|Okanagan Lake in Kelowna, British Columbia, Canada. Waves affect snails and insect larvae more on sandy shores than shores with tree roots or reeds.
Up to 10,000 organisms can be found on a square meter of water bottom, of which a lot are also terrestrial insect larvae. Scientists call the whole group macrozoobenthos - these are all invertebrates living on the bottom and still visible with naked eyes. Researchers at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) now study the impact that ship-induced waves can have on these small animals.
The larva of Calopteryx splendens, a dragonfly, crawls on a stone in shallow water. Then operates Friederike Gabel the wave machine. A wave, comparable to that of a sport boat, runs along the three-metre-long canal.
The larva is washed out - "detached" say the researchers - and paddle around several minutes helplessly in the water until it found again the "solid ground" under its feet. "If they stay suspended in the water, the larvae take the risk to be eaten" explains F. Gabel, a specialist of the effect of waves on invertebrates. In addition, the larva spent energy to fix them back, which has negative effects on their growth and reproduction. The researchers fear that ship-induced waves increase larval mortality and subsequently biodiversity, which would have a long-term effect on the ecological quality of rivers and lakes.