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Evidence of cultural eutrophication of the Gulf of Gdańsk based on diatom analysis

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Pędziński J. , Witak M.

Oceanological and Hydrobiological Studies

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2019

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tom Vol. 48, No. 3

247--261

EN

The objective of this study was to reconstruct the environmental changes in the Gulf of Gdańsk in the last 200 years. Four subbottom sediment cores were analyzed with respect to diatom flora and anthropogenic effects. The so-called “anthropogenic assemblage” – a result of cultural eutrophication – was observed in the surface sediments. Changes in the species composition may have been caused by the increased use of fertilizers, nitrogen loads and increasing organic matter concentration. Three phases (A, B and C) were distinguished based on the floristic spectrum, which clearly indicates trophic changes in the study area.

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Biodiversity of the benthic diatom flora in the coastal zone of the Gulf of Gdańsk: a case study of the Gdynia–Sopot transect

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Hetko D. , Witak M. , Oliwa S.

Oceanological and Hydrobiological Studies

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2022

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tom Vol. 51, No. 2

224-238

EN

The objective of this study is to determine microhabitat preferences of benthic species occurring in epilithic (living on stones), epipsammic (growing on sand), epipelic (growing on mud) and epiphytic (living on seagrass) assemblages of the shallows of the Gulf of Gdańsk (southern Baltic Sea). The study material was collected from 19 sites along the Gdynia-Sopot coastal zone, including the Port of Gdynia. Most of the identified diatom taxa were observed in two or three microhabitats. However, diatom species living in only one type of microhabitat and those occurring in all analyzed microhabitats were also recorded. Autecological preferences of the identified diatoms indicate organic pollution of the coastal zone of Gdynia and Sopot. However, a higher frequency of α-mesosaprobionts and polysaprobionts indicates an increase in organic pollution in the Port of Gdynia and Marina Sopot, which is associated with intense port activity and large tourist traffic.

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Biodiversity of benthic diatom flora in the coastal zone of Puck Bay (southern Baltic Sea) : a case study of the Hel Peninsula

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Witak M. , Pędziński J. , Oliwa S. , Hetko D.

Oceanological and Hydrobiological Studies

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2020

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tom Vol. 49, No. 3

304--318

EN

The paper presents the results of the analysis of diatoms from surface sediments (stones, sands) and macroflora (seagrass, macroalgae) collected at 16 sampling sites located along the inner coastal zone of Puck Bay (southern Baltic Sea) along the Hel Peninsula. The main diatom species of epilithon, epipsammon and epiphyton were characterized with respect to their autecological preferences (habitat, salinity, trophic status, saprobity). Three groups of diatoms were distinguished with respect to the type of substrate based on the results of benthic flora analysis: diatoms (i) of one type of substrate, (ii) of two types and (iii) those occurring on all types of substrates. Moreover, the distribution of benthic diatom communities indicates ecological differences in the study area. Marine and brackish-water species were observed in large numbers in the coastal zone of the Outer Puck Bay, whereas freshwater flora occurred with a higher frequency in the coastal zone of the Puck Lagoon. The content of polysaprobionts and of α-mesosaprobionts indicates that the region of the Hel Tip is highly eutrophicated and very polluted. The coast in the vicinity of Kuznica is less polluted, whereas the best environmental conditions are found in the Jurata–Jastarnia region, as evidenced by the frequency of diatoms that are β-mesosaprobionts.

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Canthaxanthin in recent sediments as an indicator of heterocystous cyanobacteria in coastal waters

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Krajewska M. , Szymczak-Żyła M. , Kobos J. , Witak M. , Kowalewska G.

Oceanologia

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2019

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tom No. 61 (1)

78--88

EN

The mean share of heterocystous cyanobacteria in total chlorophyll-a production in coastal waters, based on cyanobacterial marker carotenoid and chloropigments preserved in recent sediments (0-5 cm, ca 30 years), has been studied in the Gulf of Gdańsk (southern Baltic) and for comparison in the Oslofjord/Drammensfjord (southern Norway). First of all, Baltic cyanobacteria, both from laboratory cultures and field samples, were analysed to select marker heterocysteous cyanobacteria carotenoids for sediments. The pigment relation to diatom percentages of different salinity preferences has been tested, to confirm origin of cyanobacteria. The results indicate that canthaxanthin is the best marker of heterocystous cyanobacteria in the southern Baltic Sea. These filamentous cyanobacteria inflow to the Gulf of Gdańsk from the open sea and their abundance has increased in the last thirty years, in comparison with previous time. In that period they made up ca 4.6% of the total chlorophyll-a production in the Gulf of Gdańsk. The estimate for Oslofjord, at the same assumptions, suggests that heterocystous cyanobacteria occurred there also (up to 5.8% of the total chlorophyll-a production), were of marine origin, but their abundance has decreased during the last thirty years. Such an estimate may be used in environmental modelling and can be applied to other coastal areas, once the marker pigments of the main cyanobacteria species have been identified, and the percentage of total chlorophyll-a produced in a basin, preserved in sediments, has been determined for such area.