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1

Do toxic cyanobacteria blooms pose a threat to the Baltic ecosystem?

Mazur-Marzec H., Pliński M.

Oceanologia

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2009

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No. 51 (3)

293-319

EN

Cyanobacteria, otherwise known as blue-green algae, are oxygenic, photosynthetic prokaryotes. They occur naturally in many fresh, marine and brackish waters worldwide and play an important role in global carbon and nitrogen cycles. In their long history, cyanobacteria have developed structures and mechanisms that enable them to survive and proliferate under different environmental conditions. In the Baltic Sea, the mass development of cyanobacteria is compounded by a high level of eutrophication. The dominant species in the Baltic, the filamentous Aphanizomenon flos-aquae and Nodularia spumigena, can fix dissolved atmospheric N2, as a result of which they can outcompete other phytoplankton organisms. Heterocystous, filamentous cyanobacteria also make a significant contribution to the internal nutrient loading in the Baltic. The blooms of N. spumigena are of particular concern, as this cyanobacterium produces nodularin (NOD), a hepatotoxic peptide. The concentration of the toxin in the sea is regulated mainly by dilution with uncontaminated water, photolysis, sorption to sediments and microbial degradation. The transfer of the toxin in the Baltic trophic chain through zooplankton, mussels, fish and birds has been reported, but biodilution rather than bioconcentration has been observed. Cyanobacterial blooms are thought to pose a serious threat to the ecosystem. Their harmful effects are related to the occurrence of a high biomass, oxygen depletion, a reduction in biodiversity, and the production of toxic metabolites.

2

Attempts to eliminate cyanobacterial blooms in Lake Łasińskie

Wiśniewski R.

Environment Protection Engineering

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2002

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Vol. 28, nr 1

15-25

EN

In the years 1998-2001, investigations of Łasińskie Małe and Zamkowe Lakes were conducted. The two lakes are shallow and very susceptible to degradation. Very high trophic level, high pollution level and recurring annual cyanobacterial blooms have caused that lakes have not been recreationally used since 1994. The aim of investigations was to work out the programme of reservoirs restoration. In order to test the methods, in June 1998 trials of cyanobacterial bloom inhibition in natural, isolated bath area were undertaken. Main measures were exposure of barley straw bales and addition of FeCl3. After one month considerable changes in the composition of phytoplankton were recorded. The drastic slump in the biomass of Aphanizomenon flos-aquae and domination of eucariotic algae were observed. Water transparency substantially increased. The measures were repeated and the method was modified and developed in the successive years. The main causes of temporarily worse effects were damage of isolating barriers in the bathing area and seasonal increase in BOD5 caused by influx of fine-grained organic suspension from unidentified source.

PL

W latach 1998-2001 prowadzono badania na Jeziorze Łasiński Małym i Jeziorze Zamkowym. Obydwa jeziora są płytkie i bardzo podatne na degradację. Powtarzające się corocznie intensywne zakwity sinicowe stanowią główną przyczynę ograniczonego wykorzystywania rekreacyjnego obydwu zbiorników. Celem badań było opracowanie programu rekultywacji zbiorników. Aby przetestować zaproponowane metody, w czerwcu 1998 r. Podjęto zabiegi zmierzające do ograniczenia zakwitu sinic w rejonie odizolowanego, naturalnego kąpieliska miejskiego. Sprowadzały się one głównie do zastosowania zarówno balotów słomy jęczmiennej, jak i chlorku żelaza. Po miesiącu odnotowano znaczne zmiany w składzie fitoplanktonu. Stwierdzono drastyczny spadek biomasy Aphanizomenon flos-aquae i dominujący udział glonów eukariotycznych. Istotnie wzrosła przezroczystość wody. Prace w rejonie kąpieliska powtarzano w następnych latach, modyfikując i wzbogacając metodę. Powodem gorszych okresowo efektów, zwłaszcza w 2001 r., było rozszczelnienie osłony izolującej kąpielisko i wzrost BZT5 spowodowany dopływami drobnej zawiesiny organicznej z niezidentyfikowanego źródła.

3

The response of Aphanizomenon flos-aquae (l.) ralfs to changes of environmental conditions

Burchardt L.

Oceanological Studies

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1998

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Vol. 27, No. 1

9-14

EN

The comparison of data on the concentration of specimens in populations of Aphanizomenon flos-aquae (L.) Ralfs in habbiting various types of trophic lakes (Pańczakowa and Szyszka 1983/84, Burchardt 1987, Agnostidis et al. 1988, Jeska 1997) revealed the relationship between water transparency and density of this taxon in the vertical profile of hyper-, meso-, and oligotrophic lakes.