As coastal plants that can survive in salt water, mangroves play an essential role in large marine ecosystems (LMEs). The Red Sea, where the growth of mangroves is stunted, is one of the least studied LMEs in the world. Mangroves along the Central Red Sea have characteristic heights of ~2 m, suggesting nutrient limitation. We assessed the nutrient status of mangrove stands in the Central Red Sea and conducted a fertilization experiment (N, P and Fe and various combinations thereof) on 4-week-old seedlings of Avicennia marina to identify limiting nutrients and stoichiometric effects. We measured height, number of leaves, number of nodes and root development at different time periods as well as the leaf content of C, N, P, Fe, and Chl a in the experimental seedlings. Height, number of nodes and number of leaves differed significantly among treatments. Iron treatment resulted in significantly taller plants compared with other nutrients, demonstrating that iron is the primary limiting nutrient in the tested mangrove population and confirming Liebig's law of the minimum: iron addition alone yielded results comparable to those using complete fertilizer. This result is consistent with the biogenic nature of the sediments in the Red Sea, which are dominated by carbonates, and the lack of riverine sources of iron.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We thank KAUST workshops, Coastal and Marine Resources Core Labs, and Analytical core lab for help with sampling and analyses and the Presidency of Meteorology and Environment (PME) for providing weather data. We also thank Joao Curdia for help with the nutrient addition experiment and Vincent Saderne for providing data on light levels under mangrove canopies in the region. We also thank Virginia Unkefer for reviewing the manuscript and Heno Hwang for his illustration of the nursery experiment. The research reported in this paper was supported by King Abdullah University of Science and Technology.