Abstract. Methane and carbon dioxide were measured with an autonomous and continuous running system on a ferry line crossing the Baltic Sea on a 2-3 day interval from the Mecklenburg Bight to the Gulf of Finland in 2010. Surface methane saturations show great seasonal differences in shallow regions like the Mecklenburg Bight (103-507 %) compared to deeper regions like the Gotland Basin (96-161 %). The influence of controlling parameters like temperature, wind, mixing depth and processes like upwelling, mixing of the water column and sedimentary methane emissions on methane oversaturation and emission to the atmosphere are investigated. Upwelling was found to influence methane surface concentrations in the area of Gotland significantly during the summer period. In February 2010, an event of elevated methane concentrations in the surface water and water column of the Arkona Basin was observed, which could be linked to a wind-derived water level change as a potential triggering mechanism. The Baltic Sea is a source of methane to the atmosphere throughout the year, with highest fluxes occurring during the winter season. Stratification was found to promote the formation of a methane reservoir in deeper regions like Gulf of Finland or Bornholm Basin, which leads to long lasting elevated methane concentrations and enhanced methane fluxes, when mixed to the surface during mixed layer deepening in autumn and winter. Methane concentrations and fluxes from shallow regions like the Mecklenburg Bight are predominantly controlled by sedimentary production and consumption of methane, wind events and the change in temperature-dependent solubility of methane in the surface water. Methane fluxes vary significantly in shallow regions (e.g. Mecklenburg Bight) and regions with a temporal stratification (e.g. Bornholm Basin, Gulf of Finland). On the contrary, areas with a permanent stratification like the Gotland Basin show only small seasonal fluctuations in methane fluxes.

In December 2014, the third strongest salt water inflow into the Baltic Sea occurred since 1880. It was assumed that the inflow would turn the entire bottom water of the Baltic Sea from anoxic into oxic conditions for an extended period. However, already in late 2015, the central Eastern Baltic Sea had turned back into anoxic conditions. This rapid oxygen decline was in fact surprising since a weaker inflow in 2003 ventilated the Baltic Sea for a longer period of time. With the aid of an ecosystem model of the Baltic Sea, the two inflows in 2003 and 2014 were analyzed in detail. Although the 2014 inflow event was twice as strong as the 2003 inflow event, oxygen transport continued after the latter one, supplying about the same amount of oxygen again. In addition to the major inflow event, a series of smaller inflows in 2003 supplied the extra oxygen transport. Therefore, the strength of a major inflow event alone cannot be used to predict the oxygenation impact. Instead, it is necessary to consider smaller events, in particular those occurring just before and after a major inflow event, as well. An element tagging method showed that the share of oxygen imported across the Danish Straits on the total oxygen arriving at the central Eastern Baltic Sea is between 10% and 20%. Therefore, the oxygen concentration of the inflowing water seems to be of less importance for the oxygenation effect on the central Baltic Sea due to the strong dilution effect.

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G . ROPKE et al. : Influence of Exciton Gas and Electron-Hole Plasma 2 15 phys. stat. sol. (b) 100, 215 (1980) Corrections to the energy levels of ground state excitons embedded in a gas of excitons, electrons, and holes are obtained within the framework of the Green's function technique. Contributions of the interaction with free carriers and excitons are considered in the first Born approximation, and plasmon effects are taken into account. Numerical values are given for the exciton energy shift linear in the densities a t different temperatures and different electron-hole mass ratios.Im Rahmen der Technik der Greenschen Funktionen werden die Korrekturen zur Grundzustandsenergie eines Exzitom berechnet, das in ein Plasma aus Exzitonen, Elektronen und Lochern eingebettet ist. Es werden die Beitrage der Wechselwirkung mit freien Ladungstragern und mit Exzitonen in der ersten Bornschen Niiherung betrachtet, und Plasmoneffekte werden berucksichtigt. SchlieSlich werden numerische Werte fiir die in den Dichten lineare Verschiebung des exzitonischen Grundzustandes bei verschiedenen Temperaturen und Elektron-Loch-Massen-verhLltnissen gegeben.

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Methane and carbon dioxide were measured with an autonomous and continuous running system on a ferry line crossing the Baltic Sea on a 2–3 day interval from the Mecklenburg Bight to the Gulf of Finland in 2010. Surface methane saturations show great seasonal differences in shallow regions like the Mecklenburg Bight (103–507%) compared to deeper regions like the Gotland Basin (96–161%). The influence of controlling parameters like temperature, wind, mixing depth and processes like upwelling, mixing of the water column and sedimentary methane emissions on methane oversaturation and emission to the atmosphere are investigated. Upwelling was found to influence methane surface concentrations in the area of Gotland significantly during the summer period. In February 2010, an event of elevated methane concentrations in the surface water and water column of the Arkona Basin was observed, which could be linked to a wind-derived water level change as a potential triggering mechanism. The Baltic Sea is a source of methane to the atmosphere throughout the year, with highest fluxes during the winter season. Stratification was found to intensify the formation of a methane reservoir in deeper regions like Gulf of Finland or Bornholm Basin, which leads to long lasting elevated methane concentrations and enhanced methane fluxes, when mixed to the surface during mixed layer deepening in autumn and winter. Methane concentrations and fluxes from shallow regions like the Mecklenburg Bight are rather controlled by sedimentary production and consumption of methane, wind events and the change in temperature-dependent solubility of methane in the surface water. Methane fluxes vary significantly in shallow regions (e.g. Mecklenburg Bight) and regions with a temporal stratification (e.g. Bornholm Basin, Gulf of Finland). On the contrary, areas with a permanent stratification like the Gotland Basin show only small seasonal fluctuations in methane fluxes

Transition zones between marine and freshwater environments are characterized by a pronounced salinity gradient and concomitant variation in invertebrate species richness. Here we use the β-diversity concept to depict the species turnover of macrobenthic species along the salinity gradient of the Baltic Sea with salinities ranging from 34 in the transition zone to the North Sea to less than 5 in the Bothnian Sea. Based on 250 data sets from 72 locations that were grouped into 2 habitats defined according to their depths and sediment types (shallower: 15 to 19 m, fine to medium sand; deeper: 20 to 35 m, silt to silty sand), we calculated the Jaccard dissimilarity index (β 1-J ) as a measure of species turnover. To keep the focus on the salinity gradient, sediment characteristics and the time period covered by the data sets (spring and summer 1995 to 2005) were predefined. The mean hydrographic parameters, including temperatures, salinities and dissolved oxygen (DO) concentrations of the sample locations were derived from model calculations based on data gathered over a 3 yr period before sampling. At the deeper stations, the total number of macrofaunal species was 255, while at the shallower ones, 172 taxa were found. Statistical analyses revealed salinity to be the main structuring factor for macrobenthic species turnover. High correlations between the β 1-J index and mean salinities in both habitats (Spearman's rank correlation coefficient ρ = 0.88 in shallower and ρ = 0.86 in deeper areas) confirmed these findings. β-diversity values with median β 1-J varied between 51 and 65% within the salinity classes eu-, poly-, α-meso-and β-mesohaline, while values of 75 to 100% characterized between-group comparisons. Furthermore, these high β-diversity values depict a discontinuous change in the communities and are found at salinities of around 10, 18, and 30, which ties in fairly well with the existing salinity boundaries postulated by the Venice System. KEY WORDS: Species turnover · β-diversity · Salinity gradient · Macrofauna · Venice System · Baltic Sea Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 436: 101-118, 2011 102 agreed on the Venice System (Caspers 1959), in which the following generalized salinity class boundaries were defined: euhaline zone > 34 to 30, polyhaline zone 30 to 18, α-mesohaline zone 18 to 10, β-mesohaline zone 10 to 5, α-oligohaline zone 5 to 3, β-oligohaline zone 3 to 0.5, and limnetic zone 0.5 to 0. The System is widely used, e.g. in the implementation of the European Union's (EU) Water Framework Directive in the coastal waters of the Baltic Sea (von Weber 2004). The Venice System's boundaries are also consistent with distribution limits determined by coenosis (Hiltermann 1963). Nevertheless, other studies have claimed that no objective criteria exist for these boundaries (e.g. Bulger et al. 1993). Except for the minimum species richness at salinities from ~5 to 8, the boundaries of the Venice System cannot be derived from Rema...

Variations of the spectral lines in high dense ion plasmas with temperature and pressure may be characterized by the broadening aa well as by t@ shift of spectral lines. For dense hydrogen-and alkali-plasmas (free carrier density larger than lW$3m3) one of the possible mechankms responsible for line profiles is considered to be the Coulomb interaction with free charged mrriers. Using thermodynamic Green's functions, a systematic approach to the theory of spectral lines starting from the complex dielectric function is outlined. "he line shift is derived from a perturbiltive treatment of the two-particle Green's function in the sufrounding plasma. The shift of several lines proportional to the carrier density is evaluated as a function of the temperature and compared with experimental results.Inhaltsiibersicht. Bnderungen im Linienspektrum hochdichter Ionenplasmen mit Temperatur und Druck konnen durch eine Verbreitemg sowie durch eine Verschiebung der Spektrallinien beschrieben werden. Fiir dichte Wasserstoff-und Alkaliplasmen (Dichte der freien Ladungstriiger g r o h r als 1016/cms) wird als ein moglicher Mechanismus fiir die hderung im Linienprofil die Coulombwechselwirkung mit freien Ladungstriigern betrachtet. Ein systematischer Zugang zur Theorie von Spektrallinien ausgehend von der komplexen dielektrischen Funktion und unter Verwendung thermcdynamischer Greenscher Funktionen wird benutzt. Die Linienverschiebung wird aus einer stijrungstheoretischen Behandlung der Qreenschen Funktion zweier Teilchen in einem Plasma abgeleitet. Die Verschiebung verschiedener Spektrallinien, die proportional zur Dichte der freien Ladungstriiger ist, wird in Abhiingigkeit von der Temperatur ausgewertet und mit experimentellen Werten verglichen.