Epiphytic diatoms of the Tisza River, Kisköre reservoir and some oxbows of the Tisza River after the cyanide and heavy metal pollution in 2000

The Tisza River is a large tributary of the Danube River. The largest reservoir of the river is the Kisköre reservoir, and there are furthermore a great number of oxbows in the vicinity of the river. In February and early spring 2000 serious amounts of cyanide and heavy metal pollution were spilled into the Tisza River. The Kisköre Reservoir of the Tisza was less polluted than the river itself. However, the four oxbows investigated were flooded by the Tisza River in April 2000. Epiphytic diatom samples were taken in February and October 2000 along the Tisza River, in November and December 2000 at the Kisköre Reservoir and in May and July 1996, October 2000 and June 2001 at the four Tisza oxbows. The aims of this study were to obtain preliminary data about the species composition of the attached diatoms of these waters, to evaluate the impact of the pollution on epiphytic diatoms and to evaluate the natural protection value of these waters. Epiphyton of the Tisza River was dominated by Achnanthidium minutissimum, Amphora pediculus, Cocconeis placentula, Diatoma moniliformis in February and by Achnanthidium minutissimum and several Nitzschia spp. in October. A number of teratological frustules were observed. In the Kisköre reservoir, Amphora pediculus, Cocconeis pediculus, C. placentula, Cyclotella meneghiniana, Gomphonema angustum, Nitzschia dissipata were dominant. In 1996 Staurosira, Staurosirella and Navicula species dominated in the oxbows, whereas in 2000 Aulacoseira distans, Achanthidium minutissimum and Nitzschia spp. became dominant. Based on results from the literature, we are of the opinion that the characteristic Achnanthidium minutissimum - Nitzschia spp. dominance of the Tisza River and the oxbows is partly due to the heavy metal pollution. A number of endangered species, two new elements for the Hungarian diatom flora - Navicula austrocollegarum and Navicula streckerae - and two probably invasive species, Diadesmis confervacea and Didymosphenia geminata were found

Sampling strategies for phytoplankton investigations in a large river (River Danube, Hungary)

The results of phytoplankton studies ont he Hungarian stretch of the Danube are analysed with the focus on questions of a sampling frequency. Phytoplankton samples were taken weekly upstream and downstream of Budapest during a long-term project. Six short-term periods were investigated more intensively, with 4-8 samples/day over a 2-4 day period. The qualitative composition of phytoplankton samples were investigated. It is suggested that the sampling frequency should vary during the year in a large eutrophic river like the Danube. It is important to have up-to-date details of water discharge, too. There is a need to know both the present water discharge and the pattern of probable changes int he near future, using forecasts of the water discharge registration service. In mid-winter the sampling frequency can be monthly. Int he adjacent cool seasons, in February-March and in November, sampling shoud be at a 2-3 week frequency. From April to October the frequency can be biweekly in high water periods (during the floods), but we recommend sampling every 7-10 days under low flow conditions. A special „time average” sampling-method is useful int he low water period

Nature conservation oriented algal biodiversity monitoring investigations in the main arm and some dead arms of the River Tisza I. Benthic diatoms

Benthic diatoms started to be studied as part of the Hungarian National Biodiversity Monitoring Programme in some dead-arms within the Pilot Project area in 1996 and continued in 2000-2001. The investigations had a nature conservation oriented biodiversity monitoring focus but besides the diversity of diatom communities, the water quality of the dead-arms was also described on the basis of benthic diatom species composition an relative abundance by using the trophic and saprobic condition scale of Hofmann. A considerable nutrient content was detected in the investigated dead-arms; besides algal blooms and the spreading of macrophytes, benthic diatom investigations always supported this fact. On the basis of a German red list several valuable species were found in the studied dead-arm. This valuable algal flora can only be protected by the conservation of the habitats (dead-arms) and its catchments area