Chapter 10: Mangrove Forests and Seagrass Beds

Question 1

What is a mangrove?

Answer 1

• woody trees or shrubs that grow at the sea/land interface in tropical estuaries and inlets.
• true mangroves
• mangrove associates

Question 2

what is the difference btwn true mangroves and mangrove associates?

Answer 2

True: only occur in the interface
Associate: found elsewhere, such as rainforests

Question 3

what are the three main types of mangroves?

Answer 3

• riverine mangroves
• tide-dominated mangroves
• basin mangroves

Question 4

Riverine mangroves

Answer 4

• low tidal range and dominance of FW flow
• deltas of major rivers
• most of mangrove forests in Asia

Question 5

Tide-Dominated mangrove

Answer 5

• fully intertidal and full-strength seawater
• high-wave action
• ‘fringing’ mangroves
• pioneer spp

Question 6

Basin mangroves

Answer 6

• the landward side of fringing mangroves

- low tidal currents and wave action

Question 7

Where are mangroves found?

Answer 7

• coincides very closely with coral reefs
• 20*C isotherm on either side of the equator
• modified by either warm currents extending distribution or cold currents in the tropics
• muddy shores

Question 8

Where is the highest and lowest diversity of mangroves?

Answer 8

• Highest: indo-west pac

- Lowest: carribbean/w-atl.

Question 9

Describe the pattern of distribution of species for mangrove forests

Answer 9

a) the fringing mangrove of species at sea edge (pioneer)
b) other true mangrove families (behind fringe spp), mid-swamp
c) behind the true mangroves are the associated mangroves and forest plants

Question 10

what two main factors limit plant distribution?

Answer 10

• increased salt level

- waterlogged sediment

Question 11

How do mangroves survive living in a marine environment with waterlogged mud? (3)

Answer 11

• rhizophora
• bru-guiera
• avicennia

Question 12

Rhizophora

Answer 12

root system which extends the tree up to 2m off the ground

Question 13

Bru-guiera

Answer 13

root system that breaks the soil surface and produces ‘knees’ above the sediment surface

Question 14

Avicennia

Answer 14

root system symbolic of mangroves

• vertical tubes (pneumatophores)
• abundant lenticles for air uptake (on each tube)

Question 15

What two problems does a haline environment present to mangroves?
how is this fixed?

Answer 15

a) disrupts cellular mechanisms
- > secretion of excess salt through the bark or leaves
b) reduces the osmotic difference btwn the root and the sediment
- > only takes water from the top 50cm of soil (FW less dense than seawater)
- >exclude 90 salt at root

Question 16

how do mangroves reproduce?

Answer 16

• flowers pollinated by wind or bees
• vivipary (embryo) grows on plant
• falls from parent and carried by current until it settles and takes root.

Question 17

what are some terrestrial organisms associated with mangroves

Answer 17

• insects (ants termites and mosquitos)
• beetles
• vertebrates (crab-eating frog)
• birds

Question 18

what are some marine organism associated with mangroves?

Answer 18

• barnacle, seasquirt
• algal communities, snails
• tree bark provides ecological niche
• mudskipper, crabs in muds
• leaf litter provide food for grapsid crabs.

Question 19

what roles do mangrove play in ecosystems?

Answer 19

• shoreline stabilization
• nutrient input
• energy flux between mangrove and marine system
• provision of a nursery for fish species that recruit to local fisheries and coral reefs

Question 20

where are seagrass found?

Answer 20

shallow and sheltered coastal waters

-anchored in sand or soft areas

Question 21

how do seagrasses reproduce?

Answer 21

They are angiosperms:

• hydrophilous pollination
• clonal propogation
• ramet
• rhizomes
• seasonal leaf growth

Question 22

which species rely on these as grazers?

Answer 22

• dugongs
• manatees
• turtles

Question 23

are some factors structuring the assemblages associated with seagrass?

Answer 23

• highly productive systems
• obligate inhabitants
• nursery, shelter, and food supply
• pipefish and sea horse (strong association with SG beds and can lead to their protection)

Question 24

what are the ecological roles that seagrass beds play?

Answer 24

• CO2 storing and O2 production
• Nursery for several species
• Stabelizing sediment
• settling of particles and clearing the water