Aquatic Mollusks: Occurrences, Identification and Their Use as Bioindicators of Environmental Conditions (Salinity, Trace Elements and Pollution Parameters) in Jordan

Abstract

Mollusks living in surface water in Jordan can be used as indicators of water quality. They are predominantly represented by gastropods and only locally by bivalves. Within this framework, gastropod species of the genera Theodoxus, Melanopsis, Melanoides, Physa, Bulinus, Galba, Hydrobia, Ovatella, Falsipyrgula, Prosostenia, Pseudamnicola proved to be useful. Most commonly encountered are Theodoxus, Melanopsis Melanoides and Physa, and their presence alone presents good information about the quality of the water body they are living in. The results of the study indicate that Theodoxus and Melanopsis represent indicators of pure and clean fresh water while Physa is an indicator of polluted water. Of very special interest is the fauna in King Abdullah Canal influenced by the fauna of Lake Tiberias, represented by Falsipyrgula, and the bivalves of the two species of Unionidae and of Corbicula. Species of Falsipyrgula. Pseudamnicola, Melanoides, and Prosostenia tolerate increasing water salinity which when reaching sea water salinity Ovatella becomes present. Locally Pseudamnicola documents influence of mineral water which can tolerate high Sr²⁺ and Br⁻ concentrations. Other members of Gastropods, especially Planorbis, Gyraulus and Ancylus have almost disappeared from running or standing fresh water in Jordan because of increasing pollution. The bivalves, Unio, Pisidium, Sphaerium, and Corbicula are found confined to freshwater environment. With exception of King Abdullah Canal where they used to be useful indicators for the quality of its water, they are rare in Jordanian waters. The study concludes that aquatic mollusks, mainly gastropods, can easily be used as biological indicators of environmental quality of surface water bodies. It is a fast, easy and trustful way of observing changes taking place in the environment, especially salinity, added chemical and pollution parameters.