christiansen C., Bartholdy J.

Oceanologia

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2008

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No. 50 (1)

23-41

EN

Short sediment cores from the eastern Gotland Basin were investigated using a multi-proxy approach in order to reconstruct the environmental conditions of the area during the past 1000 years. Sediment data and facies were discussed in relation to hydrographic features (salinity, oxygen) and climate change. During the medieval warm period (MWP), from about 900 to 1250 AD, the hydrographic and environmental conditions were similar to those of the present time (modern warm period, since about 1850): a temporally stable halocline, caused by regular saline water inflows from the North Sea, prevents vertical mixing and leads to bottom water anoxia and the deposition of laminated, organic-rich sapropels. During the period from about 1250 to 1850, referred to as the cold phase (including the Little Ice Age), the environmental conditions of the central Baltic Sea were distinctly different: the lower salinity, resulting from reduced North Sea water inflows, allowed vertical convection of the water column and long-term stable ventilation of the sea bed (oxic stage). Both the productivity of the planktonic ecosystem as well as the preservation of organic matter in the sediments improved during the warm periods. The anthropogenic impact can be identified within the recent laminated sequence by a temporal reconstruction of pollutant deposition. Our findings imply a climate-change driven shift in the environmental conditions and the ecosystem of the Baltic from the north to the south and back to the north.

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Spatial variability of recent sedimentation rates in the Eastern Gotland Basin (Baltic Sea)

Hille S., Leipe T., Seifert T.

Oceanologia

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2006

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No. 48 (2)

297-317

EN

n order to study recent sedimentation rates in the Eastern Gotland Basin, 52 short sediment cores collected from the deepest part (< 150 m) of the Basin in 2003 were investigated. The upper parts of all the cores were distinctly laminated and dark in colour, followed by a homogeneous, greyish lower part. The thickness of the laminated sequences varied from 17 to 300 mm. 210Pb dating analyses of selected cores revealed that the change from non-laminated to laminated sediments happened about 100 years ago, indicating a shift from predominantly oxic bottom water conditions to anoxic conditions. Used as a time marker, this shift in the sediment texture enabled sediment accumulation rates to be estimated for all sediment cores. The observed mean linear sedimentation rate for the whole basin was 0.93 š 0.67 mm y-1. The respective bulk sediment accumulation rates ranged from 10.5 to 527 g m-2 yr-1 with an average of 129 š 112 g m-2 yr-1, indicating a high spatial variability of sedimentation rates within the basin. This agrees very well with the long-term sedimentation pattern since the Litorina transgression. The observed pattern clearly reflects the hydrographic conditions at the seafloor as studied by modelled near-bottom current velocities.

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High resolution Single Particle Analysis by scanning electron microscopy : a new tool to investigate the mineral composition of agglutinated foraminifers

Bartholdy J., Leipe T., Frenzel P., Tauber F., Bahlo R.

Studia Geologica Polonica

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2005

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Vol. 124

35-65

EN

A high resolution Single Particle Analysis by scanning electron microscopy (SEM) and X-ray microanalysis is introduced as a new technique to investigate components of tests of aggluti- nated foraminifers. In a feasibility study, specimens of Nodulina dentaliniformis (Brady, 1881) from surface sediment of the Lübeck Bight (southwestern Baltic Sea) were investigated. A chemical mapping of a selected part of the surface of the last chamber as well as analysis of isolated foraminiferal shell grains and the ambient sediment were carried out. The investigations point to the non-selectivity of the foraminifer to use specific minerals but a selectivity to use specific grain sizes and shapes.

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Sedimentary deposition and reflux of phosphorus (P) in the Eastern Gotland Basin and their coupling with P concentrations in the water column

Hille S., Nausch G., Leipe T.

Oceanologia

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2005

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No. 47 (4)

663-679

EN

In order to describe the role of sedimentary processes for the phosphorus (P) cycle in the open Baltic Proper, P deposition and reflux were quantified for the predominately anoxic sediments of the Eastern Gotland Basin. The study is based on investigations of 53 surface sediment samples and pore water samples from 8 sediment cores. The average P deposition rate was estimated at 0.20 g š 0.18 g -2 yr-1, the fluctuation being due to variable bulk sediment deposition rates. P refluxes were estimated by applying Fick's First Law of Diffusion. A fairly good positive correlation between sedimentary P deposition and P release was obtained. P release from sediments by diffusion exceeds net P deposition by a factor of 2. This suggests that 2/3 of the deposited gross P is recycled in the sediments and released back into the water column; only 1/3 remains in the sediment permanently. A budget calculation demonstrates that the released dissolved inorganic phosphorus (DIP) accounts for the observed increase in DIP concentrations in the deep water during periods of stagnation, which is noticeable even at the surface P concentrations. Under such conditions and with the present remediation conditions it is not possible to freely manage P concentrations in the water column on short time scales.

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Deposition of organic matter and particulate nitrogen and phosphorus at the North Sea-Baltic Sea transition - a GIS study

Jansen D. L., Lundqvist D. P., Christiansen C., Lund-Hansen L.C., Balstrom T., Leipe T.

Oceanologia

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2003

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No. 45 (2)

283-303

EN

A GIS (Geographical Information System) based study on deposition in the North Sea-Baltic Sea transition area has been carried out. The study is based on (i) a digital bathymetry model, (ii) 93 available 210Pb / 137Cs sedimentation rate estimations, (iii) grain-size distributions, organic matter, C, N and P content of 64 top 1 cm sediment samples from the study area, and (iv) GIS-based modelling of resuspension potentials based on wind statistics. With the use of regression statistics on depth, resuspension potential and sediment characteristics, results are extrapolated area-wide from the 64 sampling positions. The area is divided into sediment types and classified as accumulation or erosion/transport bottoms. Model results show good agreement with existing maps of sediment distributions, indicating that the sediment distribution is governed to a large extent by wind-induced waves. Correlations of sediment types, their deposition rates and their N and P contents were used to estimate spatial deposition rates. In all, the yearly deposition in the study area amounts to 2.8 million tons of organic matter, 0.14 million tons of total nitrogen, and 0.035 million tons of total phosphorus. Correlations of sediment types and dry bulk densities were used to infer spatial inventories of organic matter and total nitrogen and phosphorus in the top 1 cm of the sediments. A total of 100 million tons of organic matter, 4 million tons of total nitrogen, and 0.019 million tons of total phosphorus are contained in the top 1 cm of the sediments in the study area. In general, the deep parts of the study area with low resuspension potentials act as sinks for the fine-grained sediments and their associated particulate nutrients.

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The contribution of the fine sediment fraction to the Fluffy Layer Suspended Matter (FLSM)

Pempkowiak J., Bełdowski J., Pazdro K., Staniszewski A., Leipe T., Emeis K.-C.

Oceanologia

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2002

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No. 44 (4)

513-527

EN

Fluffy Layer Suspended Matter (FLSM) is a layer of fairly concentrated suspended matter resting on the sea floor. Its passage to the depositional basins in the Pomeranian Bay - Arkona Deep System of the Baltic Sea is estimated to take around six months. In the course of this migration, the properties of FLSM change as a result of ageing and the influx of fresh particles from the water column, and possibly also because of mass exchange with the uppermost sediment layers. Measurements of radioisotopes (210Po, 210Pb, 137Cs) have demonstrated that in shallow water this topmost layer of sediments, from 8 cm to 3 cm in thickness, is subject to mixing. This creates redox profiles favourable to biota and bioturbation. Basing on 210Pb/210Po disequilibria and the 210Po excess, it was estimated that under steady state conditions from 1.5 to 2.2% of fine fraction (FSF) in the mixed layer of sediments is freshly imported from FLSM. This implies replacement of FSF from the sediments and its incorporation into FLSM. On the assumption that the surface density of FLSM is 10 mg cm-2, FSF freshly exported from sediments actually comprises up to 15% of FLSM. Therefore, the properties of FLSM are strongly influenced by the processes taking place in the sediments, although FLSM by definition is independent of sediments.

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Variations in organic matter bound in fluffy layer suspended matter from the Pomeranian Bay (Baltic Sea)

Pazdro K., Staniszewski A., Bełdowski J., Emeis K. C., Leipe T., Pempkowiak J.

Oceanologia

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2001

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No. 43 (4)

405-420

EN

Fluffy layer suspended matter (FLSM) and surface sediment samples from the Pomeranian Bay were examined for fatty acid, lipid and organic matter contents. FLSM is a several-centimetre-thick layer of fairly concentrated particulate matter lying on the sea floor significantly affecting the flux of matter to depositional basins. Analyses of fatty acids were used to establish sources and decomposition rates of labile organic matter along a transect from the shallow, highly dynamic, Odra estuary to the Arkona Basin, a deep, low energy, depositional area. In FLSM and sediments respectively, the ranges of organic matter contents were 4.0-25.0% and 5.1-23.0%, those of lipids 0.1-5.4% and 0.30-1.67%, and those of fatty acids 50-991 žg g-1 dry wt. and 100-546 žg g-1 dry wt. In shallow waters, the contents of these compounds are very variable, mirroring variations in biological activity and hydrological conditions. The high percentage of polyunsaturated fatty acids in shallow areas indicates the presence of fresh, undegraded, labile organic matter of autochthonous origin. Fatty acids, the most labile components, are transported as suspended matter attached to minerals and finally accumulated in the depositional area in the form of condensed organic macromolecules. The intensity of bacterial decomposition of organic matter in this system is reflected in the high percentage of branched fatty acids. The low fatty acid content in the organic matter is attributed to the high rate of decomposition of the labile organic matter. No linear correlation was found between the contents of fatty acids and lipids.

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Temporal and spatial changes of cadmium in the near-bottom suspended matter of the Pomeranian Bay - Arkona Deep system

Staniszewski A., Pazdro K., Bełdowski J., Leipe T., Emeis K. C., Pempkowiak J.

Oceanologia

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2000

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No. 42 (4)

483-491

EN

Owing to the high toxicity of cadmium (Cd) towards biota and the considerable quantities of this element entering the environment from anthropogenic sources, interest in its biogeochemistry is increasing. This is also true for the marine environment, which serves as a sink for both natural and anthropogenic Cd loads entering the hydrosphere and the atmosphere. The distribution of Cd in the coastal zone of the marine environment is governed primarily by the flux of the so-called fluffy layer suspended matter (FLSM), which spreads across the top of the sea floor as a several-centimetre-thick layer containing highly concentrated suspended matter. Both total contents and solid speciation of Cd was measured in FLSM collected in the Pomeranian Bay - Arkona Deep system (Western Baltic Proper) in the course of the three-year-long study. Seasonal changes in the total Cd content (0.5-1.8 žg g–1 dry matter) were attributed to the contribution of organic suspensions originating from algal blooms. The decreasing content of Cd in FLSM offshore is due to the input of Cd-rich suspended matter from the River Odra (Oder), and the decreasing organic matter content in FLSM with increasing depth. The contribution of labile fractions (adsorbed and bound to iron III hydroxides) was found to be from 50 to 75% of the total content. In view of the substantial mobility and bioavailability of the fractions, this is a highly alarming feature.