INTERTIDAL ZONE
LITTORAL ZONES
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Characterized by highly dynamic, well marked zonation of organism’s, maximum
stress on life
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Tides are the periodic rise and fall of sea level over time
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Supralittoral – Beach zone to the edge of the sea.
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Sublittoral – continental shelf
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Intertidal – Between High tide and low tide mark
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Spring tides - Neap tides (Twice each day)
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Diurnel tides – Semidiurnal tides (One tide each day)
Types of Intertidal habitat
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Sandy shore
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Muddy shore
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Rocky shore
INTERTIDAL ROCKY SHORE
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Rocky shores are areas of bedrock exposed between the extreme high and
extreme low tide levels on the seashore
Vertical Distribution Pattern for Animals and Algae
ECOSYSTEM
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The ecosystem is complex, as it has interaction between terrestrial and aquatic
systems
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Energy supply - primary production by seaweeds and phytoplankton; organic
detritus derived from adjacent land and other intertidal habitats
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The problem prevailed are evaporation, waves, gradients of temperature and
salinity
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Living community - hardy plants and animals, specially adapted for coping with the
harsh environment
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Rocky area support a preponderance of epifaune – rich and diverse communities
of marine plants and invertebrates as well as birds and fishes.
PHYSICAL CHARACTERISTICS
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Bedrock: resistant bedrock, such as granite, slate and quartzite, erodes slowly and
produces steep gradients
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Wave action: exposure to wave action, related to dominant wind direction, storms,
controls plant and animal attachment.
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Tidal regime: tide range determines the area of shore exposed to the air.
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Climatic conditions: weather conditions include summer and winter temperature
extremes, humidity, precipitation and wind exposure.
Environmental problems
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Animals encounter wide fluctuations in temperature and salinity
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Rainfall and land run off lower the salinity
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Animals exposed to heavy wave action and current motion
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Desiccation during low tide
ZONATIONS OF ROCKY SHORES
• Feature - Vertical zonation according to geographical location, tidal range,
exposure to wave action/protected etc
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Zonation is largely based on sessile species such as lichens, algae, barnacle’s,
mussels etc.
Vertical zonation of rocky shore
Vertical zonation of rocky shore
Super littoral Zones
• Encrusting black lichens (algae and fungi)
(Black Zone) and blue green algae.
Certain species, littorina – periwinkles and Large isopods (Ligia) and primitive
insects (Machilis)
Below the super littoral
• Periwinkles – Littorina sp- dense 10,000/m2, Barnacle Zone – white Zone, Mussel
Zone
Green Zone
• Attached algae & sessile animals
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Adaptation is an alteration or adjustment in structure or habits, often hereditary,
by which a species or individual improves its condition in relationship to its
environment
Common limpets
Green Sea Anemone
FOOD WEB –ROCKY SHORE
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There are so many connections between food chains that we can think of every
organism (plant or animal) as part of a complicated FOOD WEB rather than as a
link in a straight chain
ADAPTATION OF ROCKY SHORE ORGANISMS
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Bivalve molluscs and barnacles – over come desiccation by closing their shells
tightly snails retreat into their shells and sealing the shell aperture.
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Marine algae have strong attachment to rocks by special hold fast.
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Barnacles, oysters, tunicate cementing on to the substratum
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Mussels attached by byssal threads
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Limpets, chitons have suction like attachment
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Sea urchins and clams – boring into the hard surfaces
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Crabs, isopods live in rock crevices
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Productivity of intertidal rocky area is about 100g C/m2/Y average annual
productivity
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May go upto 1000g C/m2 /yr in some favorable area
–
–
–
–
Limpets, chitin, Sea urchin, littorie - grazers –herbivores
Mussels, barnacles clams tunicates politic – filter feeders
Starfish, snails, birds, predators
Scavengers –
isopods, crabs etc.
INTERTIDAL SANDY SHORE
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Sandy beaches - exposed to sever wave action; makes the transition from land to
sea
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Support high proportion of in faunal species
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Beaches serve as buffer zones or shock absorbers that protect the coastline, sea
cliffs or dunes from direct wave action
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It is an extremely dynamic environment where sand, water and air are always in
motion
FORMATION
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Formed through the deposition of sand resulting from the erosion of glacial till and
bedrock in the area of occurrence
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Sandy beaches are soft shores that are formed by deposition of particles that have
been carried by water currents from other areas
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The two main types of beach material are quartz (=silica) sands of terrestrial origin
and carbonate sands of marine origin
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The carbonate sand is weathered from mollusk shells and skeletons of other
animals
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Other material includes heavy minerals, basalt (=volcanic origin) and feldspar.
PHYSICAL CHARECTERSTICS
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Substrate: includes particle sizes ranging from fine gravel to sandy mud
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Wave action: exposure to wave action, related to dominant wind direction, storm
and ocean-swell conditions, and influence of tidal and alongshore currents affects
the mobility of the sand
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Tidal regime: tidal range determines the area of shore that is exposed to the air
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Water–land interaction: water conditions include summer and winter temperature
extremes, turbidity and salinity
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Climatic conditions: air conditions include summer and winter temperature
extremes, humidity, precipitation and wind.
ECOSYSTEM PROPERTIES
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There is no significant primary production, except by blue-green algae and diatoms
that occur on the surface of sandy mud in sheltered conditions
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Energy input -from the phytoplankton and from particulate organic matter
(detritus) derived from the land and adjacent intertidal habitats
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Herbivorous and detritus feeding and carnivorous animals are included in the sand
infauna
Environmental characteristics
– Sand grains are quartz particles mixed with shell fragments
– Sand particle size varies from < 0.1 to 2 mm.
– Sandy beaches typically have a gradual slope means, sediments drains and
dries slowly
– Oxygen decreases with depth of soil
– Anaerobic conditions are due to sulphide layers.
– Substrate is unstable due to tidal water
– Continual shifting of the surface layer
– Sand contain relatively low organic matter
– Organisms burrow into sand dig low tide
– No large attached plants
– The dominant printing producers – diatoms, dinoflgellates and blue green
algae
– Primary productivity is very low <15g Cm2/yr
BIOLOGICAL DIVERSITY
Plants
• Due to the mobility of the substrate, plant life is very limited in both diversity and
abundance
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Seaweeds are mostly absent, but diatoms and bluegreen algae may be common in
sheltered, sandy, mud conditions
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Ulva and Enteromorpha develop in summer on many sandy-mud flats.
Animals
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On exposed beaches, polychaete worms (Nephtys) and molluscs (Tellina, Spisula,
Ensis) occur at low-tide level
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Isopod and amphipod crustaceans also occur at the mid- and low-tide levels
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At the high-tide mark, amphipods are common, feeding on organic matter in the
drift line, and overlap in their occurrence with insects, including the larvae of flies
and beetles
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Ribbon worms (Cerebratulus spp.), polychaetes (Nereis spp. and Nephtys spp.),
bivalves (Mya arenaria, Macoma balthica) and mud snails (Nassarius,) are typical
Macrofauna
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Macrofauna- exceptionally high densities
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Molluscs, crustaceans and polychaetes are the most important. Low diversity
compared to rocky shore.
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Polycheates, bivalves and crustaceans are dominant forms
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Amphipods and isopods burrow during day and feed at night on detritus
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Ghost crab (Ocypoda) – dominant scavenger in sandy beats
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High species diversity of macro fame at mid and lower tidal zones.
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Fast burrowing Donax – Tellina – clams present in large numbers
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Larger razon clams (Ensis, Siliqua) are common
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Cockles (Cardium) Arca sp. – thick shelled bivalves also common in sandy
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Snails – Olivella, Natica, Polinices – predator and abundant in sandy shores
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Sand dwelling polychaetes (Napthys, Glycera) are predators /scavengers are
deposit feeder at Mid / Low tide level
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Crustaceans - Mole crab (Emerita) present at mid tidal level
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Prawns (Crangon) – Sandy shore crustacean
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Echimodesms – Heart urchins, sand dollers star fish sea cucumber – deposit feeds
present at lower tidal levels.
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Sand eels, flatfish are also burrow into good.
Meiofauna
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The dominant - nematodes and harpacticoid copepod with other important groups
including turbellarians, oligochaetes, gastrotrichs, ostracods and tardigdades
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Meiofauna interstitial fauna present both sand grass
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Biomass of meiofauna varied between 10 and 2g/m2
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Average numbers to be 106/m2
INTERTIDAL MUDDY SHORE
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Muddy shore habitats are areas of mud and sandy mud exposed between the
extreme-high-tide and extreme low-tide marks.
FORMATION
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Mud flats form from the deposition of mud in sheltered tidal water, particularly in
estuaries where there is a large sediment supply
PHYSICAL CHARECERSICS
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Substrate: particles range from fine sand to silt, and are often compacted into clay.
drainage is poor, and anaerobic conditions exist just below the sediment surface.
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Wave action: the surface sediment is mobile in moderate waves due to exposure
to wave action related to wind and to a tidal and longshore currents.
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Tidal regime: tidal range determines the area of shore that is exposed to the air.
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Water–land interaction: water conditions include summer and winter temperature
extremes, formation and movement of ice, turbidity and salinity.
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Climatic conditions: air conditions include summer and winter temperature
extremes, humidity, precipitation and wind.
SPECIAL FEATURES
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Vast numbers of a few species of infauna depend on a diet of organic detritus
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Ex: Corophium sp with a population density of 15 000/m2 and Macoma balthica
3500/m2
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Support large groups of migrating shore birds during the late summer
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Migratory fish also visit to feed on the benthic (e.g., Corophium) and epibenthic
species (e.g., Neomysis, Mysis etc.).
ECOSYSTEM PROPERTIES
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Primary production is limited to diatoms and other microscopic and filamentous
algae and grass
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Most energy enters the system from the plankton, or as organic detritus derived
from the land or adjacent tidal marshes
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The detritus --------->bivalve molluscs, amphipods and polychaete---------->
carnivores, migratory shore birds
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The crustacean, Corophium volutator occurs in the Bay of Fundy intertidal mud
flats and is an important food source for the migratory Semipalmated Sandpiper.
BIOLOGCAL DIVERSITY
Plants
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Limited to microscopic algae (diatoms) and filamentous algae on the sediment
surface, and occasionally seaweeds, such as Fucus spp. attached to stones
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Some Cord Grass is found at the first stage of tidal-marsh succession, and eel grass
occurs on the lower shore
Successional sequence
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In sheltered areas, the deposition of sediment on the shore will eventually raise
the level so that seeded or ice-transported cord grass may become established.
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The cord grass expands from the point of colonization by vegetative means and
accelerates the rate of sediment deposition, developing into the low marsh.
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When the substrate of the marsh rises to the mean-high-water mark through the
accumulation of sediment, the cord grass gives way to marsh hay and associated
plants, and the high marsh develops.
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With further sediment deposition, the vegetation becomes mainly freshwater:
cattail, rushes and reeds, possibly in association with spruce (swamp).
ANIMALS
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Animals - detritus-feeding infauna that can tolerate exposure at low tide.
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Polychaete worms (Spiophanes wigleyi, Clymenella torquata), amphipods
(Corophium volutator) and bivalves (Mya arenaria, Macoma balthica) are
common
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Scavengers and carnivores – polychaetes (Neanthes virens), crustaceans
(Chiridotea caeca, Crangon septemspinosus) and molluscs (Ilyanassa obsoletus,
Lunatia heros)
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Sessile epifauna species, such as barnacles and slipper limpets, occur attached to
small
stones
lying
on
the
mud
surface
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Mud flats are also important feeding areas for migratory shore birds, such as the
Semipalmated sandpiper, and land mammals (particularly raccoons)