intertidal zone. littoral zones characterized by highly dynamic, well marked zonation of...
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INTERTIDAL ZONE
LITTORAL ZONES
• Characterized by highly dynamic, well marked zonation of organism’s, maximum stress on life
• Tides are the periodic rise and fall of sea level over time
• Supralittoral – Beach zone to the edge of the sea.
• Sublittoral – continental shelf
• Intertidal – Between High tide and low tide mark
• Spring tides - Neap tides (Twice each day)
• Diurnel tides – Semidiurnal tides (One tide each day)
Types of Intertidal habitat
• Sandy shore
• Muddy shore
• Rocky shore
INTERTIDAL ROCKY SHORE • 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
• The ecosystem is complex, as it has interaction between terrestrial and aquatic systems
• Energy supply - primary production by seaweeds and phytoplankton; organic detritus derived from adjacent land and other intertidal habitats
• The problem prevailed are evaporation, waves, gradients of temperature and salinity
• Living community - hardy plants and animals, specially adapted for coping with the harsh environment
• Rocky area support a preponderance of epifaune – rich and diverse communities of marine plants and invertebrates as well as birds and fishes.
PHYSICAL CHARACTERISTICS
• Bedrock: resistant bedrock, such as granite, slate and quartzite, erodes slowly and produces steep gradients
• Wave action: exposure to wave action, related to dominant wind direction, storms, controls plant and animal attachment.
• Tidal regime: tide range determines the area of shore exposed to the air.
• Climatic conditions: weather conditions include summer and winter temperature extremes, humidity, precipitation and wind exposure.
Environmental problems
• Animals encounter wide fluctuations in temperature and salinity
• Rainfall and land run off lower the salinity
• Animals exposed to heavy wave action and current motion
• Desiccation during low tide
ZONATIONS OF ROCKY SHORES • Feature - Vertical zonation according to geographical location, tidal range,
exposure to wave action/protected etc
• 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
• 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 • 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
• Bivalve molluscs and barnacles – over come desiccation by closing their shells tightly snails retreat into their shells and sealing the shell aperture.
• Marine algae have strong attachment to rocks by special hold fast.
• Barnacles, oysters, tunicate cementing on to the substratum
• Mussels attached by byssal threads
• Limpets, chitons have suction like attachment
• Sea urchins and clams – boring into the hard surfaces
• Crabs, isopods live in rock crevices
• Productivity of intertidal rocky area is about 100g C/m2/Y average annual productivity
• 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
• Sandy beaches - exposed to sever wave action; makes the transition from land to sea
• Support high proportion of in faunal species
• Beaches serve as buffer zones or shock absorbers that protect the coastline, sea cliffs or dunes from direct wave action
• It is an extremely dynamic environment where sand, water and air are always in motion
FORMATION
• Formed through the deposition of sand resulting from the erosion of glacial till and bedrock in the area of occurrence
• Sandy beaches are soft shores that are formed by deposition of particles that have been carried by water currents from other areas
• The two main types of beach material are quartz (=silica) sands of terrestrial origin and carbonate sands of marine origin
• The carbonate sand is weathered from mollusk shells and skeletons of other animals
• Other material includes heavy minerals, basalt (=volcanic origin) and feldspar.
PHYSICAL CHARECTERSTICS
• Substrate: includes particle sizes ranging from fine gravel to sandy mud
• 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
• Tidal regime: tidal range determines the area of shore that is exposed to the air
• Water–land interaction: water conditions include summer and winter temperature extremes, turbidity and salinity
• Climatic conditions: air conditions include summer and winter temperature extremes, humidity, precipitation and wind.
ECOSYSTEM PROPERTIES
• There is no significant primary production, except by blue-green algae and diatoms that occur on the surface of sandy mud in sheltered conditions
• Energy input -from the phytoplankton and from particulate organic matter (detritus) derived from the land and adjacent intertidal habitats
• 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
• Seaweeds are mostly absent, but diatoms and bluegreen algae may be common in sheltered, sandy, mud conditions
• Ulva and Enteromorpha develop in summer on many sandy-mud flats.
Animals
• On exposed beaches, polychaete worms (Nephtys) and molluscs (Tellina, Spisula, Ensis) occur at low-tide level
• Isopod and amphipod crustaceans also occur at the mid- and low-tide levels
• 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
• Ribbon worms (Cerebratulus spp.), polychaetes (Nereis spp. and Nephtys spp.), bivalves (Mya arenaria, Macoma balthica) and mud snails (Nassarius,) are typical
Macrofauna
• Macrofauna- exceptionally high densities
• Molluscs, crustaceans and polychaetes are the most important. Low diversity compared to rocky shore.
• Polycheates, bivalves and crustaceans are dominant forms
• Amphipods and isopods burrow during day and feed at night on detritus
• Ghost crab (Ocypoda) – dominant scavenger in sandy beats
• High species diversity of macro fame at mid and lower tidal zones.
• Fast burrowing Donax – Tellina – clams present in large numbers
• Larger razon clams (Ensis, Siliqua) are common
• Cockles (Cardium) Arca sp. – thick shelled bivalves also common in sandy
• Snails – Olivella, Natica, Polinices – predator and abundant in sandy shores
• Sand dwelling polychaetes (Napthys, Glycera) are predators /scavengers are deposit feeder at Mid / Low tide level
• Crustaceans - Mole crab (Emerita) present at mid tidal level
• Prawns (Crangon) – Sandy shore crustacean
• Echimodesms – Heart urchins, sand dollers star fish sea cucumber – deposit feeds present at lower tidal levels.
• Sand eels, flatfish are also burrow into good.
Meiofauna
• The dominant - nematodes and harpacticoid copepod with other important groups including turbellarians, oligochaetes, gastrotrichs, ostracods and tardigdades
• Meiofauna interstitial fauna present both sand grass
• Biomass of meiofauna varied between 10 and 2g/m2
• Average numbers to be 106/m2
INTERTIDAL MUDDY SHORE
• Muddy shore habitats are areas of mud and sandy mud exposed between the extreme-high-tide and extreme low-tide marks.
FORMATION
• Mud flats form from the deposition of mud in sheltered tidal water, particularly in estuaries where there is a large sediment supply
PHYSICAL CHARECERSICS
• 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.
• 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.
• Tidal regime: tidal range determines the area of shore that is exposed to the air.
• Water–land interaction: water conditions include summer and winter temperature extremes, formation and movement of ice, turbidity and salinity.
• Climatic conditions: air conditions include summer and winter temperature extremes, humidity, precipitation and wind.
SPECIAL FEATURES
• Vast numbers of a few species of infauna depend on a diet of organic detritus
• Ex: Corophium sp with a population density of 15 000/m2 and Macoma balthica 3500/m2
• Support large groups of migrating shore birds during the late summer
• Migratory fish also visit to feed on the benthic (e.g., Corophium) and epibenthic species (e.g., Neomysis, Mysis etc.).
ECOSYSTEM PROPERTIES
• Primary production is limited to diatoms and other microscopic and filamentous algae and grass
• Most energy enters the system from the plankton, or as organic detritus derived from the land or adjacent tidal marshes
• The detritus --------->bivalve molluscs, amphipods and polychaete----------> carnivores, migratory shore birds
• 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
• Limited to microscopic algae (diatoms) and filamentous algae on the sediment surface, and occasionally seaweeds, such as Fucus spp. attached to stones
• Some Cord Grass is found at the first stage of tidal-marsh succession, and eel grass occurs on the lower shore
Successional sequence
• 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.
• The cord grass expands from the point of colonization by vegetative means and accelerates the rate of sediment deposition, developing into the low marsh.
• 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.
• With further sediment deposition, the vegetation becomes mainly freshwater: cattail, rushes and reeds, possibly in association with spruce (swamp).
ANIMALS
• Animals - detritus-feeding infauna that can tolerate exposure at low tide.
• Polychaete worms (Spiophanes wigleyi, Clymenella torquata), amphipods (Corophium volutator) and bivalves (Mya arenaria, Macoma balthica) are common
• Scavengers and carnivores – polychaetes (Neanthes virens), crustaceans (Chiridotea caeca, Crangon septemspinosus) and molluscs (Ilyanassa obsoletus, Lunatia heros)
• Sessile epifauna species, such as barnacles and slipper limpets, occur attached to small stones lying on the mud surface
• Mud flats are also important feeding areas for migratory shore birds, such as the Semipalmated sandpiper, and land mammals (particularly raccoons)