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A. Mangroves

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. c. Distribution. 240,000 km 2 worldwide 2,700 km 2 in Florida 68 spp worldwide 10 spp in the Americas.

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A. Mangroves

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  1. 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

  2. c. Distribution • 240,000 km2 worldwide • 2,700 km2 in Florida • 68 spp worldwide • 10 spp in the Americas

  3. 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

  4. B. Three Main Genera • Rhizophora (red mangrove) • R. mangal and R. racemosa most common New World spp • High prop roots and dangling roots are common (Figure 11-8) • More cold tolerant

  5. 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

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

  7. C. Geomorphological settings • need gentle wave/tidal action to bring nutrients • salinity allows them to out compete FW species

  8. 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

  9. b. Riverine – along tidal affected rivers • Grow to 21 m tall • Rhizophora dominated, but with few prop roots • Avicennia and Lagunicularia also present • Salinity 10-20 ppt

  10. 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 >50ppt: Avicennia, if low: lagunicularia, 30-40ppt mixed forest

  11. d. Dwarf – isolated, low productivity, low FW, low nutrients • Grow to 2-5m shrubs • Fringe of everglades, Florida Keys • Hammock – one type • buildup of peat • Rhizophora dominated

  12. E. Understory – lacking due to variety of stressors • Mangrove ferns (Acrostichum spp) are common, 3 spp worldwide

  13. F. Salinity • Not required for mangroves • Much higher in soil than in water

  14. G. Zonation

  15. 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

  16. Crabs – mangrove maintenance • Burrow, oxygenate soil, drag leaves into soil, aid in decomposition • Selectively eat dropped hypocotyls

  17. J. Hurricanes

  18. 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

  19. K. Mangrove effects on estuaries • Net export of organic matter and nutrients • Provides nursery areas and food sources for fisheries

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