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Prepared by Diana Wheat-LBCC

� Compare and contrast the various types of

estuaries, including their origin, size, shape,

and general location on earth.

� Distinguish and describe the different types of

habitats found in a typical estuary.

� Evaluate the different types of osmotic capabilities of estuarine species.

� Discuss threats to estuaries.

� Summarize uses by humans.

Where the Fresh water (rivers & streams) meets the Ocean.

Also known as bays if ship traffic occurs there.Salinity and currents fluctuates with the tides.Often an area rich in nutrients.Ecotone of possibly

high biodiversity.Also called:� Fjords� Sound� Tide/mud flats� Inlets� Salt Marshes

Estuaries are classified by:

> Mode of formation

e.g. glaciers, deposition, sea level rise

> Patterns of water circulation

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I. Coastal plain

Broad and shallow embayments

Continuously modified

by wave erosion

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II. Bar-built

Formed by a barrier island trapping water near the

coast that enters from a river or stream

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III. Coastal lagoon

� Large embayment with little freshwater input

IV. Delta

Estuary with a broad, poorly defined fan-shaped mouth

The Mississippi River Delta, showing the

sediment plumes from the Mississippi

and Atchafalaya Rivers, 2001.

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V. Tectonic

� Created when the underlying land sank because of

crustal movements of the Earth e.g. San Francisco

Bay

VI. FjordEstuary that is deeply entrenched into a landform—carved out by a glacier

Seen in:NorwayAlaskaCanadaChileIcelandNew Zealand

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Salt marshes

� Very wet grasslands

� Include many halophytes

▪ Pickleweed, marshgrass, cordgrass

A true plant – not a seaweed.

Contributes to GPP.

Habitat for many fish/invertz.

Reduce erosion from tides/storms

Food for many animals including sea turtles, & marsh herbivores.

An area the size of a football field is

lost every day on a world wide

average.

These are areas of refuge and

protection– including to human

interests.

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Mudflats

� Made of rich, thick mud exposed to air at low tide

� Include many diatoms, seaweeds, and seagrasses

Courtesy of James Sumich

Oyster plots on the mudflat in Netarts Bay. OSU research

Photo credit: Tiffany Woods, Oregon Sea Grant

Channels

� Always filled with

water

� Include many

planktonic, nektonic,

and benthic organisms

▪ Crabs, fish, oysters,

zooplankton, phytoplankton

(c) ollirg/Shutterstock

� Estuaries have frequent salinity changes.

� Animals and plants living in estuaries must have

special adaptations.

� Osmoconformers - body fluids fluctuate with

changing salinity e.g. soft bodied epifauna.

� Osmoregulators – animals that regulate to some

degree their body fluid composition e.g. crabs

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I.Stenohaline – Tolerance to limited salinity ranges -

most FW fish, can’t tolerate higher salinity and

Haddock, can’t tolerate lower salinity. “steno”

means “narrow.”

II. Euryhaline – Tolerance to a wide range of salinity.

e.g. sharks often rely on shallow inshore areas for

nurseries – including wetlands.

Migratory species like Salmon, Herring

" There has long been a belief that the sea, at least, was inviolate, beyond man's

ability to change and to despoil.

But this belief, unfortunately, has proved to be naive."

Rachel Carson

� Withdrawing water at unsustainable rates

- Surface and groundwater are being depleted

- One-third of the world’s people are affected by shortages.� Most water (FW) is used in agriculture� People also engineer waterways

- Dams, levees, diversion canals

- For supplies, transportation, and flood control� Dredging: Clearing waterways for commerce.� Pollution: including plastics, toxins, antibiotics,

thermal, organic matter e.g. sewage, oil spills, dioxins� Coastal development – loss of mangroves, eel grass

beds, salt marshes etc.� Overfishing

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� Shellfish & crab harvesting

� Fishing – especially dredging

� Mariculture – oysters/shrimp

� Boating sports e.g. kayaking, paddleboarding

� Cruises for tourists

� Commerce – shipping/bays� Bird watching

� Vacation spots e.g. tropical lagoons

NOAA education portal

https://oceanservice.noaa.gov/education/tutori

al_estuaries/welcome.html

Ocean Blue Projecthttps://www.oceanblueproject.org/