Hard substrate communities
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Hard Substrate Communities. Hard substrate = rocks, old shells, pilings, jetties, piers, docks Intertidal – perhaps best know marine community. Tides = periodic rise and fall of sea level.

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Hard Substrate Communities

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Hard substrate communities

Hard Substrate Communities

Hard substrate = rocks, old shells, pilings, jetties, piers, docks

Intertidal – perhaps best know marine community


Tides periodic rise and fall of sea level

Tides = periodic rise and fall of sea level

  • Caused by gravitational attraction of sun and moon and centrifugal force generated by the rotation of the earth-moon system around the sun

  • Periodicity of 24 hours, 50 minutes


Hard substrate communities

  • gravitational attraction: sun and moon pull at the Earth’s oceans, causing a tidal bulge

  • the tidal influence of the Moon is about twice that of the Sun


Hard substrate communities

  • Two classifications of tide based on the orientation of the Sun and Moon.

  • Spring tide : Sun, Moon and Earth are all in a line (full or new moon), Sun and Moon act together to create one large tidal bulge, and causes the greatest tidal differences because the.

  • Neap tide: Sun and Moon are at right angles from each other (quarter moon phase), when the, smaller tidal bulge.

  • distance of Moon: 50K km difference. perigee (nearest), the gravitational pull is ~40% greater than at apogee (farthest).


Hard substrate communities

  • Approximately two high tides and two low tides each day

  • when it is high tide at one coastal location, it is low tide along a different coast a quarter of the way around the Earth.

  • Bay of Fundy, eastern Minas Basin, on the - Moon near perigee @ spring tide, HT up to 16 meters above LT.

  • The geogr. location, shape of the shoreline, water depth key reasons for tidal variations.


Result of the tides

Result of the tides –

  • Exposure in the air for periods every day

    • Greater temperature differences

    • Desiccation/water loss – time of exposure changes as tide advances

    • Intense solar radiation


Waves

Waves

  • Mechanical effect

  • Creates a “splash zone”

  • Mixing – chemicals, dissolved gases, suspended particles


Salinity changes

Salinity changes

  • Rainfall, freshwater runoff

  • Tidal pools – evaporation exceeds precipitation


Hard substrate communities

Barnacles


Hard substrate communities

Barnacles


Hard substrate communities

Mytilus californianus


Hard substrate communities

Nucella (Thais)


Hard substrate communities

Limpets


Hard substrate communities

Starfish - Pisaster


Hard substrate communities

Sea Anemones


Hard substrate communities

Tunicates


Hard substrate communities

Bryozoans


Hard substrate communities

Sea Urchins


Hard substrate communities

Algae


Adaptations organisms

Adaptations – Organisms

  • Minimize water loss/desiccation during exposure

    • Hide out in most crack, crevice, under algae

    • Tolerate tissue desiccation, rehydrate at high tide

    • Structural behavioral modifications – close up, clamp down, mucus, gills in cavity


Adaptations organisms1

Adaptations – Organisms

  • Minimize thermal stress

    • Large size, surface/volume ratio

    • Light/heat reflection

    • Evaporative cooling


Adaptations organisms2

Adaptations – Organisms

3. Avoid destruction in waves

  • Attach to substrate

  • Thicker shells

  • Clamp to substrate

    4. Salinity stress


Conspicuous horizontal banding or zonation of organisms

Conspicuous horizontal banding, or zonation of organisms


Stephenson stephenson 1949 universal scheme to describe

Stephenson & Stephenson 1949universal scheme to describe

  • Supralittoral – splash zone

    • Littorina (periwinkle), encrusting lichens and algae

  • Midlittoral – barnacle and mussels zone

  • Infralittoral – algae and more diverse mix of animals

  • Sublittoral – subtidal zone


Hard substrate communities

Why?

  • Period of submergence – “critical tidal level” (Doty 1945)

  • Desiccation – sets upper limits to organisms

    • north vs south-facing slopes

    • irregularities

  • Thermal stress

  • Sunlight


Joseph connell 1961

Joseph Connell 1961

Coast of Scotland:

Chthamalus stellatus

Balanus balanoides

Thais lapillus (now Nucella)


Robert paine 1966

Robert Paine 1966

  • Observed structure of the food web in rocky intertidal from Washington to Costa Rica

  • Washington – predatory starfish Pisaster and Nucella, the drill – lots of diversity

  • Costa Rica – no starfish, the drill Nucella is the top predator – less species diversity

  • What was going on??

  • Went back to Washington and experimented


Paine s experiments

Paine’s experiments:

  • Removed starfish from rocks and observed results

  • With Pisaster ~ 15 species

  • Without ~ 8 species (plots dominated by Mytilus, the best competitor for space)

  • Pisaster - “Keystone species” – indirectly controls the structure of whole community


Connell in california 1970

Connell in California (1970)

  • Balanus glandula (like Chthamalus)

  • Balanus cariosus

  • Refuge in space (Balanus glandula)

  • Refuge in size (Balanus cariosus)


Paul dayton 1971

Paul Dayton 1971

Space is key – processes involved in getting, keeping, and using space

  • Physical stress – desiccation, etc.

  • Physical disturbance – waves, drift logs

  • Predation – biological disturbance

  • Competition

  • Natural death


Dayton s experiments

Dayton’s experiments:

  • Fucus – whip effecton barnacles vs protection from desiccation

    • Treatment = removalof Fucus

  • Limpets – eat algae; disturb and/or eat barnacles

    • Treatment = “dog dishes” to exclude limpets

  • Thais – drills mussels and barnacles

    • Treatment = cages to exclude

  • Pisaster – eats mussels and barnacles, etc.

    • Treatment = removal


Dayton s conclusions

Dayton’s conclusions:

  • Sessile marine organisms compete for space

  • Three levels of “biological disturbance”

    • Grazing by limpets

    • Predation by Thais/Nucella

    • Predation by Pisaster

  • Pattern in nature = mosaic of disturbance and recovery; disturbance maintains patchiness, keeps diversity high


Impact of connell paine and dayton s work on field of ecology

Impact of Connell, Paine, and Dayton’s work on field of ecology

  • Shift in thinking about how communities are organized

  • Earlier view – competitive dominant has broadest niche, diversity the result of specialization to avoid competition

  • New view – dominants often less abundant, inferior competitors can have broader niche, predators and disturbance create diversity by preventing competition


Rocky intertidal paradigm

Rocky Intertidal Paradigm

  • Upper limits of distribution are primarily determined by physical factors

  • Lower limits of distribution are primarily determined by biological interactions (competition for space and predation)

  • Predation or physical disturbance can prevent competitive exclusion (enhancing species diversity) by keeping superior competitors at low densities

  • In benign physical environments, predation is most important in determining community composition

  • In harsh physical environments, predation intensity is reduced and competition is most important in determining community composition


Exceptions and limitations of rip

Exceptions and Limitations of RIP

  • Upper limits of distribution are primarily determined by physical factors

  • Lower limits of distribution are primarily determined by biological factors (competition for space and predation)

    • Starvation restricts upper reaches

    • Larval settlement determines the limits of distribution

      -- shorter period of inundation means reduced probability of settlement in upper reaches

      -- larvae chose where they settle

      -- adult larval interactions affect settlement patterns


Exceptions and limitations of rip1

Exceptions and Limitations of RIP

4.In benign physical environments, predation is most important in determining community composition

  • In harsh physical environments, predation intensity is reduced and competition is most important in determining community composition

    • Assumes prey have a greater physical tolerance than predator, can find refuges in space

    • Variations in recruitment determine the level of competition

    • Importance of predator selectivity and competitive hierarchy

    • In same environment, both predation and competition are important, both for different life stages


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