Oceans 11 – Dalesandro
Notes – Subtidal Zone
-The subtidal zone lies below the low-tide zone. It is the final area in the
littoral zone.
· This zone is not exposed to air, even at low tide.
· During extreme low tides, this zone may be briefly exposed to air.
-This area contains a very complex and biodiverse community of
organisms that live here full-time, including fish.
· Some of the most common organisms found in this layer
(besides fish) are sea urchins, periwinkles, crabs, and various
kinds of seaweed such as kelp.
· Sea stars and sea cucumbers are also plentiful here.
-Wave action is still felt in the subtidal zone, as the bottom of
breaking waves rub against the sandy or rocky sea floor.
· Because of this wave action, the organisms living in the
subtidal zone must have ways of either anchoring themselves,
or the ability to walk or swim (to avoid being swept out to sea).
-Pollution is a major threat to the subtidal zone. It is the place where any
runoff from beaches and the backshore ends up.
· Concentration of pollutants can be much higher here when
compared to the intertidal zone or the open ocean.
· Some creatures, such as sea anemones, are very sensitive to
toxins and will disappear from the subtidal zone first, before
dying in other zones with less concentrated pollution.
-Some pollution can be natural, like algal blooms which are uncontrolled
growths of (sometimes toxic) microscopic plants that can poison sealife.
Subtidal Zone – Organism Fact Sheet 9 – Sea Urchin
· Sea urchins are more properly called Echinoideans. There are over 950 species of sea urchins, with many more species yet to be discovered.
· They use tube feet to travel around the sandy bottom, in the same manner as sea stars do.
· To defend themselves against predators, sea urchins have many sharp spines, except on the very bottom where their mouth is located. Some species even have poisonous spines.
· Sea urchins eat just about anything they can catch and overpower, including algae, small sea cucumbers, baby crabs, and mussels.
· Sea urchins will also scavenge dead material.
· Animals that eat sea urchins include sea otters and wolf eels. Some giant whelks and sea stars will also tackle an urchin.
· Sea urchins, like sea cucumbers, and sea stars, have no brains.