Aquatic Macrophytes Composition in Lentic Water Bodies - Comparison Between the Ecoregions in Bulgaria - page 2

Most of them are representatives of the families: Potamogetonaceae (10%), Cyperaceae (10%), Lamiaceae (6%), Alismataceae (5%), Polygonaceae (5%), Poaceae (5%), Lemnaceae (4 %), Hydrocharitaceae (4%), etc.

The number of macrophyte species is approximately the same in both lakes (77%) and reservoirs (73%), especially it refers to helophytes. There is no difference between the two ecoregions, according to the species encountered, except for Isoetes lacustris glacial relict (Pirin Mts. - Eastern Balkans), Sparganium angustifolium and Subularia aquatica (Pirin Mts., Rila Mts. - Eastern Balkans) and Strationtes aloides restricted to Danube marshes and lakes and Azolla filiculoides (Pontic Province).

Approximately 57% of the species encountered are helophytes, while the hydrophytes are 43%. The latter are divided into the following groups: pleustophytes - Spirodela polyrrhisa, Lemna spp., Salvinia natans, etc.; submerged macrophytes - Myriophyllum spicatum, Potamogeton spp., Najas spp., etc.; floating leaves macrophytes - Hydrocharis morsus-ranae, Nymphaea alba, Nuphar lutea, etc.

In 2013 we have found a new locality of the Critically Endangered species Utricularia australis in the Sofia floristic region – Negovan Sandpit Lake.

The invasive species Elodea nuttallii is characterized by rapid vegetative reproduction and expansion throughout the country and has the potential for significant disruption of ecosystems (Petrova et al., 2012; Savchovska et al., 2013).

Some of the aquatic plants species are protected by different acts and conventions, as follows:

  • 12 species are protected by the state biodiversity act (Aldrovanda vesiculosa, Isoetes lacustris, Nuphar lutea, Nymphaea alba, Nymphoides peltata, Salvinia natans, Sparganium angustifolium, Stratiotes aloides, Subularia aquatica, Thelypteris thelypteroides, Trapa natans, Utricularia australis);
  • 15 species are listed in the Red List of the vascular plants in Bulgaria (Petrova & Vladimirov, 2009): Critically Endangered (Aldrovanda vesiculosa, Stratiotes aloides, Utricularia australis); Endangered (Isoetes lacustris, Nuphar lutea, Nymphaea alba, Nymphoides peltata, Trapa natans), Vulnerable (Salvinia natans, Thelypteris thelypteroides, Subularia aquatica, Utricularia vulgaris); Near Threatened (Lemna gibba); Data Deficient (Callitriche palustris) and Least Concern (Sparganium angustifolium);
  • 8 species are in the Red Data Book of the Republic of Bulgaria (Peev et al., 2011): (Aldrovanda vesiculosa, Stratiotes aloides, Isoetes lacustris, Nuphar lutea, Nymphaea alba, Nymphoides peltata, Trapa natans, Utricularia australis);
  • 3 species are included in the Bern Convention (1979)(Aldrovanda vesiculosa, Salvinia natans, Trapa natans);
  • 1 species is in the Habitat Directive (92/43/EEC) (Aldrovanda vesiculosa).

 

Conclusions

As most of the macrophytes are with cosmopolitan distribution there is no difference between the two ecoregions, according to the species encountered (Table 1). The only exceptions are Isoetes lacustris, a glacial relict for Pirin Mts. and for Sparganium angustifolium and Subularia aquatica both restricted to Pirin Mts. and Rila Mts. in the Eastern Balkans – ecoregions 7. Two species are found only in the Pontic Province (ecoregions 12) - Stratiotes aloides and Azolla filiculoides both restricted to Danube marshes and lakes.

The lack of difference in the species composition between the two ecoregions means that the ecoregions could be omitted from the typology of the lakes as far as the macrophytes are concerned. Thus, additional parameters, such as total alkalinity or residence time can be incorporated into the typology of the lakes, according to System B of the Water Framework Directive (WFD, 2000).

 

Acknowledgments

The financial support through Project № DO 02-341/2008 provided by National Science Fund at the Ministry of Education, Youth and Science is gratefully acknowledged.