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Chemometric exploration of sea water chemical component data sets with missing elements

Smoliński A., Falkowska L., Pryputniewicz D.

Oceanological and Hydrobiological Studies

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2008

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Vol. 37, No.3

49-62

EN

The results of the application of chemometric methods, such as principal component analysis (PCA) and its generalization for N-way data, the Tucker3 model, for the analysis of an environmental data set are presented. The analyzed data consists of concentration values of chemical compounds of organic matter, and their transformed products, in a short-term study of a sea water column measured at the Gdańsk Deep (.[fi]= 55°1’N, [lambda] = 19°10’E). The main goal of this paper is to present improved approaches for exploration of data sets with missing elements, based on the expectation-maximization (EM) algorithm. The most common methods for dealing with missing data, generally consisting of setting the missing elements to zero or to mean values of the measured data, are often unacceptable as they destroy data correlations or influence interpretation of relationships between objects and variables. The EM algorithm may be built into different computational procedures used for exploratory analysis (i.e. EM/PCA or EM/TUCKER3).

2

Chosen anions and cations in the precipitation over the coastal zone of the Gulf of Gdańsk

Siudek P., Falkowska L., Lewandowska A., Pryputniewicz D., Bełdowska M., Gic P.

Oceanological and Hydrobiological Studies

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2006

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Vol. 35, No.1

39-53

EN

The study of the chemical composition of precipitation was carried out from November 2002 till October 2003, in the urbanized area of the Gulf of Gdańsk. About 88% of the collected samples showed acid value, and the average pH was 5.14. The highest acid values were found in summer when sulfates were the dominant ions. The highest concentrations of nitrates were noted between autumn and spring, and the precipitation pH was less acidic than in summer. The coastal station at the Gulf of Gdańsk was characterized by more effective neutralization of precipitation in the heating season as compared to the other urbanized areas. It was found that the neutralization process in the coastal zone was much more intense due to the sea salt particle presence in aerosols rather than in gaseous ammonia. The most intensive neutralization of precipitation was observed between late autumn and spring. In May, when offshore winds dominated, the values of neutralization coefficient (NF) for Na+ and NH_4+ were 1.3 and 0.2, respectively. It was evidenced that the specific combination of meteorological parameters (velocity and direction of wind, humidity and temperature of air) had a significant influence on the chemical composition of precipitation.

3

The impact of solar radiation on changes in chlorophyll a concentration in the sea surface microlayer in the southern Baltic

Falkowska L., Pryputniewicz D., Magulski R., Dunajska D., Sikorowicz G., Kowacz M.

Oceanological and Hydrobiological Studies

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2005

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Vol. 34, No.3

109--123

EN

The potential effect of an increase in ultraviolet radiation on organic matter in the sea surface microlayer and subsurface bulk seawater was evaluated in spring during three sampling periods in 1997, 1998, and 2000. The phytoplankton concentration is high in the water of the southern Baltic during this period. The results of temporal changes in chlorophyll a, phaeopigments, and oxygen concentrations were taken into account. An inhibitory effect (expressed as a decline in chlorophyll a concentrations) on biological processes in the sea surface microlayer as well as in the subsurface layer occurred around noon and in the early afternoon. High levels of ultraviolet radiation intensified chlorophyll a reduction. The measurements conducted in the microlayer and the subsurface layer indicated the possibility of photodamage to phytoplankton under natural conditions when there is an excessive increase of UV-B radiation in comparison to PAR. A significant increase in the phaeophytin a concentration and a decrease in the chlorophyll a concentration was observed at noon when the UV-B/PAR ratio was high.

4

Stratification of particulate organic carbon and nitrogen in the Gdańsk Deep (southern Baltic Sea)

Burska D., Pryputniewicz D., Falkowska L.

Oceanologia

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2005

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No. 47 (2)

201-217

EN

Particulate organic carbon (POC) and nitrogen (PON) concentrations and fluxes were measured during an experiment in the Gdańsk Deep in late spring (30.05.-06.06.2001). The vertical POC and PON concentration profiles were characterised by the highest values in the euphotic layer, a gradual decrease with depth, and an increase below the halocline. The hydrophysical conditions had a decisive impact on POC and PON fluxes in the water column. Preferential removal of nitrogen from suspended mater was observed in the entire water column (maximum - in the vicinity of thermocline). There were also differences in the diurnal effectiveness of nitrogen removal as compared to carbon removal. The removal rate was highest at night.

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Diurnal variations in nitrogen, phosphorus and iron compounds in the southern Baltic Sea

Sikorowicz G., Falkowska L., Burska D., Dunajska D., Pryputniewicz D., Magulski R., Lewandowska A.

Oceanologia

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2005

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No. 47 (2)

243-263

EN

In order to assess their short-term variability, nutrient concentrations were measured at standard depths at 2 h intervals in the deepest region of the Gdańsk Deep during the first ten days of June 2001. The mean concentrations of nutrients in the euphotic zone were: NN (NO_2-, NO_3-, NH_4+) - 1.93 žmol dm^-3, PO_4^3- - 0.12 žmol dm^-3 and Fetot - 0.11 žmol dm^-3. During daylight hours, when the rate of assimilation was fastest, concentrations of nitrogen, phosphorus and iron compounds were very low. The phosphate concentration fell to a minimum (0.03 žmol dm^-3) between 04:00 and 10:00 hrs, while total iron dropped to 0.01 žmol dm^-3 between 10:00 and 16:00 hrs. Both levels were below the limiting values for phosphorus and iron. At night, concentrations of NO_3- and PO_4^3- rose by 25%, those of NH_4+ and Fetot by 35%. The mean molar ratios of N_N:PO_4^3- and Fetot:PO_4^3- in the surface layer were subject to significant daily fluctuations. The molar N_N:PO_4^3- ratio was higher than the optimum value established for the Baltic Sea. Below the halocline, the concentrations of dissolved iron and phosphorus rose as a result of diffusion from sediments in response to changing redox conditions.

6

Short-term fluctuations of chlorophyll α fluorescence versus diurnal variations of solar radiation in the surface water of the Gdańsk Basin

Magulski R., Falkowska L., Dunajska D., Pryputniewicz D., Sikorowicz G.

Oceanological and Hydrobiological Studies

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2004

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Vol. 33, No. 3

57--68

EN

Measurements of chlorophyll α fluorescence accompanied by solar radiation measurements were carried out during two spring cruises in the region of the Gdańsk Basin. Chlorophyll α fluorescence, similarly to that of chlorophyll a concentration in the seawater, showed considerable diurnal variability. The measurements provided statistically significant negative correlation coefficients that indicated that chlorophyll α fluorescence is inhibited as solar PAR and UV radiation intensity increases. The approximate range of radiation intensity that corresponded to a clearly marked decline in chlorophyll α fluorescence and chlorophyll α concentration was determined. It was revealed that the decline in chlorophyll a concentration in the surface water layer resulted from the photodegradation of chlorophyll α as well as phytoplankton grazing. In both cases, the resulting observation was an increase of pheophytine a concentration. The vertical migration of phytoplankton was identified as an additional process induced by high radiation levels.

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Adenosine triphosphate in the marine boundary layer in the southern Baltic Sea

Pryputniewicz D., Falkowska L., Burska D.

Oceanologia

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2002

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No. 44 (4)

461-473

EN

Changes in adenosine triphosphate (ATP) concentration were measured in the offshore and coastal waters of the Gdansk Basin in spring. As regards the vertical distribution, it was found that high ATP concentrations occurred mainly in the euphotic layer (above the thermocline) and near the bottom (below the halocline). The high concentrations of ATP in the euphotic layer resulted from primary and secondary production, while the other maximum was due to the presence of bacteria actively degrading organic matter. Changes in ATP concentration in the euphotic layer were closely correlated with the phase of the day. An increase in ATP concentrations in the surface microlayer was observed in the evening and at night, probably as a result of heterotroph proliferation. During daylight, ATP production was inhibited by increasing radiation, hence its concentrations in the sea surface microlayer were considerably lower. Strong winds exerted a significant influence on ATP concentrations in the surface microlayer and in the subsurface water. Windstress depressed ATP concentrations. The biomass of living microorganisms in the microlayer was comparable with the microbiomass beneath the halocline.