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• A new alien species in Hungary: Limnobium laevigatum (Hydrocharitaceae)

  9-15

  Norbert Riezing

  Views:

  252

  The South American Spongeplant (Limnobium laevigatum (Humb. & Bonpl. ex. Willd.) Heine) is a floating aquatic plant native to freshwater habitats of tropical and subtropical Central and South America. It is frequently used for ornamental purposes in ponds and aquariums, and became invasive in the recent decades around the world. It has a high reproductive potential and a high dispersal capacity as well. It can form massive floating mats causing light limitation and creating anoxic conditions in the underlying water column, which strongly reduces native animal and plant biomass and diversity. It can also hamper navigation and water flow in rivers and canals. It has been introduced to the United States, Australia, Indonesia, Japan, Zambia and Zimbabwe. There is only one previous record in Europe (Belgium). This article is about the first record of Limnobium laevigatum in Hungary. I found two localities situated near Tata-Naszály and Dunaalmás (North-western part of Hungary). Both localities are fed by hot-water springs. It forms a small but dense population in Dunaalmás located near to the hot spring. The population in Tata-Naszály can be found in a 1.3 km long section of a stream, where it formed a sparse population in 2018.

• Contributions to the flora of the Danube River in Komárom-Esztergom and Fejér counties (Hungary)

  157–168

  Norbert Riezing

  Views:

  275

  The present paper focuses on the aquatic and Nanocyperion vegetation of the Danube flood­plain. Most of the data show the results of the surveys in 2019 at low water levels. The Nanocyperion and aquatic vegetation of the Komárom-Esztergom County section is relatively well researched com­pared to the Fejér County section which was previously poorly known. In the last decade, two rare spe­cies – Hippuris vulgaris and Hydrocharis morsus-ranae – have disappeared between Gönyű and Neszmély (Komárom-Esztergom County). In contrast, several new invasive plants have appeared: Salvinia molesta, Myriophyllum aquaticum, Limnobium laevigatum, and Crassula helmsii (first record from Hungary). Vallisneria spiralis and Elodea canadensis were detected again after several decades. Elodea nuttallii and Azolla sp. have become more widespread and abundant than previously. New and uncommon Nanocyperion species were the native and protected Lindernia procumbens and the inva­sive Lindernia dubia. New invasive plants in the studied Danube sections were: Cyperus esculentus, Euphorbia maculata, and Eleusine indica. The native Veronica catenata and Schoenoplectus triqueter have become more wide­spread than before. Polygonum graminifolium was an interesting find of open pebble surfaces in several parts of the examined area, which has no recent records in Hungary from before 2015 (published here).