Salt marsh 鹽沼 en.wikipedia.org
• The boundaries of the salt marsh roughly
coincide with high spring tide and low spring
tide
• A salt marsh, also known as a coastal salt
marsh or a tidal marsh, is a coastal ecosystem
in the upper coastal intertidal zone between
land and open salt water or brackish water
that is regularly flooded by the tides.
Salt marsh
• It is dominated by dense stands of salt-tolerant
plants such as herbs, grasses, or low shrubs.[1][2]
These plants are terrestrial in origin and are
essential to the stability of the salt marsh in
trapping and binding sediments.
• Salt marshes play a large role in the aquatic food
web and the delivery of nutrients to coastal
waters. They also support terrestrial animals and
provide coastal protection
Animation of spring and neap tides
oceanservice.noaa.gov
http://www.mmscrusaders.com/news
cirocks/tides/tideanim.htm
The bulge under the moon is produced due to
gravity "stretching" the water, pulling it toward
the moon. The bulge produced on the
opposite side of the Earth is made because the
moon tries to pull the Earth out from under
the water!
Tide 潮汐
• Together, the gravitational pull of the moon and the
sun affect the Earth’s tides on a monthly basis. When
the sun, moon, and Earth are in alignment (at the time
of the new or full moon), the solar tide has an additive
effect on the lunar tide, creating extra-high high tides,
and very low, low tides — both commonly called spring
tides. One week later, when the sun and moon are at
right angles to each other, the solar tide partially
cancels out the lunar tide and produces moderate tides
known as neap tides. During each lunar month, two
sets of spring and two sets of neap tides occur (Sumich,
J.L., 1996).
Tide潮汐
• When the moon is full
or new, the gravitational
pull of the moon and
sun are combined.
• At these times, the high
tides are very high and
the low tides are very
low.
http://wiki.answers.com/Q/What_is_a_spring_tide
aguahedionda.org
http://en.wikipedia.org/wiki/Salt_mar
sh
Rivers provide the salt marsh with a source of
sediments沉積物 and nutrients.營養鹽
oceanclassrooms.com
濕地 鹽原 鹽沼
紅樹林
亞潮帶
ozcoasts.gov.au
Effects of dredging 挖泥
1.
Dredging results in the short term degradation of animals, vegetation and microbial
communities that live in the dredged sediment. This reduces the estuary's capacity for
nutrient cycling, primary production and habitat provision and can have flow on effects
up the food web. Though these effects tend to be short lived, in some cases they may
trigger long-term changes.
2.
Changes in channel profile caused by dredging can increase tidal area, wave height and
water velocity, resulting in bank erosion. Eroding banks threaten mangroves and other
mud-bank communities and can lead to increased turbidity. Suspended sediment in the
water column blocks light, reducing benthic primary productivity and inhibits the ability of
benthic plants to recover from impacts of dredging.
3.
Dredging exposes anaerobic layers of sediment, potentially disturbing and remobilising
toxic sediments, releasing contaminants. This has implications for water quality.
4.
Dredge spoil needs to be deposited somewhere, though this could be deemed habitat
2.
Changes in channel profile caused by dredging can increase tidal area, wave height and
water velocity, resulting in bank erosion. Eroding banks threaten mangroves and other
Effects of dredging 挖泥
mud-bank communities and can lead to increased turbidity. Suspended sediment in the
water column blocks light, reducing benthic primary productivity and inhibits the ability of
benthic plants to recover from impacts of dredging.
3.
Dredging exposes anaerobic layers of sediment, potentially disturbing and remobilising
toxic sediments, releasing contaminants. This has implications for water quality.
4.
Dredge spoil needs to be deposited somewhere, though this could be deemed habitat
creation, it can smother existing habitats and frequently contains contaminants which
often move and bioaccumulation through the food web. The impacts of dredge spoil
disposal can range from short term to long term.
5.
Changes to tidal range and wave action can result in mangrove encroachment into
saltmarsh areas
Food Webs in Specific Wetland Types.
Salt Marsh
kingfish.coastal.edu
Supplimentory reading
• http://kingfish.coastal.edu/biology/sgilman/7
78EcologyFoodWebs.htm
• Producers: the marsh grasses, Spartina and
Juncus mostly, plus various other salt tolerant
plants as well as lots of algae
Benthic Habitat
Probably less than 10% of the above ground primary productivity in a saltmarsh
actually gets grazed,. Most plant biomass dies and decays and is passed through the
detrital food web where the major consumers are bacteria and fungi. These are then
consumed by the smallest animals—worms, copepods, rotifers, larval stages of benthic
invertebrates, in other words, plankton. The bigger benthic invertebrates are either
scavengers (crabs, snails) or filterers (oysters, mussels).
Reminder
• 1. Ecology: a word comes from the Greek word
oikos which means "home" and so ecology is the
study of organisms with themselves, each other,
and their habitat—their home.
• 2. Population : a group of the same species living
in the same place at the same time.
• 3. Community: to all the organisms interacting
with one another and sharing available resources
within a defined area.
Reminder
• 4. An ecosystem: all communities in a
particular area as well as all the abiotic factors
affecting that area.
• 5. Ecotones or ectones: Ecosystems sort of
fade into one another as them meet. They are
not sharply defined. These in-between zones
are called ecotones or ectones.
Salt marsh
http://science.kennesaw.edu/~jdirnb
er/oceanography/LecuturesOceanogr
/LecSaltMarsh/LecSaltMarsh.html