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Mangrove Ecosystems: Definitions, Distribution, Zonation, Forest Structure, Trophic Structure, and Ecological Significance
By Karen L. McKee
Trophic Structure
Trophic structure refers to the complex interrelationships among the various organisms in an ecosystem through the transfer of food energy from one trophic level to another. The first trophic level (the producer level) is comprised of green plants; the second trophic level (primary consumer level) is comprised of herbivores (plant-eaters); the third trophic level (secondary consumer level) is comprised of carnivores, etc. These trophic levels are linked through food chains; food chains form interlocking patterns called food webs. There are two basic types of food chains: the grazing food chain (green plants to grazing herbivores to carnivores) and the detrital food chain (dead organic matter to detritus-feeding organisms to predators of detritivores).
The traditional view is that mangrove ecosystems are based on the detrital type of food web (Odum & McIvor 1990). Work by Heald (1969) and Middleton & McKee (2001) demonstrated that the leaves of the mangroves fall into the water where they are then consumed by various detritivores, which are in turn eaten by fish and other organisms that feed on the detritus consumers. The grazing pathway is considered to be unimportant in mangroves, since it has been estimated that only 5% of the leaf material is removed by grazing insects before leaf abscission.
This value may be an underestimate, however, since work by Onuf et al. (1977) shows substantial variation in leaf herbivory among mangrove species and locations . In addition, the contribution of wood-feeding insects to the grazing pathway has not been quantified. Wood-boring beetles may consume living wood and in the process kill branches or whole trees (Feller & McKee 1999; Feller 2002). These activities produce standing dead wood that is then utilized by secondary wood feeders such as termites, which in turn support secondary consumers such as arthropods, lizards, snakes, and birds (Feller & Mathis 1997).
Source :
MANGROVE ECOLOGY WORKSHOP MANUAL
Edited by IIka C. Feller & Marsha Sitnik |
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