Lower Eulittoral Zone

Middle Tide Zone: Also called the Lower Mid-littoral Zone (Lower Eulittoral) . This turbulent area is covered and uncovered twice a day with salt water from the tides. Organisms in this area include anemones, barnacles, chitons, crabs, green algae, isopods, limpets, mussels, sea lettuce, sea palms, sea stars, snails, sponges, and whelks.

The midlittoral or Eulittoral zone is covered and uncovered twice a day by the tides. Animals in this zone have adapted to being immersed in air and sea water. Anemones close when the tide is out, keeping in the moisture necessary for survival. Mussels close their shells tightly "clam up" for the same purpose, and open to feed as the tide brings in their food. Cockes ensure they are either back in their groove or in a nice niche when exposed.

There is less time of exposure to air as you get lower into the zone. These organisms while less tolerant of air are better adapted to wave exposure. Dense strands of kelp can occur here and all this provides living and hiding spaces for a variety of inverts. (hydroids, bryozoans, nudibranches, worms, crabs, tunicates. Some are more conspicuous like the sea anemones, sea urchins, and sea stars.

Some anemones have algae living with them but all capture food, sea urchins graze on the algae in this zone which increases species diversity. Exceptions are that often only one or two species of algae grow when the urchins are very active but then control of urchins by sea otters and sea birds, lobster and fish all return things to normal.

Some inverts. can BURROW or BORE into hard substrates: rock, coral, wood by either mechanical abrasion or chemical dissolution. Some mussels, date mussels, secrete acid and dissolve limestone, gribbles are small wood-boring isopods that simply chew into wood. Teredo (shipworm) are also filter feeders as well as eat wood.

Tide pools are depressions of varying size in the intertidal such as when the tide is out, standing water is left behind like an oasis for algae and animals. They are subjected to great fluctuations in regard to temp. salinity, acidity, dissolved oxygen content... The higher the pool is in the littoral zone, the longer the pool will be exposed, or isolated from the flush of the oceans waves. Depth in the pool is important, as is the overall size. If then tide is out at night, the release of CO2 from the respiring animals and plants will increase (NO Ps) and increase the acidity of the pool. During the day, PS will cause the pH to increase. The larger pools in the mid zones allow the inverts, seastars etc. to live higher up on the rocks and therefore be able to feed in the upper areas longer. In California. some kelps get started in these pools but once a series of spring tides in June arrive (esp. sunny days), the species living beyond their limits will be killed off.

Sea Star at water's edge, zero tide level. Not an indicator of the Mid Tide Zone, nor even commonly found there (at low tide), the sea star has a profound effect on the Mid Tide Zone due to its presence there at high tide.

Zonation & particle size.

Mudflats, sandflats and estuarine channels that are emersed at low tide are not treated as separate habitats in this classification but should be categorised on the basis of substratum type in the littoral section. Estuarine channels that retain water at low tide (freshwater or brackish) should be considered in the sublittoral section. Reedbeds in estuaries should be categorised as reed and large sedge swamps.

Table 1: Particle size ranges for loose rocky material and sediment

Littoral Rocky Habitats

Littoral rock includes rocky habitats of the littoral, or intertidal zone that extends from the upper limit of the supralittoral, or spray zone, to the MLWS tide mark. The extreme lower shore, or sublittoral fringe is excluded. Rock includes bedrock, stable accumulations of loose and mainly angular rock (ranging in size from boulders to pebbles), and intertidal peats. Shores with mixed substrata of rock and sediment are included in the littoral rock section. Accumulations of rounded and mobile rocky material, or shingle, should be considered under shingle and gravel shores.