Quantifying aquatic insect deposition from lake to land

Area of Science:

• Ecology
• Biogeochemistry
• Ecosystem Science

Background:

• Organisms crossing ecosystem boundaries, like aquatic insects with terrestrial adult stages, are vital for nutrient and energy transfer.
• The ecosystem-level impact of aquatic insects on terrestrial environments is often overlooked due to their small individual size.

Purpose of the Study:

• To develop and demonstrate a method for quantifying aquatic insect deposition (e.g., kg N x m(-2) x yr(-1)) onto shorelines.
• To assess the nutrient contribution of aquatic insects to adjacent terrestrial ecosystems.

Main Methods:

• Utilized emergence traps to estimate total insect emergence from Lake Mývatn (2008-2011).
• Employed aerial insect traps and a local-maximum decay function model to predict midge deposition patterns inland.
• Measured soil nutrient availability using resin bags to correlate with insect deposition zones.

Main Results:

• Estimated whole-lake insect emergence ranged from 3.1-76 Mg/yr (dry mass).
• Developed a dispersal model predicting midge abundance with high accuracy (R2 = 0.89), with peak deposition 20-25m inland.
• Quantified high-midge year deposition (100 kg x ha(-1) x yr(-1)) within 50m of shore, providing substantial Nitrogen (10 kg N x ha(-1) x yr(-1)) and Phosphorus (1 kg P x ha(-1) x yr(-1)) inputs.

Conclusions:

• Aquatic insects represent a major, quantifiable nutrient source for terrestrial ecosystems.
• Insect-driven nutrient deposition significantly influences terrestrial soil nutrient dynamics, with potential to alter ecosystem processes.
• The demonstrated approach is generalizable to other aquatic-terrestrial interface ecosystems.