But rounder shells are remarkably strong too and can act like ball-bearings -
That's a six-inch ruler, by that way - 15 centimetres.
It features in a number of these photos to give an idea of scale.
- while anything even remotely weedy is bound to be slippery -
- and beds of seaweed are more treacherous than ice - just as slippery but hiding all the bumps and hollows.
PLEASE TAKE CARE
Never walk and look around at the same time: STOP to plan your next moves or admire the scenery.
ALL EXPLORATIONS ARE DONE ENTIRELY AT YOUR OWN RISK.
But the highest true indicator of the marine environment is the presence of a slightly sooty-looking layer on the otherwise bare rocks (most clearly over to your left as you face out to sea).
(a) is the splash zone layer, darkened by the extremely tough microscopic lichen Verrucaria maura.
Each animal appears to be a permanent fixture. But it feeds by moving around, 'grazing' on minute algae and lichens on the rocks in its immediate area while it's under water, returning exactly to its home station where its shell forms an almost airtight fit with the rock.
It may be interesting to speculate as to how they know when to set off for home - by timing or by the pressure of water above them perhaps?
Apart from the encrusting lichens and some microscopic vegetation which nourishes the limpets, the highest obvious plant life consists of the first of the family of "wrack" algae. None of the algae produce flowers: instead they reproduce from enlarged 'conceptacles' towards their tips. Algae come in red, green and brown families: all the wracks, and kelps which we meet lower down, are manifestly browns.
These are acorn barnacles, Semibalanus balanoides.
This channelled wrack, Pelvetia canaliculata, is the smallest of the wracks, extending right up to mean high water level. Although evidently very tough it forms only a relatively narrow band: other species can out-compete it wherever conditions are slightly easier - slightly less exposed to prolonged drying. Photographed in late summer, the yellowish swellings on the ends of the fronds on the right contain the male and female 'conceptacle' cavities: the actual reproductive bodies are microscopic.
Rough periwinkles, Littorina saxatilis, are to be found anywhere on the upper shore - on drying rocks, in shallow pools, often gathered in large numbers in crevices and hollows as here -
- seen as the tide is coming in to re-wet them from the left. They graze on lichens and other vegetable matter in the area, sometimes (albeit rarely) leaving visible tracks of their expeditions.
Not all marine lichens share the dull colour of the splash zone. While not covering any large areas, a white lichen, Tephromela (or Lecanora) atra is to be seen on many stones and boulders where they are dry for part of the day.
It gets its name from its fronds (thalli) usually being twisted, forming an irregular mass.
The next Fucus to be met on a journey down-shore is the bladderwrack, Fucus vesiculosus.
The very characteristic feature, the one that gives this wrack its name, is the presence of the gas-filled bladders which help to keep the seaweed vertical when under water. But they develop only as the plant matures, so spreads of young bladderwrack may in fact be quite bladderless!
There's another mid-shore wrack which is sometimes found sharing the bladderwrack or lower parts of the shore. But it's not another Fucus. It delights in the name of Ascophyllum nodosum or more commonly 'egg wrack'. Like the bladderwrack it has flotation bladders but as swellings on 'stems' rather than otherwise flat fronds.
|A filamentous red alga called Polysiphonia lanosa commonly attaches itself to the egg wrack: it is an epiphyte - more a case of piggy-back than of parasite.|
|It has very characteristic reproductive receptacles in due season.|
|Another piggy-back occupant of the zone is a minute tube-worm that builds coiled chalky tubes glued to the surface of wrack fronds. It gets its nourishment from passing plankton, not from its host. Its name? Spirorbis spirorbis and/or S. rupestrus or even Janua pagenstecheri.|
Officially classified as a red seaweed, this pepper dulse, Osmundea (or Laurencia) pinnatifida, can be any colour from this near-black to almost yellow-buff. It is reportedly collected and dried, in both Scotland and the Channel Islands, for use as a spice.
A cross-section looks like a centimetre-high sand dune with only the upper surface showing any evidence of vegetable life.
The red tinge in this pool is due mainly to a very ubiquitous red alga called coralweed, Corallina officinalis. It is one of a small group of algae that accumulate lime within their tissues.
Of course, tidal pools can make up a whole study of their own. But it is unfortunate from the point of view of a website compiler that the vast majority of interesting inhabitants are past masters at (a) hiding by camouflage or (b) hiding under weeds or rocks, or else (c) they are so nearly transparent as to be virtually invisible or (d) they move too fast to be caught even in a photograph. The commonest exceptions have up to 192 stinging tentacles apiece, so they're not worried about being seen! They are the sea anemone (a-nem-on-ee) animals that normally stick to rocks under water but can withstand being exposed by tides. They can withdraw their tentacles altogether: they then look like blobs of coloured jelly.
Much the commonest are the beadlet anemones, Actinia equina. They can be up to 5 cms across, individuals varying quite widely in colour as shown here. The two large pictures are of the same creature, on the left with tentacles expanded and on the right showing off its ring of blue spots during the process of withdrawing into itself.
Indeed, that ecosystem is sometimes referred to as a 'laminaria forest', though other species are present too, even including epiphytes growing on the stipes of the laminaria.
On the left, the red epiphyte is one of a whole group of possible red algae using the laminaria stipes for support. The white sea mat on the right, seen after being stranded ashore, is in fact a cylindrical colony of zooid animals.
Almost identical in colour to the oarweed (b), dabberlocks (a) (Alaria esculenta) has a ruffled lamina with a mid-rib. In contrast, complementing the big brown algae and colonising spaces between their holdfasts, lesser algae and encrusting lichens occur, as shown below between the cuvie plants, Laminaria hyperborea.
(Just in case you're wondering ... Even the brown seaweeds make use of chlorophyll, the green pigment that enables most land plant leaves to photosynthesise. As brown seaweeds decompose it is fairly common for the dark pigments to degrade first, leaving the chlorophyll to show itself unmasked.)
|Looking up-shore from the low-water end of the path.
Higher than the Laminaria kelps (a) are the Fucus wracks (b). [Those exposed rocks over there are nearly all carboniferous limestones from 300m years ago.]
Another of the few green algae is the very thin, apparently flimsy sea lettuce, Ulva lactuca.
There is not a lot of it in the Snook area but a few patches do occur on the left, fairly well down the path. It looks extremely vulnerable but is actually a very tough plant.
|(a) is the thongweed on a rock and waving in the water.
(b) is some fully immersed Laminaria.
Did you expect to find sponges growing in Northumberland seas? Not, perhaps, very useful for washing the car, but the 'breadcrumb sponge' is a genuine static Poriferal animal - yes, ANIMAL! It forms areas of greenish, brownish, even orange-coloured patches on fairly sheltered rock surfaces anywhere below mid-shore, commonly in kelp areas. Nourishment is obtained mainly from bacteria and other micro-organisms in the seawater passing through its body and out via the volcano-like openings. You can find lots more details if you look up Halichondria panicea.
A few limpets are found within these low-water systems. But they may well be a different species from their cousins higher up the shore: known as China limpets, Patella ulyssiponensis, they're a bit lopsided, with a fairly smooth off-centre summit to their shells.
If you're very lucky, or if you have the guidance of a real expert, you might even spot rarities to add yet further interest to your exploration. Included among that category might be 'stalked jellyfish' - small creatures attached to rocks or seaweeds with all the normal characteristics of very small jellyfish but anchored to one place rather than swimming through or drifting with currents of the open sea. (One expert, Dr. Heather Sugden of Newcastle University's School of Marine Science and Technology will be interested in reports of any rarities you find.)
|Incredible as it may seem, barnacles mate! Each is equipped with an extendible penis which can reach over to a neighbour: eggs develop into microscopic nauplius larvae, initially on-board so to speak: they then grow and moult repeatedly over winter as part of the plankton. The outcome is, come the following April and May, different, boat-shaped cyprid larvae (arrowed in red) that are equipped to swim and explore: they can analyse their surroundings so as to find a suitably textured bare rock - sufficiently close to existing barnacles to facilitate more hanky-panky in due course.|
In life it would have been scurrying through the laminaria forest, whereas a healthy octopus would normally be out beyond tidal depths. The wisp of its black ink shows clearly against the white ruler.
The small starfish might well have been at home, patrolling between the stipes of the kelps. His name is Henry - Bloody Henry, actually - but whether it's Henricia oculata or Henricia sanguinolenta is uncertain.
The grey seal looks astounded at being named Halichoerus grypus, but is best left to contemplate his problems without disturbance: it is very unlikely to be a case of unintentional stranding -
- even if the youngster seems singularly to fail to qualify as a 'grey' seal at all.
It's actually a red alga. It grows initially like a thin paint-like deposit, later forming more irregular layering. Amazingly, the same organism can also take on a more conventional seaweed form, when it is know as Maerl.
Beasties down at the millimetre scale are very easily found by any interested investigator. All these specimens were samples of multitudes occurring on the tough blades of Laminaria kelp, towards the lowest parts of the shore. The iridescent blue-rayed limpets (Helcion pellucidum recently changed to Patella pellucida) can occur singly or in groups, alone or with companion species. Of a similar size, slightly smaller, the banded chink shells (Lacuna vincta) are probably the commonest of a number of different species of snails within the ecosystem. Those were easy to find and not too difficult to photograph. Moving with frustrating rapidity at times, a variety of isopods live out their lives withstanding the churning of kelp bed waters. The active specimen that climbed onto my finger was almost certainly an Ideotea, perhaps I. neglecta or I. granulosa.
A favoured resting place is to be found wherever the tatty end of a Laminaria blade rolls up on itself, affording some minimal degree of shelter. When unrolled, this specimen was found to include the familiar blue-rayed limpets and banded chink shells. Across the centre, a slightly larger isopod is clambering over what may be common flat periwinkles, Littorina obtusata.