Docstoc

Marshes

Document Sample
Marshes Powered By Docstoc
					Marsh Plants
               Objectives
• Be aware of the different types of marshes
• Understand the stressors of a salt marsh
• Understand the ecological role of the marsh
• Understand how SAV is adapted to living in
  an aquatic community
• Have a general understanding of the role of
  sea grasses
  Kinds of Chesapeake marshes
• Salt marshes - found closest to the ocean
  near the mouth of the Bay
  – high amount of salt water
• Brackish marshes - found in the middle
  regions of the Bay and mid tributaries of
  lower Bay
  – mix of salt water and fresh water
• Fresh water marshes - found near the
  headwaters of most tributaries
  – minimal mixing with salt water is minimal
   The Terrain Can Be Difficult
• Water salty enough to kill most other forms
  of vegetation
• Soft muddy bottom that doesn't offer much
  support
• A water-logged oxygen poor substrate
• The ebb and flow of tidal currents twice a
  day
Marsh Location
•   This false color infrared - visible
    image is composed of three
    separate Thematic Mapper images
    acquired in the summer of 1993.
    TM bands 4,3 and 5 were used
    here. In general, red areas show
    healthy vegetation, green areas are
    urban. Light-blue to white areas are
    generally indicative of bright soil -
    they possibly represent agricultural
    areas. Marshes appear as a deeper
    blue. Large marsh islands, such as
    Bloodsworth, are visible near the
    center of the picture. Black areas
    represent open water.
            SO…. Why Bother?
                            • Spartina alterniflora-
• Plants that have            saltmarsh cord grass in the
  adapted to these
  conditions have the         low marsh
  narrow edge of land
  between the low and
  high water mark to
  themselves.
  – Spartina spp.:
    dominant in the lower
    ends of the Bay
              Spartina patens
• Spartina patens, or
  saltmeadow hay is in
  the high marsh-
  different from S.
  alterniflora in being
  shorter and wiry and
  forms "cowlicks"
     Adaptations: To High Salt Concentration

•   Xerophytic adaptations- adaptation to low water stress- salt
  water is very drying to tissue
• Two possible ways of adapting to salt
     – get rid of the salt that comes in,
    a.) One method that Spartina spp. use is to remove the salt via salt
    glands - a group of cells that collect and pump salt out onto the surface
    of the plant. Then the rain and tides wash the salt off the plant.
     – deal with it once it gets into the cells.
    a.) Other marsh plants deal with the potentially harmful salt in their
    cells by taking up water to dilute the salt content.
    b.) seen in plants that have succulent leaves and stems
 Adaptation: To Soft Sediments
• Most marsh plants are well anchored
  because marsh soils are soft and muddy,
  and because there is mechanical stress from
  the tidal currents. Many plants, like
  Spartina spp., are doubly anchored.
• Grow by thick rhizomes just under the soil
  surface.
  – 2 types of roots along the rhizome
     • thin water-absorbing roots
     • deep stout roots that lack root hairs but act to anchor
       the plants.
      Adaptation: To Low O2
• Most marsh grasses are rooted in anaerobic
  soils. All cells require oxygen. Problem is
  how to get O2 to the roots and rhizomes.
  – They have lacunae in the roots and rhizomes
    that allow the O2 produced in the leaves to
    diffuse (move) down to cells that need oxygen
    in the roots and rhizomes.
         Ecological Importance of
                 Marshes
• Their massive rhizome surface and deep roots
  stabilize the soft sediments and reduce erosion.
• They improve water quality
• The marshes are habitat for many animals:

• Harbor sources of nitrogen fixation
• Decay of marsh plants releases vitamins and minerals
• Oxygenate waters
               Succession
• Defined as a gradual change in an
  ecosystem whereby species are
  introduced/replaced over time; usually
  culminating in a stable climax community.
• The terrestrial/ aquatic interface is a
  dynamic region subject to rapid physical,
  chemical, and biological change.
       Improved Water Quality
• Trap sediment, which helps water quality
• Absorbing excess nutrients and pollutants- before
  they enter the bay
• Provide food for the food chain. The marsh plants
  and SAV are seldom eaten directly - but rather as
  are eaten as detritus (plant matter after it has died-
  it becomes covered by bacteria which are then
  eaten). Estuarine ecosystems have a detrital food
  chain - where everyone eats detritus or eats what
  eats detritus.
       Habitat: Where Home Is
• Oysters and mussels attached to the rhizomes
• Periwinkles - small snails that move up and down
  the Spartina sp. stems with the rise and fall of the
  tide
• Juvenile species of fish and crabs
• Large wading birds like egrets and herons
• Mammals like nutria and muskrat
  Submergent Aquatic Vegatation:
              SAV
• Also called hydrophytes spend lives underwater
• Hydrophytes have adaptations to aquatic life
  – SAVs evolved from terrestrial plants that re-invaded
    the sea
  – Holes or spaces (called lacunae -Latin for space) in
    the tissue of the seagrass.
     • Up to 60% of leaf volume is air space
     • Allows for gas exchange (O2,CO2) throughout plant
     • Aid in Flotation- upright leaves get more light than
       sunken leaves
       Adaptations continued
• Location of Chloroplasts
  – in seagrasses the chloroplasts are in the
    periphery of the plant - intercept more light
• Adaptation to constant water movement
  – leaves are thin, strap-like and supple. Allows
    them to withstand tidal currents and wave
    action.
                  More still
• Thick tangled mat of rhizomes that keep
  them attached to the soft bottom- not roots
  – an adaptation to soft substrate bottom of the
    Bay - mostly a soft muddy substrate -
  – allow fast vegetative growth- primary mode of
    reproduction
• Adaptation to water pollination
  – Their pollen are released in gelatinous strands
    that are carried by water currents
             Role of Sea grasses
• Rhizomes stabilize bottom
• Leaves baffle wave energy (less destructive to shoreline)
• Promote sedimentation (silt falls out), thereby improving
  water quality
• Provide habitat/nursery/shelter for hundreds of organisms,
  including: sea horses, grass shrimp, small fishes.
• Grass beds are a major source of detritus, and the estuarine
  food chain, unlike terrestrial food chains, is based on
  detritus - few plants eaten directly.
• Grass beds are a direct food source for some animals -
  especially diving ducks Until recently the bay grasses were
  like an underwater carpet along the shallow waters of the
  bay
Examples of SAV
                     References
•   http://www.dnr.state.md.us/bay/sav/importance.html
•   http://www.assateague.com/marsh-cg.html
•   http://www.dnr.state.md.us/bay/sav/key/index.html
•   http://www.chesapeakebay.net/info/wetlds1.cfm

				
DOCUMENT INFO