Marine Biology
Lecture 7: Estuaries
What is an estuary?

Definition

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“Partially enclosed embayment where fresh
and salt water meet.”
Biological perspective

One of the most biologically productive types
of ecosystems in the world
Types of estuaries in Oregon
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Drowned river mouth
River dominated
Bar built
Blind
Bar-built estuary

Cape Hatteras,
North Carolina
Bar Built Estuary
Stony Brook Harbor, Long Beach
Parts of an estuarine system
Salinity profiles

Positive “salt wedge” estuary
Salinity classifications (cont.)

Negative (“evaporate”) estuary
Effects of tides on salinity
Other physical characteristics

Substrate
General description
 Relationship to salinity

Other physical characteristics (cont.)

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Temperature
Wave action and currents
Turbidity
Oxygen
Salinity tolerance of organisms
Osmoconformers vs. osmoregulators
Estuarine food webs

Sources of energy
Organic matter
 Phytoplankton
 Algal mats
 Plants

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Primary consumers
Planktovores
 Detritovores

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Key predators
Estuarine food webs
Focus: Niche partitioning in birds
Prey location tactics
Common estuarine animals
in Oregon
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Worms (a variety)
Clams (a variety)
Snails (in some)
Ghost shrimp (Calianassa californiensis)
Sand shrimp (Crangon spp.)
A variety of crabs

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Cancer magister can be found in estuaries, although
they are stenohaline and found near the bottom
Predatory fish
Birds
Common estuarine organisms
in Oregon

Worms: a variety

Abarenicola sp.
Common estuarine organisms
in Oregon
Saxadoma nutalli: butternut clam
Protothaca staminia: littleneck
Mya arenaria: soft-shelled clam
Photos: Melissa Phipps
Macoma nasuta: bent-nosed clam
Common estuarine organisms
in Oregon

Snails

Cerithidea sp.:
California horn snail
Common estuarine organisms
in Oregon

Callianassa californiensis: the ghost shrimp
Common estuarine organisms
in Oregon

Crangon sp.: the sand shrimp
Salt Marshes
Mangroves
Mangrove prop roots