Chapter 14 Marine Science (14.3 Estuaries as ecosystems)

Organisms in the estuaries are normally

euryhaline

(tolerate a wide range of salinities). Eury means "combining" and haline means "salt."

Rarely there are stenohaline organisms,

because these can only tolerate a narrow salinity range.

Steno means "narrow" and haline means "salt."

Some are osmoregulators and have mechanisms

for keeping their internal concentration stable

Others are osmoconformers and have internal concentrations

that vary with that of their surroundings.

Water dilutes the solution:

it makes it more watery!

Water will flow into a solution

where there is a lower water concentration

(higher solute concentration)

The solute

is whatever is dissolved into the solvent, such as salt in seawater.

Water is the

universal solvent

If the solution has more solute,

it is called hypertonic.

When cells are in a solution that is hypertonic (more solute)

the water from the cells will flow out, dehydrating the cells.

When cells are in a solution that is hypotonic (less solute)

the water from outside will flow in, hydrating the cells.

Osmosis

is the movement of water through a semipermeable membrane (it flows to the hypertonic solution)

Salinity

- depth contributes to salinity profile.

Salinity is not uniform

(saltwater is more dense and sinks below fresh water) as water is brought in by tides: salt wedge.

Plankton and fishes are

open water organisms

Many marine species spend at least a portion of their lives

in an estuary, mostly as larvae.

Estuaries are

nurseries and provide protection to smaller organisms

Salmon spend part of their life cycle in fresh water and brackish water,

and their adult lives are spent mostly in the ocean.

Salmon are

osmoregulators.

Spawn/Spawning:

to release eggs

Anadromous fishes:

Species of fish that migrate from the sea to freshwater to spawn (Pacific salmon).

Catadromous fishes:

Species of fish that migrate from freshwater to the sea to spawn (N. American eel).

Larva (larvae plural)

the immature stage of an animal that undergoes a metamorphosis, extreme changes during development from early life to adulthood

Salmon larval stage

is the alevin.

North American freshwater eels are

catadromous (they do the opposite)...

some mangrove species posses

pneumatophores, vertical root extensions that help in the exchange of gases

(sediments often anoxic)

Mangrove trees

- found in tropical and subtropical coasts

- typically replace salt marshes in these areas

- high primary production

- species-rich community (marine as well as terrestrial species); birds nest in the branches

- protect coasts against wave action from storms

Salt Marshes

Cordgrass (spartina species) dominates along water edge in most salt marshes

- high primary production

- nursery for young of many species

- contribute detritus to the estuary for filter feeders and deposit feeders

- Salt marshes often flood at high tide

During low tide the soft bottom of the estuary

may be exposed, revealing mudflats

Mudflats are below

the salt marshes

Infauna

similar to those in the intertidal zone

Various worms, clams, shrimps, and crabs

will burrow in the sediment.

Expel Excess Solutes

salt glands in cordgrass (Spartina) and mangroves

Flowering plants in estuaries

concentrate solutes in tissues as in pickleweed (salicornia) succulents native to salt marshes

Flora and fauna have various strategies

for handling excess salt

Sea grass beds

- can be found in some estuaries if water clarity permits.; need sunlight for photosynthesis

- high primary production

- food source and habitat for fish and other organisms

- help stabilize substrate

Oyster reefs (shellfish reefs)

- Are found in many estuaries

- Beds of oysters on which many other species grow and thrive

- May provide the only hard substrates in many estuaries

- Filter the water