Marine Biology Chapter 14: Estuaries

bar-built estuary

estuary formed when islands or geographical barriers form a wall between freshwater from rivers and saltwater from the ocean

coastal plain estuary

estuary formed between glacial periods; water from melting glaciers raises the sea level to flood coastal plains and low-lying rivers (aka drowned river valley estuary)

cordgrass

a plant in the genus Spartina; the dominant vegetation in North American salt marsh communitities

drowned river valley estuary

an estuary formed between glacial periods, when water from melting glaciers raises the sea level and floods coastal plains and low-lying rivers (aka coastal plain estuary)

embayment

area of coastline where portions of the ocean are cut off from the rest of the sea

estuary

a region where freshwater is mixed with saltwater

euryhaline

able to tolerate a broad range of salinities

fjord

a deep valley cut into the coastline by glaciers and filled with a mixture of freshwater and saltwater

high marsh

the region of a salt marsh closest to shore that is covered briefly by saltwater each day

low marsh

the portion of a salt marsh that occupies the lower intertidal zone and that is covered by tidal water much of the day

negative estuary

an estuary in which the surface water flows toward the river and the water along the bottom moves out to sea

osmoconformer

an animal whose tissues and cells can tolerate dilution

osmoregulator

an animal that can maintain an optimal salt concentration in its tissues regardless of the salt content of its environment

partially mixed estuary

an estuary that has a strong surface flow of freshwater and a strong influx of seawater

positive estuary

an estuary in which the surface water from the river flows out to sea and saltwater from the ocean moves into the estuary along the bottom

pseudofeces

large, semisolid particles produced by bivalves and consisting of phytoplankton and detritus that they filter but do not consume

salt-wedge estuary

an estuary in which the seawater moves in and out along an angled boundary known as a salt wedge

salt wedge

angled boundary between saltwater and freshwater in an estuary caused by rapid river flow that prevents saltwater from mixing with freshwater

tectonic estuary

an estuary that forms when earthquakes cause the land at the mouth of a river to sink, allowing seawater to cover it

tidal flat

An area of estuary that is exposed at low tide and covered at high tide.

tidal overmixing

occurs in estuaries at high tide; dense seawater at the surface moves upstream faster than lighter freshwater at the bottom, the seawater sinks causing mixing

well-mixed estuary

estuary with low river flow and tidal currents affecting water circulation, resulting in a seaward flow of water and uniform salinity at all depths