The document discusses rocky shores and sandy shores. Rocky shores have distinct zones populated by specific organisms due to vertical zonation. Organisms in different zones have adaptations to stresses like oxygen levels, temperature, desiccation, and predation. Sandy shores have adaptations like rapid burial to withstand unstable substrates and strong wave action. Common organisms include crustaceans, bivalves, polychaetes, and anomuran crabs. Mud banks form along Kerala coast during the southwest monsoon due to processes like underground mud discharge and upwelling, providing calm waters that benefit fishermen.

1. PRAGATI INWATI
MFK2112
COF, MANGALURU

2.  Inter tidal areas having solid rocky bottom, large boulders and
igneous rocks are called rocky coasts.
 The term ‘Rocky shores’ is the common name of shores made
of hard material such as granite, basalt or softer material such
as chalk or limestone.

3.  Generally rocky intertidal shore will have steep slopes as the
structures are like vertical structures.
 Rocks provide a hard surface on which marine organisms can
attach themselves.
 When the tide is out, the rocks are exposed and during this
period large number of organisms such as seaweeds and other
attached organisms are visible to the naked eye of the
observer.
 Distinct zones on the rocks are populated with specific
groups of organisms; this is called vertical zonation. It is a
nearly unique feature of the intertidal zone.

4. Zonation of rocky shore
1. Supratidal zone
2. Mid-littoral zone
3. Sub-littoral zone

5.  The upper regions around the high-tide mark are exposed to
air during most of the time.
 The organisms in this region are subject to severe stresses
related to respiration, desiccation, temperature changes and
feeding.
 This upper region is called the supratidal or splash zone. It
is moistened by the spray of breaking waves and it is only
covered during the highest tides and during storms.

6.  The most characteristic organisms of this zone are the
periwinkles (Littorina) and neritids (Nerita).
 They are composed of fungi and microscopic algae living
together and sharing food and energy to grow.

7.  This zone is known as the Middle zone or the Middle Beach
zone.
 It is the true intertidal zone, subjected to daily ebb and flood
of the tides.
 As such, the animals living in this zone are immersed in water
during high tide and exposed to air and drying during low
tide.
 Another characteristic feature of this zone is the formation of
tidal pools.

8.  Several groups of animals live attached to rocks, hiding in
their crevices or in the tide pools.
 Molluscs, crustaceans and rock boring worms like
sipunculids are common in this zone.
 Acorn barnacles (Balanus) are often so abundant in this zone,
that it is referred to as the ‘Balanoid zone’ .

9.  This is the lowest zone and bared only by the ebbing spring
tides.
 This zone is the region below the intertidal zone and is
continuously covered by water.
 It is typically rich in animal and plant species.
 Life on the rocky shore is mainly governed by tides.

10.  In general it resulted in two types of adaptations namely
morphological and behavioral.
 Some of the forms such as limpets and barnacles have
developed thick shells and strong power of attachment to
withstand the force of battering waves.
 There are others which have developed soft and flexible
bodies, such as sea weeds and hydroids.
 Hard shell also helps them to maintain the moisture inside.

11.  Active swimming forms such as crabs and shrimps and a few
molluscs hide themselves inside crevices.
 There are algal grazers such as limpets, top shells and sea
urchins, detritus feeders such as crabs and filter feeders such
as barnacles and bivalves.

12. Stresses and adaptations
1. Oxygen
 Most intertidal animals depend on aerobic respiration by
extracting oxygen from water.
 Other intertidal animals have gills and cannot tolerate
prolonged air exposure. Since gills only function when they are
moist, these animals need to avoid desiccation.

13.  In response to desiccation stress, some sessile species
(periwinkles) have adapted their gills to allow gas exchange with
the air.
 Other species (barnacles) store air bubbles in cavities in the
gills that supply oxygen to the moisture around the gills.
 The main adaptation strategy of sessile animals to prolonged
air exposure is to slow down their metabolism and associated
oxygen consumption.

14. 2. Sunlight
 Sunlight is one of the most important parameters that influence
the organisms.
 When there is too much sunlight particularly during summer
and day time, organisms dry out and the capacity to capture
light energy can be weakened.
 Too little sunlight reduces the growth and reproduction of the
organism, because photosynthesis is reduced.

15. 3. Temperature
 The intertidal zone can experience extreme temperature
changes within a single day.
 The organisms in this zone must be resistant to these changes
to survive.
 Most of the marine organisms are ectothermic and need the
warmth from the environment to survive.
 Under tropical conditions when the temperature is too high,
heat stress appears. Heat stress accelerates rates of metabolic
processes.

16. 4. Salinity Stress
 Salinity stress can occur as the organisms are either submerged
in seawater or experience during part of the life cycle.
 When the osmolality of the cell is lower than the surrounding
medium, the cell loses water from the internal fluids to the
environment (hyper-osmotic stress).
 When the intracellular osmolality is higher than the
environment, there is an influx of water into the cell from the
environment (hypo-osmotic stress).

17. 5. Desiccation Stress
 Organisms are threatened by desiccation during emersion at low
tides.
 Dehydration due to evaporative water loss is the most common
mechanism.
 Highly mobile organisms can avoid the desiccation by
migrating to a region that is more moist and cool.
 Less mobile organisms reduce metabolism by maintaining only
vital functions and attach more firmly to the substrate.

18. 6. Predation
 There exist a wide variety of strategies to escape from
predation.
 The first strategy is calcification which makes it more difficult
for the predator to eat these organisms.
 This adaptive mechanism is evolved in algae that make them
tougher and less nutritious.
 A second one is the production of chemicals, usually produced
as secondary metabolites.

19.  These chemicals can be produced all the time such as toxins.
 Bioluminescence is another strategy to avoid predators.
 The light is used for warning, blinding, making scare,
misleading or attracting the predator.

20. 7. Wave Action
 One way to protect organisms from waves is permanent
attachment.
 Another way to be protected is to burrow themselves into the
sediment.
 Attachment can be done by different structures.
 Bivalves usually use threads (byssal threads) to attach to rocky
surfaces or to other organisms, but it can also be done by a
foot.

21.  Some of the common animal groups found in the rocky
shores are algae & lichens, sponges, sea anemones, marine
worms, crustaceans, molluscs, echinoderms (e.g. starfish) and
some fishes.

22. Sandy shore
Sandy shore are area where deposits of sand or other
sediments cover the shoreline.
Sandy shore made up of the minutes grains of sand or crushed
shells and rock.

23. PHYSICAL FEATURES OF SANDY SHORES AND
ADAPTATIONS OF ORGANISMS
 1. Substratum
 As most of the sandy shores are exposed to strong wave
action, the substratum will naturally be unstable.
 There will be more pronounced changes throughout the year
due to the increased wave action which may remove most of
the sand and thus these changes significantly modify the
slope of the beach.

24.  Many of the forms are known to exhibit tidal migration and
may move up and settle in the narrow beach.
 For example, bivalve species such as Donax incarnates, and
D. cuneatus, Hippa, Albunea and Bullia melanoides are known
to exhibit such tidal migration.

25. 2.Wave action
 Wave action is the important physical factor in the sandy
shore environment.
 Strong wave action causes erosion of the beach, which leads
not only to the reduction of width of the beach but also the
dislodgement of the organisms from their original habitat.
 To prevent from being dislodgement, the sandy shore animals
must either be adapted to burry rapidly or be adapted to
burrow deeply.

26.  For example, the fauna such as Donax cuneatus (wedge
clam) and Emerita holthuisi (mole crab), are to known to
live in the mid-littoral beach .
 Possess the adaptation of burying rapidly into the sand to
avoid desiccation due to exposure to air.

27. 3.Temperature and desiccation
 With regard to the effect of temperature, the conditions on sandy
beaches are as similar as those on rocky shores.
 During the day time of low tide period, the broad area of the
intertidal zone is exposed and the top surface of the sand gets
heated up and this lead to the increase of temperature in the sand
surface.
•

28.  As most of the sandy shore organisms are good burrowers,
they dig rapidly and penetrate deep into the sand when the
surface becomes too warm.
 The problem of desiccation is not felt by most organisms of
the sandy shore because water is within their reach if they
dig into the sand a little.

29. 4. Salinity
 Salinity of the interstitial water usually approximates to that of
the sea, except at the surface layers where the values may be
high, owing to evaporation, or low as a result of freshwater
influence.
 When a stream of freshwater passed over the surface of the
intertidal sand, there would be a little effect on the salinity of
the interstitial water at a depth of 25-30 cm, where it
approaches the seawater.

30. • The animals living near the surface will have to burrow
themselves to deeper levels to escape the adverse effects of
lowered salinity.
• Many sandy shore organisms like the burrowing prawn
Callianasa and Upogebia, which have only very narrow
salinity tolerance (stenohaline)

31. Organisms of sandy shore
1. The supralittoral fringe zone :
 It is populated by two main types of crustaceans, the ghost
crabs (Ocypode spp.) in the tropics and the talitrid amphipods
(beach hoppers) in the temperate regions.
 Sub littoral fringe, is occupied by anomuran crabs in the tropics
and amphipod crustaceans in the temperate regions.
 The upper regions of almost all the sandy shores are occupied
by the talitrid amphipods or Ocypode crabs.

32.  In India, crabs of the genus Ocypode viz. O. ceratophthalma,
O. macrocera and O. platytarsis are very common.
 These crabs inhabit the dry sands just above the surf zone and
lead an almost terrestrial life.

33. Mid-littoral region :
 This region possesses a dense fauna of amphipods such as
Bathyporeia and Urothoe, and isopods.
 The amphipods, Bathyporea (Bathyporea pilosa , B. pelagica)
and Urothoe are capable of both swimming and burrowing and
they feed on minute particles of organic matter present in the
intertidal water.

34.  The isopod is known to migrate shoreward when the erosion
of beach occurs.
 Many polychaetes like Nephthys and Glycera are present in
the mid-littoral zone.

35. Besides these amphipods, isopods and polychaetes, the mid-
littoral zone is occupied by a number of bivalve molluscs which
are highly adapted for a life in sand.
 Of the many species known the most important include
Cardium, Donax, Tellina, Macoma, etc.
 They are all burrowers and are comparatively slim when
compared to those in muddy shores.
Tellina and Donax prefer clean sand while Macoma and
Cardium live in more muddy sand.

36. Sub-littoral :
 The most characteristic organisms of this region are anomuran
crabs belonging to the hippidae for the tropical shores and
amphipods like Bathyporeia and Haustorius for the temperate
seas.
 Emerita holthuisi, E. asiatica and Albunea symnista are the
anomurans, most common along the sandy shores of India, and
they are all well-adapted to live in the wave-beaten shores.
 The sub-littoral fringe zone of the sandy shores is inhabited by a
number of animals. These include many molluscs like Oliva,
Harpa and Tonna.

37.  Other animals found in this zone include the worm-like sand
cucumbers (Leptosynapta), enteropneusts (Saccoglossus,
Ptychodera), sea-anemones (Peachia and Halicampa), the
shrimp Crangon and shore fishes like Glossogobius.
 There are many other true marine animals which visit the
intertidal sands mainly for breeding.
E.g. king crabs and the sea-turtles

38.  The calm, turbid region in the coastal waters of Kerala are
called the mud banks.
 Two well known mud banks are formed along the coast of
Cochin and Alleppy.

39. CHARACTERISTICS
 These mud banks appear during the southwest monsoon
season.
 The mud gets churned up and this mud is kept in suspension
making the water highly turbid.
 The muddy waters are free from surface disturbance because
there being no waves even during peak monsoon season.

40.  Portion of the beach corresponding to mud banks are free
from wave action, while regions of the adjacent beach
experiences severe erosion.
 The mud banks act as a barrier and save the beach being
eroded.
 Mud bank form close to the beach and extend in a semi
circular shape towards the sea and maximum seaward limit
being at 6 fathoms.

41. (1) Underground Discharge of Mud from Backwaters
(2) Wave Action on Bottom Mud
(3) Upwelling and Mud Bank Formation
(4) Flocculation and Deflocculation

42. 1. Underground Discharge of Mud from Backwaters:
 This theory was put forwarded by John Rhode in 1886.
 The mud bank is formed by an underground discharge of mud
by the hydraulic pressure developed during the monsoon due
to the increased water level.
 The addition of water during monsoon season increases the
hydraulic pressure from above towards the bottom.

43. 2. Wave Action on Bottom Mud:
 The mud of the sea bed itself is kept in suspension in the mud
bank.
 Du-cane and others suggested that high wave generated by
the pre-monsoon winds feed energy continuously to keep the
mud in suspension.

44. 3. Upwelling and Mud Bank Formation:
 This theory was put forwarded by Ramasastry and Myrland in
1959.
 According to this, mud bank formation is associated with
upwelling and divergence near the bottom between 20 and 30
m depth along the coastline.
 This produces vertical acceleration resulting in lifting of fine
bottom mud.

45. 4. Flocculation and Deflocculation:
 Suspended particles in sea water either be deflocculated or
flocculated depending on whether the salinity is high or low.
 In lower salinity conditions, particles remain in suspension,
while in higher salinity condition, they get flocculated.
 A flocculated suspension can be deflocculated by lowering
the salinity.
 This deflocculation takes place when the salinity falls down
2.5 ppt and flocculation above 20 ppt.

46. MUD BANKS AND FISHERIES
 These mud banks are boon to marginal fisherman of Kerala.
 The calm condition facilities marginal fisherman to venture
into the sea during peak monsoon season and operates the
available gears to catch the maximum fish wealth.
 This phenomenon has left an indelible mark in the fisherman’s
society, which they celebrate with lot of pomp and show at the
time of mud bank formation.

47.  This phenomenon is locally referred as ‘chagara’.
 Mud banks are rich in penaeid prawns, oil sardine, mackerel,
Stolephorous and various other soles.
 Since bottom mud is churned and kept in suspension, the
food present at the floor of the sea is made available to
various commercially important pelagic fishes, even some of
the demersal forms do migrate to overlying waters for
feeding.

48.  The higher phosphate content of sediment facilitates increased
primary productivity leading to increased zooplankton
population.
 Commercially important fishes tend to carry around these
areas for feeding making the mud banks rich in fishery wealth.

49. Reference
• Habitat Ecology and Diversity of Rocky Shore Fauna, Kunal Satyam,
Ganesh Thiruchitrambalam , 2018, Pondicherry University, Port Blair, India.
• Edgar, GJ 1984 , 'General features of the ecology and biogeography of
Tasmanian subtidal rocky shore communities' , Papers and Proceedings of the
Royal Society of Tasmania.
• The ecology of sandy shore by A. C brown and A. McLachlan

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