The area just above the high water mark that is covered by sea only in times of flood or storm. What we call the beach is also included in this zone, because the spray from the waves has an impact on life there. Also the heaps of seaweed cast ashore there acts as a basis for a considerable part of the animal life there.


The area between the high tide and low tide marks. The extent of this zone is determined by more than one factor.
1. The fortnightly variation in tidal range, from a high and low maximum (spring tide) shortly after full and new moon (when the moon is clossest to the earth) to a minimum range (neap tide) a weak after each spring tide.
2. The configuration of local coast lines, which has a profound effect on the tidal range.
The tidal zone varies greatly from place to place, while the rythm and the intensity of tidal action must have an extreme effect on the fauna and flora.


The region from the low tide mark down to about 200m depth. It comprises only a small area along the coast of the open ocean and corresponds roughly to the limit of the continental shelf. This zone also concurs with the epipelagial of the free water masses, which is a zone where where light from the suface is still extremely important.


The sublittoral zone or the continental shelf slopes gently up to the 200m mark where the angle suddenly increases and the seabed fals sharply towards the deap sea proper. This steap zone is called the bathyal or archibenthal zone (continental slope) which at a depth of 2 000m - 3 000m passes into the smoother deep sea bed. The continental slope is very far from being smooth. It can be furrowed by immense fissures, the socalled submarine canyons, and the epifauna and infauna are seldom clearly seperated.


This zone includes by far the largest area of the deep sea bed proper (2 000m up to about 6 000m). 84% of the bottom of the ocean (more than half of the globe) is deeper than 2 000m and 82% is at depths of between 2 000m to 6 000m. Here the surroundings are in a very stable habitat, the temp is never over 4^oC . Around one half of the abyssal area is covered by the calcareous shells of globigerina and coccolithophores. Another seventh is covered by fine red deep-sea mud, with a very small organic content and with a scanty fauna.
The number of animal species, many of them cosmopolitan, is significantly reduced and is seperated into two sharply devived groups - mud eaters and predators.


The ultra-abyssal zone that cosists of the area from 6 000m to the bottom of the deepest trench, but it covers less than 2% of the ocean bottom. It is definitely poulated by creatures eventhough these creatures are poorly represented when you compare it even with the abyssal zone.
The temperature of the water of all of these trenches range from 1·2^oC to 3·6^oC (somewhat lower than those in the most parts of the abyssal zone). The trenches in close vicinity of land(most are) have a richer animal life than those in the open ocean. Previous counts of species beneath 6 000m provided ±366 species, however, this is a very small number when compaired to the abyssal and continental slope.
Most of the large predators including fish, crabs, and seastars are completely absent, and the deeper you submerge the more dominant the Mud-Eating sea cucumbers(holothuriens), which constitutes for about 90% of all animal weight in the deepest samples).



GO: | HOME | ECOLOGY |
| MARINE SPECIES |
| THE UNEXPLAINED |