Pleuston are organisms that live in the thin surface layer existing at the air–water interface of a body of water as their habitat. 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.
The term neuston is used either:
Neustons, broadly defined, are made up of some species of fish (see flying fish), beetles (see whirligig beetle), protozoans, bacteria and spiders (see fishing spider and diving bell spider). Springtails in the genera Podura and Sminthurides are almost exclusively neustonic, while Hypogastrura species often aggregate on pond surfaces. Water striders such as Gerris are common examples of insects that support their weight on water's surface tension. By extension, the term may also refer to non-organismal floating aggregations (see, e.g., Great Pacific Garbage Patch).
Plankton (organisms that float or drift within the water) are distinguished from nekton (organisms that swim, powerfully, in the water), and benthos (organisms on the bottom of a body of water).
There are different environmental factors such as flood pulses and droughts, and these environmental factors affect species such as pleuston, whether the effects lead to more or less variations in the species. When flood pulses (an abiotic factor) occur, connectivity between different aquatic environments occur. Species that live in environments with irregular flood patterns tend to have more variations, or even decrease species and variations; similar idea to what happens when droughts occur.