Temporal changes of aquatic macrophytes vegetation in a lowland groundwater feed eutrophic course [Klatovske Rameno, Slovakia]

Klátovské rameno is the lowland slow-flowing groundwater feed eutrophic tributary of the Malý Dunaj River (Danube Plain), where our study of temporal changes of aquatic macrophytes vegetation was realised in 1999 and 2005. For survey of aquatic vascular macrophytes the Kohler’s method (Janauer 2003) was used, which is compliant with European standard EN 14184. Altogether 35 aquatic macrophyte species were recorded during the survey. Nuphar lutea persisted as the most dominant species in 1996 and 2005. Species diversity increased slightly after the nine years: ten species immigrated to the watercourse. The changes in species abundance have shown weak differences, however the abundance of Sparganium emersum has increased markedly. Alien species Elodea canadensis and both S. emersum and Hydrocharis morsus-ranae significantly enlarged their distribution in the stream. The ecological quality of the river, based on the aquatic macrophytes assessment criteria, was slightly impaired after nine years, but still 90% of its studied course has a high or good ecological status

Typha control efficiency of a weed-cutting boat in the Lac de Guiers in Senegal : A preliminary study on mowing speed and re-growth capacity

Prolific growth of Typha australis in the lower part of the Senegal River and the Lac de Guiers resulted from changed ecological conditions following the construction of two high dams in the Senegal River. Fluctuation of the water level has decreased markedly and the water has changed from brackish to fresh as the inflow of salt water from the ocean is prevented. The efficiency of a hydraulic weed cutting boat (model Conver 480 H) has been tested in various plots in the Lac de Guiers. This lake, connected with the Senegal River, is economically very important as it is the city of Dakar's major drinking water supply and also provides irrigation water for vast agricultural areas. Cutting, performed at 20 cm and 50 cm below the water surface, was very effective in removing Typha stands. However, due to the excessively thick stems of the Typha plants, cutting took much more time compared to similar operations in Europe. It was estimated that approximately 35 h were required to clear one ha of dense Typha stands. Directly after cutting re-growth was observed during a relatively brief period (approximately three months), however, subsequently all newly formed growth tips in the plots had suddenly disappeared. It was concluded that this sudden collapse was linked to a destruction of the root zone due to anoxic conditions. Eventual re-growth was relatively slow as after one year the plots were still largely free from Typha plants. Efficiency of mowing was not related significantly to depth of cutting

Typha control efficiency of a weed-cutting boat in the Lac de Guiers in Senegal : A preliminary study on mowing speed and re-growth capacity

Prolific growth of Typha australis in the lower part of the Senegal River and the Lac de Guiers resulted from changed ecological conditions following the construction of two high dams in the Senegal River. Fluctuation of the water level has decreased markedly and the water has changed from brackish to fresh as the inflow of salt water from the ocean is prevented. The efficiency of a hydraulic weed cutting boat (model Conver 480 H) has been tested in various plots in the Lac de Guiers. This lake, connected with the Senegal River, is economically very important as it is the city of Dakar's major drinking water supply and also provides irrigation water for vast agricultural areas. Cutting, performed at 20 cm and 50 cm below the water surface, was very effective in removing Typha stands. However, due to the excessively thick stems of the Typha plants, cutting took much more time compared to similar operations in Europe. It was estimated that approximately 35 h were required to clear one ha of dense Typha stands. Directly after cutting re-growth was observed during a relatively brief period (approximately three months), however, subsequently all newly formed growth tips in the plots had suddenly disappeared. It was concluded that this sudden collapse was linked to a destruction of the root zone due to anoxic conditions. Eventual re-growth was relatively slow as after one year the plots were still largely free from Typha plants. Efficiency of mowing was not related significantly to depth of cutting

Combined effects of water column nitrate enrichment, sediment type and irradiance on growth and foliar nutrient concentrations of Potamogeton alpinus

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