The structure of Marine Ecosystems: An alternative

In The Structure of Marine Ecosystems (1974), Steele developed a simulation model which suggested that the stability of planktonic communities was dependent on a threshold response allowing phytoplankton a refuge in concentration below which herbivorous zooplankton did not feed. Observations from the North Sea were presented to support this hypothesis. In order to more realistically represent the simulated herbivores, Calanus spp., several of Steele's assumptions have been modified. The results of the revised model indicate that feeding thresholds are not essential for the long-term realism and stability of the simulated system and suggest an alternative, ecosystem control through predation.Contribution no. 861 from the Department of Oceanography, University of Washington. This study was supported by NSF Grant DES 74-22640 to B.W. Frost.