Oceanologia No. 43 (3) / 01

Contents

Papers

Communications

Papers

A simple formula for the net long-wave radiation flux in the southern Baltic Sea
Oceanologia 2001, 43 (3), 265-277

Tomasz Zapadka2, Sławomir B. Woźniak1, Bogdan Woźniak1,2
1Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, PL-81-712 Sopot, Poland; woznjr@iopan.gda.pl
2Institute of Physics, Pomeranian Pedagogical Academy, Arciszewskiego 22 B, PL-76-200 Slupsk, Poland; zapad@wsp.slupsk.pl

Keywords: long-wave radiation flux, net infra-red radiation, energy exchange between the sea and the atmosphere

Manuscript received 17 May 2001, reviewed 11 June 2001, accepted 27 June 2001.
Abstract
This paper discusses problems of estimating the net long-wave radiation flux at the sea surface on the basis of easily measurable meteorological quantities (air and sea surface temperatures, near-surface water vapour pressure, cloudiness). Empirical data and existing formulae are compared. Additionally, an improved formula for the southern Baltic region is introduced, with a systematic error of less than 1 W -2 and a statistical error of less than 20 W -2.
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Circulation of groundwater due to wave set-up on a permeable beach
Oceanologia 2001, 43 (3), 279-290

Stanisław R. Massel
Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, PL-81-712 Sopot, Poland; smas@iopan.gda.pl

Keywords: surface waves, sandy beaches, filtration, mathematical modelling

Manuscript received 18 July 2001, reviewed 2 August 2001, accepted 7 August 2001.
Abstract
Sandy beaches are highly exploited but very dynamic and fragile environments. Driven by waves, the water flow through the beach body is able to transport oxygen, and hence help to maintain biological activity in the porous media. The paper presents a theoretical attempt to predict the groundwater circulation due to wave set-up. Two systems of circulations have been discovered, related to two different gradients of the set-up height. For the offshore gradient, the horizontal excess pressure gradient induces flow in the offshore direction. However, closer to the shore, the pressure gradient is reversed and the resulting flow moves shorewards.
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Measurement of phytoplankton photosynthesis rate using a pump-and-probe fluorometer
Oceanologia 2001, 43 (3), 291-313

Taras K. Antal2, Pavel S. Venediktov2, Dimitrii N. Matorin2, Miroslawa Ostrowska1, Bogdan Woźniak1, Andrei B. Rubin2
1Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, PL-81-712 Sopot, Poland; ostra@iopan.gda.pl
2Department of Biophysics, Faculty of Biology, Moscow State University, Moscow, 119899 Russia

Keywords: phytoplankton, primary production, plant luminescence, fluorometric method

Manuscript received 21 June 2001, reviewed 26 July 2001, accepted 1 August 2001.
Abstract
In this work we have studied the possibility of determining the rate of phytoplankton photosynthesis in situ using a submersible pump-and-probe fluorometer in water areas differing in their trophic level, as well as in climatic and hydrophysical characteristics. A biophysical model was used to describe the relationship between photosynthesis, underwater irradiance, and the intensity of phytoplankton fluorescence excited by an artificial light source. Fluorescence intensity was used as a measure of light absorption by phytoplankton and for assessing the efficiency of photochemical energy conversion at photosynthetic reaction centers. Parameters of the model that could not be measured experimentally were determined by calibrating fluorescence and irradiance data against the primary production measured in the Baltic Sea with the radioactive carbon method. It was shown that the standard deviation of these parameters in situ did not exceed 20%, and the use of their mean values to estimate the phytoplankton photosynthetic rate showed a good correlation between the calculated and measured data on primary production in the Baltic (r = 0.89), Norwegian (r = 0.77) and South China (r = 0.76) Seas.
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Influence of selected abiotic factors on the decomposition of chlorophylls
Oceanologia 2001, 43 (3), 315-328

Grażyna Kowalewska, Małgorzata Szymczak
Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, PL-81-712 Sopot, Poland; Kowalewska@iopan.gda.pl

Keywords: chlorophylls, blue-green algae, decomposition, abiotic factors

Manuscript received 10 November 2000, reviewed 21 December 2000, accepted 27 July 2001.
Abstract
The paper presents the results of experiments to determine the influence of selected physico-chemical factors - oxygen, visible light and temperature - on the decomposition of (1) chlorophylls a, b and c, chlorophyll a derivatives and beta-carotene in acetone solution, and (2) chlorophyll a and beta-carotene in axenic cultures of the blue-green algae Anabaena variabilis. The results indicate that both in acetone extracts and in blue-green algae cultures these pigments were most sensitive to light and oxygen; temperatures of up to 25oC had no marked influence on these compounds. Under anoxia in acetone solution, the stability towards light decreased in the order chlorophyll a, chlorophyll b, chlorophylls c. Chlorophyll a, moreover, was less stable than its derivatives - phaeophorbides, phaeophytins, pyrophaeophytins and steryl chlorins - but more stable than beta-carotene, in the last case also in the blue-green algae cultures. Decomposition of all the pigments proceeded mainly via the breakdown of the porphyrin macrocycle, since the decomposition products were not detected in the VIS range. On the basis of these experiments one can state that while light and oxygen may have a decisive direct influence on the distribution of chlorophylls and beta-carotene in sediments, in the natural environment, temperatures of up to 25oC may have very little immediate effect.
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Stability of cyanotoxins, microcystin-LR, microcystin-RR and nodularin in seawater and BG-11 medium of different salinity
Oceanologia 2001, 43 (3), 329-339

Hanna Mazur, Marcin Pliński
Institute of Oceanography, University of Gdańsk, al. Marszałka Piłsudskiego 46, PL-81-378, Gdynia, Poland; hmm@sat.ocean.univ.gda.pl

Keywords: cyanobacteria, hepatotoxins, microcystin, nodularin

Manuscript received 15 March 2001, reviewed 7 June 2001, accepted 11 July 2001.
Abstract
Microcystins and nodularin are potent hepatotoxins produced by fresh and seawater cyanobacteria. The persistence of three hepatotoxins - microcystin-LR, microcystin-RR and nodularin - was investigated in sterile BG-11 medium of different salinity and in water collected from the Gulf of Gdańsk. After 21 days of incubation at 17 ± 1oC and constant illumination of about 40 µmol photon m-2 s-1 the concentration of toxins decreased by about 30-37%. No significant changes in toxin concentration in the BG-11 media of different salinity were observed. When toxins were incubated in non-sterile seawater, their concentrations decreased markedly. It is likely that some strains of bacteria are responsible for the breakdown of the toxins. Nodularin turned out to be more resistant to biodegradation than the two microcystins. The influence of certain components of cyanobacteria cells on the accelerated rate of toxin degradation was also considered.
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Estimation of zooplankton mortality caused by an Arctic glacier outflow
Oceanologia 2001, 43 (3), 341-351

Marek J. Zajączkowski, Joanna Legeżyńska
Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, PL-81-712 Sopot, Poland; trapper@iopan.gda.pl"

Keywords: Arctic, plankton mortality, glaciers

Manuscript received 2 July 2001, reviewed 18 July 2001, accepted 25 July 2001.
Abstract
The outflow of freshwater from underwater channels in the Kongsbreen tidal glacier in Kongsfjorden, Svalbard, 79oN, was measured as 138.8 m3 s-1 at the peak of the melting season. Experiments on local marine plankton mortality show that when exposed to salinities below 9 PSU, all copepods die within 15 minutes. We estimate that during 100 days of the melting season, as many as 85 tonnes wet weight (WW) of plankton is removed from the water column due to osmotic shock, which makes up 15% of the standing zooplankton biomass of the fjord. The dead zooplankton sinks after exposure to low salinities and is probably an important food source for scavenging benthic fauna in the fjord. This mechanism could be responsible for the high numbers of Onisimus caricus near the glacier front.
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Communications

Experimental study of the formation of steep waves and breakers
Oceanologia 2001, 43 (3), 353-363

Stanisław R. Massel1, Jarosław Tęgowski1, Maria Chomka1, Marcin Wichorowski1, Jerzy Dąbrowski1, Carl T. Stansberg2, Vibecke Moe2
1 Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, PL-81-712 Sopot, Poland; smas@iopan.gda.pl
2Norwegian Marine Technology Research Institute, P.O. Box 4125 Valentinlyst, N-7450 Trondheim, Norway;

Keywords: surface waves, wave breaking, mechanical wave generation, experimental studies

Manuscript received 23 July 2001, reviewed 30 July 2001, accepted 2 August 2001.
Abstract
Breaking waves (whitecaps) are one of the most important and least understood processes associated with the evolution of the surface gravity wave field in the open sea. This process is the principal means by which energy and momentum are transferred away from a developing sea. However, an estimation of the frequency of breaking waves or the fraction of sea surface covered by whitecaps and the amount of dissipated energy induced by breaking is very difficult to carry out under real sea conditions. A controlled experiment, funded by the European Commission under the Improving Human Potential Access Infrastructures programme, was carried out in the Ocean Basin Laboratory at MARINTEK, Trondheim (Norway). Simulation of random waves of the prescribed spectra by wave makers provided a very realistic pattern of the sea surface. The number of breaking waves was estimated by photographing the sea surface and recording the noise caused by the breaking waves. The experimental data will serve for calibration of the theoretical models of the sea surface fraction related to the whitecaps.
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Comparison of primary production and pelagic community respiration rates in the coastal zone of the Gulf of Gdańsk
Oceanologia 2001, 43 (3), 365-370

Joanna K. York1, 2, Zbigniew Witek1, *, Sylwia Labudda1, Stanisław Ochocki1
1Sea Fisheries Institute, H. Kollataja 1, PL-81-332, Gdynia, Poland;
*corresponding author; e-mail: zwitek@mir.gdynia.pl
2current address: Boston University Marine Program, Marine Biological Laboratory, Woods Hole, MA 02543, U.S.A

Keywords: primary production, respiration, oxygen, Baltic, coastal zone

Manuscript received 27 April 2001, reviewed 27 June 2001, accepted 24 July 2001.
Abstract
The organic matter production/respiration balance in the coastal water column was examined, both the primary production and community respiration being measured with the oxygen light-and-dark bottle method. Community respiration (CR) was always lower than the gross primary production (GPP) measured at a standard light intensity of 390 µm-2 s-1, which amounted, on average, to 30% of GPP. During most of the in situ sampling period, the coastal system (6-7 m depth) was found to be autotrophic, with depth-integrated GPP ranging from 6.7 mmoles O2 m-2 d-1 in December to 214.2 mmoles O2 m-2 d-1 in August, and CR ranging correspondingly from 6.0 to 177.7 mmoles O2 m-2 d-1. However, on some occasions heterotrophic conditions were recorded: depth-integrated GPP<CR. In summer (August) this was caused mainly by low water transparency, which repressed photosynthesis, while in winter (December) it was due to the short period of daylight.
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