Habitat complexity and benthic predator-prey interactions in Chesapeake Bay

Area of Science:

• Marine Ecology
• Bivalve Population Dynamics
• Predator-Prey Interactions

Background:

• Soft-shell clam (Mya arenaria) populations decline with predator activity, persisting at low densities.
• Hard clam (Mercenaria mercenaria) populations exhibit stable age distributions.
• Habitat complexity and predator presence are key factors influencing bivalve populations.

Purpose of the Study:

• To investigate how habitat and predators control bivalve densities and distributions.
• To compare the vulnerability of Mya arenaria and Mercenaria mercenaria to predation.
• To understand density-dependent predator-prey interactions in bivalve communities.

Main Methods:

• Field caging experiment focusing on Mya arenaria survival under predator exposure.
• Laboratory mesocosm experiments with both Mya arenaria and Mercenaria mercenaria in various habitats.
• Quantification of predator search times and encounter rates in relation to prey density and habitat.

Main Results:

• Field clams exposed to predators experienced 76.3% higher mortality than caged clams, with blue crabs as a primary predator for juvenile Mya.
• Mya arenaria showed lower survival in sand and seagrass habitats compared to shell hash or oyster shell.
• Predator foraging efficiency decreased at lower prey densities, with a more pronounced effect on Mya than Mercenaria, leading to higher Mercenaria survival.

Conclusions:

• Habitat complexity may offer a low-density refuge for Mya arenaria against predation, but habitat loss can lead to unsustainable clam densities.
• Mercenaria mercenaria demonstrates higher survival due to predator inefficiency when feeding on this species.
• Understanding density-dependent predator-prey dynamics is crucial for conserving marine resources and maintaining food-web integrity.