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Expressions of shallow gas in the Gdansk Basin

Majewski P., Klusek Z.

Zeszyty Naukowe Akademii Marynarki Wojennej

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2011

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R. 52 nr 4 (187)

61-71

EN

In the paper, a short introduction to present-day acoustic and seismoacoustic inventory of shallow gas occurrence and its expression in the Gdansk Basin is presented. Signals of various frequencies and beamforming were employed during surveys conducted from the board of r/v ‘Oceania’. Such a set of diverse acoustic signals was exploited in order to obtain a better recognition of different forms of shallow gas existence in the area. The utilized frequency started from about 1 kHz once a boomer was used in sounding, up to 40–60 kHz in the case a chirp echosounder. At acoustic transects classical echosounders working at 12 and 38 kHz were applied. Some details of the qualitative analysis and the technicalities of the algorithms are given. Variety of examples of echo images obtained in different frequency bands, associated with different forms of gas occurrence is presented.

PL

W artykule dokonano wprowadzenia do współcześnie prowadzonych metodami akustycznymi detekcji i rozpoznawania różnorodności postaci występowania gazu w osadach dennych Basenu Gdańskiego. W celach lepszego rozpoznania form występowania gazu w górnej warstwie osadów w rejsach badawczych r/v „Oceanii” zastosowano sondowanie dna za pomocą sygnałów akustycznych zróżnicowanych pod względem częstotliwości oraz ukształtowania wiązki. Zakres częstotliwości sygnałów akustycznych wykorzystanych w sondowaniu dna zawierał się w granicach od około 1 kHz (boomer) poprzez 12/38 kHz do szerokopasmowych w granicach 40–80 kHz. Na wielu transektach akustycznych do obrazowania ukształtowania dna i warstwy naddanej zastosowano również sonar boczny i echosondę wielowiązkową. W artykule przedstawiono niektóre elementy analizy jakościowej oraz przybliżono szczegóły techniczne algorytmów pozwalających na identyfikację gazu w osadach. Zaprezentowano także liczne przykłady obrazów echa otrzymane dla sygnałów akustycznych w różnych pasmach częstotliwości, powiązanych z występowaniem gazu w osadach.

2

Communities of heterotrophic protists (protozoa) in the near-bottom zone of the Gdańsk Basin

Rychert K.

Oceanological and Hydrobiological Studies

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2011

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Vol. 40, No.3

68-73

EN

Biomass and generic diversity of heterotrophic protists (protozoa) were studied in the near-bottom zone at five stations located in the inner Gulf of Gdańsk and in offshore waters during June 2002. The highest protozoan biomass was observed in the inner Gulf of Gdańsk and close to the mouth of the Vistula River. Protozoan biomass decreased offshore. In well-oxygenated waters heterotrophic flagellates constituted 39-51%, of the protozoan biomass, ciliates constituted 18-25%, and heterotrophic dinoflagellates 29-39% of the protozoan biomass. These findings confirmed previous studies that showed that a high abundance of heterotrophic dinoflagellates is a distinct feature of the Gulf of Gdańsk. At one station located in the Gdańsk Deep, where the near-bottom zone was anoxic, the contribution of heterotrophic flagellates decreased to 18% and ciliates’ share increased to 82% of the protozoan biomass. No dinoflagellates were observed in the anoxic zone.

3

Porewater nutrients (phosphate, ammonia and silicate) in the eastern part of the southern Baltic Sea

Graca B., Witek Z., Burska D., Białkowska I., Pawelec A., Bolałek J.

Oceanological and Hydrobiological Studies

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2006

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Vol. 35, No.3

237-256

EN

In the present work, results of studies concerning phosphate, ammonia and silicate in porewaters of the eastern part of the southern Baltic sediments are presented. A strong interaction was observed between the investigated compound concentrations and the sea bottom type, defined by means of the sediment water content (W) and loss on ignition (LOI) values. High concentrations and an exponential increase in concentration downwards in the sediment depth profile was observed in regions named here transport/accumulation bottom (LOI?4%, W?50%). Lower concentrations and irregular changes in concentration with depth occurred in regions designated as erosion bottom type (LOI<4, W<50%). Only in areas under strong anthropogenic influence (Vistula river mouth, the vicinity of Gdynia harbour), in the erosion type bottom concentration periodically raised to the level observed in the transport/accumulation bottom areas. The mass of nutrients accumulated in porewaters in the 10 cm thick layer of surface sediments of the Gulf of Gdańsk in September 2000 was estimated to be 910 t P-PO43-, 2780 t N-NH4+ and 5430 t DSi, while in March/April of 2001 estimated values equalled 908 t P-PO43-, 1860 t N-NH4+ and 3080 t DSi. In the erosion bottom areas, approximately 12 t, 210 t and 650 t of P-PO43-, N-NH4+ and DSi, respectively, were flushed out of the sediments during the intensive autumn-winter mixing.

4

Nanoflagellates in the Gdańsk Basin: coexistence between forms belonging to different trophic types

Rychert K.

Oceanologia

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2006

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No. 48 (2)

323-330

EN

Nanoflagellates are important bacterivores, but their role is often underestimated because forms capable of phagotrophy and containing chlorophyll (mixotrophs) are excluded from analyses. Research conducted in the coastal zone of the Gdańsk Basin (Baltic Sea) revealed seasonal changes in the relationship between the biomasses of small (1-8 žm) nanoflagellates with (NFChl+) and without chlorophyll (NFChl-). Three distinct patterns were distinguished: (i) spring, when the biomass of NFChl+ was lower than that of NFChl-, (ii) summer and autumn, when NFChl+ were dominant (about 90%), and (iii) late autumn and winter, when the prevalence of NFChl+ was lower (71-79\%). Additional studies showed the existence of spatial differences in the composition of the nanoflagellate community. These spatial differences were not shaped by freshwater input. The possible importance of mixotrophic forms in the Gdańsk Basin is discussed.

5

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.