A. Mangroves

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A. Mangroves

• Or Mangal
• from mangue (tree) and grove (stand of trees)
• Replace salt marsh as the dominant coastal
  ecosystem in subtropical and tropical regions
• Facultative halophytes

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c. Distribution

1. 240,000 km2 worldwide
2. 2,700 km2 in Florida
3. 68 spp worldwide
4. 10 spp in the Americas

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Distribution Continued

• Found on coastlines between 25? N and 25?S
  latitude, dependent on temperature
• Rhizophora - survive 2-4? C for 24 hrs
• Avicennia survives 2-4? C for several days

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B. Three Main Genera

1. Rhizophora (red mangrove)
2. R. mangal and R. racemosa most common New World
   spp
3. High prop roots and dangling roots are common
   (Figure 11-8)
4. More cold tolerant

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• b. Avicenna (black mangrove)
• i. A. germanaus most common in New World
• ii. Can tolerate very high salinity (60 ppt) and
  very anoxic conditions
• iii. Known for having pneumatophores

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• Lagunicularia (white mangrove)
• L. racemosa most common in New World
• Affinity for lower salinity areas

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C. Geomorphological settings

1. need gentle wave/tidal action to bring nutrients
2. salinity allows them to out compete FW species

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D. Hydrodynamic settings

• Fringe protected shorelines, some canals,
  rivers and lagoons
• Grow to 13 m tall
• Accumulate organic matter
• Found in S. Fla, Puerto Rico, Mexico, Texas
• Avicennia found in salinity to 59 ppt, Rhizophora
  to 39 ppt
• Overwash islands one type of fringe mangrove
• Rhizophora dominated
• sensitive to ocean pollution

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b. Riverine along tidal affected rivers

1. Grow to 21 m tall
2. Rhizophora dominated, but with few prop roots
3. Avicennia and Lagunicularia also present
4. Salinity 10-20 ppt

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c. Basin- inland depressions, behind fringe, in
stagnant water

• Grow to 9m tall
• Soil conditions highly anoxic, saline
• Avicennia and Lagunicularia with many
  pneumatophores
• If salinity gt50ppt Avicennia, if low
  lagunicularia, 30-40ppt mixed forest

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d. Dwarf isolated, low productivity, low FW,
low nutrients

1. Grow to 2-5m shrubs
2. Fringe of everglades, Florida Keys
3. Hammock one type
4. buildup of peat
5. Rhizophora dominated

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E. Understory lacking due to variety of
stressors

• Mangrove ferns (Acrostichum spp) are common, 3
  spp worldwide

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F. Salinity

1. Not required for mangroves
2. Much higher in soil than in water

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G. Zonation
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H. Adaptations

• Salinity exclusion and excretion
• Prop roots and drop roots Rhizophora
• Pneumatophores Avicennia 20-30 cm above
  sediment
• Lenticels found on a b, let oxygen into plant,
  moves through arenchyma to root rhizosphere
• Viviporous seedlings Rhizophora seeds
  germinate on tree
• i. Hypocotyls (seedling) drops, floats till
  touches sediment, roots

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Crabs mangrove maintenance

1. Burrow, oxygenate soil, drag leaves into soil,
   aid in decomposition
2. Selectively eat dropped hypocotyls

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J. Hurricanes
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Hurricanes Continued

• mangrove succession to stable community in
  average time between major hurricanes
• Wipe out larger mangroves, small trees in gaps
  survive and act as a seed bank

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K. Mangrove effects on estuaries

1. Net export of organic matter and nutrients
2. Provides nursery areas and food sources for
   fisheries

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