TROPHIC UNFOLDING OF A CONTINENTAL-SHELF ENERGY-FLOW NETWORK

Trophic structure of a continental shelf ecosystem is analyzed using a general method for partitioning (unfolding) network models of energy flows and standing stocks, including those with cycles, according to the number of times that energy-matter was transferred in the system. Model criteria that allow a trophic interpretation of unfolding analysis and procedures for modifying existing models to meet these criteria are presented. The analysis quantifies the distribution of trophic levels to compartments and that of compartments to trophic levels, and the energy contents, dissipations, and productivities of trophic levels. Ninety-nine percent of gross primary production dissipated by trophic level V in an ocean food-web model without microbial cycles as opposed to trophic level X in the continental-shelf ecosystem model with cycles. Progressive efficiencies of the first seven of eight trophic levels in the acyclic model varied between 0.01 and 0.52. Progressive efficiencies in the model with cycles converged to above 0.50 after four trophic levels.