Ostracods as environmental indicators in Manzala Lagoon (NE Egypt)

Ostracods have been used as bio-indicators for the quality of aquatic ecosystems. Unfortunately, limited number of studies have been done on the ostracods from the northern coastal lagoons of Egypt. Therefore, the present work is an attempt to examine the Recent ostracod assemblages from the bottom sediments of Manzala Lagoon, Egypt. The detection of their response to the environmental parameters is another target. The studied community consists of a relatively diverse assemblage, where 19 species belonging to 16 genera are identified. Due to the prevalence of brackish conditions in the lagoon, all sites are inhabited by the most common brackish species, Cyprideis torosa (Jones), where its relative abundance ranges between 96.2 and 100 %. Also, the current study records minor occurrence of Loxoconcha elliptica Brady, Leptocythere castanea (Sars) and Cypridopsis vidua (Müller) in some sites. Moreover, the presence of allochthonous marine assemblage is limited to the area near the connection to the Mediterranean sea. In addition, ostracods show different responses to the type of bottom sediments, where Cyprideis torosa can inhabit both muddy and sandy substrates, whereas Cypridopsis vidua is restricted only to the muddy substrate. Furthermore, the occurrence of marine assemblage is restricted to sandy substrate near the inlet of seawater. The response of ostracods to heavy metal pollution is also documented. However, the studied sites are heavily polluted with Cd, only some individuals of C. torosa are still alive, reflecting its toeleranc to pollution. Furthermore, the variations in the values of pH have no observed effects on the structure of the examined ostracods, as they completely lie in the alkaline side. Also, there is no remarkable relationship between the depth and the patterns of distribution of ostracods. Consequently, salinity, substrate sediment types and the levels of pollution are the most important factors controlling the distribution of ostracods in the studied lagoon. Geographically, the identified ostracods show a great similarity to those observed in other Mediterranean lagoons.