A measure of how far down light penetrates through water. The deeper light penetrates, the clearer the water.

Deficiency in the amount of oxygen reaching body tissues.

Oxygen deficiency in an environment.

A steep temperature change in a body of water such as a lake, marked by a layer above and below which the water is at different temperatures.

Zone of a sea, lake or river which is close to the shore. Often has an abundance of nutrients and light; high in biodiversity

The ecological zone at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers.

A river or stream flowing into a larger river or lake. Most originate at the sources in higher elevation.

A landform that forms from deposition of sediment that is carried by a river as it flows toward the mouth. Enters slower-moving or stagnant water.

A winding curve or bend of a river or road. Comes from the Greek word "to wander".

The well-lit, open surface waters zone in a lake away from the shore. This is the part of the lake where most photosynthesis occurs.