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  • We are here at Folgers Marsh on the island of Nantucket and

  • we are going to talk about what a salt marsh is. Salt marshes are

  • communities of grass - and the animals associated with them -

  • that form in quiet embayments between the high tide low tide marks.

  • It is an interesting habitat because it is both

  • an aquatic habitat - flooded with salty water -

  • and a terrestrial habitat. When the tide comes in

  • - as we see here at high tide - the water moves over the surface of the grass

  • and is partially an aquatic habitat.

  • The grasses are experiencing salty-water, which is not

  • a great condition for them. But these grasses are

  • adapted to tolerate it.

  • Animals move onto the marsh and get some protection from predation.

  • Things like little shrimp and little fish can move onto the surface

  • of the marsh.

  • There is a gradation of species on the marsh -

  • from this edge or this low tide or low marsh mark

  • to the high tide mark as you move back.

  • At the edge we have this species called 'Spartina alterniflora'

  • - or salt marsh cordgrass. It can grow

  • pretty tall in some areas, and as you move back

  • onto the marsh it stuts.

  • It is most covered by the tide for the longest period of time

  • - tides come in and out on a six hour cycle

  • twice a day. It can tolerate being

  • flooded by water because it has aerial roots.

  • Plants take in oxygen through air not their water.

  • The animals that live on the marsh however, most of them are

  • aquatic animals. Things like mussels and fiddler crabs.

  • They get oxygen from the water. I am going to talk a little about the animals

  • in the marsh. You can see there are birds feeding.

  • This is [an] important habitat for feeding

  • - things like egrets, herons

  • and osprey. The water that comes in through

  • the marsh channels - and flows throughout the marsh -

  • is [an] important habitat for crabs

  • and smaller juvenile fish of some commercially important species such as

  • flounder and

  • bluefish. We also have smaller species that are

  • salt marsh creek inhabitants that provide food for the

  • crabs and the other larger fish. At the edge

  • of the marsh there is a mussel that is attached

  • to the substrate and to the

  • roots of the 'Spartina alterniflora'. This mussel called the ribbed mussel

  • - 'Geukensia demissa' - has a mutualistic

  • association with the grass. It provides

  • nitrogen and stabilizes the roots,

  • while the plant provides a place for it

  • to attach to - and a little bit of protection from predators.

  • You also find fiddler crabs. Fiddler crabs make little burrows

  • along the edge

  • - and there [are] actually three species of fiddler crab that live

  • in this marsh. Some live in this more sandy habitat

  • another species lives in more muddy habitat[s]. As you go

  • back through the marsh towards the road there is actually

  • a source of fresh water, and you get a third species that lives

  • in that more brackish water - or less

  • salty water. Fiddler crabs make burrows, and this burrow

  • help aerate the substrate.

  • One condition of a marsh is that when it is flooded you have a lot of microbial

  • action going on.

  • It depletes the water that is in the sediment of oxygen.

  • As you move back - if you were to dig a hole

  • and let it fill with water - that water would be very smelly because of the microbial

  • action - sulfur.

  • It also would have very little oxygen if any oxygen at all.

  • This is also a physiological stress for plants and animals.

  • So you can see [that] a salt marsh is a very unique

  • community of plants and animals that

  • live in this area the coast.

  • It is an important habitat, it is a habitat that provides a lot

  • of primary production. Which means the grasses take in carbon dioxide

  • and turn that into organic carbon.

  • It also is an important habitat for

  • the coastline behind it. It provides protection from

  • storm damage [as] a buffer zone between

  • the sea and the land.

  • Thirdly, it is an important habitat for

  • these important commercial species and juvenile fish that use the salt marshes

  • to grow larger - they use the food provided by the other smaller organisms

  • that

  • eat the detritus provided by the plants.

We are here at Folgers Marsh on the island of Nantucket and

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B2 中上級

塩沼の紹介 (Intro to Salt Marshes)

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    QAM Chen に公開 2021 年 01 月 14 日
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