Oral Session #95: Trophic Structure.
Presiding: D. Wise
Thursday, August 8. 1:00 PM to 3:45 PM. Palo Verde Room, Radisson.

Hydrology, nutrient supply, and food web dynamics in the Everglades marshes: A modeling study .

DONG, QUAN*,1, 1 Everglades National Park, Homestead, Florida

ABSTRACT- Three hypotheses about the dynamics of aquatic food webs in the Everglades marshes were evaluated with a modeling approach: (a) hydrology determines the trajectory features of trophic groups, and flood pulses transmit through food webs linearly or monotonically; (b) phosphorus enrichment increases primary production that trickles-up across trophic levels; but does not alter food web structures; (c) consumption and predation control the features of trajectories of trophic groups. The model was able to reconstruct many dynamic and structural features. The simulation with different hydrology and P supply suggested that hydrology, P supply and trophic interactions interact to determine the dynamics of the lower trophic levels. The modeling analysis led to three new hypotheses: (1) the intermediate hydroperiod hypothesis, (2) the detrital link enhancement hypothesis, and (3) the nonlinear pulse transmission hypothesis. The intermediate hydroperiod hypothesis suggests that the largest pulses and variability in consumer groups concur with intermediate hydroperiods. The detrital link enhancement hypothesis suggests that P enrichment enhances detrital links in the detritally dominated marshes. The nonlinear pulse transmission hypothesis suggested that top-down and bottom-up controls acted in disconcert or concert with hydrology, and modified the trajectories that were solely determined by hydrology. The pulse transmitted up through the trophic structure nonlinearly.

KEY WORDS: trophic interactions, flood pulse, detritally-dominated food web