Practice question

Neuston are organisms that live at or immediately adjacent to the air-water interface. Some rest on top of the surface film, termed epineuston, while others occupy its underside, termed hyponeuston. Examples include water striders, floating microbial communities, certain algae, fish eggs, larvae, and small invertebrates. Surface tension creates a specialized habitat, and strong gradients in light, temperature, oxygen, and chemicals distinguish it from deeper water. Wind can aggregate neuston into slicks, while ultraviolet radiation and pollutants concentrated at the surface impose stress. Benthos live on or within the bottom; periphyton grow attached to submerged substrates; and nekton actively swim through the water column. The everyday verb “float” can also describe plankton, which drift with currents throughout the water, but among the terms listed, neuston specifically refers to life associated with the water surface. Their position lets some species obtain atmospheric oxygen or exploit floating food, yet also exposes them to waves and desiccation. Occupation of the surface microlayer is therefore the decisive feature.