Potential and Constraints of Macrophyte Manipulation for Shallow Lake Management

Palic and Ludas lakes are shallow Pannonian lakes, which have undergone rapid eutrophication. High concentrations of nutrients, along with significantly high values of fecal indicators in water samples, indicate that the Palic-Ludas canal, which connects them, contributes to the pollution of the recipient Lake Ludas, a central part of a special nature reserve. In order to improve water quality in the canal and decrease nutrient load of Lake Ludas, it is suggested to use environmentally friendly solutions, so-called bio-barriers (bio-bridges and biobanks), which will contribute to self-purification efficiency. The given model assumes 10 zones with bio-bridges and 0.4 ha covered by biobanks, using plants common in the area, e.g. Typha spp., Phragmites spp., Juncus spp., Scirpus spp. and Carex spp. The main disadvantage of this technology is occupation of large area; thus, the solution seems to be undersized. It removes 4% TN/year and 8% TP/year of the total amount necessary to achieve good ecological status. Nevertheless, the role of bio-bridges in permanent nutrient removal, through preventing the deposition of organic matter at the bottom sediment and later return of nutrients in water, together with indirect influence through enhancement of biodiversity should not be underestimated.