For semi-quantitative biological recording, the MNCR SACFOR
scale was used.
The following definitions for physical habitat
characteristics are taken from guidance notes for MNCR field
recording (Appendix 8 in Hiscock ed. 1996). Some terms are
modified for use in the classification.
Salinity - The
categories are defined as follows (the points of separation
approximate to critical tolerance limits for marine species):
Fully marine
|
30-40 ‰
|
Variable
|
18-40 ‰
|
Reduced
|
18-30 ‰
|
Low
|
<18 ‰
|
Wave exposure - These
categories take account of the aspect of the coast
(related to direction of prevailing or strong winds), the
fetch (distance to nearest land), its
openness (the degree of open water offshore) and
its profile (the depth profile of water adjacent
to the coast). Estimation of wave exposure requires inspection of
charts and maps.
Extremely exposed
|
This category is for the few open coastlines which face into
prevailing wind and receive oceanic swell without any offshore
breaks (such as islands or shallows) for several thousand km and
where deep water is close to the shore (50 m depth contour
within about 300 m, e.g. Rockall).
|
Very exposed
|
These are open coasts which face into prevailing winds and
receive oceanic swell without any offshore breaks (such as islands
or shallows) for several hundred km but where deep water is not
close (>300 m) to the shore. They can be adjacent to
extremely exposed sites but face away from prevailing winds (here
swell and wave action will refract towards these shores) or where,
although facing away from prevailing winds, strong winds and swell
often occur (for instance, the east coast of Fair Isle).
|
Exposed
|
At these sites, prevailing wind is onshore although there is a
degree of shelter because of extensive shallow areas offshore,
offshore obstructions, a restricted (<90o) window to open water.
These sites will not generally be exposed to strong or regular
swell. This can also include open coasts facing away from
prevailing winds but where strong winds with a long fetch are
frequent.
|
Moderately exposed
|
These sites generally include open coasts facing away from
prevailing winds and without a long fetch but where strong winds
can be frequent.
|
Sheltered
|
At these sites, there is a restricted fetch and/or open water
window. Coasts can face prevailing winds but with a short fetch
(say <20 km) or extensive shallow areas offshore or may
face away from prevailing winds.
|
Very sheltered
|
These sites are unlikely to have a fetch greater than
20 km (the exception being through a narrow (<30o) open
water window, they face away from prevailing winds or have
obstructions, such as reefs, offshore.
|
Extremely sheltered
|
These sites are fully enclosed with fetch no greater than
about 3 km.
|
Ultra sheltered
|
Sites with fetch of a few tens or at most 100s of
metres.
|
In the habitat classification
exposed (as in exposed littoral
rock) encompasses the extremely exposed,
very exposed and exposed
categories, whilst sheltered (as in
sheltered littoral rock) encompasses
sheltered to ultra sheltered
categories.
Tidal currents (or streams)
(maximum at surface) - This is maximum tidal current
strength which affects the actual area surveyed.
Note for shores and inshore areas this may differ
considerably from the tidal currents present offshore. In
some narrows and sounds the top of the shore may only be covered at
slack water, but the lower shore is subject to fast running
water.
Very strong
|
>6 knots
(>3 m/sec.)
|
Strong
|
3-6 knots
(>1.5-3 m/sec.)
|
Moderately strong
|
1-3 knots
(0.5-1.5 m/sec.)
|
Weak
|
<1 knot
(<0.5 m/sec.)
|
Very weak
|
Negligible
|
In the habitat classification tide-swept
habitats typically have moderately strong or stronger tidal
currents.
Zone - These
definitions primarily relate to rocky habitats or those where algae
grow (e.g. stable shallow sublittoral sediments). For use of the
terms
infralittoral and circalittoral in the
classification, especially for sediments, refer also to
Table 5.
Supralittoral
|
Colonised by yellow and grey lichens, above the
Littorina populations but generally below flowering
plants.
|
Upper littoral fringe
|
This is the splash zone above High Water of Spring Tides with
a dense band of the black lichen by Verrucaria maura.
Littorina saxatilis and Littorina neritoides
often present. May include saltmarsh species on shale/pebbles in
shelter.
|
Lower littoral fringe
|
The Pelvetia (in shelter) or Porphyra
(exposed) belt. With patchy Verrucaria maura, Verrucaria
mucosa and Lichina pygmaea present above the main
barnacle population. May also include saltmarsh species on
shale/pebbles in shelter.
|
Upper eulittoral
|
Barnacles and limpets present in quantity or with dense
Fucus spiralis in sheltered locations.
|
Mid eulittoral
|
Barnacle-limpet dominated, sometimes mussels or dominated by
Fucus vesiculosus and Ascophyllum nodosum in
sheltered locations. Mastocarpus stellatus and
Palmaria palmata patchy in lower part. Usually quite a
wide belt.
|
Lower eulittoral
|
Fucus serratus, Mastocarpus stellatus, Himanthalia
elongata or Palmaria palmata variously dominant;
barnacles sparse.
|
Sublittoral fringe
|
Dominated by Alaria esculenta (very exposed),
Laminaria digitata (exposed to sheltered) or Laminaria
saccharina (very sheltered) with encrusting coralline algae;
barnacles sparse.
|
Upper infralittoral
|
Dense forest of kelp.
|
Lower infralittoral
|
Sparse kelp park, dominated by foliose algae except where
grazed. May lack kelp.
|
Upper circalittoral
|
Dominated by animals, lacking kelp but with sparse foliose
algae except where grazed.
|
Lower circalittoral
|
Dominated by animals with no foliose algae but encrusting
coralline algae.
|
Substratum
Bedrock
|
Includes very soft rock-types such as chalk, peat and
clay.
|
Boulders
|
Very large (>1024 mm), large (512-1024 mm), small (256-512
mm)
|
Cobbles
|
64-256 mm
|
Pebbles
|
16-64 mm
|
Gravel
|
4-16 mm
|
Coarse sand
|
1-4 mm
|
Medium sand
|
0.25-1 mm
|
Fine sand
|
0.063 - 0.25 mm
|
Mud
|
<0.063 mm (the silt/clay fraction)
|
Each division of sediment type above represents
two divisions on the Wentworth scale (Wentworth 1922).
In the habitat classification, bedrock, stable
boulders, cobbles or pebbles and habitats of mixed boulder, cobble,
pebble and sediment (mixed substrata) as well as
artificial substrata (concrete, wood, metal) are collectively
referred to as rock. Highly mobile cobbles and
pebbles (shingle), together with gravel and coarse sand are
collectively referred to as coarse sediments.
Mixed sediment consists of heterogeneous mixtures
of gravel, sand and mud and may often have shells and stones
also.