Importance of Aquatic Insects to Terrestrial Consumers and Ecosystems

Aquatic and terrestrial ecosystems are ecologically connected to each other as energy and nutrients cross the boundary between the two habitats. Emerging aquatic insects represent an important pathway in which freshwater ecosystems can support terrestrial food webs. Emerging insects significantly contribute to the diets of riparian predators, such as birds, bats, and spiders. As larvae, they feed in aquatic habitats and emerge as terrestrial adults that mate and reset the cycle. Unlike terrestrial plants or insects, aquatic insects contain considerable amounts of long-chain polyunsaturated fatty acids (LC-PUFA), which are important for growth and reproduction of riparian predators


Diagram of DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). Both are polyunsaturated fatty acids (PUFAs) and essential fatty acids (EFAs). Picture retrieved from Sigma-Aldrich Co. LLC.

Long-chain Polyunsaturated Fatty Acids (LC-PUFA)

Fatty acids are an important component of lipids in microorganisms, plants, and animals. They are mostly found in the universal cell membranes, but are also an important energy source and precursor for many biomolecules.

Long-chain polyunsaturated fatty acids (LC-PUFA) are a special category of fatty acids. They are mainly produced by phytoplankton (i.e., algae) in aquatic ecosystems. They are required for growth and reproduction of both aquatic (i.e., zooplankton and fish) and terrestrial organisms (i.e., birds). These PUFAs are also important for the cardiovascular, immunologic, and cognitive health of humans.

However, organisms higher up the food chain cannot effectively produce LC-PUFA themselves to meet their own physiological demand. Therefore, they must obtain them from their diet (these fatty acids are called EFA; essential fatty acids). Terrestrial plants cannot produce PUFAs such as EPA and DHA (Figure 2) and thus, terrestrial organisms (i.e., birds and bats) must ultimately obtain them from aquatic sources such as emerging insects.


Bird’s eye view of Mindelsee. Photo Credit: BUND/BW

Project Goals

The overall objective of this project is to determine how important aquatic ecosystems are to surrounding terrestrial ecosystems. In particular, we are focused on the importance of emerging aquatic insects to terrestrial predators near the shores of Mindelsee.

The goals of this project is to:

  • Quantify the transfer of biomass and essential fatty acids from aquatic to terrestrial ecosystems via emerging insects
  • Quantify the distance these emerging aquatic insects travel into the terrestrial environment

Aquatic insect traps installed in 2015 on Lake Mindelsee. Photo Credit: N. Schlotz

Aquatic Sampling (on Mindelsee)

We have deployed insect emergence traps at different water depths on Lake Mindelsee towards the forested area and reed area (Figure 3). These traps will catch the aquatic insects that are emerging from the lake and potentially entering the terrestrial environment.


Picture of terrestrial trap

Terrestrial Sampling (around Mindelsee)

These terrestrial insect traps have been deployed in both the forested and reed area to try and catch the aquatic insects that are emerging from Lake Mindelsee. We have traps located at 1, 10, 25, 50, 100, 250, 500 and 1000 meters away from the lake to see how far these aquatic insects will be available for the terrestrial organisms in the area such as the many species of breeding birds