Aspects of the ecology of hydrophytes in temporary freshwater rockpools in Gozo

Abstract

This study generally covers the basic physical and hydrobotanical characteristics of fifteen temporary freshwater rockpools in Gozo during the period October 1997 to March 1998. The pools are filled with rainwater which dries up because of evaporation and transpiration. A total of twenty-one species of plants were observed in the pools. Five species were aquatic/amphibious and sixteen were terrestrial. The most abundant hydrophyte was Lythrum hyssopifolia and the others were Zannichellia palustris, Elatine gussonei, Ranunculus saniculaefolius and Damasonium bourgaei. The most abundant terrestrial plants in the pools were Plantago lagopus and Dittrichia viscosa. The species richness ofhydrophytes depended on the maximum length of the hydroperiod since longer hydroperiods were correlated with more hydrophytes. The species richness ofhydrophytes was negatively correlated with the species richness of terrestrial plants. The species richness of hydrophytes was not found to be significantly correlated with the size of the rockpools. The hydrophytes were found by cluster analysis and PCA to fall in two groups, one group containing Zannichellia palustris and Lythrum hyssopifolia were present in almost all pools and the other group containing Elatine gussonei, Damasonium bourgaei and Ranunculus saniculaefolius were rarely in these pools. A germination experiment was done to check a hypothesis about competition but the results were not clear. Terrestrial plants were mainly found at the edges of the pools, where hydroperiods were short and hydrophytes were found in the middle, deeper portions of the pools where water stayed for more time giving longer hydroperiods.