Rocky Shore Communities

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Rocky Shore Communities
MR2505 Lecture 3
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Rocky Shore Communities
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Rocky Shore Communities
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Rocky Shore Communities
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Rocky Shore Communities
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Rocky Shore Communities
http//www.tonya.me.uk/Marine/tidalzones.asp
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Rocky Shore Communities

• Described as inhospitable environment
• Exposure to the Elements e.g. Wind and Wave
  Action
• Lack of Shelter
• Ice (geographical location)
• But in some cases Very Rich Diversity of
  Organisms

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Rocky Shore Communities

• Zonation (horizontal banding)
• Plants and Animals
• Universal Patterns Identified

A dark belt of brown seaweeds, a white belt of
barnacles and a black belt of lichens dominate
the lower, middle and upper shore levels
respectively.
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Rocky Shore Communities
Notice that the flora are dominated by brown
seaweeds. At the bottom of the shore, exposed to
air only during short periods of low water during
Spring tides, are 'kelps' or laminarians in this
case, species of the genus Laminaria which can
grow to several metres in length a tough stipe
supports a floppy frond. Above this, between MLW
and MHW, the main seaweeds are 'wracks' or
fucoids, especially species of the genus Fucus
but also Ascophyllum nodosum and Pelvetia
canaliculata . Seaweed size tends to grow smaller
towards the top of the shore. This is in part a
result of tougher conditions here, but also a
result of interactions amongst species.
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Rocky Shore Communities
Where do red and green seaweeds fit into the
picture of zonation? According to an old theory,
the zonation of seaweeds was a response to the
changing colour of light penetrating the sea.
Thus green seaweeds were found at the top of the
shore, where average water cover was small and
light close to white brown seaweeds at greater
depth, adapted to green light and red seaweeds
at greatest depth, adapted to the prevailing blue
colour of light penetrating here. However, a
better explanation is this. Red seaweeds are less
tolerant of dessication and less good at
competing with brown seaweeds on shores on the
west coast of Scotland, so they tend to be found
as an understory, or in rock pools, or growing on
other seaweeds. Green seaweeds such as
Enteromorpha are not very resistant to
dessication and are heavily grazed, but they can
grow quickly, and seem to fluorish in regions of
nutrient enrichment - e.g. where sewage pipes
cross the beach.
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Rocky Shore Communities
http//www.epa.qld.gov.au/nature_conservation/habi
tats/marine_habitats/rocky_shore/
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Rocky Shore Communities

• Communities vary from shore to shore despite
  vertical zonation
• Wave exposure
• Zonation more obvious where fewer plants e.g.
  barnacles
• Ballantines scale (figure)

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Rocky Shore Communities

• Sheltered versus exposed (protection versus wave
  action)
• Increasing exposure brown algae to barnacles,
  mussels and red algae
• In-between shores mosaic of fucoids, barnacles
  and bare rock
• Pattern varies around the World though

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Rocky Shore Communities

• Also differences in vertical zones with different
  exposures (Figure 3.2)
• Distributions of flora and fauna are not just the
  result of physical factors
• Wave forces are responsible for some organisms
  but not for all

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Rocky Shore Communities

• Differences in environment e.g. water temperature
  and turbidity
• Some organisms exist in more than one type of
  environment, but show physical differences in
  size and form e.g. kelp, algae etc
• Physical and biological factors are responsible

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Rocky Shore Communities

• Wave action both influences structure and
  community composition by eliminating organisms
  that can not withstand the waves, but also alters
  the balance of competition, predation, and
  grazing pressures
• Difficult to devise a general model
• Other factors that need to be taken into account
  are rock type and texture etc.
• Localised features such as crevices, gullies,
  caves etc.

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Rocky Shore Communities

• Unique environments include
• fast flowing water
• submersion
• reduced illumination
• reduced salinity

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Rocky Shore Communities

• Littoral ecosystems
• Food webs
• Two examples provided by Little and Kitching
  (Figures 8.1a and b)
• Show how communities work albeit simplified
• Provides a basis for questions to be asked
• Are communities stable or changeable?

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Rocky Shore Communities
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Rocky Shore Communities
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Rocky Shore Communities
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Rocky Shore Communities

• On sheltered shores algal-dominated communities
  are stable
• Moderately exposed shores are much more variable
• Exposed shores show little overall variation but
  small scale mosaic patterns change frequently

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Rocky Shore Communities

• The changes that take place are deemed to be a
  combination of both physical and biological
  interactions
• Disturbance lies at the root of the change
• For example, wave action leads to physical
  removal
• Mobile ice in different climates desiccation
  Sand Scour etc
• Result is often a mosaic community

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Rocky Shore Communities

• Competition also influences the community
  structure
• Interspecies interactions affect succession and
  therefore structuring of communities
• Competition for space, food
• Balance between physical and biological factors

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Rocky Shore Communities

• Also Predation, Grazing and Recruitment
• Paines hypothesis of Keystone Species that can
  free up space for others
• But... not all predators are dominant because of
  recruitment of prey physiological limitations of
  predator prey may have refuge from predator
  resistance to predator (chemicals or behaviour
  patterns)

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Rocky Shore Communities

• Grazing different because it is a different
  process and involves different species
• Recruitment miniature adults important in the
  density of populations e.g. larval supply

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Rocky Shore Communities

• Macroalgae and Microalgae
• Dominate on some shores
• Brown, green and red
• Blue-green, diatoms etc.
• Microalgae more important in the food chain than
  macroalgae
• Microalgae have high rate of production

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Rocky Shore Communities

• Distribution varies according to exposed shore
  etc. and also locally
• Exposed shore less evident than sheltered shore
• Variety of species always increases towards the
  sub-littoral zone
• Green algae less abundant Enteromorpha, Ulva,
  Cladophora

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Rocky Shore Communities

• Primary production of algae is substantial
• Eaten by grazers (but less of the larger sizes)
• Large plants end up as detritus
• Algal defences growing out of reach temporal
  escape (growing or fruiting when grazing pressure
  is least) deter grazers through structural
  adaptations chemical

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Rocky Shore Communities

• Brown Algae
• Fucoids and Laminarians or Kelps
• Different habitat and distribution
• Laminarians are affected by wave action,
  competition and sea urchins

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Rocky Shore Communities

• Green Algae
• Enteromorpha for example occurs anywhere on the
  shore, but usually high-shore, Ulva on the lower
  shore, as is Cladophora
• Generally sheltered environments
• Very frequent and rapid reproduction aids
  colonization

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Rocky Shore Communities

• Red Algae
• Very varied form frondose and branching,
  filamentous, encrusting
• Live low on the shore (but some at top)
• Some live in tidal pools
• Like brown and green algae contain chlorophyll
  a, but also red pigments phycoerythrins (absorb
  blue and green light)

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Rocky Shore Communities

• Microalgae
• Provides most of the food that the limpets,
  winkles, topshells and other herbivores survive
  on
• Evidence of vertical zonation
• Different diatom assemblages on different
  substrate
• Effects of grazers at different times of the year

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Rocky Shore Communities

• Grazers or Herbivores
• Live algae
• Dead algae (detritus) are detritivores
• Molluscan grazers most prominent on rocky shores
• Major control on algal vegetation
• Lower shore sea urchins
• Mesograzers amphipods and isopods overall
• Limpets and Winkles and many others specialise in
  intertidal life

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Rocky Shore Communities

• Grazers may determine community structure
• Intertidal
• Subtidal
• Limpets widespread, at all intertidal levels,
  adaptable, strong, resist wave attack and
  predators, demonstrate homing and territoriality,
  different feeding times
• Can be affected by desiccation
• Predators deterred by Stomping and Mushrooming

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Rocky Shore Communities

• Winkles
• Common around the world
• Very adaptable
• Evidence of Zonation
• Preference for algal foods
• Others are Topshells, Mesograzers (amphipods and
  isopods), Sea Urchins

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Rocky Shore Communities

• Suspension Feeders
• Barnacles and bivalves (mussels) on wave-exposed
  shores
• Largely sessile
• Many others around the world
• Many man-made substrates docks, ship hulls,
  offshore platforms
• Fouling communities

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Rocky Shore Communities

• Rocky shores suspension feeders are sessile
• Depends on local conditions for supply of food
  and nutrients
• Tolerate conditions of flow, wave action,
  desiccation,
• Mussels, Barnacles, Polychaetes, Sea Anemones,

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Rocky Shore Communities

• Interaction between species
• For example, efficiency of grazers e.g. limpets
• Competition
• But differences exist between sheltered and
  exposed shores

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Rocky Shore Communities
Habitat-modifying, dominant species such as
algaes, seagrass, corals, and mussels are known
as ''foundation species' or 'ecosystem engineers'
because they provide habitat for a high diversity
of species. This is achieved through increasing
the heterogeneity of habitat, reducing the water
flow, stabilising the substrate, increasing
sedimentation, reducing light, and providing
substrate for species to live on.
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Rocky Shore Communities

• Impact of man
• Trampling
• Pollution (sewage, heat)
• Oil Spills
• Oil Cleanups
• Sea Level Rise / Climate Change

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Rocky Shore Communities
Another example of the effects of grazing is
illustrated by following the events that occurred
after the Torrey Canyon oil spill in England in
1967. Beaches were treated with 10, 000 tonnes of
oil dispersants, which proved, however, more
toxic than the oil to most sea-shore life. Most
animals on the shore were killed, imcluding many
Patella (limpets) which were normally present in
large numbers. There followed a settlement of the
green seaweeds Ulva and Enteromorpha spp. During
the late summer and autumn of 1967, Fucus
vesiculosus began to appear, and in places the
large brown seaweeds Laminaria digitata and
Himanthalia grew 1.5 - 2 m further upshore than
normal. Animal life was still reduced in number
during 1968, but a few barnacles settle in areas
free from Fucus. Patella settled and removed much
of the Fucus in 1972-1973, and there was a return
to the limpet-barnacle community by 1973-1974.
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Rocky Shore Communities

• http//life.bio.sunysb.edu/marinebio/rockyshore.ht
  ml
• http//www.scsc.k12.ar.us/2000backeast/ENatHist/Me
  mbers/CearleyD/Default.htm
• http//www.swan.ac.uk/biosci/empress/ecology/ecolo
  gy.htm
• http//www.justblue.co.za/General/Habitats/RockySh
  ores.htm
• http//www.epa.qld.gov.au/nature_conservation/habi
  tats/marine_habitats/rocky_shore/
• http//henge.bio.miami.edu/coastalecology/GECoasta
  lMapping.htm
• http//www.mindbird.com/oceanography___marine_biol
  ogy.htm
• http//www.ukmarinesac.org.uk/communities/intertid
  al-reef/ir7_4.htm
• http//www.eicc.bio.usyd.edu.au/talks/

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Rocky Shore Communities

• http//www.biol.canterbury.ac.nz/MERG/research/hfs
  .html
• http//www.cyberport.co.uk/natural_world/ecology_o
  f_portland_harbour/ecology_of_portland_harbour.htm
  
• http//www.lesspress.com/science/
• http//nearshore.ucsd.edu/photogallery-bottom.html
  
• http//www.aberystwyth-today.co.uk/ITW/area/areaed
  itdetail.cfm?id76486

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• BENEDDETTI-CECCHI, L. (2001). Variability in
  abundance of algae and invertebrates at different
  spatial scales on rocky shores. Marine Ecology
  Progress Series 215, 79-92.
• BROEKHUYSEN, G.J. (1940). A preliminary
  investigation of the importance of desiccation,
  temperature and salinity as factors controlling
  the vertical distribution of certain intertidal
  marine gastropods in False Bay, South Africa.
  Transaction of the Royal Society of South Africa
  28, 255-295.
• GIBBONS, M.J. (1988). The impact of wave exposure
  on the meiofauna of Gelidium pristoides (Turner)
  Keutzing (Gelidiales Rhodophyta). Estuarine,
  Coastal and Shelf Science 27, 581-593.
• GIBBONS, M.J. GRIFFITHS, C.L. (2000). A
  comparison of macrofaunal and meiofaunal
  distribution and standing stock across a rocky
  shore, with an estimate of their productivities.
  Marine Biology 93, 181-188.
• POVEY, A. KEOUGH, M.J. (1991). Effect of
  trampling on plant and animals populations on
  rocky shores.  Oikos  61, 355-368.
• SOUTHWARD, A.J. (1958). The zonation of plants
  and animals on rocky sea shores. Biological
  Reviews 33, 137-177.
• P.G. Moore and R. Seed (editor), The Ecology of
  Rocky Coasts Essays Presented to J.R. Lewis
• George A Knox. The Ecology of Seashores. CRC
  Press  2000  
• Brosnan, D.M. and Crumrine, L.L. (1994) Effects
  of human trampling on marine rocky shore
  communities. J. Exp. Mar. Biol. Ecol., 177,
  190-197