Egg banks in hypersaline lakes of the South-East Europe

Hypersaline lakes have been stimulating the interest of biologists for a long time, principally on account of their simple biological composition [1]. Over the last decades, the scientific literature on salt lakes has grown with the appearance of a large number of papers, and new research directions, e.g. ecology of hypersaline environments [2], agriculture applied to saline lakes [3], and saline lake conservation and management [4]. Recently, research on saline lake species assemblages has developed in scope and intensity. A general rule on the composition of biological communities has been recognised with an inverse correlation existing between species richness and salinity [1], with a small number of trophic roles each represented by just one species [5]. The species composition differs in saline waters of different chemistry [6,7], being characterized by marine originated fauna with Artemia shrimps where Cl-1 anions where dominant, and by non marine Calanoida copepods (family Diaptomidae) where SO4-2 is the main anion.Thanks to the ability of many species to produce resting stages, coupled with long lasting periods of lacking of suitable conditions for active populations, hypersaline lakes hide a potential biodiversity (in terms of dormant species) which cannot be investigated by collecting organisms only from the water column. In fact, commonly during both dry-hot and freezing-cold seasons, most species stay in a dormant stage in the bottom sediments. The rest could even last for years if suitable conditions do not return (e.g. in the case of progressively rising salinity), giving a progressive reduction of active biodiversity (as in the case of the Aral Sea, see [8]). In these cases only a small portion of the biodiversity is expressed, the majority of species being temporarily resting as cysts in the sediments. Even on the return of suitable conditions, only a portion of the cysts produced will hatch, while the other ones go to storage the persistent cyst ban