A mini-model of a tropical marine lagoon is given in Figure III-14. The lagoon is bordered by a belt of mangroves (M) with area A which surrounds a shallow basin containing productive algal communities in the water and on the shallow bottom I m deep or less. Larger organisms such as young shrimps and fishes consume the detritus from the mangroves and algae. The lagoon water exchange with the sea through a small narrow channel that flows more out than in because of the fresh water received from the land runoff.
The mini-model illustrates food chain patterns in ecosystems and the recycle of mineral nutrients. As already of detritus storage permits the higher consumers to develop a prey-predator oscillation. These cause the nutrient cycle and production oscillate and auto catalytic pathways to the higher consumers. This is an example of the ways the larger species can control the periodicities of ecosystems. The external sources, sun, nutrient inflow and tidal patterns are held constant. They are source limited inputs which set the general carrying capacity of the system so far as support of higher organisms.
For a scale of time of months and years, the ups and downs of phytoplankaton due to their own storage fluctuations are too short to affect the components higher in the food chain with longer turnover times. Therefore the nutrients and the algal production rates are shown without storages, responding without delay to any changes in their inputs and outputs.
Examples of Other Ecosystems with Recycle Oscillations
In some ways, especially in the way prey-predator oscillations control the longer period oscillations of nutrients and plant production, the model illustrates shallow aquatic ecosystems of freshwater as well as marine type. Some terrestrial ecosystems such as the Arctic tundra may operate similarly but with time in years rather than in months.
"What if" Experimental Problems
COMPUTER MINIMODELS AND SIMULATION EXERCISES
FOR SCIENCE AND SOCIAL STUDIES
Howard T. Odum* and Elisabeth C. Odum+
* Dept. of Environmental Engineering Sciences, UF
+ Santa Fe Community College, Gainesville
Center for Environmental Policy, 424 Black Hall
University of Florida, Gainesville, FL, 32611
Autorização concedida gentilmente pelos autores para publicação na Internet
Laboratório de Engenharia Ecológica e Informática Aplicada - LEIA - Unicamp
Mileine Furlanetti de Lima Zanghetin
Campinas, SP, 20 de julho de 2007