Rocky & Boulder ShoresRocky & Boulder Shores

MR2505

Lecture 2

MR2505

Lecture 2

Rocky Shores• Rocky shores - areas of bedrock revealed

between high and low tide levels on the seashore

• Ecosystem present is complex• Why? interaction between terrestrial and

aquatic systems • Plants and animals are distributed on the

shore in horizontal zones that relate to the tolerance of the species to either their exposure to air or submergence in water during the tidal cycle.

• Zonation (see later) is often clear and very ‘abrupt’

• Tide pools often have rich communities of organisms normally associated with the lower shore or sub-tidal habitats

• The plants are typically algae (seaweeds) and lichens

• In sheltered muddy locations e.g. cord grass and Eel-grass may occur

• Animals include marine benthic fauna tolerant to various periods of exposure to the air at low tide, and vagrant terrestrial species including insect larvae.

http://www.npwrc.usgs.gov/resource/1998/classwet/rocky.htm

•Rocky shores are found all over the world.

•Rocky shores are not all the same. For example, in the USA on the Pacific Northwest coast you will find steep, rocky cliffs. In Maine, you will find rocky coasts, too, but they slope gently into the sea.

• Marine plants and animals that live along these rocky shores have adapted to a habitat that changes every day. In the intertidal zone, water levels along rocky shore may drop 12 feet or more between high and low tide. That means that organisms living on the rocks may be exposed to the air for 10 hours or more between high tides. And when the tides roll in, these same organisms must be able to withstand the waves which often hit with incredible force.

Rocky Shores

Five Islands Provincial ParkRising majestically from the shores of the Bay of Fundy, Five Islands Provincial Park is one of Nova Scotia's premiere outdoor destinations. The park features 90 metre (300 ft.) sea cliffs overlooking the world's highest tides

Factors modifying the tidal environment

•Exposure to wave action and "fetch"

•Shore topography

•Slope

•Cracks and crevices

•Pools

•Aspect

•Microhabitats

•Climatic factors (sun, wind, rain and frost)

•Biotic factors

Rocky Shores

•The seashore is a boundary between the land and the sea and due to this transition creates a very diverse habitat.   •There are two high and two low tides in approximately 24 hours around the British coast. The times and levels vary due to the gravitational pull of the moon. •Life on a rocky shore is harsh due to many factors including high and low tides, temperature changes, salinity levels and the vagaries of the weather. The flora and fauna which live there have adapted to these changes in various ways to enable them to survive.•Rocky shores are abundant in wildlife due to the variety of habitats it encompasses. Within a rocky shore there are rock pools, damp crevices, bare rock and sand all which offer homes to many species.

Rocky Shores

Rocky ShoresPHYSICAL ASPECTS

Rocky shores form as a result of marine weathering and erosion of the overburden and the bedrock, due to a combination of rising sea level and wave action, in areas where there is a low sediment supply.

l. Bedrock: resistant bedrock, such as granite,slate and quartzite, erodes slowly and producessteep gradients. Less-resistant sedimentary bedrock is commonly eroded into a wave-cut platform with gentle slopes. Differential erosion of soft and hard rocks

2. Wave action: exposure to wave action, relatedto dominant wind direction, storms and ocean swell shapes the environment. Conditions will control e.g. plant and animal attachment

3. Tidal regime: tidal range determines the area of shore exposed to the air. There is considerableregional variation

4. Climatic conditions: weather conditions include summer and winter temperature extremes,humidity, precipitation and wind exposure. http://museum.gov.ns.ca/mnh/nature/nhns/h2/h2-1.pdf

Rocky shoresWhere the shore is composed of rock outcrops, the characteristic species are:

•Silene maritima           

•Scilla verna

•Artemisia maritima

•Crithmum maritimum

•Carex distans (in rock crevices)

•Carex extensa (in rock crevices)

•Armeria maritima

•Blysmus rufus (in wet rock crevices)

•Limonium binervosum (at one site only, in Co Down)

•Cochlearia danica

•Cochlearia officinalis

•Spergularia rupicola

http://www.habitas.org.uk/flora/habitats/rockyshores.htm

Rocky Shores

ECOSYSTEM

• Energy supply is obtained through primary production by seaweeds and phytoplankton and through organic detritus derived from adjacent land and other intertidal habitats (e.g., tidal marshes). This energy is directly utilized by a variety of herbivorous and detritus- feeding animals on the shore, which are, in their turn, preyed upon by several levels of carnivore on the shore, by fish entering the habitat at high tide and by terrestrial animals, particularly birds, entering at low tide.

PLANTS

• The plants are typically algae and lichens. In sheltered or muddy locations where there is some sediment accumulation amongst the rocks and in tide pools, Cord Grass and Eelgrass may also be found.

• The seaweeds and lichens are distributed on the shore in horizontal zones that relate to tolerance of the species to either exposure to air (seaweeds) or submergence in water (lichens) during the tidal cycle

Rocky Shores

Zonation

•Few features of the shores are more obvious than zonation. •All shores, no matter how large or small the tidal range (max. 17m Bay of Fundy) have at least some degree of zonation or vertical banding of the organisms living on them.

•Types of Zonation

• Horizontal– Local (small scale differences)– Geographical (climate / currents)

• Vertical– Tides– Degree of wave action

•Just as plant communities occupy definite bands or zones on mountains corresponding to tolerances to decreasing temperature with increasing elevation, so intertidal communities occupy definite zones on the shore. Compared to the mountains though, the shorelines are much compressed vertically.

•Generally where the range of tides is small or where the slope of the beach is steep, the zones are generally narrow. Where the slope of the beach is flat and the range of tides is great, then the zones are wide. Heavy wave action widens the zones, both above and below the calm water limits and the upper and lower borders of the zones are less distinct.

Rocky Shores

Horizontal Zonation (Distribution)

•Geographical Scale•Sea temperature•Air temperature•Water currents (larval distribution)•Local Scale•Substrate•Salinity•Wave•Exposure•Topography

Rocky Shores

The Tidal Environment

•Shore Zonation - the problems

•Physical pounding by waves

•Being dislodged to unsuitable level

•Desiccation: evaporative / physiological

•Temperature variation

•Reproduction

•Planktonic dilutions

•Settlement in suitable benthic regions

Rocky Shores

Factors determining zonation

• Rule of limiting factors (applies to adults and juveniles / larval stages) • Tides and their characteristics• Types and frequency of tides• Tidal levels for semi-diurnal tides• Immersion / emersion frequency

Rocky Shores

Rocky Shores

•Degree of shore exposure

•Physical effects – emersion, light regime, dessication, temperature

•Biological interactions – larval settlement, competition, predation, grazing, behaviour

•Relative influences of physical and biological factors

• Conspicuous plants inhabit different zones• Splash Zone Above the extreme-high-water mark but

reached by storm waves, the splash zone is generally bare of vegetation. There may be grasses growing in cracks of rocks and some patches of lichens (e.g., Xanthoria parietina).

• Upper Shore: Rocks bare at the top but, below the level of high water of spring tides, the upper shore supports algae (e.g., Codiolum spp., Calothrix crustacea) and lichens (Verrucaria spp.)

• Middle Shore - The middle shore supports dense growth of brown rockweeds Ascophyllum nodosum and Fucus spp. The red seaweed Porphyra and Fucus serratus and green seaweeds, such as Cladophora spp., are common in some places. The epiphytic Polysiphonia lanosa can be found growing on the Ascophyllum.

• Lower Shore - Below the dense rockweeds on the lower shore, there is a conspicuous zone of Irish Moss and calcareous algae (Lithothamnium spp. and Corallina officinalis). Below this, kelps (Laminaria spp.) are present but only visible at low water of spring tides. This zone continues into the sub-littoral benthic habitat

• The seaweed growth is usually well developed on all rocky shores but is best in exposed, clearwater conditions.

• In certain parts of the world ice action and turbidity limit seaweed growth.

Rocky Shores

Rocky Shores

Rocky Shores

Rocky Shores

http://www.mesa.edu.au/friends/seashores/zonation.html

Rocky Shores

Rocky ShoresFor Example

•The barnacle zone is the first clearly demarcated zone at the top of the shore and this zone occurs on almost every shore in the world.

•This is followed by a zone of mixed barnacles and seaweeds, the mid tide region is marked by mussels and goose barnacles and beneath this zone is another of barnacles and algae and several whelks and limpets.

•Below this zone and marking the beginning of the lower intertidal zone is the clearly marked zone of brown algae (kelp) interspersed with chitons, starfish, and surf grass.

•The zones are by no means constant in composition, number, width and these factors vary from season to season, year to year, shore to shore, and even rock to rock.

ANIMALS

• The animals include marine benthic epifauna tolerant to various periods of exposure to the air at low tide, and vagrant terrestrial species. A system of horizontal zonation of the aquatic fauna is apparent.

• Upper Shore - On the bare rock surfaces, there are very few animals present, except the Rough Periwinkle.

• Middle Shore - At the top, there is a conspicuous zone of barnacles, which is limited at its lowest extent by the growth of rockweed. There is a variety of herbivorous animals, including Rough Periwinkles, Smooth Periwinkles, Common Periwinkles and amphipod crustaceans. Sessile species include Hydroids (Sertularia spp.) and Blue Mussels. The Green Sea Urchin is found at lower levels. Carnivores which feed mainly on the molluscs include Dog Whelks and Purple Starfish.

•Lower Shore - Lower down the shore, the diversity of animals increases as more species are tolerant to the shorter period of exposure at low tide. This is particularly true where animals can find shelter under rocks or seaweeds. Herbivores include Common Periwinkles, Limpets, Green Sea Urchins, isopods and amphipods. The sessile particulate feeders include sponges, hydroids, tube worms (Spirorbis spp. On seaweeds), Horse Mussels, brittle starfish and tunicates. The carnivores include Sea Anemones, Scale Worms, Purple Starfish, Rock Crabs and Sea Slugs.

•Vagrant terrestrial species, insects, birds and mammals enter the rocky-shore habitat at low tide to feed. Several shore-bird species feeding on rocky shores include Ruddy Turnstones; Herring Gulls are also typical.

Rocky Shores

Rocky Shores

Spiral Wrack (Fucus spiralis)

Channelled Wrack (Pelvetia canaliculata)  

Upper Shore

Rocky Shores

Beadlet Anemone (Actinia

equina) Edible Periwinkle (L. littorea)     Shore Crab (Carcinus maenas)

Mussels (Mytilis edulis) Common Limpet (Patella vulgata)

Middle Shore

Bladder Wrack, (Fucus vesiculosus)

http://www.marlin.ac.uk/learningzone/Seashore_life/species_list_seashore.asp

Rocky Shores

Serrated Wrack (Fucus serratus) 

Lower Shore

http://www.nature.shetland.co.uk/brc/rocky.htm

Rocky ShoresTortoiseshell limpets can grow up to 3cm across -noticeably smaller than most other limpets which you see around Shetland. The background colour of the shell can range from white to grey to pale green, and its surface is very smooth  compared with other limpets. The feature that gives this limpet its name and makes it stand out from all the others, is the dark brown stripes which run from the tip right down to the edge of the shell. They can be found on boulders or small smooth stones, particularly those with pink crusts growing on them.

Pearly Topshell (Margarites helicinus)                    

Topshells are a group of small marine snails. The shell of the pearly topshell is only about 3mm tall  -  smaller than a pea! Its colour varies  from an orange-red to cream-brown, patterned with green or purple. Topshells are found under stones or attached to seaweed on the lower shore, as well as in rock pools.

Star Barnacles (Chthamalus stellatus)

SPECIAL FEATURES

•The local modification of plant and animalzonation relates to the tide range, exposure, ice action and other environmental factors. Considerable regional variation is seen.

•Tide Pools: Where water is retained in depressions or cracks in the bedrock during the lowtide period, the plants and animals are not subjected to dessication. As a result, these pools often exhibit rich growths of organisms normally associated with the lower shore and subtidal habitats. Large pools are not strongly influenced by air temperatures, but smaller pools, particularly if located at high levels on the shore where they may not be flushed out by neap tides, experience wide ranges of temperature and salinity. In these conditions, only hardy algal species, such as Enteromorpha intestinalis, can occur.

Rocky Shores

Rocky Shores

Temperature, Salinity, Oxygen, Sediment, Light, People

This diagram shows four different rock pools. No 2 is a shallow high tidal pool in Leigh, where very few species survive: slimy green algae and tiny Stiliger sea slugs. Pool 3 is an upper mid littoral splash pool in which the neptune's necklace seaweed survives. Pools 4 and 5 are deep lower mid littoral pools from Ocean Beach, near Whangarei Heads. They are rich pools with many surviving plant species and sensitive species such as Cystophora torulosa and Pterocladia capillacea.

1. Supralittoral zone ..near sea but above the high tide mark with some marine influence (spray) 2. Supralittoral fringe...upper limit of barnacles (in quantity) to nearest higher convenient landmark (upper limit of Littorina or lower limit of land lichens. Spring tides invade part of this zone. 3. Midlittoral zone: the entire intertidal areas, from the upper limit of barnacles to upper limits of large brown algae at the lower part of the shore. The barnacle demarcation is an important reference point in the universal scheme. 4. Infralittoral fringe: the lower fringe of the intertidal ..an area extending from the upper limit of whatever organism sets the lower limit of the midlittoral zone, to the ELWS (extreme low water spring) tide mark, or in areas of waves, to the lowest level visible between waves. Organisms living here cannot tolerate complete emersion but can live in an area of broken emergence through wave action. 5. Infralittoral zone: the area between ELWS tidal level and corresponding more or less to the more commonly used "sublittoral" term.

Rocky Shores

1. Spray - This is the uppermost zone that extends from the highest reach of spray and storm waves to about the mean of all high tides. This zone is infrequently wetted. Other authors give the following names to this zone: Supra-littoral or Littorina zone Organisms living in this zone are very hardy and semiterrestrial.

2. High - This zone extends from the mean high water to about the mean flood of the higher of the two daily lows which is slightly below mean sea level. This is the zone just above the mussel beds. Other authors call this the mid-littoral or Balanoid zone.

3. Mid - This zone extends from the mean higher-low water to the mean lower low water which is the zero of the tide tables. This zone is typically covered and uncovered twice each day. Also called lower mid-littoral or lower Balanoid zone.

4. Low - This zone typically is uncovered only by minus tides. This zone can only be examined for a few hours each month. Organisms of this zone can tolerate only minimum exposure. Alsocalled the infra-littoral fringe or Laminaria zone.

http://is2.dal.ca/~theriaud/ztheriault/xmar/theriaultst.html

Rocky Shores

Rocky Shores

•Boulder/cobble shore habitats are exposed between the extreme high tide and extreme low tide marks. They form where there is erosion of glacial till on headlands and islands, and are found along the whole Nova Scotia coastline. Boulder/cobble shores are best developed along the Atlantic coast, where there are shoreline drumlins and other glacial till deposits.

•In high energy situations (waves, swell, storms), the cobbles may form a storm beach at and above the high tide mark. Little life will be found here because the boulders and cobbles are always moving. In intermediate and low-energy situations, the boulders rest on a wave-cut platform. There can be horizontal zonation in plant (seaweed) colonization related to the period of exposure at low tide. Various animals (barnacles, isopods, amphipods, periwinkles, Green Crabs, Dog Whelks, Blue Mussels and Purple Starfish) are often present except where colonization is limited by the movement of boulders and cobbles. Tend to be more ecologically barren

Boulder/Cobble Shores

FORMATIONBoulder/cobble shores form where there is erosion of glacial till on headlands and islands. In high energy situations, the cobbles may form a storm beach at and above the high-tide mark. In intermediate- and low-energy situations, the boulders rest on a wave-cut platform.

PHYSICAL ASPECTSl. Substrate: boulders provide a relatively stable hard substrate. Cobbles and pebbles are usually mobile.2. Wave action: in high-energy situations, exposure to wave action, related to dominant wind direction, storms and ocean-swell conditions, the boulders and cobbles are mobile, limiting colonization by intertidal organisms.3. Tidal regime: tide range determines the area of shore that is exposed to the air.4. Water–land interaction: water conditions include summer and winter temperature extremes, formation and movement of ice, and variations in turbidity and salinity.5. Climatic conditions: air conditions include summerand winter temperature extremes, humidity,precipitation and wind exposure.

Boulder/Cobble Shores

•Wave action, the cobbles are more stable and become colonized by encrusting lichens and flowering plants, such as Sea-lungwort and Beach Pea. Animal life is limited to various species of amphipods and fly larvae, which feed on decaying seaweed cast up by storms. Spiders and birds prey upon these animals.

ECOSYSTEM•Primary production within the habitat is limited to the seaweed growth, which is very limited or absent in exposed situations. Energy also enters the system through primary production in the plankton, and through suspended organic detritus derivedfrom the land and adjacent intertidal habitats. There are herbivores and detritus-feeders in the epifauna, but populations are often small. These animals are preyed upon by carnivores, including birds.•In more sheltered locations the boulder spaces form a particularly good environment for a wide range of animals to hide. Reef Crabs (Ozius truncatus), and Variegated Rock Crabs (Leptograpsus variegatus), are common.

Boulder/Cobble Shores

PLANTSMainly algae (seaweeds) colonize the surfaces of boulders. In intermediate- and low-energy situations, there is horizontal zonation related to the period of exposure at low tide.

Upper Shore - On the upper shore, where the cobbles are easily moved by wave action, there is no seaweed growth, but some lichens and flowering plants occur above the high-tide mark.

Middle Shore - On the middle shore, in sheltered conditions, there is a narrow black band of algae and lichens below which brown seaweeds, Fucus spp. and Ascophyllum nodosum, are conspicuous. Various filamentous algae are present in the spring. Cord Grass may be found growing in mud and gravel between the boulders at lower levels. In more exposed situations, the seaweed growth is limited by the movement of the boulders and cobbles. Where seaweeds do occur, there is usually a sparse growth of the brown seaweeds, with Irish Moss and the calcareous species Corallina officinalis and Lithothamnium spp. growing in the lower zone.

Boulder/Cobble Shores

ANIMALS

•The movement of boulders and cobbles in high-energy situations severely limits colonization by animals.

•In low and intermediate energy situations, barnacles, isopods, amphipods, periwinkles, Green Crabs, Dog Whelks, Blue Mussels and Purple Starfish are often present.

SPECIAL FEATURES

• On exposed, high-energy shores, the cobbles are often washed up to form a storm beach or berm.

Boulder/Cobble Shores

•http://museum.gov.ns.ca/mnh/nature/nhns/h2/h2-1.htm

•http://www.field-studies-council.org/outdoorclassroom/16plussearch/courseinfo.asp?no=168

•http://www.lanecc.edu/science/Zonation/marine1.htm

•http://museum.gov.ns.ca/infos/rocky/

•http://www.nature.shetland.co.uk/brc/rocky.htm

•http://www.biol.sc.edu/coral/photo-archive/molluskpics/Molluskpicsindex.html

•http://ecology.hku.hk/jupas/rocky.htm

•http://fieldtrip.britishecologicalsociety.org/rocky%20tour%201/rocky%20shore%20tour%20web/sheltered/sheltered.html

•http://www.pbs.org/americanfieldguide/teachers/oceans/Tour_files/frame.htm

Rocky Shores