Oceanologia No. 43 (2) / 01


Invited paper



Invited paper

Attenuation of ultraviolet irradiance in North European coastal waters
Oceanologia 2001, 43 (2), 139-168

Eyvind Aas1, Niels K. Højerslev2
1Department of Geophysics, University of Oslo, POB 1022 Blindern, N-0315 Oslo, Norway; eyvind.aas@geofysikk.uio.no
2Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark; nkh@gfy.ku.dk

Keywords: UV irradiance, attenuation, coastal waters, fjords, straits, optical properties

Manuscript received 20 April 2001, accepted 27 April 2001.
A total of 439 measurements of downward ultraviolet irradiance in North European coastal waters have been analysed, half of which have been taken from other authors. The depths Z(10%) where the irradiance is reduced to 10% of its surface value vary by one order of magnitude in the open coastal waters, both at wavelengths of 310 nm (0.3–10.4 m) and 380 nm (1.2–13.0 m). In the fjords and estuaries the depth ranges are reduced to 0.08–6.1 m at 310 nm and 0.18–7.7 m at 380 nm. Mixing with saline ocean waters can increase these light penetration depths to more than 10 m, while river water can reduce them to a few centimetres.
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Transformation of the Vistula Lagoon onto a canonical domain
Oceanologia 2001, 43 (2), 169-200

Włodzimierz J. Prosnak, Paweł P. Cześnik
Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, PL-81-712 Sopot, Poland; czesiek@iopan.gda.pl

Keywords: shoreline, transformation of coordinates, conformal mapping, holomorphic function, domain of solution, circular domain, computational domain, boundary conditions, inversion, Schwarz-Christoffel function, inverse of a function

Manuscript received 27 February 2001, reviewed 17 April 2001, accepted 26 April 2001.
The paper deals with the conformal mapping of finite, plane, simply connected domains, representing oceans, lakes, estuaries, bays, lagoons, and other natural water bodies of this kind. As a rule, they are bounded by geometrically complex shorelines. The partial differential problems investigated in Oceanology and posed in such domains have turned out to be difficult to solve for at least three reasons. They follow on from the mathematical properties of the differential equations governing such problems, from the just-mentioned geometrical complexity of the domains of solution, and from the sensitivity of the solutions to boundary conditions.
In view of the last reason the contours admitted as boundaries of the domains of the solution ought to be as close to the real shorelines as possible. The obviously inaccurate approximation of the shorelines by "staircases", which appears rather often (cf. Catewicz & Jankowski 1983, Lin & Chandler-Wilde 1996) as a consequence of applying finite difference methods to the solution of the partial differential problems, raises serious doubts from the point of view of Numerical Fluid Mechanics.
It is recalled in the paper that such inaccuracies are not unavoidable: that complicated plane domains can be transformed accurately by means of properly applied conformal mapping onto regular, canonical domains - in particular, onto discs or squares. Such a transformation is demonstrated on the rather difficult example of the Vistula Lagoon. The transformation begins with the decomposition of the domain into five plane subdomains, each one of which is eventually transformed onto a disc. Every such result is arrived at quite independently of the remaining subdomains, by means of a set of properly selected consecutive mappings. Hence, the final canonical domain consists in this case of a system of five discs which, however, within the framework of this differential problem, have to be treated as interconnected. The interconnections involve images of four segments of straight lines, separating the original subdomains.
The transformations and the resulting canonical domain presented in the paper are intended to be applied to the solution of certain hydrodynamical problems concerning the Vistula Lagoon, which will be published elsewhere.
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12-hour cycle of matter transformation in the sea surface microlayer in the offshore waters of the Gdańsk Basin (Baltic Sea) during spring
Oceanologia 2001, 43 (2), 201-222

Lucyna Falkowska
Institute of Oceanography, University of Gdańsk, al. Marszałka Piłsudskiego 46, PL-81-378, Gdynia, Poland; lucy@ocean.univ.gda.pl

Keywords: microlayer, nutrients, neuston stratification, diel cycle of matter transformation

Manuscript received 21 March 2001, reviewed 26 April 2001, accepted 9 May 2001.
Short-term measurements of nutrient and DOC concentrations and suspended matter (particles, chlorophyll a, phaeophytin, algae and ATP concentrations) carried out in seawater layers of varying thickness (10, 90, 250 µm and the underwater layer - 15 cm depth) in spring form the basis for a discussion of the diurnal fluctuations of nutrient and suspended organic matter concentrations. Quantitative and qualitative differences in the composition of neuston species were recorded in selected sub-layers of the chemically stratified sea surface microlayer. The non-linear regression equation was applied in a mathematical model of the diurnal fluctuations of nutrients and organic matter. Two maxima and two minima were found in the diurnal cycle of nutrient concentrations and organic suspensions in sub-layers of different thickness selected from the sea surface. The first maximum, expressed by the proliferation of phytoneuston, lasted from the very early morning till mid-morning. The second maximum occurred in the afternoon. The chlorophyll a concentration, and ATP and neuston abundance declined markedly around noon, when the biologically-damaging radiation dose increased, compelling the downward migration of organisms. At the same time, the photo-oxidation of dissolved organic matter intensified and the concentrations of inorganic forms of nitrogen and phosphorus rose. A shift (up to 2 h) between the maximum and minimum neuston concentration in these sea surface layers was indicative of phototaxis occurring within the entire surface microlayer and in the underwater layer. After sunset the decline in phytoneuston abundance could be related to zooplankton grazing as well as to respiratory breakdown.
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Static and dynamic properties of surfactant films on natural waters
Oceanologia 2001, 43 (2), 223-246

Stanisław J. Pogorzelski, Anna D. Kogut
Institute of Experimental Physics, University of Gdańsk, Wita Stwosza 57, PL-80-952 Gdańsk, Poland; fizsp@univ.gda.pl

Keywords: marine films, isotherms, virial equation, adsorption kinetics, relaxation processes, viscoelasticity

Manuscript received 6 February 2001, reviewed 17 April 2001, accepted 30 April 2001.
The paper contains the results of natural surface film surface pressure - area experiments carried out in inland waters and shallow offshore regions of the Baltic and Mediterranean Seas during 1990-99 under calm water conditions using the Langmuir trough - Wilhelmy filter paper plate system, which "cuts out" an undisturbed film-covered sea area without any initial physico-chemical sample processing. The limiting specific area Alim (268–3157 Å2/molecule-1) and mean molecular mass (0.65-9.7 kDa) of microlayer surfactants were determined from the 2D virial equation of state applied to the isotherms. Film structure signatures were derived from πA isotherm hysteresis and application of the 2D polymer scaling theory. The stress-relaxation measurements revealed a two-step relaxation process at the interface with characteristic times τ1 (1.1–2.8) and τ2 (5.6-25.6) seconds suggesting the presence of diffusion-controlled and structural organization relaxation phenomena. The results demonstrate that natural films are a complex mixture of biomolecules covering a wide range of solubilities, surface activity and molecular mass with an apparent structural organization exhibiting a spatial and temporal variability.
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Monosaccharides in the water of the Gulf of Gdańsk
Oceanologia 2001, 43 (2), 247-256

Waldemar Grzybowski, Agnieszka Maksymiuk
Institute of Oceanography, University of Gdańsk, al. Marszałka Piłsudskiego 46, PL-81-378, Gdynia, Poland; grzyb@panda.bg.univ.gda.pl

Keywords: monosaccharides, Baltic Sea, seawater

Manuscript received 20 February 2001, reviewed 23 April 2001, accepted 9 May 2001.
The concentration of monosaccharides in samples collected in the Gulf of Gdańsk area was determined in water filtered through ~0.8 µm pore size filters. Seawater concentrations ranged from about 0.2 to 1.1 mg C dm-3, the highest values being detected at the mouth of the river Vistula. Seasonality was detectable in the data distribution; the majority of autumn values lay within the 0.2–0.4 range while concentrations in the spring samples were higher and the values more widely scattered. Measurements of monosaccharide concentrations at selected points during the whole observation period showed that values increased from spring to autumn as much as 5-fold. Concomitant analyses in Vistula river water yielded concentrations from 0.4 to 1.2 mg C dm-3. These latter values were all higher than those recorded in seawater in the corresponding months.
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The effect of humic substances isolated from a variety of marine and lacustrine environments on different microorganisms
Oceanologia 2001, 43 (2), 257-261

Gotfryd Kupryszewski1, Janusz Pempkowiak2, Anna Kędzia3
1Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, PL-80-952 Gdańsk, Poland; gotfryd@chemik.chem.univ.gda.pl
2Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, PL-81-712 Sopot, Poland
3Department of Oral Microbiology, Medical University of Gdańsk, Smoluchowskiego 14, PL-80-214 Gdańsk, Poland

Keywords: humic substances, antimicrobial acivity

Manuscript received 22 September 2000, reviewed 28 February 2001, accepted 30 March 2001.
The antimicrobial activity of twelve preparations of humic substances isolated from sea water, marine bottom sediments and lake water was examined. Humic substances from marine bottom sediment samples were fractionated into humic and/or fulvic acids. The susceptibility of 11 strains of anaerobic, 8 strains of aerobic bacteria and 2 strains of yeast-like fungi to preparations of humic substances, humic and/or fulvic acids was determined employing the plate dilution technique in Brucella agar (anaerobic bacteria), Mueller-Hinton agar (aerobic bacteria) and Sabouraud agar (yeast-like fungi). Concentrations from 150 to 600 µg ml-1 of the preparations examined inhibited the growth of numerous microorganisms (Table). The results obtained seem to indicate that humic substances are involved in the self-purification of sea and lake waters.
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