Effects of desalination sewage on some vegetative characteristics of grey mangrove seedlings (Avicennia marina Forssk. Vierh)

Mangrove forests are fragile ecosystems that are very sensitive to human activities. For this purpose, in this study, for the first time, effects of desalination sewage on vegetative characteristics and vitality of mangrove seedlings have been investigated. After collecting propagules from healthy mother trees and planting them in September 2020, propagules were irrigated twice a day with water treatments of 0, 1, 2, 3, 5, 10 and 20% concentration of desalination sewage. After 6 months, vegetative characteristics and vitality of seedlings were measured in different treatments and compared using ANOVA and Kruskal Wallis test. The results showed that diameter growth (3.40 mm), height growth (50.10 cm), root length (33.58 cm) and leaf area (21.67 cm2) were the highest in the control treatment. Also, the number of leaves and the degree of vitality had significant differences in  different treatments. Also, control and 20% concentration treatments (24 and 30.41 mS.cm) had the least and highest amounts of soil salinity (p<0.05), respectively. The results showed that desalination sewage has a negative role on the vegetative characteristics of mangrove seedlings. The higher concentration of desalination sewage, the greater negative effects on vegetative characteristics. Totally, the critical effect of desalination sewage concentration on the vegetative characteristics of mangrove seedlings could be reported from 10% concentration. Therefore, it was recommended to use suitable management programs in the use of desalination set and sewage remove in order to minimize the mangrove forest damages.