ISSN:
1573-5117
Keywords:
eutrophication
;
trophic relations
;
filamentouscyanobacteria
;
ciliates
;
zooplankton
;
bacteria
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Alte Donau nowadays is an eutrophic urban lake within the cityofVienna. Increasing nutrient concentrations and massive bloomsofcyanobacteria mainly caused by Limnothrix redekei VanGoorand Cylindrospermopsis raciborskii (Wołsz.) SeenayyaetSubba Raju were recently registered. As a consequence Secchidepthwas significantly reduced especially during the summer season(minimum: 0.25 m). An investigation including water chemistry,phytoplankton, macrophytes, and sediment was initiated in 1993andextended to metazooplankton, ciliates and bacteria in 1994.Thefirst half of the year 1994 was characterised by relativelyclearwater and a high diversity of the phytoplankton compositiondue toflushing of the lake with water of better quality by the endof1993. Ciliates and metazooplankton held about 10% of thetotalbiomass of all the investigated trophic levels. The vanishingofthe remaining macrophytes enlarged the nutrient supply duringsummer 1994 and favoured the development of cyanobacteria. Thehighwater temperatures which excluded certain zooplankton species,andthe inedibility of the filaments further increased thedominance ofcyanobacteria. In November, when the algal bloom finallyceased,the highest bacterial numbers of the investigation periodoccurred.Thereafter, other algal groups, bacteria and metazooplanktongainedmore importance.Interactions are possible because of close overlap in spaceandtime due to the turbulent mixed conditions of the water bodyandthe change from the macrophyte dominated to the algaldominatedstable state. Planned restoration measures must aim tore-establishthe previous macrophyte dominated clear-waterstage.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1017098131238
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