A large variety of plants and animals inhabit West Virginia's streams. They include a diverse community of birds. For example, cedar waxwings catch insects flying above rivers; belted kingfishers plunge from overhanging branches; green herons prowl shorelines for frogs; and ospreys hover before plummeting onto fish.

Some birds reproduce along streams. Wood duck hens lead their ducklings to slackwater nurseries. Although they nest in a variety of moist habitats, other bird species, such as the song sparrow, cerulean warbler, and Acadian flycatcher, often nest along streams.

At dusk, several species of bats, such as the little brown bat, big brown bat, and red bat echo-locate flying insects by sweeping through the open space above larger streams.

An entire streamside ecosystem, including soil, plants and animals, depends on each stream. Examples include grasses, ferns, and wildflowers in the ground cover; flowering dogwood, pawpaw, and black willow in the understory; and sycamore, silver maple, and river birch in the canopy. Such riparian plants reduce streambank erosion during high water, shed nutrient-rich leaves which power the in-stream ecosystem, and neutralize polluted runoff before it reaches the stream.

Several species of emergent plants (those plants rooted in a streambed that grow upward and out of the water with parts of their body in the air) live in West Virginia's streams. A common species is water willow. Rooted in shallow beds of gravel and cobble, water willow is adapted to a variety of water levels, including complete inundation, partial emergence, and complete exposure to air. Reproducing via runners, water willow can form large patches of many stems. While submerged, water willow stands provide cover for juvenile fish and aquatic insects. The roots of water willow secure substrate particles, an early step in the formation of islands.

In general, open, sunny, warm intermediate stretches of streams support more kinds and amounts of submerged plants than either the narrow, shaded, cool headwaters or the sluggish, muddy, deep lowest reaches. Diatoms, which are single-celled plants with shells made of silicon, and green algae cling to rocks. Adapted to swifter water, wild celery undulates in the current, whereas several species of pondweed may grow dense stands in quiet backwaters. Water stargrass's bright yellow flowers exhibit underwater pollination.

Unlike lakes, where a variety of animals live suspended in the water column, most stream-dwelling animals persist on the bottom. Pick up a six-inch rock from a healthy West Virginia stream and you will likely find several species of mayflies, stoneflies, and caddis flies. Bottom-dwelling insect communities may also include midges, black flies, hellgrammites, and riffle beetles.

Other non-insect macroinvertebrates may be found in our streams. A large variety of crayfishes and mollusks, of both snail and mussel species, may be locally numerous.

Healthy streams can host dozens of fish species, with the greatest diversity contributed by darters, minnows, suckers, and sunfishes. Stream salamanders and spring salamanders may be locally common in clean streams, while the much larger hellbenders lurk under rocks in streams draining westward, in the Ohio River watershed. Among reptiles, northern water snakes seem to be ubiquitous, while in some places painted turtles bask on sunny logs. Restricted to northeast West Virginia, the wood turtle spends about half of its time in the water and half roaming across nearby floodplains and uplands.

Several species of crepuscular mammals (those active at dawn and dusk) feed in West Virginia's streams. Raccoons fish under rocks, beavers ascend banks to whittle away tree bark to expose the nutritious underlying tissue, and white-tailed deer dunk for submerged waterweed and pondweed.

In general, human activities pose the greatest danger to West Virginia stream life, including mining and industry as well as attempts to "manage" stream flow. Dredging, channelization and other forms of habitat alteration, as well as water pollution (including excess sediment and acid mine drainage), reduce the diversity of native aquatic plants and animals while sometimes enhancing the abundance of a few pollution-tolerant forms.