Bottom-up meets top-down: leaf litter inputs influence predator-prey interactions in wetlands

Area of Science:

• Ecology
• Environmental Science
• Aquatic Ecology

Background:

• Resource subsidies often supply nutrients and energy, but can also modify habitat structure.
• Organic matter inputs, like leaf litter in wetlands, can increase structural complexity and alter water clarity.
• These changes may influence predator-prey interactions by affecting prey refuge and predation rates.

Purpose of the Study:

• To investigate how leaf litter inputs, affecting benthic surface cover and water clarity, influence predator-prey dynamics.
• To examine the direct effects of altered environmental conditions on the mortality and growth of gray treefrog tadpoles (Hyla versicolor) exposed to newt predators (Notophthalmus viridiscens).

Main Methods:

• Outdoor mesocosms were used to simulate forested wetland conditions.
• Oak and red pine leaf litter were added to manipulate benthic surface cover.
• Red maple litter leachate was used to alter water clarity across three treatment levels.
• Tadpole survival and growth were monitored under these manipulated conditions in the presence of newts.

Main Results:

• Benthic surface cover from leaf litter did not significantly affect tadpole survival.
• Increased water clarity (darkening) due to maple leachate resulted in lower tadpole survival.
• Tadpole mass was reduced in treatments with higher maple leachate concentrations.
• These findings suggest an interaction between resource availability and predation risk.

Conclusions:

• Leaf litter's impact on water clarity, not surface cover, significantly affected tadpole survival.
• Changes in forest composition altering litter inputs can substantially modify wetland community interactions.
• Predation risk is modulated by environmental changes induced by organic subsidies.