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Zonation of Flora and Fauna on Rocky Shore

Depends on interaction of several factors:

  1. Lifestyle animal or plant
    1. Physiology
    2. Nutrition
      • filter feeder
      • deposit feeder
      • plant eater
      • carnivore
        c. Reproduction
      • Planktotrophic larvae: eat plankton
      • Lecithotrophic larvae: don't eat; use yolk
      • Direct Development: no distinct free swimming larval stage
      More detailed information on Larval Strategies

      2) Tolerance to environmental condition

        1. Physical
        2. Chemical

      Natural; Man made / Pollution.

      (under natural conditions, variations in physical or chemical environmental conditions usually are more intense on the upper shore, which may cause stress to some animals or plants)

      3) Competition

        1. within species (intra-specific); for space, food, mate
        2. between species (inter-specific); for space, food,

      (generally more intense on lower shore, or subtidally)


      • overgrowth / pushing off rocks;
      • spines / armour/ claws;
      • chemical interactions.

      (often get mosaics or dominance in competition)

      4) Predation

      (usually more intense on lower shore)


      5)Chance events

      times of recruitment after disturbance, eq. Storms.

      Zonation of Flora and Fauna on Rocky Shores; and then decending into the Deep: An Odesy In Photographs!

      This section is put together to get students and the general public who are interested in Environmental Science and the Environment to think about the Marine Environment and how it works, and to appreciate it. No claim is made to origonality of ideas. My own original work is listed as my Ph.D. Thesis and published works, which are listed in my C.V. Section of these web pages. However, should funding become available I would like to do some original research work (or to have some post graduate students working under my supervision do some original research) on the Intertidal or Sublittoral regions of Mullaghmore in Sligo; (See proposed Mullaghmore Project). The Photographs shown here are mostly my own, with some from Dr. Aidan Murray who worked on the Interdidal part of the Kinsale Project for Elanco; (I did my Ph.D. work in the Sublittoral section of this project; see my C.V.). Dr. Aidan Murray's photographs are acknowledged as 'Dr. A.M.'. A few bought photographs, in the public domain, are also used. I do not know who the photographers were, but if they recognise their photographs and get in contact with me I would be delighted to acknowledge them on the web. These photographs have not been published on printed media and are not used for commercial gain; but solely for educational purposes. A few of the slides appear fine when projected with plenty of light, but appear dark when scanned; some were used even though this was the case because they told a story, or the species illustrated a point I wished to tell; others were discarded.

      Splash Zone


         Typical splash zone zonation on vertical rock face (in this case on a sheltered shore at Rusheenacholla strand Carna Co. Galway), showing vertical zonation of lichen species.

         Lichens competing for space:  Note how little bare rock there is present.
         Lichens Close Up:'Dr. A.M.'

      Sea Ivory Ramalina siliquosa (Hudson) Smith.   Fruticose; Grey-green with white or pale brown disc-shaped reproductive bodies near the tip. In and above the splash zone, NW Europe.

      Xanthoria pariatina (Linnaeus) Fries.   (probably):   Foliose patches up to 100 mm across. Bright orange, becoming greenish yellow in shade; abundant darker orange reproductive bodies like small craters. Often forms a distinct narrow band just above high water of spring tides, together with Caloplaca; also very common inland. NW Europe.

      Ochrolechia parella (Linnaeus) Massalongo.   (probably / possibly):   Thallus encrusting; forms round patches 3-10cm in diameter; conspicuous , saucer-like fruiting bodies with grey, dusty spores. Distribution Atlantic, English Channel and North Sea.

      Verrucaria sp.   probably V.maura Wahlenberg.   Smooth, thin encrustation closely moulded to minor irregularities, often cracked and pitted; may cover large areas of the upper littoral below the band of orange lichens. Dull black, often mistaken for dried stranded oil. NW Europe;


         'I Stand On' (ISO) Isopods are doso-ventrally flattened; note the footprint to remind you of this! The poor photograph shows the sea slater Ligia oceanica, Order Isopoda, Family Ligiidae, on the strand. It is abundant on all rocky coasts in North West Europe, above high water mark, scurrying over damp rocks particulary at dusk. Also present in the photograph are a limpet and barnacles - more about these later.

      Upper Shore




        Winkles: Family Littorinidae: The Rough Winkle. 'Dr. A.M.'

      Mid Shore





         Barnacles on the seasore; some juvenile stages may be free-swimming, but typically as adults they are cemented to rocks occupying a large % of the surface area of the rocks. As Barnacles belong to the Phylum Crustacea they have a hard exoskeleton.
        'Dr. A.M.'
        'Dr. A.M.'
        Limpets   Patella vulgata Linnaeus (an bairneach in Gaelige) on sheltered shore and upper shore; 'Dr. A.M.' has a high conical form to its 'china-man hat' shaped shell. When the tide is 'in' it walks on its large foot, leaving a trace of mucus, over rock, scraping algal sporelings off them using its rough spiny 'tongue like' radula. When the tide is going out it returns to its 'home', a neat depression the size of the base of its shell, which it has worn in the rocks with the edges of its shell (and possibly helped by its radula). It remains stationary when the tide is out. It may live for up to about 15 years. It is a hermaphroditic, being a male for about the first 4 years then changing into a female, spawning eggs in winter. Fertilisation is external and the larvae settle after a couple of days.
        Limpets    Patella vulgata Linnaeus and possibly also some Patella ulyssiponensis Gmelin (formerly P. aspera Röding) on exposed shore and lower shore; 'Dr. A.M.' latter species has generally fewer radiating ridges, often with tubercles where crossed by the growth lines, and projecting more around the shell edges, it also has whiter tentacles around the mantle; never has a high conical form; but it has a similar biology and reproduction to the former species.

        underside view of the Toothed Winkle or Thick Top Shell or Horse Periwinkle (an fhaocha chapaill in Gaelige) Monodonta lineata (da Costa) sitting on a tuft of Lichina pygmaea showig the 'tooth' on the inside of the mouth opening that destinguishes it from the Common Periwinkle (an fhaocha dhubh in Gaelige) Littorina littorea (Linnaeus).
      M. lineata lives on the upper and middle regions of sheltered rocky shores and often in rockpools feeding on algal sporelings. It is a southern species from Madeira and Morocco north to the Channel, West Wales and West Ireland, but not in the Mediterranean. It has planktotrophic development.


      Lower Shore or Rock Pool




        Dog Whelk  Nucella lapillus; semi-exposed shore; Fast moving predatory Gastropod snail. Shell spire short in comparrison to other members of its family (Muricidae) , body whorl comprising about three-quarters total length. Colour white or various shades of beige or brown; may be banded light and dark. It has a prominant red operculum (horny flap to close shell opening). After copulation between males and females, the egg capsules are laid in clusters in early spring, releasing crawling juveniles of about 1 mm long. Feeds on barnacles and mussels, boring through shells with its toothed radula, from mean high water neaps to mean low water springs. Common on most North Atlantic Coasts from Gibraltar to Greenland.

      Dog Whelks on exposed shores have a rather blunt fat globular and short and stubby appeaeance; the whorls of their shell are smooth and not noticibly ridged. On sheltered shores their shape is much more pointy, narrow, elongated and slender; the ridges of the whorls of their shell are more elivated.

      Other species present in the photograph: (1.) Juvenile Mussels, probably Mytilus edulis Linnaeus; a blue-black filter feeding bivalve with an umbone (pointed region of shell) to the anterior, with a small anterior adductor muscle and no hinge teeth. Often held together in large masses of numerous individuals by byssus threads. Sexes are seperate; breeds early in spring and summer, producing millions of planktotrophic larvae. One of the Commonest species in the top 10 metres. A 'weed' species, or fouling organism; often fouling piers and boats and getting into seawater pipe systems as larvae and then growing rappidly into adults, clogging the pipes. Its biological zero temperature (i.e. the temperature below which the animal will not grow) is low, around 3 degrees centigrade, so it may grow (slowly) even in winter months if there is food. On sheltered shores with good feeding conditions (high levels of planktonic algae), it may grow quickly, especially in summer months or periods of planktonic algal blooms, and to a large size. In sheltered upper shore regions it may live for 15 years or more. On exposed shores mussels are nearly always small, because of poor feeding conditions. However, if the growth bands on the shell are examined (one laid down for each yearly growing season; as growth practly ceases in the coldest winter months) it may be observed that sometimes the mussels are infact quite old, even though they are very small. It may be possible to find numerous growth rings on the shells. This species may be grown commercially on ropes (suspended culture) or dredged from mussel banks (bottom culture). A common commensal organism (living with the mussels but not ding much harm) is the pea crab (Pinnotheres), which frequently occurs in the mantle cavity of the mussel, especially in those from sublittoral mussel banks. Mytilicola intestinalis is a small copeopod (Phylum Crustacea) parasite, that looks like a small red worm, that is occasionally found in the gut of mussels; It can cause wasting and the death of enormous numbers of mussels. Mussels, being such rapid filterers of sea water, can concentrate toxins present in sea water and accumulate them in their body tissues, at levels up to thousands of times more concentrated than in the original sea water, making them unfit for human consumption. They can concentrate faecal coliform bacteria (indicators of sewage contamination); or toxins produced by dinoflaggelate blooms, (a type of algal bloom, or 'red tide'), causing people who have eaten 'red tide' contaminated shellfish to get, for example, diaharetic shellfish poisoning (making them sick) or getting paralytic shellfish poisoning (where people can become paralised).

      (2.) moderate amounts of the serrated wrack or toothed wrack Fucus serratus Linnaeus.

      (3.) a few patches of sea lettuce Ulva lactuca, a green algae (Class Chlorophyceae) which can tolerate a fresh water influence and which can dominate on a shore along with other green algae, when added nutrients are present (Eutrophication).

      (4.) a few patches of a red algal species

      This photograph, showing mixed patches of fauna, algae and bare substrate, is good for describing the cycling of species within a typical zone; each patch being dominated by one of these organisms for a period and then being replaced by another for a period, and then another for a period, e.t.c., until the first species regains a predominant position on the rock; with the result that that seashore zone always contains one of the species, but one can not say which one is going to occur in any particular patch of the rocky substrate, at any particular date, in any particular year. Say a storm wipes a particular patch of rock free of organisms; green algal sporelings may settle; some might grow into large green macrophytes, e.g. the sea lettuce Ulva lacuta (or brown Fucoid algae e.g. Fucus vesiculosus or Fucus serratus may settle). The algal species, which ever one it may be, might flap around, stopping other organisms from settling on the rock; but most would be scraped off the rocks by feeding limpets, using their radula (spiky tongue on a conveyor belt system). The area may remain dominated by limpets until algae sporlings are used up. There would be bare space on the rocks. If it happened to be the correct time for barnacle settlement and many barnacle larvae were in the water column as plankton; some of these might settle on the rocks. They would attract others of their species, and in no time the rock patch would be dominated by barnacles. Barnacles are shrimp-like organisms that cement their head region to rocks and form plates around themselves sticking out their thoraccic appendages (cirri) to catch planktonic food. They are hermaphroditic (male and female in the one organism). However they cross-fertilise. The male part has a very long penis which he sticks out of his shell and into the shell of an adjacent barnacle of the same species, to fertilise the female part (eggs) of that individual. So you see, if one barnacle is not sitting close enough to other barnacles of the same species he will have a very lonly and boring life! For this reason barnacles put out chemicals to attract other barnacles of their species to sit next to them. Once barnacles cover an area densely they keep other organisms out (competition for space).They feed on plankton in the water, possibly eating the larvae of other species which would like to settle in the region. Barnacle species also compete for space with other barnacle species, outgrowing one another and pushing each other off rocks (described elsewhere in this seashore section). Barnacles also hinder the movement of other species, for example limpets, over the rocks where they are very densely packed. Eventually many dog whelks will move in to eat the barnacles (predator forraging behavior). Their empty shells will remain on the rocks and wil be colonised by very small organisms seeking shelter; for example small littorinids like Littorina neglecta and juvenile rough periwinkle species; and the small pink bivalve Lasaea rubra . Eventually the barnacle shells will fall off allowing colonisation by the larvae or spores of what ever species is in the plankton and ready to settle at the time. Perhaps green algae will settle and then limpets will follow (back to the previous state). Mussels may settle in high densities, (instead of barnacles). However, much the same thing then happens. Small (already settled) organisms seek shelter among the closely packed young mussels, often attaching to their bysus threads. The mussels may hinder movement by other organisms like limpets; thy will filter out settling larvae in the plankton, thus maintaining their dominance. Dog whelks will move into the region in large numbers to eat them (as is seen in this photograph). Eventually the mussels will be knocked off in a storm and the colonising process will start all over again, probably with a different species dominance and cycling of species. If some sea anemones settle they will clear a space around themselves by stinging organisms that come near them, using poisoned darts(nematocysts), which they shoot from their tentacles. These tentacles will also put paralised organisms into their centrally located mouth. These will be swallowed whole and digested in the central gastric cavity (gullet region). Sponges will use chemical warfare, and because of their plastic growth grow around objects. They will also filter out settling larva along with other plankton.

      Now Girls (in the complimentary Irish sence!, meaning young women; rather than to be taken in the more derogatory American sence!) Something for you!!!: Why is becomming more masculine one step in the direction to becomming more deformed??? (when it comes to doing housework!!!). Well guys!! (in the American sence, used used for both sexes; rather than in the Irish sence, only used for males; unless the Irish people have been watching too many American 'Soaps'on T.V.!) Maybe the humble Dog Whelk has the answer (Imposex!!!). Differences make the world go round: Like Johns and Jacks (loos in the States and Ireland).


      In 1998 Andy Douglas, a M.Sc. student under my supervision, and myself, analysed about 150 dog whelks for evidence of Imposex at Lissadell, County Sligo, where there is intensive commercial rearing of clams taking place; and found none. To make our observations the shell of each dog whelk had to be removed individually, by crushing it slowly in a vice-grip clamp, increasing the pressure gently, bit by bit, just until the shell split, and could then be removed from the intact tissue. Both males and females were examined and the lenth of penis measured under a high powered microscope. At the time Andy was studying the timing of the reproductive cycle of the commercially reared clams, in relation to environmental conditions and we wanted to rule out any extraneous effects, e.g. due to T.B.T. presence. Before its use as an antifoulant on the hulls of small pleasure boats was banned about 10 years ago the presence of T.B.T. in sea waters, documented by imposex in dog whelks, was widspread around the coasts of Ireland; even being recorded in harbours as small as that at Mullaghmore in County Sligo. We did not go as far as looking for development of a vas deferens in female (the initial stages) but found no evidence of any form of hermaphroditism; not even a very small penis in a female!






      Fauna: Epibenthic Invertebrates: on rock, sand, or other soft substrates; arranged taxonomically.

      Phylum Cnidaria: Class Anthozoa:

      Order Actinaria; Sea-anemones

        Dahlia Anemone Urticina felina (Linnaeus); formerly Tealia felina (L.) Base strongly adhesive and sucker-like; wharty column reaching up to 15cm when large specimens are fully extended. Characteristically with pieces of shells and gravel adhering to the column so that when closed the animal may be quite inconspicuous; especially since it often occurs in crevaces shaded from strong light. 80 to 160 stout, retractile tentacles. Colour, both of column and tentacles, very variable. Distribution Atlantic, North Sea, West Baltic and English Channel.
         Metridium senile L.
      More photos and information on sea anemones, jllyfish and corals Phylum Cnidaria

      Order Gorgonacea; Sea-fans; Colonial anthozoans whose retractible polyps have 8 branching (pinnate) tentacles supported by a central skeleton of calcium carbonate bound in a horn like substance called gorgonin.

        Phosphorescent Sea-pen Pennatula phosphorea I have seen thes while diving in Portaferry; If you touch them they will shoot down into the sediment.

      Phylum Mollusca; shellfish : Class Gastropoda; Snails and slugs

         Common whelk Buccinum undatum L.

      Phylum Crustacea

      Subclass Cirripedia; Barnacles

        Goose Barnacle Lepas anatifera Linnaeus

      Subclass Malacostraca

      Order Decapoda; 8 pairs of thoracic appendages; first and third pairs used as mouth parts, and fourth to eighth pairs (i.e. 10 in all, hence name) are used for walking and may terminate in a pincer or claw-like joint.

      Suborder Repantia; grasping forms which usually walk

      Division Brachyura; True Crabs

        Edible Crab Cancer pagurus Linnaeus

      Suborder Natantia; forms which usually swim (hence name 'natant' to swim); Prawns and Shrimps

           Shallow Sublittoral Prawn sitting on sea lettuce    Palaemon adspersus Rathke sitting on Ulva lactuca Linnaeus.

      Phylum Echinodermata; spiny skin, 5 fold symmetry: Class Echinoidea; Sea-urchins

        Common, or Edible Sea-urchin, or White Sea-urchin  Echinus esculentus Linnaeus

      Fauna: Vertebrates; animals with back bones: Fish

        Dragonet Callionymus lyra Linnaeus
        Herring Clupea harengus Linnaeus
        Lumpfish, Lump Sucker, Sea Hen Cyclopterus lumpus Linnaeus
        Whiting   Merlangius merlangus (Linnaeus) (Gadus merlangus (Linnaeus)
        Broad-nosed Pipe Fish Syngnathus typhle Linnaeus
        Pollack Pollachius pollachius (Linnaeus)
      another photo

      Quiz Question

      Familiar in more ways than one! What animal am I referring to? Answer

        Lesser Spotted Dogfish, Rough Hound or Rock Salmon Sciliorhinus caniculus (Linnaeus)
        Goldsinny Centrolabrus rupestris (Linnaeus)
        male Cuckoo wrasse Labrus mixtusPhoto by Dr. Michael Broaders, Institute of Technology, Sligo.
      Immature males orange-red colour; mature males have bright blue heads and sides, blue extending to front of dorsal fin and blue stripe on tip of tail fin; white heads indicate courtship coloration; females orange-red with 3 dark patches on rear of back.


      Fauna: Vertebrates: Mammals, Warm blooded, produce milk: Whales

        Killer Whale Orcinus orca (Linnaeus)

      Sampling Gear









        Asterina gibbosa (Pennant) Cushon Starfish, under rock
        The Chamaeleon Prawn Hippolyte varians Leach'Dr. A.M.' Colour red, brown, green, or flecked reddish-brown, depending on colour of background. Rostrum deep, with only a single dorsal tooth just in front of the eye socket. Intertidal among sea grasses and algae, or on sandy stretches adjacent to rocks. Distributed from West Norway to Mediterranean; common around British and Irish Coasts. This photograph when projected clearly shows the range of colours from one vivid bright light green specimen, through one with a paler shade of light green speckled with brown, to a brown indivilual. However it has not scanned well (all appearing dark).
        Spot the Fish! Definitely not Dog fish!

      The fish on the white sand background are easy enough to see. But how many fish can you spot on the dark background of rocks and weeds, on the right? This is due to camoflage and the feature of counter shading. Have you ever noticed that many fish have a dark top dorsal (back) region and a white belly underneath (e.g. Pollach, cod, and flat fish; especially those like pollach that live in rocky regions swimming above weeds). The dark back camoflages them from predators or prey looking down from above. The white belly decreases the contrast of their outline against the bright sky when looking up through the water from below.




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      This page was last modified on 12/06/2000

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