Insects can contribute to monitoring of environmental pollutants, especially in aquatic systems. Aquatic insects live in the water and “continuously sample the environment around them. A burst of pollutants entering the surrounding water then disappearing will be “sampled” by the insect. Pollutants that accumulate in insect tissues can be detected even after the pollution has dissipated. Direct sampling of water or aquatic soils can be used to determine levels of pollutants present in an aquatic environment at the moment the sample was collected. However, that leaves gaps between sample collections. Collecting insects and analyzing their tissue for pollutants can help fill the gap.
In some cases pollutants may enter an aquatic system and remain for a long time in an inactive environmental compartment not available to biological organisms. These pollutants will be detected in soil samples. However, to measure how much of that pollutant is available to a biological organism such as an insect, we must sample the insect. Such information is important in distinguishing past environmental insults from continued environmental degradation.
Aquatic animals that are commonly sampled for pollutant content include , fish, shellfish, crustaceans, and insects such as mayflies. A group from Belgium is investigating expansion of the list to include Damselfly larvae. The damselflies offer several advantages over other organisms in locations where they are plentiful. They lay eggs and hatch during a discrete window of time, so it is possible to estimate the length of time they have been exposed to the water and its pollutants. Very long lived animals such as fish are more difficult to age. The Damselflies are relatively tolerant of some priority pollutants that bioaccumulate. If those pollutants are present, they can be found in the Damselflies. Damselflies are predators and have gills. They can sample pollutants in the water directly with their gills, they can sample pollutants that accumulate in their prey and they secondarily sample the food that their prey consume.
Protecting our environment requires the ability to monitor pollutants, identify the risks to the environment and develop policy for implementing protective measures. Damselfly larvae can be important sentinels of their own environment.