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Title: Productivity and nutrient dynamics of Avicennia Marina (Forsk.) Vierh. mangroves grown on the Red Sea coast of Saudi Arabia
Author: Abohassan, Refaat Atalla Ahmed
ISNI:       0000 0004 2696 6137
Awarding Body: Prifysgol Bangor University
Current Institution: Bangor University
Date of Award: 2010
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This study aimed to investigate productivity, nutrient cycling and heavy metal pollution in two A. marina stands on the Red Sea coast of Saudi Arabia. The mangrove stands were located at Yanbu region (northern Red Sea) and at Shuaiba region (southern Red Sea). Aboveground biomass production was estimated by developing site specific allometric equations with height and diameter at breast height as biomass predictors. Annual litterfall production was estimated over two years using litter traps and the fate of the fallen litter (i.e. accumulation under mangrove stands. removal and export to adjacent waters) was assessed by estimating standing crop leaf litter and monitoring tidal levels and crab activities. Aerial root biomass was estimated by harvesting roots within ground quadrats; fine root biomass was estimated using random coring. Nutrient cycling in the mangrove systems was assessed by litter decomposition and the release of carbon and nitrogen from the decomposing litter. In addition. the importance of mangrove derived carbon as an energy source to the aquatic animals was estimated by DC stable isotope analysis. The levels and dynamics of eight heavy metal contaminants in mangrove systems were assessed by estimating metal levels in sediment. mangrove components and in the decomposing litter. It was found that aboveground biomass was greater in Shuaiba (18.58 ha-I) than in Yanbu (10.77 t ha") (p <0.05); the overall aboveground biomass (14.77 t ha-I) was comparable to estimates reported in other locations at similar extreme environmental conditions. Both aerial and fine root biomass was greater in Shuaiba ( 23.7 t ha" and 96.4 t ha') than in Yanbu ( 10.1 t ha" and 39.1 t ha" for aerial and fine roots respectively. and overall fine roots estimate (67.8 t ha') was comparable to estimates from subtropical and hypersaline regions. Litterfall production was similar in both sites with an overall production of 3.57 t ha" / and litterfall accumulated on the forest floor rather than being exported to adjacent waters owing to low tidal ranges. No significant differences were found in litter decomposition with an overall k value of 0.0076 and half life of 91 days. The levels of carbon and nitrogen at the end of the decomposition period were higher than at the beginning (p <0.05) indicating changes in the leaf chemical composition and microbial activities. However, nitrogen levels in fresh leaves were significantly higher than in senescent leaves indicating nitrogen resorption. The mangrove derived carbon was of moderate importance to a number of crab and fish species; however, this importance was offset by the contribution of other carbon sources to the diet of these animals. Heavy metal pollution in the studied sites was low compared to other contaminated regions, however, heavy metal levels were always higher in the polluted site (Yanbu) than in the minimally exposed site (Shuaiba) indicating the need for monitoring and assessment in other similar sites on the Red Sea coast.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available