Metal sources to the Baltic clam Macoma balthica (Mollusca: Bivalvia) in the southern Baltic Sea (the Gulf of Gdansk)

Metal concentrations of Cu, Fe, Mn, Ni, Pb and Zn in an infaunal facultative deposit-feeding bivalve, the Baltic clam Macoma balthica, in the Gulf of Gdansk (southern Baltic Sea) were assessed and compared to selected concentrations of metals in the environment. Between October 1996 and September 1997, dissolved and easy extractable (by 1M HCl) metal fractions of total suspended particulate matter (TPM) in the overlying water and of surficial sediments (<63 microm) were measured monthly at five sublittoral sites in the Gulf of Gdansk, and accumulated tissue metal concentrations in M. balthica were determined simultaneously. The study highlights the importance of sediment geochemistry as a factor modifying ambient trace metal bioavailabilities. Surficial sediments appeared to contribute most to the accumulation of Cu and Pb in M. balthica, reflecting the high metal availability in the Gulf. Assimilation of Cu from sediments is controlled by Mn components possibly through an inhibitory effect of Mn oxyhydroxides, while Pb accumulation from sediments depends on the organic content of the sediment. A dual metal uptake pathway, with a suspended particulate-bound fraction and surficial sediments, was apparent for Mn and Zn. Partitioning of Mn in sediments was related to the concentration of labile Fe, with increased levels of Fe tending to inhibit the accumulation of Mn by the clam. Tissue accumulated Zn might have been altered by the clam's internal regulation, making Zn tissue concentrations, to some degree, independent of its environmental level. The principal source of Ni accumulated by the clams exists in the soluble phase.     

Suboxic and Anoxic Conditions of Deep Waters in the Gdansk Basin of the Baltic Sea

Oceanology - Long-term variability of the concentrations of oxygen and hydrogen sulfide in deep waters of the Gdansk Basin of the Baltic Sea for the last 25 years was considered. The dependence of...     

Dissolved organic carbon in the southern Baltic Sea: Quantification of factors affecting its distribution

During a cruise of r/v ‘Oceania’ in May 2006, seven vertical dissolved organic carbon (DOC) concentration profiles were produced against a background of CTD, chlorophyll a (chl a) and phaeopigment concentration profiles. The results indicate distinct vertical and spatial DOC fluctuations, ranging from 248 ± 7 μmol C dm⁻³ at 70 m depth at the westernmost station G/06 to 398 ± 5 μmol C dm⁻³ at 5 m depth at station A/06 in the western Gulf of Gdańsk. DOC concentrations were the highest at 10 m depth, where phytoplankton activity was relatively intensive, as reflected by the active chl a concentration distribution. DOC concentrations decreased towards the sea bottom.     

Bioaccumulation of polybrominated diphenyl ethers (PBDEs) in flounder (Platichthys flesus) in the southern Baltic Sea

Concentrations of seven polybrominated diphenyl ether (PBDE) congeners were examined in flounder (Platichthys flesus) and sediment in three southern Baltic Sea sites, representing a range of exposure conditions, in order to evaluate spatial differences in PBDE contamination. Additionally, PBDEs were measured in muscle, liver, and gonads of flounder from one of the sites in order to examine inter-tissue distribution. Mean muscle Σ₇PBDE levels, in the range of 10–21 ng g⁻¹ lipid, showed inter-site differences attributed to the distance from the Gulf of Gdańsk, and were overall lower than reported earlier in herring, sprat, and salmon. Biota sediment accumulation factors (BSAFs) for Σ₇PBDE and individual BDE congeners, in the range of 0.5–24.5, were generally consistent with predicted models for persistent hydrophobic halogenated contaminants. Wet weight (wet wt) PBDE levels in muscle and liver, but not in gonads, were related to tissue lipid content and did not correlate with the fish length and weight. These tissues differed in PBDE levels and profiles as a result of varying lipid content and presumably lipid composition and congener-specific physico-chemical properties.     

Spatial macrozoobenthic distribution patterns in relation to major environmental factors- A case study from the Pomeranian Bay (southern Baltic Sea)

The aim of this study was to identify potential environmental “key factors” causing spatial distributions of macrozoobenthic communities to improve our understanding concerning benthic biotic/abiotic interactions and ecosystem functioning. To this end benthic and environmental data, collected over a period of 4 years (2003–2006) at 191 sampling stations in the Pomeranian Bay (southwest Baltic Sea), were analysed. This represents the most comprehensive study performed in this respect in the Baltic Sea up to date and also the necessary first step towards a model able to predict macrofaunal distributions regarding autecological species-environment interactions. Based on species abundances, distinctive macrobenthic community patterns were identified and evaluated via univariate correlation methods, multivariate numerical classification and ordination techniques (e.g. PCA, CCA). These patterns were caused by clear responses of several benthic species to certain prevailing environmental conditions. The observed distribution of selected species followed a strong gradient of depth and was explained best by the sediment parameters total organic carbon (TOC), median grain size and sorting. By using different statistical methods these abiotic/biotic interactions were modelled allowing to extend our knowledge concerning ecosystem functioning, and provide a tool to assess natural and anthropogenic forced changes in species distribution.     

Stratification-induced hypoxia as a structuring factor of macrozoobenthos in the open Gulf of Finland (Baltic Sea)

Long-term (1965–2000) changes of macrozoobenthos and hydrography have been studied in the Gulf of Finland (GoF). For the first time, statistical multivariate time series analysis is applied to Baltic Sea data to verify the relationship between biota and interacting environmental factors causing large-scale hypoxia in the open sea. For macrozoobenthos, a consistent long-term development of the assemblages was found over the study area. In the period before the 1990s, very sparse macrozoobenthos prevailed, followed by a notable expansion of macrofauna between the late 1980s and early 1990s and leading to a maximum of total abundance and species number between 1991 and 1996. After that, a sudden collapse of the communities took place in 1996–1997. The hydrographical changes included a continuous decrease in salinity and density stratification until the early 1990s, after which an increase took place again. In contrast, low mean and minimum dissolved oxygen concentrations were observed at the beginning of the study period, followed by increasing values in the late 1980s and early 1990s, and a simultaneous decline of oxygen conditions in 1996. Based on non-linear trends estimated by dynamic factor analysis (DFA), high and significant correlations were found between total macrofauna abundance, number of species, salinity, oxygen conditions, strength of stratification and freshwater run-off. The results confirm that oxygen is obviously a fundamental factor that determines the state of the macrozoobenthos in the deep GoF, overruling other abiotic factors. However, the improvement of the oxygen conditions is apparently caused by the long-term decrease of salinity and loss of stratification in the relatively shallow GoF, reflecting large-scale changes in hydrography of the Baltic Sea during the long 1977–1993 stagnation period. Thus the development in GoF is opposite to the deeper basins in the central Baltic. We conclude that salinity and stratification are probably linked with climatic variability via freshwater run-off, which may be important in regulating the oxygen conditions and state of macrozoobenthos in GoF.     

Microbially mediated methane and sulfur cycling in pockmark sediments of the Gdansk Basin, Baltic Sea

In the Russian sector of the Gdansk Basin (Baltic Sea), high organic matter influx fuels microbial processes resulting in the formation of reduced sediments with elevated methane concentrations. Investigated areas of geoacoustic anomalies (～245 km²) were found to contain three distinct geomorphologic structures (pockmarks), with a total area of ～1 km². Methane anomalies recorded in the water above one of these pockmarks were traced as high as 10 m above the bottom. In pockmark sediments, sulfate reduction and anaerobic oxidation of methane (AOM) occurred at high rates of 33 and 50 µmol dm^?3 day^?1, respectively. Integrated over 0–180 cm sediment depths, AOM exceeded methanogenesis almost tenfold. High AOM rates resulted from methane influx from deeper sediment layers. The δ¹³C signature of methane carbon (?78.1 to ?71.1‰) indicates the biogenic origin of pockmark methane. In pockmark sediments, up to 70% of reduced sulfur compounds was possibly produced via AOM.     

Variability of the Baltic Sea level and floods in the Gulf of Finland

The statistical analysis of the long-term data on the variability of the Baltic Sea level has revealed the complicated character of the wave field structure. The wave field formed by the variable winds and the disturbances of the atmospheric pressure in the Baltic Sea is a superposition of standing oscillations with random phases. The cross spectral analysis of the synchronous observation series of the level in the Gulf of Finland has shown that the nodal lines of the standing dilatational waves are clearly traced with frequencies corresponding to the distance from the nodal line to the top of the gulf (a quarter of the wave length). Several areas of the water basin with clearly expressed resonant properties may be distinguished: the Gulfs of Finland, Riga, and Bothnia, Neva Bay, etc. The estimations of the statistical correlation of the sea level oscillations with the variation of the wind and atmospheric pressure indicate the dominant role of the zonal wind component during the formation of the floods in the Gulf of Finland. The probable reason for the extreme floods in St. Petersburg may be the resonance rocking of the eigenmode oscillations corresponding to the basic fundamental seiche mode of the Gulf of Finland with a period of 27 h when the repeated atmospheric disturbances in the Baltic Sea occur with a period of 1–2 days.     

Sediment contaminants and contaminant levels and biomarkers in caged mussels (Mytilus trossulus) in the southern Baltic Sea

Sediment from four southern Baltic Sea locations and caged mussels were analyzed for PCBs, organochlorine pesticides and metals (Cu, Zn, Cd, Pb, Hg). In mussels, which were additionally analyzed for 16 individual PAHs, a set of biomarker responses was measured to derive an integrated biomarker response (IBR) index as a part of integrative assessment of pollution in this area. Concentrations of PCBs, ΣDDT, and metals in sediment and mussels, greatest within the Gulf of Gdańsk area, showed decreasing gradients outwards from the Gulf. Sediment quality quotients (SQQs) and biological impact quotients (BIQs), reflecting on sediment- and mussel-accumulated contaminants' potential for biological effects, respectively, pointed out to the Gulf of Gdańsk to be of greatest concern among the examined sites. The IBRs corresponded poorly with the SQQs and BIQs, nevertheless, provided a line of evidence indicative of biological effects of contaminants to support more complex processes of environmental status assessment.     

Hydrological and Hydrochemical Underpinnings of Primary Production and Division of the Russian Sector in the Gdansk Basin of the Baltic Sea

Oceanology - The distribution patterns of absolute and specific values of primary production in the upper 10-m layer depending on the physical and chemical condition of the marine environment...     

Microhabitat preferences and depth distribution of combtooth blennies (Blenniidae) in the Gulf of Trieste (North Adriatic Sea)

The microhabitat preferences and depth distribution of blenniid species (Blenniidae) in the Gulf of Trieste (North Adriatic Sea) were surveyed using the all‐occurrence sampling method, a non‐destructive visual census method, aided by SCUBA diving. Fourteen species were identified during the entire survey. Four species showed to be indiscriminate in their microhabitat choice while 10 species were classified as infrequent in the surveyed coastal area. A statistically significant correlation was found between the blenniid assemblage and nine microhabitat variables. The blenniid assemblage was divided in two main groups, by the use of canonical correspondence analysis, electivity index, and the depth distribution analysis. The first group comprises species that dwell in surface waters and show a high positive correlation with boulders, the presence of Mytilus galloprovincialis, cirripeds and empty holes bored by Lithophaga lithophaga. The second group includes species that mostly inhabit deeper waters and show a high positive correlation with rocks covered by precoralligenous bioformations.     

Ore Sands in Curonian Spit Sediments (Baltic Sea)

Oceanology - For the first time, the results of a study of ore sands formed during storm waves and winds on the sea beach of Curonian Spit and in the quieter wind environment on the beach of the...     

Seasonal changes in the distribution and exchange of inorganic nitrogen between sediment and water in the Northern Baltic (Gulf of Bothnia)

The concentration profiles of nitrate plus nitrite, ammonium, and redox potential in sediment and water column were determined in late winter and summer at a sampling site off Norrbyn, northern Sweden, in the Gulf of Bothnia. The sediment had an oxidized surface layer during winter and spring, and nitrification occurred. Nitrate but not ammonium was present in the water column at this time. During summer a layer of planktonic detritus was deposited onto the sediment and led to its deoxygenation and reduction. Ammonium was then the predominant form of inorganic nitrogen in the water column.Laboratory experiments confirmed that nitrification in the surface layer of sediment prevented ammonium export during winter. Enhanced temperature or organic detritus deoxygenated the surface sediment and inhibited nitrification, and export of ammonium from the sediment increased. Although nitrification was important in determining the flow of nitrogen in the sediment it accounted for at most only 5% of the total oxygen uptake by the sediment.     

Pathways of suspended particles transport in the bottom layer of the southern Baltic Sea depending on the wind forcing (Numerical Simulation)

A random-walk model for a nonuniform diffusivity media coupled with an ocean circulation model has been applied to describe the pathways of suspended particles transport in the bottom boundary layer (BBL) of the southern Baltic Sea. The circulation model is based on the Princeton Ocean Model, in which the vertical grid size is logarithmically refined towards the bottom in order to resolve the BBL. Fields of the flow velocity and eddy diffusivities simulated by the POM, along with the settling velocity of the suspended particles, are used as an input for the random-walk model. A number of numerical experiments were performed to study the pathways of suspended particles in the southern Baltic BBL depending on the wind conditions. In particular, the suspended particles introduced into the BBL in the center of the Bornholm Basin at westerly and southerly winds are found to be trapped in the basin provided that the particles’ settling velocity is equal or greater than 2 m/day. The trapping phenomenon is explained by the combined effect of the Ekman transport convergence in the BBL due to the cyclonic gyre and the gravitational settling of the particles.     

Severity of sea ice in the Southern Baltic Sea, Gulf of Finland and Gulf of Bothnia up 21st century

The study focused on the evaluation of probable changes in the severity of sea ice conditions occurring in 3 selected areas of the Baltic Sea: the Gulf of Bothnia, Gulf of Finland and the Southern Baltic Sea up to the year 2100. The areas have been chosen due to the high intensity of marine traffic (the Gulfs??of Bothnia and of Finland) and due to differences in sea ice conditions; winters in the Gulf of Bothnia were characterized as the most severe, whereas in the Southern Baltic were classified as the mildest ones. Consequently, three scenarios were taken into account in the study: A2 (slow rate of global economic development, market scenario), A1B (regional scenario, rapid economic development, with ecological priorities), B1 (sustainable, median economic development with strong ecological priorities), all three constructed on the basis of Special Report on Emissions Scenarios (SRES models of greenhouse gas emission). The probable changes of sea ice conditions expressed as severity index S were calculated from these models. The main results of the investigation are as follows, the variety of sea ice conditions occurring in specific regions of the Baltic will remain stable (i.e. the most severe winter conditions will still occur in Gulf of Bothnia, while the mildest in the Southern Baltic Sea). The most significant changes are likely to occur in the Southern Baltic, where some winters without ice cover in the Vistula Lagoon may happen. Nonetheless, some extremely severe winters will occur and also within specific seasons more winters with a lower number of days with ice will occur.