Mangroves

Question 1

Where are mangrove communities found

Answer 1

• Tropical environments
• Estuaries (mix of fresh and salt water)
• Most common in Florida

Question 2

3 Conditions needed for a mangrove community

Answer 2

• High salt content in water (nearshore waters as opposed to rivers, though not as high as the ocean)
• Anoxia (lack of oxygen)
• Frequent tidal flooding

Question 3

Red Mangrove tree

Answer 3

• rhizophora mangle
• dominant plant species
• arching prop roots that anchor in sand
  > roots exposed in low tide, roots covered but trunk and leaves exposed in high tide

Question 4

How do mangrove communities get their nutrients?

Answer 4

• Brought in by the tide; outgoing tide flushes the system and released nutrients into the ocean
• Organic debris is trapped by a thick net of roots; decaying debris provides nutrients to the soil (therefore the plant) and feeds juvenile animals like plankton and small fish

Question 5

How do mangrove communities protect the earth?

Answer 5

• prevents erosion:
  > roots held soil together against flood waters and storms
  > absorbs water and energy of storms
  > natural barriers of shores behind them

Question 6

How do mangrove communities protect animals inhabiting it?

Answer 6

• nursery for young; books and crannies for young fish, crabs and mollusks to hide
• complex web of life
• a hard substratum for anchoring algae, oysters and sponges while they filter feed

Question 7

What are the three challenges to mangrove growth?

Answer 7

• anoxia (low oxygen)
• dehydration (loss of freshwater)
• high salinity (hypersaline conditions)

Question 8

Countries with the largest area of mangroves

Answer 8

• indonesia
• brazil
• australia
• nigeria
• mexico

Question 9

How do humans endanger mangrove communities?

Answer 9

• lenticels are highly susceptible to clogging by pollutants
• toxins, poisons and chemicals can kill large numbers of mangrove trees
• coastal developments call for their removal
• shrimp agriculture

Question 10

Why do mangroves smell?

Answer 10

• low oxygen soil hosts anaerobic bacteria, freeing up nitrogen gas, soluble iron, inorganic phosphates, sulfides and methane gasses

Question 11

How do mangroves reproduce

Answer 11

1. Buoyant seeds (“propagules” that produce their own food through photosynthesis) drops into water and travels great distances
2. remains dormant for weeks or months until they find a suitable environment (can survive desiccation)
3. once ready to root, it changes it’s density so that the elongated shape now floats vertically rather than horizontally to lodge in the mud to root

Question 12

How do mangroves limit water loss?

Answer 12

• Lots of hot sun causes evaporation so:
  > restrict the opening of their stomata or to prevent dehydration
  > vary the orientation of their leaves to avoid the harsh midday sun and so reduce evaporation from the leaves

Question 13

Why is hyper salinity a problem for mangroves and how do they solve it?

Answer 13

• too much salt kills plant life
• solution:
  > impermeable, waxy roots create an ultra-filtration mechanism to exclude salts
  > salt that accumulates in vascular tubes is concentrated in old leaves which are then shed

Question 14

Why is anoxia a problem for mangroves and how do they solve it?

Answer 14

• lots of decay uses the oxygen in soil
• solution:
  > lenticels: pores in the bark that take in air
  > pneumatophores: specialized root-like structures stick up (as much as 3 feet) out of the soil like straws for breathing