Marine biological zones and the factors determining them
Table 5 Marine biological zones and the
factors determining them
|
Zone
|
Typical upper boundaries around Britain and
Ireland
|
Immersion
|
Thermal
stability
|
Light
|
Salinity
|
Wave
action
|
|
Adlittoral
|
|
Spray only
|
Highly variable
|
Photic
|
Saline influence
|
None
|
|
Supralittoral
|
+10 to +6 m
|
Spray and splash
|
Highly variable
|
Photic
|
Euryhaline
|
Highly variable
|
|
Eulittoral
|
+7 to +4 m MHWS
|
Regular immersion and
emersion
|
Highly variable
|
Photic
|
Euryhaline
|
Highly variable
|
|
Infralittoral
|
+1 to 0 m MLWS
|
Immersed (intermittent spring tide
emersion of sublittoral fringe)
|
Variable - eurythermal
|
Euphotic
|
Euryhaline
|
Variable
|
|
Circalittoral
|
-5 to -20 m
|
Immersed
|
Moderately variable -
mesothermal
|
Mesophotic (sparse algae, algal
crusts)
|
Mesohaline / Stenohaline
|
Moderately variable
|
|
Circalittoral offshore
|
-40 to -80 m
|
Immersed
|
Stable - stenothermal
|
Aphotic
|
Stenohaline
|
Stable
|
|
Bathyal
|
-200 m
|
Immersed
|
Very stable - stenothermal
|
Aphotic
|
Stenohaline
|
Stable
|