INVESTIGATING THE EFFECTS OF SALINITY AND NUTRIENT ADDITION ON THE GROWTH OF AVICENNIA ALBA SEEDLINGS

Abstract

Mangrove rehabilitation projects, targeted at restoring vital ecosystem system services of mangrove forests after degradation, are often less than successful because effects of abiotic factors like salinity and nutrient on growth and performance of mangrove seedlings are often disregarded, or poor understood. This study aims to investigate both the independent and interactive effects of salinity and nutrient addition on growth of seedlings of Avicennia alba, a seafront, pioneer mangrove species with high potential for colonizing mudflats by regeneration. This was achieved via a 90-day mesocosm experiment involving 150 A. alba seedlings grown from propagules collected from Mandai mangrove mudflats in Singapore. A total of 24 treatments made up of 4 salinity treatments (0, 10, 20, 30 and 40 psu), 4 nutrient treatments (2.5, 5.0, 25.0 and 50.0 mgL- 1) and 16 permutations of these salinity and nutrient treatments were applied with six replicate seedlings. Mortality and morphological traits such as stem height, maximum leaf area and biomass were parameters of growth that were observed and recorded at various intervals throughout the 90-day experiment. Results show that survival and growth of A. alba seedlings are negatively correlated to salinity. Threshold to seedling survival was observed to be at 20 psu, with optimum level of salinity for growth at 0 to 10 psu. Nutrient addition was not found to have significant independent effects on the growth of A. alba seedlings, and interactions between salinity and nutrient were not evident.