Temporary rainwater rockpools as repositories of biological diversity in the Maltese Islands

Abstract

Ephemeral freshwater rockpools in solution pockets on karstland are subject to regular cycles of alternate flooding and desiccation that are correlated with patterns of precipitation. The aquatic phase of the pools extends from September/October to February/March and the dry phase from April to September. The bi-seasonal extremes of abiotic habitat variation result in a species assemblage characterised by adaptations for survival of the drought period. The resident biota of the pools is dominated by small crustaceans and chlorophytic algae. These habitats are not and the biota of these pools limited in extent of distribution through the Maltese Islands. A species characteristic of these of local or regional ecological significance. These include Branchipus schaeferri and B. visnyai (Crustacea : Anostraca), Cyzicus tetracerus (Crustacea : Conchostraca), Triops cancriformis (Crustacea : Notostraca) and Riella helicophylla (Bryophyta : Hepaticae), Darnasonium bourgei (Angiospermae : Alismataceae), Elatine gussonei (Angiospermae : Aletinaceae) and Crypsis aculeata (Angiospermae : Poaceae) from the flora.