estuaries

Question 1

location

Answer 1

where freshwater meets the ocean

Question 2

substrate

Answer 2

mud, small particles

Question 3

temperature

Answer 3

variable

Question 4

energy

Answer 4

low

Question 5

turbidity

Answer 5

high (water clarity is low)

Question 6

what are the chemical characteristics?

Answer 6

Salinity: variable - “salty & fresh”

Nutrients: high; from land and from surrounding plants

Oxygen: variable

Hydrogen sulfide: abundant in sediment below a few mm

Question 7

what are the types of estuaries?

Answer 7

salt wedge, well-mixed, partially mixed, fjord type

Question 8

describe the salt wedge estuary

Answer 8

the mouth of a rapidly flowing river empties directly into salt water / tidal currents are weak

the river pushes back the seawater creating a sharp boundary that separates an upper less salty layer from an intruding wedge-shaped salty bottom layer – stratified, not mixed

e.g. the mouths of the Mississippi, Columbia and Hudson rivers

Question 9

describe the well-mixed estuary

Answer 9

strong tidal mixing and low river flow

sea water is mixed throughout the shallow estuary

the mixing is so complete that the salinity is the same top to
bottom and decreases from the ocean to the river.

shallow estuaries e.g. Witty’s Lagoon

Question 10

describe the partially mixed estuary

Answer 10

tidal flow erases the salt wedge

salt water is mixed upward and fresh water is mixed
downward

deeper estuaries

e.g. Puget Sound and San Francisco Bay

Question 11

describe the fjord type estuary

Answer 11

a deep elongated basin that is U-shaped and a ledge or barrier that separates the basin from the sea.

moderately high river input and little tidal mixing.

fjord type estuaries are found along glaciated coasts such as British Columbia, Alaska, Chile, New Zealand, Norway

Question 12

biological characteristics

Answer 12

Permanent dwellers and visitors

Diversity – low (for permanent dwellers); moderate if visitors
are included

Productivity – high

Biomass – high

Euryhaline species – estuarine species are tolerant to wide
range of salinities

e.g. barnacles, oysters, green crab (invasive)

Question 13

estuary function/significance

Answer 13

Nurseries for fish & invertebrates

Habitat for larval, juvenile and adult fish, including foraging, refuge
and physiological transition sites for anadromous fish (salmon!)

Spawning habitat for salmon, eulachon and herring

Bird wintering, moulting and breeding habitat

Staging areas along migratory corridors for millions of birds

Rich feeding areas for aquatic and terrestrial mammals e.g. seals,
river otters, mink, wolves, deer, bear

Water filtration

Nutrient cycling

Detritus processing

Question 14

human impacts

Answer 14

Overharvesting & overfishing

Invasive species e.g. green crab Carcinus maenus

Aquaculture e.g. oysters

Coastal development e.g. Hong Kong, New York

Rivers entering estuaries are modified / dam
construction e.g. Colorado River

Chemical pollution from run-off

Agricultural run-off of excess nutrients leading to dead
zones! e.g. Chesapeake Bay

Climate change – increasing seawater temperatures &
sea level rise

Question 15

species

Answer 15

barnacles - euryhaline enzymes for salinity and closing up