Responses of the seagrass Halodule uninervis (Forssk.) Aschers. to hypersaline conditions

Desalination of seawater has become an important and growing field due to the present water shortage in some countries. This activity may result in some environmental impacts, mainly generated by the discharge into the sea of the brine produced, which can affect marine benthic communities. The present study aims to study the response of the seagrass Halodule uninervis (Forssk.) Aschers. to hypersaline stress. The results showed that H. uninervis fully tolerate salinity up to 50 psu by accumulation of the organic osmoprotactants (free amino acids, proline and soluble sugars) and inorganic osmoprotactants specially Na+ and K+. Sublethal effects appeared at 55 psu and the plants fully recovered when returned to normal salinity. Salinities 60 and 65 psu have a drastic effect on this seagrass and the plants did not recover after returning to the normal conditions. The results indicated that H. uninervis can tolerate salinity above control by 15 psu. To conserve this plant, it is recommended that the brine must be diluted at least to 50 psu before discharging it into the sea.