MARINE ECOSYSTEMS COVER MORE THAN 70 PERCENT OF THE EARTH'S SURFACE, WITH AN AVERAGE DEPTH OF 3750 M; MARINE ECOSYSTEMS ARE OF SINGULAR ECOLOGICAL SIGNIFICANCE. UNLIKE TERRESTRIAL AND FRESH WATER ECOSYSTEMS, THE SEA IS IN A CONTINUAL CIRCULATION.
THE MARINE ECOSYSTEM IS BEING DIVIDED INTO VARIOUS ZONES : -
THE DI-GRAMMATICAL REPRESENTATION OF VARIOUS ZONES OF MARINE ECOSYSTEM
LITTORAL ZONE : - THE LITTORAL ZONE IS THE SHORELINE BETWEEN THE LAND AND THE OPEN SEA. IT IS SUBJECT TO PHYSICAL VIOLENCE OF WAVES AND TIDES AND TO FLUCTUATIONS IN TEMPERATURE, MOISTURE AND LIGHT INTENSITY. ALGAE, BARNACLES, STARFISH, ETC., INHABIT THE ROCKY SHORES, WHILE GHOST CRABS, SAND DOLLARS, POLYCHAETES, INHABIT THE SANDY SHORES. MUD FLATS WHICH OCCUR IN BAYS ARE OCCUPIED BY HARBOUR ALGAE, CLAMS AND CRUSTACEA.
STAR FISH BELONGS TO AESTEROIDEA CLASS AND ECHINODERMATA PHYLUM. IT CAN SWALLOW A PREY BIGGER IN SIZE THAN ITS MOUTH.
THE GHOST CRABS ALSO KNOWN AS SAND CRABS BELONGS
TO MALACOSTRACA CLASS AND
OCYPODE GENUS."THESE CRABS ARE CALLED 'GHOSTS' BECAUSE THEY ARE TRANSLUCENT, AND BECAUSE OF THEIR ABILITY TO DISAPPEAR FROM SIGHT ALMOST INSTANTLY, SCUTTLING AT SPEEDS UP TO 10 MILES PER HOUR, WHILE MAKING SHARP DIRECTIONAL CHANGES.NERITIC ZONE : - THE NERITIC ZONE IS UNDERLAIN BY A CONTINENTAL SHELF, EXTENDING OUTWARD TO ITS EDGE ABOUT 200 METERS DEEP. IT IS A HIGHLY PRODUCTIVE ECOSYSTEM. THIS REGION ABOUNDS IN EXTENSIVE ALGAL COMMUNITIES, CLAMS, SNAILS, WORMS AND ECHINODERMS THAT DOMINATE THE BOTTOM.
PELAGIC ZONE : - THE PELAGIC ZONE IS THE OPEN SEA AND CONSTITUTES ABOUT 90 PERCENT OF THE TOTAL OCEAN SURFACE. PLANKTONIC DIATOMS AND DINOFLAGELLATES PRIMARILY OCCUPY THE SURFACE PELAGIC ZONE.
PLANKTONIC DIATOMS AND DINOFLAGELLATES OCCUR ALONG THE SURFACE. SHRIMPS, JELLYFISH, AND CTENOPHORES ARE ACTIVE SWIMMING FORMS. IN THE DEEP WATERS MANY FISH ARE BIOLUMINESCENT WHILE SOME HAVE LIGHT PRODUCING ORGANS.
BENTHIC ZONE : - THE BENTHIC ZONE EXTENDS FROM THE EDGE OF THE CONTINENTAL SHELF TO THE DEEPEST OCEAN TRENCHES. ORGANISMS HERE ARE HETEROTROPHIC, MANY BEING ANCHORED IN MUDDY OOZE MADE UP LARGELY OF SILICEOUS AND CALCAREOUS SHELVES OF SNAILS, DIATOMS. AMONG THE ROOTED SPECIES ARE SEA LILIES, SEA FANS, SPONGES,AND BRACHIOPODS. SNAILS, CLAMS ARE EMBEDDED IN THE MUD WHILE STARFISH, SEA CUCUMBERS AND SEA URCHINS MOVE ON ITS SURFACE.
SEA URCHINS ARE SMALL, SPINY, GLOBULAR ANIMALS THAT BELONGS TO ECHINOIDEA.
SEA CUCUMBERS ARE ECHINODERMS FROM CLASS HOLOTHUROIDEA.
SEA SPONGES ARE ANIMALS OF THE PHYLUM PORIFERA. THEIR BODIES CONSISTS OF JELLY LIKE MESOHYL SANDWITCHED BETWEEN TWO THIN LAYERS OF CELLS.
PHOTIC ZONE : - PHOTIC ZONE IS THE ZONE TILL WHICH THE SUNLIGHT REACHES INSIDE THE SEA SURFACE.
APHOTIC ZONE : - APHOTIC ZONE IS AFTER THE PHOTIC ZONE IT EXTENDS UPTO THE DEPTH OF THE SEA. THE SUNLIGHT DOESNOT REACH THIS ZONE.
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