Pleuston

Pleuston are the organisms that live in the thin surface layer existing at the air-water interface of a body of water as their habitat.[1] Examples include some cyanobacteria, some gastropods, the ferns Azolla and Salvinia and the seed plants Lemna, Wolffia, Pistia, Eichhornia crassipes and Hydrocharis. Some fungi and fungi-like protists may be also found.

References

Look up pleuston in Wiktionary, the free dictionary.
  1. "Pleuston". Merriam-Webster Online.