Variability in inorganic and organic nitrogen uptake associated with riverine nutrient input in the Gulf of Riga, Baltic Sea

Concentrations and rates of uptake of dissolved organic nitrogen (DON, free amino acids, and urea) and inorganic nitrogen (DIN, nitrate, and ammonium) were measured along two transects in the Gulf of Riga, a sub-basin of the Baltic Sea, during May and July 1996. Concentrations of total dissolved nitrogen (TDN) were 23±3 μg-at N 1⁻¹ in the northern region (mouth) and 41±5 μg-at N 1⁻¹ in the southern region (head) of the Gulf. Rates of nitrogen uptake, determined with¹⁵N-labeled substrates, reflected differences in TDN concentration between the regions. In May, uptake of DIN+DON measured 0.17 and 0.43 μg-at N 1⁻¹ h⁻¹ in the northern and southern parts of the Gulf, respectively. In July, DIN+DON uptake measured 0.38 and 0.68 μg-at N 1⁻¹ h⁻¹ in the north and south, respectively. Most of the variability in total nitrogen flux between the northern and southern regions was due to heterogeneity of DON utilization. Uptake of urea and dissolved free amino acid were up to 6 and 3 times greater in the south compared to the north. As evidenced by size-fractionation, plankton size structure appeared to play a role in the uptake of DON. The community in the southern part was largely composed of cells <5 μm, while up to 67% of the community in the northern part was composed of cells >5 μm. Our results indicate that DON was a major source of nitrogen to phytoplankton, particularly in the southern part of the Gulf.     

Statistische Untersuchungen zur Meteorotropie der fulminanten Lungenembolie

Zusammenfassung Die fulminante Lungenembolie (252 sorgfältig geprüfte Fälle der Jahre 1929 bis 1940 aus dem Sektionsgut des Pathologischen Instituts der Universität Köln) zeigt in Köln keine Beziehung zum Durchzug meteorologischer Fronten. Dagegen ist in dem Jahr des Sonnenfleckenmaximums 1937 eine zwar schwache, aber statistisch gesicherte Beziehung zu den durch die erdmagnetischen Charakterzahlen beschriebenen solaren Störungen vorhanden. Dieser Zusammenhang wurde durch die Bearbeitung des Sektionsmaterials von 13 westdeutschen pathologischen Instituten erhärtet (226 Embolien).

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Summary The fulminant lung embolism (252 carefully examined cases of the years 1929–1940 of the results of the Pathologic Institute of Cologne University) shows no correlation with the passage of meteorological fronts in Cologne. But in the year 1937, a year with a sun-spot maximum, there is a weak but statistically significant correlation with solar disturbances, described by the international magnetic character-figures. This connexion has been asserted furthermore by the analysis of the obduction material of 13 pathological institutes of western Germany (226 embolisms).

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Résumé L'embolie pulmonaire foudroyante (252 cas soigneusement contrôlés des années 1929 à 1940 et tirés du matériel d'autopsies de l'Institut pathologique de l'Université de Cologne) ne montrent à Cologne aucune relation avec les passages des fronts. Par contre l'année du maximum de taches solaires 1937, il existe une relation faible mais statistiquement prouvée avec les perturbations solaires traduites par les caractères magnétiques internationaux. Cette relation a été rendue plus vraisemblable par le dépouillement du matériel d'autopsies de 13 instituts pathologiques de l'Allemagne occidentale (226 embolies).

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Mit 5 Textabbildungen.     

Inputs of iron,manganese and aluminium to surface waters of the Northeast Atlantic Ocean and the European continental shelf

Dissolved Fe, Mn and Al concentrations (dFe, dMn and dAl hereafter) in surface waters and the water column of the Northeast Atlantic and the European continental shelf are reported. Following an episode of enhanced Saharan dust inputs over the Northeast Atlantic Ocean prior and during the cruise in March 1998, surface concentrations were enhanced up to 4 nmol L^− 1 dFe, 3 nmol L^− 1 dMn and 40 nmol L^− 1 dAl and returned to 0.6 nmol L^− 1 dFe, 0.5 nmol L^− 1 dMn and 10 nmol L^− 1 dAl towards the end of the cruise three weeks later. A simple steady state model (MADCOW, [Measures, C.I., Brown, E.T., 1996. Estimating dust input to the Atlantic Ocean using surface water aluminium concentrations. In: Guerzoni. S. and Chester. R. (Eds.), The impact of desert dust across the Mediterranean, Kluwer Academic Publishers, The Netherlands, pp. 301–311.]) was used which relies on surface ocean dAl as a proxy for atmospheric deposition of mineral dust. We estimated dust input at 1.8 g m^− 2 yr^− 1 (range 1.0–2.9 g m^− 2 yr^− 1) and fluxes of dFe, dMn and dAl were inferred. Mixed layer steady state residence times for dissolved metals were estimated at 1.3 yr for dFe (range 0.3–2.9 yr) and 1.9 yr for dMn (range 1.0–3.8 yr). The dFe residence time may have been overestimated and it is shown that 0.2–0.4 yr is probably more realistic. Using vertical dFe versus Apparent Oxygen Utilization (AOU) relationships as well as a biogeochemical two end member mixing model, regenerative Fe:C ratios were estimated respectively to be 20 ± 6 and 22 ± 5 μmol Fe:mol C. Combining the atmospheric flux of dFe to the upper water column with the latter Fe:C ratio, a ‘new iron’ supported primary productivity of only 15% (range 7%–56%) was deduced. This would imply that 85% (range 44–93%) of primary productivity could be supported by regenerated dFe. The open ocean surface data suggest that the continental shelf is probably not a major source of dissolved metals to the surface of the adjacent open ocean. Continental shelf concentrations of dMn, dFe, and to a lesser extent dAl, were well correlated with salinity and express mixing of a fresher continental end member with Atlantic Ocean water flowing onto the shelf. This means probably that diffusive benthic fluxes did not play a major role at the time of the cruise.     

Precise Positioning of Ocean Bottom Seismometer by Using Acoustic Transponder and CTD

We have obtained precise estimates of the position of Ocean Bottom Seismometers (OBS) on the sea bottom. Such estimates are usually uncertain due to their free falling deployment. This uncertainty is small enough, or is correctable, with OBS spacing of more than 10 km usually employed in crustal studies. But, for example, if the spacing is only 200 m for OBS reflection studies, estimates of the position with an accuracy of the order of 10 m or more is required.The determination was carried out with the slant range data, ship position data and a 1D acoustic velocity structure calculated from Conductivity–Temperature–Depth (CTD) data, if they are available. The slant range data were obtained by an acoustic transponder system designed for the sinker releasing of the OBS or travel time data of direct water wave arrivals by airgun shooting. The ship position data was obtained by a single GPS or DGPS. The method of calculation was similar to those used for earthquake hypocenter determination.The results indicate that the accuracy of determined OBS positions is enough for present OBS experiments, which becomes order of 1 m by using the DGPS and of less than 10 m by using the single GPS, if we measure the distance from several positions at the sea surface by using a transponder system which is not designed for the precise ranging. The geometry of calling positions is most important to determine the OBS position, even if we use the data with larger error, such as the direct water wave arrival data. The 1D acoustic velocity structure should be required for the correct depth of the OBS. Although it is rare that we use a CTD, even an empirical velocity structure works well.     

Validation of very high cloud droplet number concentrations in air masses transported thousands of kilometres over the ocean

The microstructure of orographic clouds related to the aerosol present was studied during the second Aerosol Characterisation Experiment (ACE‐2). Very high cloud droplet number concentrations (almost 3000 cm⁻³) were observed. These high concentrations occurred when clouds formed on a hill slope at Tenerife in polluted air masses originating in Europe that had transported the order of 1000 km over the Atlantic Ocean. The validity of the measured droplet number concentrations was investigated by comparing with measurements of the aerosol upstream of the cloud and cloud interstitial aerosol. Guided by distributions of the ratios between the measurements, three criteria of typically 30% in maximum deviation were applied to the measurements to test their validity. Agreement was found for 88% of the cases. The validated data set spans droplet number concentrations of 150–3000 cm⁻³. The updraught velocity during the cloud formation was estimated to 2.2 m s⁻¹ by model calculations, which is typical of cumuliform clouds. The results of the present study are discussed in relation to cloud droplet number concentrations previously reported in the literature. The importance of promoting the mechanistic understanding of the aerosol/cloud interaction and the use of validation procedures of cloud microphysical parameters is stressed in relation to the assessment of the indirect climatic effect of aerosols.     

MOSES, a promising concept for marine research

The objective of the EUROMAR project Mobile Station for Environmental Services (MOSES) is the optimization, promotion and harmonization of the design and use of containerized laboratories. The project is designed to study and implement innovative mobile laboratories having the same dimensions as standard shipping containers. They are used in specific environmental activities and designed to be installed on board a ship, an offshore platform or used on land as a multi-activity operative base.