Smithsonian National Zoological Park l Friends of the National Zoo



Settle Down: Turbidity and Water Quality


Living or growing in or on the water.
A wide area of water extending into land from a lake or the sea.
Chesapeake Bay
An estuary formed where a large, wide area of the Atlantic Ocean extends inland; it is bordered by Maryland and Virginia.
An indication of the clearness, or transparency, of water and thus, how deeply light can penetrate into water. Low clarity in a natural body of water is a sign of runoff, erosion, or algae blooms; very clear water doesn’t support diverse plant and animal life.
A system of interdependent plants, animals, and micro-organisms interacting with each and the physical and chemical environment.
The process by which soil or land is worn away by wind, water, ice, gravity, and human land use and activities such as farming, logging, and road building that increase runoff.
A large area near the mouth of a river (or rivers) where the river’s fresh water mixes with the sea’s salt water, and is affected by tides.
A variable, measurable characteristic.
The process by which green plants convert sunlight into energy.
Contaminants introduced into an environment that causes harm to the environment and the health of plants and animals.
Water, from natural and human sources, that flows over land and into a body of water.
Secchi disk
To measure water clarity, a disk divided into black and white quarters is dropped into water and when it is no longer visible, the distance from the water surface is called the Secchi disk depth.
Small pieces of soil, rock fragments, and plant and animal matter transported from land into water bodies by rain, wind, or ice. Sediment can carry nutrients and pollutants into a watershed.
Particles formed when minerals and organic materials from the remains of dead plants and animals are broken down by climate changes and organisms.
A measurement of the materials in water that block the sunlight’s ability to pass through it, affecting the water’s clarity. Turbidity increases from soil erosion, pollution, runoff, flooding, algae growth, and even marine life that can agitate sediment which has settled on the bottom of a waterway.
A geographical land area whose water drains into a particular stream or river. Large watersheds, such as that of the Chesapeake Bay, is formed of several smaller watersheds.