Edward M. Barrows - US grants

Primary productivity of mangroves is an important source of nutrients for adjacent marine systems. The level of productivity is affected not only by environmental factors but also by other components of the mangrove community. Nutrient enrichment might have direct impact on aquatic food webs by increasing primary productivity of mangroves, but enrichment to coastal waters might be mitigated because as much as 20% of mangrove leaf material is removed by herbivores. The objective of this study is to determine the effects of nutrient enrichment on primary productivity of the key mangrove species, Rhizophora mangle, and on rates of insect herbivory in a controlled experiment in which nutrient availability in sediment is manipulated. The following hypotheses will be tested: 1. Nutrient enrichment causes increased leaf production and terminal branch production, internodal elongation, and flowering. 2. Nutritional quality (e.g., CNP ratio, water content) of mangrove tissues increases following nutrient enrichment of the sediment. 3. Nutritional quality of mangrove tissues correlates with rates of insect herbivory by both leaf feeders (folivores) and twig borers (xylovores). 4. Secondary use of R. mangle twigs by insects and their kin, e.g., predators, parasites, twig-nesting ants, etc., increases with rate of primary herbivory. 5. Proportions of species in the twig-feeding guild of R. mangle change following nutrient enrichment. This research will contribute to the knowledge base on mangrove ecology and may provide important information useful in conservation of mangroves.//