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Seagrass Josie Strahle. Grow in meadows Reproduce sexually and asexually Flower in summer emerged to 1.5m Originated on land and adapted to water High genetic diversity. Significance of Seagrasses. Provide nursery areas for juvenile fish and crustaceans

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Seagrass Josie Strahle

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Grow in meadows
  • Reproduce sexually and asexually
    • Flower in summer
    • emerged to 1.5m
  • Originated on land and adapted to water
  • High genetic diversity
significance of seagrasses
Significance of Seagrasses
  • Provide nursery areas for juvenile fish and crustaceans
  • Provides food and habitat to endangered sea turtles and manatees
  • Also support mollusks, gastropods, insects, and other plants
  • High productivity, supports biodiversity
  • Export carbon, nitrogen, phosphorus to coastal food webs
  • Stabilize sediment on sea floor - improve water quality
seagrasses as nurseries
Seagrasses as Nurseries
  • Fish move to meadow as larva, move off shore when grown
  • Some studies report that growth is faster in seagrass beds than in non-vegetated environments
  • Importance varies geographically
    • meadows more important as nurseries in United States than in Australia
    • More important in tropical Caribbean then in Indo-Pacific region
Usually Flat, linear leaves with parallel veins
  • Tallest - Thalassodendron ciliatum - 126 cm
  • Smallest - Halophilia minor - 2 cm
  • Oval-shaped leaf
  • Ball formed by surf - Australia
  • Grows in intertidal
Johnson’s seagrass - 1-2 inches tall
  • Can grow in very shallow water
  • Able to take up nutrient through roots and shoots
  • Fixed nutrients from detritus are then released by leaching and microbial mineralization
    • increases nutrient levels and energy flow in meadows
  • Woody underground root
  • grows close to shore
Can tolerate range of salinity: above or below normal sea water
    • flourishes at salinity of 2, 12, 40%
    • 60% and above damaged plants
  • Epidermal cells exposed to high salinity show changes
    • mitochondria closer to plasma membrane
    • smaller vacuoles
    • complex wall in growths
    • density of mitochondria and choloroplasts increased
    • Smaller vacuoles
destruction of meadows
Destruction of meadows
  • Because habitat is close to shore, seagrasses susceptible to destruction
loss of meadows
Loss of Meadows
  • National Marine Fisheries Service petitioned to list the seagrass as endangered in 1998
  • Seagrass meadows being destroyed
    • Physical factors such as storms can destroy seagrass
    • Mostly human causes
Dredging, anchor mooring, boat propellers
  • Erosion due to seawalls
  • Sedimentation, high salinity, poor water quality
  • Sewage discharge
  • Most significant seagrass killers are algae blooms
algae blooms
Algae Blooms
  • Excessive nutrient inputs leads to algae blooms
    • waste water and farm run-off
  • Block out light
    • density of plants reduced
    • productivity reduced
    • light reduction can cause the collapse of a meadow in two years
Once destroyed, meadows take decades to reestablish
  • Some cannot grow back because young plants need shelter of full grown plants