Showing papers by "Jonathan H. Grabowski published in 2004"

Habitat complexity disrupts predator–prey interactions but not the trophic cascade on oyster reefs

Abstract: Despite recognition of the significance of both food web interactions and habitat complexity in community dynamics, current ecological theory rarely couples these two processes Experimental manipulations of the abundance of the two predators in an oyster-reef trophic cascade, and the structural complexity provided by reefs of living oysters, demonstrated that enhanced habitat complexity weakened the strengths of trophic interactions The system of tri-trophic interactions included oyster toadfish (Opsanus tau) as the top predator that consumed the mud crab (Panopeus herbstii), which preys upon juvenile oysters (Crassostrea virginica) On reefs of low complexity, toadfish controlled mud crab abundances and indirectly determined the level of mortality of juvenile oysters The indirect effects of toadfish on oysters emerged through their influence on how intensely mud crabs preyed on oysters Augmentation of habitat complexity by substituting vertically oriented, living oysters for the flat shells of dead o

Habitat complexity mitigates trophic transfer on oyster reefs

Abstract: Structured habitats within several aquatic systems have been characterized as having higher abundances of both predators and their prey. Understanding this somewhat paradoxical phenomenon requires teasing apart how habitat complexity influences predator-prey dynamics. To determine whether habitat complexity influences predator foraging efficiency, we measured pre- dator foraging rates within structurally simple and complex habitats. We selected as our test system mud crabs feeding on juvenile hard clams within biogenic reefs formed by the eastern oyster. At low and intermediate crab densities, foraging rates of mud crabs were similar between simple and com- plex habitats. However, at high crab densities foraging rates were higher for crabs in the complex reefs than in the simple reefs. In addition to providing refuge to both intermediate predators and their prey, habitat complexity appears to enhance predator foraging efficiency by reducing interference competition among predators. In systems where interference competition among densely populated predators may be intense, complex habitats may not provide survival benefits to all trophic levels.