intertidal zone. littoral zones characterized by highly dynamic, well marked zonation of...

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)