Answer:
Intertidal zone is the shortline between land and open sea. Two
intertidal zones as selected are the rocky intertidal reef and
Mangal.
Contrast between zonation patterns of rocky intertidal
reef and Mangal-
Rocky intertidal reef is divided into splash fringe level, high
tide level, low tide level, low fringe level, marine or subtide
level whereas Mangal zonation is composed of mud lobstermound
system, main forest, sand bank and mud flats.
Abiotic/ biotic factors that shape the zonation
observed:
Rocky intertidal reef-
Definition-
A rocky intertidal reef is the intertidal area that consists of
solid rocks.
Major group of
organisms-
This zone is composed of the following organisms:
- Green algae and cyanobacteria.
- Snails, barnacles, chitons, crabs, isopods, mussels, sea stars
(high tide zone).
- Sea weed, hydroids, sea cucumber, sea lettuce, sea urchin,
shrimps, tube worms (low tide zone).
Responsible
factors-
Abiotic
factors:
- Air- Air
differs physically from sea water in diverse and important
features. This influences the ability to exchange gas and their
overall thermal balance with the surrounding environment. The zone
heat up in day, so an adaptation to heating of the organisms is the
vaporization of internal water reserve.
- Light- Light is
adequate in all zonations except the sub tidal zone. Light in high
tuti zone limits the growth of many types of organisms. Algae in
the high tide zone can avoid absorbing too much light by changing
the pigment they produce.
- Temperature-
The zone experiences extreme temperature changes, so not many
organisms found in the high tide or low tide zone; instead many
organisms found in between two types of zones. When the organisms
are submerged, they are buffered against temperature changes, as
the water is isothermal. Organisms gone through hot and cold stress
and this can be overcome by circulation of body fluids of
animals.
- Salinity- It
can occur high at external medium and in surface films. Salinity
stress can be overcome by incorporating ions in the internal body
fluids.
- Dessication- In
low tides, dessication is the major factors that can cause water
loss. This can be reduced by maintenance of intracellular
osmolytes.
- Wave action-
Wave actions can limit the growth of organisms in high tide zones.
One way to protect organisms from waves is permanent attachment to
the reef.
Biotic
factors-
Predation -
Predation regulates number of organisms.
Some strategies to avoid predation is calcification,
bioluminescence, camouflage etc.
Mangal-
Definition-
Mangals are salt marshes in the coastal shore.
Major groups of
organisms-
The zone is composed of following organisms-
- Avucennia (main forest).
- Nypa
- Tiger (main forest)
- Crabs, lobsters (sand bank)
- Anaerobes
- Rhozophora, Ceriops.
Responsible
factors-
Abiotic
factors:
- Air- Oxygen is
low in the soil of the Mangal. To overcome this, Mangal trees
develop pneumatophores and prop themselves above the water level
with stilt roots and can then absorb air in their bark
(lenticels).
- Salinity- Salt
content is high in mangroves. To combat with the problem, the
leaves are covered with white salt crystals.
- Water- Limited
fresh water is available in the zone due to high salt content. To
overcome this, mangrove limits the amount of water loss.
Biotic
factors-
- Nutrient-
Because of little oxygen available, anaerobic bacteria liberate
nitrogen gas, soluble iron which make the soil much less nutrients.
Pneumatophores allow mangroves to absorb gases directly from the
atmosphere.
- Survival of
offspring- Harsh environment regulates the survival of
offsprings. To overcome this, mangrove plants are viviparous and
seedlings grow either within the fruit or outside the fruit.
- Predation-
Predation limits the number of organisms in the forest zone.