estuaries

what is an estuary?

semi-enclosed coastal areas where freshwater from rivers mixes with seawater

Estuary characteristics

very productive areas ecologically

highly impacted by human activity

Outwelling

movement of materials and nutrients from estuaries out into ocean

Salinity

mixing of fresh water causes fluctuations in salinity but this will vary in location from the river or water depth

salt wedge

higher salinity water sinks to bottom

What causes the salt wedge to move back nd forth?

tides

this is how organism get exposed to ranges of salinity

tidal currents

strong movement of water due to tides moving in narrow areas of estuaries

substrate is mostly

sand or soft mud

characteristics of substrate

particles of sediment brought down stream

reduced oxygen creates anoxic conditions

anaerobic respiration bacteria present

temperature

varies due to shallow depths

water clarity

fine suspended particles make water cloudy

what can impact suspension feeders?

poor visibility of water

Estuary ecosystem

harsh environment= low biodiversity

Euryhaline

tolerate wide range of salinity

stenohaline

tolerate only narrow range of salinities

Brackish

water of intermediate salinity

What will organisms of higher internal salt compared to environment do?

they will absorb water thru osmosis

Osmoconformers

ex) tunicates

what do osmoconformers do?

allow body salinity to change w environment

Partial osmoregulators

crustaceans

characteristics of partial osmoregulators

isotonic in seawater (osmoconformers)

hypertonic in fresh water (osmoregulators)

osmoregulators

ex) vertebrates like fish

osmoregulators

keeps body salinity constant: gets rid of excess water or absorb more salt by active transport using gills/ kidneys

Estuarine plants

most were land plants evolved to live in higher salinities/

estuarine plants: Cordgrass (Spartina)

excretes extra salt thru salt glands

estuarine plants: some succulents

bring in water to dilute salt

what does muddy bottom require?

adaptations to move thru substrate or to get more oxygen

Saltmarshes(tidal marshes)

present in temperate and subarctic, extensive grassy areas extending inland from mudflats

are salt marshes flooded at high tide?

YES

what are wetlands?

saltmarshes+ freshwater marshes

Do salt marshes have a muddy bottom?

yes, and it’s also dominated by salt tolerant plants (unlike mudflats)

where are cord grasses located in the muddy bottom?

near mudflat margin closer to ocean side

cordgrasses protect coast from what?

wave action

what are the plants like closer to land?

they are still salt tolerant

Function of the bacteria in mud

decompose dead plant material

are mudflats exposed at low tide?

yes

how are mudflats similar to soft bottom coastal areas?

there is desiccation at low tide

also changes in salinity

mudflats: who provides primary production?

diatoms

mudflats: The bacteria produce…

hydrogen sulfide used by sulfur bacteria for chemosynthesis

mudflats: the types of animals are…

infauna (polychaete worms, bivalves, crustaceans)

what do the infauna feed on?

detritus

common predators (mudflats)

birds (low tide) and fish (high tide)

Mudflats also have…

suspension and deposit feeders

Channels

open water columns

do channels have high economic importance?

YES